and Radiation Officer
There are hazards in the laboratory and chemicalsfigure prominently among them. In addition to the physical properties ofreactive chemicals, traditionally the focus of life safety in the laboratory, theirtoxicity is of recent and growing concern. Although the toxic properties ofcertain chemicals has been known for thousands of years, the significance ofrisks associated with toxic chemicals in the laboratory on the health oflaboratory workers is only lately coming to light. While exposures to highlytoxic or acutely toxic substances are, given their short-term effects, easy toidentify, the long-term effect of exposure to certain chemicals is much moredifficult to predict. However, the list of compounds for which there is sufficientevidence for carcinogenicity is growing (see appendix at the end of thissection). Many of these chemicals are commonly found in laboratories. TheOSHA Laboratory Standard cites five studies on the long-term effects ofexposure to toxic substances in the laboratory. While the results are notconclusive, they suggest an increased incidence of pancreatic and possibly braintumors and lymphohaematopoietic malignancies among laboratory chemists.
Although it is simple to say that at some level all chemicals are toxic and directcontact should be avoided, special attention must be given to limiting exposureto those that are acutely toxic, present reproductive hazards and the selectedchemicals listed in the appendix.
Unlike the regulation of radioactive materials or infectious agents for whichprecise standard laboratory guidelines exist, the regulation of chemicals hasbeen made the responsibility of those in the laboratory. In essence the OSHA
Laboratory Standard requires that laboratories develop a Chemical Hygiene Plan that is available to all laboratory workers. The plan includes standard operating protocols (SOPs) for the use, storage, and disposal of hazardous chemicals, using the best knowledge and techniques available. These Sops must include the use of engineering controls and personal protective equipment within the boundaries of "designated areas," which in many instances may mean the entire laboratory. This places much of the burden on laboratory supervisors and also on all laboratory workers, who must learn to familiarize themselves with the physical and health hazards associated with chemicals in their laboratory and to implement standard operating protocols which will minimize their exposure to them. A basic understanding of exposure, dose and toxicity is essential to this process.
The nature and quantity of a chemical as well as the mode and duration of theexposure determine the risk inherent in contacting the chemical. ThresholdLimit Values (TLV) issued by the American Conference of GovernmentalIndustrial Hygienists (ACGIH) may be used as guides for assessing the severityof an exposure. Note that through the adoption of the TLVs by OSHA asPermissible Limit Values (PELs), these PELs now carry the weight of law fordetermining safe exposure as well as levels at which actions must be taken to
reduce exposure. A list of these chemicals as well as those for which NIOSHhas published Recommended Exposure Levels (RELs) appears in the appendixto this section.
Time Weighted Averages (TWA) refer to the average airborne concentration of substances to which it is believed nearly all workers may be repeatedly exposed during a normal 8-hour workday and 40-hour week, day after day without adverse effect. Because of wide variation in susceptibility, individuals may experience discomfort from some substance at concentrations at or below the threshold limit; a smaller percentage may be affected more seriously by aggravation of a preexisting condition or by development of an occupational illness.
Short Term Exposure Limit (STEL) is a 15 minute time-weighted average exposure which should not be exceeded at any time even if the eight-hour time-weighted average is within the TLV. If a STEL is not specified, short term exposures should exceed three times the TWA for no more than a total of 30 minutes per day. These levels are not necessarily conservative when applied to the research setting, where exposures to and synergistic effects from chemicals must also be considered. Likewise, individual experiences and sensitivities should be evaluated. For example, pregnant women and particularly their fetuses may be susceptible to levels lower than anticipated for most adults (see list of chemicals with reproductive hazards).
Although the repeated use of some hazardous chemicals may justify the use of specific monitors, if available, for the most part it is your vigilance upon which you must rely. This includes the appearance of vapors, moist surfaces, mixing patterns, color changes, skin, eye, or respiratory.
Do not ignore any of these signs and take steps to minimize your contact.
Some chemicals have characteristic odors. A list of odor thresholds has been compiled by the American Industrial Hygiene Association (AIHA; see GENERAL REFERENCES). While you should not use your nose to estimate chemical concentration because of the potential for overexposure, it can be of great practical value in identifying the source of an odor. Individual factory responses, fatigue, and acclimation are important factors. Remember that not all hazardous chemicals have odors and for some the level for olfactory detection may be too high to be of protective value. See the comparison of odor thresholds and TLVs for some hazardous chemicals in the Table 1.
Although all chemicals may be toxic at some level, the dose absorbed is the critical factorimpacting the health of the individual. Since individuals may be more or less tolerant orsusceptible to chemical exposures and the precise dose at which toxic effects will be manifestedvaries over a range. At certain dosages, some chemicals with known toxic properties elicit noresponse or may even have a beneficial effect. The ancient treatment of syphilis with mercury maynot be the best example, because it was not realized that compounds such as metallic mercury areonly partially excreted and can accumulate in fat and other tissues eventually causing a toxiceffect. It is possible that the shorter life expectancies of the ancients precluded the manifestationfor those chronic effects. A better example might be reproductive hormones which are essentialto our health, yet at high concentrations, e.g., those initially used in oral contraceptives, may becarcinogenic. Symptoms related to chronic exposures are often distinct from the symptomsassociated with acute exposures. Since most toxicological data is based upon data from workwith other species, it is helpful to be able to compare dosage by weight and surface area in orderto evaluate the data. Following a screening for mutagenicity using Salmonella (Ames test), thedosage of a chemical required to produce death in 50% of the treated animals (LD50) is usuallythefirst determination of toxicity with a new chemical. Customarily this test is performed on rodentsusing oral or intraperitoneal routes of administration. When the dose received is not known, thelethal concentration of chemical in air or water that causes death to 50% of the subjects (LD50) isusually determined.
The dosages of different chemicals required to produce harmful health effects vary 10 billion-fold(Table 2). The acutely toxic chemicals, e.g., mold toxins of which aflatoxin is the most familiar,are at the low end of this range where single doses of less than 10 mg/kg body weight can belethal. For some chemicals, LD50s are included in the information that manufactures are requiredto provide to purchasers discussed below. The EPA and OSHA's Appendices A and B to theHazard Communication Standard (29 CFR 1910.1200) consider the following "acutely toxic:"
which "is otherwise capable of causing or significantly contributing to an increase in seriousirreversible, or incapacitating reversible, illness." The accompanying table (Table 3) of relativehazard levels based on animal data provides a fuller perspective of the dose range.
Understanding the concepts of toxicity, exposure and dose can help effectively minimize the riskassociated with working with hazardous chemicals. Check the chemicals in your laboratoryagainst the PELs and the RELs. If you think that an exposure exceeding these values is likely,check with your laboratory supervisor for steps to minimize exposure, e.g., work in a fume hood,wear gloves. Arrange with those responsible for environmental health and safety to review thedata and monitor your exposure, if they think it necessary. For quick identification of chemicalswhich may require special handling, in addition to the chemicals for which PELs and RELs exist,the EPA's Acutely Hazardous and Extremely Hazardous Substances, are included in the appendixalong with a list of substances regulated by OSHA as carcinogens. The EPA's ExtremelyHazardous list is used with Title III of SARA (community right-to-know) and was developedusing the above mentioned criteria for acutely toxic chemicals and their dispersal potential. Ashort list of selected chemicals with known reproductive hazards follows, but a more complete listis given by Shepard T.H. 1983. Catalog of Teratogenic Agents, 4th ed):
Some Common Chemicals With Known Reproductive Hazards
Where questions exist about the hazardous characteristics of a chemical, rapid access to severalcomputerized databases at the National Library of Medicine is available through the MedicalLiterature Analysis & Retrieval System (MEDLARS). These include:
Read the labels on reagent bottles so that you know beforehand what hazards are involved. Ifsufficient information is not given, as part of compliance with Right-to-Know laws, thoseresponsiblefor environmental health can provide information about the various Material Safety Data Sheets(MSDS) for most common chemicals that are on hand. All containers of chemicals must belabeledclearly. Do not use any substance in an unlabeled or improperly labeled container. Chemicalswithprinted labels which have been partly obliterated, scratched over, or crudely labeled by handshouldnot be trusted and, together with unlabeled containers, should be disposed of promptly to avoidadverse reactions. If there must be a transfer to another container, careful attention must be paidtorelabeling: the new label must contain all cautions from the original label; do not use initials orabbreviated names. Carefully read the label before removing a reagent from its container. Readitagain as you promptly recap the container and return it to its proper location. Names of distinctlydifferent substances are sometimes nearly alike and using the wrong substances can lead toaccidents.
All of the precautions listed in the section on GENERAL SAFETY PRATICES should befollowed.
To avoid direct contact with chemicals, particular attention must be given to using a fume hoodand selecting personal protective equipment appropriate for the chemicals handled. Select gloves thatarenot readily degraded and/or permeated by the specific chemicals used. A table in the appendix totheGENERAL SAFETY PRACTICES provides information on the resistance of different glovematerials to some common chemicals.
Purchase of Chemicals: "The decision to procure a specific quantity of a specific chemical is a commitment to handle itresponsibly from receipt to ultimate disposal. Each operation in which it is handled and eachperiodbetween operations presents opportunities for misadventure."
When acquiring toxic or hazardous chemicals, obtain the smallest quantity sufficient for yourwork since their storage may constitute a hazard and disposal costs negate most volume discounts. In1990disposal costs in the U.S. northeast for labpacked chemicals averaged $10.00 per pound ofchemicalwaste. Purchase chemicals in shatter-proof containers when available.
Although storing chemicals in alphabetical order may seem convenient, it increases the chancesthat incompatible materials will mix in the event of leaks, spills, breakage, floods or fires. Physicalhazardscan be reduced by purchasing the minimal amounts of chemicals required and requesting that theybesupplied in shatter-proof containers. Storing heavier items on lower shelves, but not on the floor,willfurther reduce these hazards. While separating chemicals into mutually exclusive compatiblegroupsfor separate storage is ideal, it is difficult to reach a consensus of what those groups should be.
Moreover, for these groups to be truly exclusive, requires many sub-divisions with appropriateseparate and well-maintained storage locations.
Unlike dedicated chemical storage rooms within which partitioned areas or separate storagecabinets or drums can be allocated to specific groups of chemicals, laboratory space must alsoaccommodatepersonnel, fixtures and equipment. Inevitably this means there will be only a few possible distinctlocations for storing chemicals. For convenience these locations are typically under sinks forcorrosives, under fume hoods for flammable and volatile chemicals, and on shelves near a set ofbalances for general chemicals. An explosion-proof refrigerator may be needed to storeflammablechemicals that tend to decompose at room temperature. Due to the reactivity of oxidizers, it isimportant to segregate them from other chemicals at all storage locations. Ordering the minimalamounts of the chemicals required is especially important for highly hazardous materials, e.g.explosives, carcinogens, acutely toxic chemicals. These materials should not be purchased inexcessso that storing them will not be necessary. For this reason no storage category for explosives islistedbelow. Given that fewer separate storage locations will be available than ideal, secondarycontainersshould be used to separate incompatible chemicals within storage groups. For example,chemicallyresistent plastic trays of adequate size should be used to both separate and contain corrosiveliquidssuch as acids and bases. Also, containers may be useful for keeping track of small amounts ofextremely toxic and controlled substances.
The use of a basic color code affixed upon receipt will greatly aid in identifying the correctchemical group and facilitate proper storage and inspection, especially by laboratory staff withoutbackgroundsin chemistry. Chemicals, particularly those known to decompose with time, should also bemarkedwith the date of receipt. In addition to checking the physical condition of primary and/orsecondarycontainers, chemicals should be inspected regularly for signs of decomposition, such asdiscoloration,turbidity, caking, moisture in dry chemicals, particulates in liquids, and the buildup of pressure inthevessel. Any of these conditions is adequate cause for disposing of the material as soon aspossible.
The storage scheme outlined in Table 4, although incomplete by many standards, is a practicalstartingapproach for a working laboratory and should be further tuned to specific requirements.
When transporting chemicals from one area to another, place the chemical bottle into a plasticbucketas a secondary container in case of breakage.
A flammable liquid is any liquid mixture, substance or compound with a flash point below 100F,when tested in a Tagliabue open cup tester. Liquids have vapor pressures below 40 psi absoluteat100F. The flash point is the lowest temperature at which a flammable liquid gives off vaporsufficient to form an ignitable mixture with air near the surface of the liquid or within the vesselused.
Flammable liquids and solids must be separated from oxidizing materials. Flammable solvents
requiring refrigeration should only be stored in flammable storage refrigerators in which electricalcontacts are isolated from solvent vapors. All domestic type refrigerators must have signswarningof the danger of storing volatile or flammable chemicals, such as alcohol, acetone, and ether.
Carcinogens and highly toxic chemicals should be stored inside of marked containers in a centrallaboratory location. (See appendix for list of selected chemicals.)
It is recommended that laboratories have no more than 5 gallons of flammable liquid (15 fororganic chemistry laboratories), 1 pound flammable solids, 5 pounds oxidizable materials, 1 poundunstable(reactive) materials, and no explosives except under special circumstances and then only with theexplicit approval of environmental health.
Do not pipet by mouth. Use an aspirator bulb, a pipetting device or a loose-fitting hose attachedto a water aspirator. When pouring chemicals, hold the bottle with its label toward your palm toprotectthe label in case some reagent drains down the outside of the bottle. Do not pour towardsyourselfwhen adding liquids or powders. Use a funnel if the opening is small. Use a glass rod betweentheoutside of the funnel and the neck of the receiving bottle so that air can be displaced. If a stopperorlid is stuck, use extreme caution in opening the bottle. Friction caused by removing tops cancausean explosion of sensitive substances. When a flammable liquid is withdrawn from a drum or whena drum is filled, the drum and the other equipment must be electrically grounded. Remove fromthecontainer only approximately what is needed, discarding any excess. Never return a chemical toitsoriginal container.
Always add a reagent slowly; never "dump" it in. Observe what takes place when the first smallamount is added and wait a few moments before adding more; some reactions take time to start.Witha gloved hand, feel the outside of the receiver vessel. If it is hot, cease the additions and seekadviseon whether this is part of the reaction profile. If so, the receiver vessel should be placed on ice. Ifanexpected reaction does not initiate, seek advice before adding more reagent.
To avoid violent reaction and splattering while diluting solutions, always pour concentratedsolutions slowly into water or into less concentrated solutions while mixing,TABLE 4. Summary of Chemical Storage Arrangements
Placing these two groups of chemicals near a fume hood is convenient. Separating theflammable chemical group makes it easy to calculate the total volume of flammablechemicals stored per room.
Flammable: Alcohols, Amines, Amides, Imines, Imides, Hydrocarbons, Esters,Aldehydes Ethers, Ketones, Ethylene OxideVolatile: Chloroform, Methylene chloride, Carbon tetrachloride Ethers areperoxidizable.
These solids are usually stored under mineral oil.
Sulfur, Phosphorus, Phosphorus pentoxide,Hydrides Metals, e.g. Sodium, Potassium and MetalDusts Corrosives [Acids and Bases]
Store acids and bases below eye-level in a dedicated area, e.g., in separate plastic traysunder sink.
Store nitric acid separately.
Hydroxides, Phenol, Cresols, Halogens Acids, Peracids, AnhydridesPerchloric, Nitric and Chromic Acids areoxidizers.
Sulfuric and Acetic Acids are dehydratingagents.
Hydrofluoric Acid requires specialprecautions.
These chemicals may be storedalphabetically.
Selenides, Phosphides, Carbides, Nitrides
Halides, Sulfates, Sulfites, Thiosulfites
Phosphates, Acetates, Isocyanates, Amides
Silicates, Carbonates, Carbon, Glycols,
Borates Sulfides, Polysulfides, Sulfoxides, Nitriles
Store separately from the rest. Store peroxidizing chemicals at minimumtemperatures required to preventdecomposition. Avoid freezing orprecipitation of peroxides; either processincreases their heat- or shock-sensitivity.Avoid grinding or using metal spatulas withperoxides.
Chlorates, Perchlorates, Chlorites,Hypochlorites Peroxides, Hydrogenperoxide, Hydroperoxides
Borates, Chromates, Manganates,Permanganates
Amides, Nitrates, Nitrites
Chemicals Requiring Refrigeration
Flammable materials should be placed in an explosion-proof refrigerator. Oxidizersshould be grouped in separate secondarycontainers.
Flammable Oxidizers Other Acetaldehyde Dibenzoyl peroxide
Methyliodide Dimethylether Hydrogenperoxide Methylbromide
Carcinogens, Extremely Toxic Chemicals and Controlled Substances
These materials should be stored in aseparate area or container to facilitate therequired tracking of their use storage anddisposal.
See lists of chemicals in Appendix.
When available, antidotes should be on hand for extremely toxic materials (see Table 5).preferable on a mechanical stirrer. The more concentrated solution is usually heavier and any heatevolved is better distributed. This procedure is particularly applicable in diluting acids. Alwaysweargoggles and use the hood when diluting concentrated solutions.
Beakers should be supported by holding them around the side with one hand. If the beaker is 500ml or larger, support it from the bottom with the other hand and consider using heavy-dutybeakers.
When setting the beaker down, deposit slowly on the clean surface of the bench. If the beaker ishot,use gloves and place the beaker on a protective pad. Flasks should be grasped by the neck, not bya side arm. Large flasks (3-liter) should be supported at the base when lifted. A round bottomedflask should rest on a properly sized cork ring when not assembled for reaction.
Never look down the opening of a vessel unless it is empty.
The fume hood is the most important piece of protective equipment in a laboratory. SeeGENERAL SAFETY PRACTICES for guidelines and discussion of their use and limitations.
Most spills in the laboratory involve comparatively small quantities of chemicals which can readilybe neutralized and cleaned up by laboratory personnel. It is recommended that the laboratorysupervisor be notified and that spill control procedures be performed under his/her supervision.
Arrange for disposal of chemicals with environmental health or chemistry stores.
If a spill is of such size (> 1 liter) and/or potential hazard that additional assistance or equipmentis required, contact environmental health at 243-2881; after hours, dial your emergency contactnumber, e.g., 243-4000. Give the following information:
1. Name of person calling
2. Type of spill and approximate quantity
3. Location: building, floor, and room number
Measures to be taken while waiting for assistance:
1. If a flammable liquid spilled, shut down all electrical equipment and extinguish all flames.
2. If volatile chemicals are involved, open windows for ventilation (but close doors).
3. If an infectious or particulate agent is involved, close all windows and shut off ventilation.(Wait 30 minutes for aerosol to settle before reentering room.)
4. Clear laboratory of all personnel.
5. Close all doors to corridor or adjacent rooms. Hang an appropriate warning sign on the door.
Spills and accidents involving hazardous materials must be immediately reported to thoseresponsible for environmental health and safety.
In all cases immediately alert neighbors, laboratory supervisor, and/or department head.
If chemicals are spilled on the body, quickly remove all contaminated clothing while using thesafety shower or sink. If a large area is affected or if chemical is highly toxic and skin permeable, callyouremergency contact number, e.g., 1111, to summon medical assistance. Seconds count and notimeshould be wasted because of modesty. Immediately flood the affected body area in cold water forat least 15 minutes. Do not use neutralizing chemicals, unguents, creams, lotions or salves. Resumerinsing if pain returns. Report to those responsible for employee health and notify the head of thedepartment or the environmental health and safety office as soon as possible. Delayed reactions,often the next day, may occur and should be reported.
Alkali solutions spilled onto the skin may not be as painful as an acid burn; in fact, they may notbenoticeable until some time later. The reason for this is that acids precipitate a protein barrier oncontact with skin, and this both prevents the acid from penetrating further and also causes pain.Alkalisolutions do not precipitate a protein barrier; the tissue may become thoroughly soaked anddeeplydamaged with relatively little discomfort, resulting in an insidious wound. For this reason the skinthat has been splashed with alkali should be continuously flushed to reach the alkali that hassoakedinto the tissue.
TABLE 5. Poisons and Antidotes
ANTIDOTE - Mechanism of Action
Alkaloids (Quinine, Physostigmine, Strychnine)
Potassium permanganate - 1:10,000 (gastric lavage)
Gastric lavage; chlorpromazine (i.m.) - decreases cerebral effects
Dimercaprol, BAL (i.m.) - chelation
Phytonadione (vitamin K1) - reverses hypoprothrombenemia; stops hemorrhage due tooverdose of anticoagulant therapy
Cardiac glycosides (Digitalis)
Potassium chloride versenateTM - chelates calcium
Calcium glucanate (i.v.); vitamin B complex (i.m. or i.v.)
Sodium nitrate (i.v.) or amyl nitrate inhaled followed by sodium thiosulfate
Phenobarbital sodium; amytal sodium
DDT and chlorinated hydrocarbons
Symptomatic Rx only
BAL, versenate, penicillamine - chelation
Hydrocarbon ingestion (e.g., gasoline)
Phosphate-buffered saline lavage; emesis; oxygen
Iron and iron salts
Emesis; sodium dihydrogen phosphate or sodium bicarbonate (gastric lavage); fluid replacement;desferrioxamine mesylate (i.v.) - chelation
Lye and other caustics
Symptomatic phosphate buffered saline (weak acid - 1% acetic acid). In severe cases, open airway and administeroxygen, arrange gastroscopy
Dimercaprol (BAL) versenateTM - chelation
Dimercaprol (BAL) - chelation
Sodium bicarbonate (i.v.); emesis; ethanol
Combat acidoses; to inhibit oxidation to toxic metabolites
Naloxone hydrochloride - antagonist
Early gastric lavage; saline cathartics; fluid replacement
Copper sulfate 0.2% lavage; dexamethasone
Phosphate esters and
Atropine; pralidoxime chloride (ProtopamTM)
Activated charcoal; naloxone hydrochloride (i.v.); open airway and supply oxygen and IV fluids
Emesis if conscious; early gastric lavage; vigorous fluid
IV; replace potassium; supply oxygen
Hydration and acid minimization
Emesis and airway lavage if conscious; lavage for 24 hours or longer
Phytonadione (vitamin K1)
A list of poisons and antidotes is provided in Table 5.
LABORATORY OR AREA DECONTAMINATION
If chemicals are spilled on the floor or work area, seek the advice of your supervisor orenvironmental health.
When cleaning up spills, wear safety glasses and gloves impermeable to the substance, considertheneed for a respirator and apply an absorbent material which will neutralize the liquids. Workfromthe perimeter of the liquid spill inward and then use a dust pan to collect solid materials into abag.If the spill is on the floor, some absorbent should be sprinkled on the spot to prevent slipping. Donot use vermiculite. If water or some other agent is used as a diluent, be sure it is compatiblewiththe spilled material and other chemicals in the area (see listing of incompatible chemicalselsewherein this section). The laboratory supervisor will be responsible for designating the proper cleanupprocedure. If a flammable or toxic chemical is spilled, call environmental health at 243-2881 forassistance. Warn everyone to extinguish flames and turn off spark-producing equipment such asbrush-type motors and bunsen burners. Shut down all equipment, close the doors and windows,and vacate the room until it is decontaminated.
Wall-mounted spill control stations containing agents for absorbing and neutralizing such spillsmay be located in corridors readily accessible to the laboratories. Clean-up kits for mercury, cyanide,andhydrofluoric acid spills are available. Contact your purchasing agent or ChemistryStores forreplacement kits when necessary.
SPILL KIT USE
1. Tear open corner of bag of neutralizing agent and pull out spout.
2. Apply the agent to the spill from perimeter inward.
3. After foaming subsides, dilute with water until color changes from red/pink to blue/green.
4. Pick up neutralized waste with the scoop and transfer to plastic disposal bag.
5. Wipe up residual absorbent with a moistened sponge.
6. Place sponge, scoop, and gloves in disposal bag and seal; arrange for disposal as chemical waste.
Caustics (Bases, i.e., ammonium, potassium, and sodium hydroxides)
1. If concentrated, add equal volume of water or ice.
2. Tear open bag of neutralizing agent at corner and pull out spout.
3. Squeeze bag to break up lumps and apply agent to the spill from the perimeter inward
4. Thoroughly mix the agent and spill material with brush provided until material turns orange/yellow throughout, adding more if required.
5. Open bag of liquid absorbent and apply to treated spill to absorb liquid.
6. Pick up saturated absorbent with plastic scoops and transfer to plastic disposal bag.
7. Wipe up residual absorbent with moistened sponge
8. Place sponge, scoop, and gloves in disposal bag and seal. Arrange for disposal as chemical waste.
Flammable Solvents (For 500 ml of solvent or less)
1. Immediately remove all sources of ignition and provide maximum ventilation.
2. Open bag of absorbent by tearing top corner and pull out flap to form spout.
3. Apply sufficient quantity of materials to absorb all of the solvent (1 bag for 30 to 150 ml).
4. Thoroughly mix the absorbent and solvent with scoops provided. The absorbent shouldregain its appearance as a dry, free running, non-adhering powder. Clumping indicates flammable condition.
5. Pick up the absorbent with scoops and transfer to disposal bag along with gloves and scoops.
Seal and arrange for disposal as chemical waste.
Mercury spills, commonly from broken thermometers, result in a large number of very smallparticles that are difficult to clean up. Small particles of mercury have an increased rate of vaporization,dueto the higher ratio of surface area to volume, and this can cause greater contamination of the airthancan be safely handled by normal ventilation. The safe exposure limit can be exceeded by a singlebroken thermometer if not cleaned up properly. This can be further aggravated by highertemperatures, such as a broken thermometer in an oven. As a precaution, place a container underneath allmercury sources, such as manometers and barometers, and use "unbreakable" (Teflon-coated) ornon-mercury thermometers.
To clean the spill, wear protective clothes and gloves. Sprinkle the contaminated area withmaterial from the spill kit which will combine with the smaller mercury droplets to form a solid compoundthatwill no longer vaporize as readily. Alternatively, use an aspirator bulb, scotch tape or place asmallpiece of dry ice on the surface of the mercury which very quickly freezes (m.p. -38 C) and canthenbe transferred with tweezers. Collect materials with a circular sweeping motion. All mercury andsweepings should then be disposed of through normal chemical waste procedures. Containerswith liquid should be tightly sealed and unbreakable.
A spill of an alkali metal (e.g., sodium, potassium) should be smothered with powdered graphite,sand, or Class D extinguisher and removed to a safe location where it can be disposed of byreactionwith a dry secondary alcohol. Particles of alkali metal splattered on the skin should be rapidlyremoved, and the skin flushed quickly with water. If any metal on the skin becomes ignited,deluge it with cold water immediately.
Reactive chemicals are substances which, under certain ambient or induced conditions, enter intoviolent reactions with spontaneous generation of large quantities of heat, light, gases (flammableandnon-flammable), or toxicants that can be destructive to lives and property. Types of reactive chemicals have been loosely categorized:
In general, protect explosive substances from shock, elevated temperatures, rapid temperaturechanges, and other reactive chemicals. Some examples: nitroglycerin, nitrocellulose, and organicperoxides. Many substances, when mixed, are potentially explosive (such as hydrazines and nitric acid).
Note that the following compounds readily form peroxides upon:
Storage (3 Months)
Concentration (12 Months)
Methyl i-butyl ketone
Methyl ether (glyme)
Initiation of P olymerization (12 Months)
di-Vinyl acetat e
Methyl acetylen e
*Storage in metal containers slows peroxide formation.
OXIDIZING AND REDUCING SUBSTANCES
In many oxidizing and reducing reactions, both agents must be present. In some cases, one or theother substance may create a hazard by coming into contact with a normally innocuous substance.
These reactions tend to generate heat and are often explosive, e.g., glycerol and potassiumpermanganate blended at room temperature for a few minutes react violently producing fire. Thefollowing examples of typical oxidizers may:
Increase Rate of Combustion
Nitric acid 70% or less
Perchloric acid 60% or less
Cause Spontaneous Ignition
Hydrogen peroxide (27.5-52%)
Sodium chlorite (more than 40%)
Decompose With Catalyst or Heat
Hydrogen peroxide (52-91%)
Calcium hypochlorite (over 50%)
Perchloric acid (60-72.5%)
Cause Explosive Reaction When Exposed to
Catalyst, Heat, Shock, or Friction
WATER SENSITIVE SUBSTANCES
These chemicals react with water, steam, and moisture in the air to evolve heat and/or flammable or explosive gases. Isolate water-sensitive substances fromother reactive compounds, and store in a cool, waterproof area. Somesubstances that liberate only heat are: strong acids and bases, acid anhydridesand sulfides. Some substances that liberate flammable gases when exposed towater are: alkali metals, hydrides, nitrites, carbides, and anhydrous metallicsalts.
AIR REACTIVE SUBSTANCES
These materials are capable of rapid release of energy by themselves, as by self-reaction or polymerization, for example white phosphorus. Also includedin this category are substances that can be easily ignited by common sources ofheat when mixed with air; for example: alkali metals, ammonium nitrate,ammonium perchlorate, ammonium permanganate, benzoyl peroxide, boronhydrides, dinitrobenzene, lithium hydride, sulfur.
ACID REACTIVE SUBSTANCES
These chemicals react with acid to evolve heat, flammable and/or explosive gases, and toxicants. Some examples are: alkali metals, hydroxides, carbides,nitrites, arsenic and related elements, cyanides, sulfides, and structural alloys(most metals).
SPECIAL ORGANIC COMPOUNDS
These compounds are unstable and may decompose spontaneously or through contact with the immediate environment (air, water, and other reactants).Some examples: diazonium compounds, diazomethane, chlorinationintermediates, butadiene, nitration intermediates, organic sulfates,polymerization reactions, and highly nitrated compounds.
Pyrophoric agents burn when exposed to air. In general, they require absoluteprotection against air. Examples: phosphorus and activated zinc.
ACETIC ACID with chromic acid, nitric acid, hydroxyl-containing compounds, ethylene glycol, perchloric acid, peroxides, and permanganates
ACETONE with concentrated sulfuric & nitric acid mixtures or chloroform & bases
ACETYLENE with copper(tubing), halides, silver mercury and their compounds
ALKALI METALS: aluminum, calcium, lithium, magnesium, potassium andsodium with water or chlorinated hydrocarbon, carbon dioxide, halogens
AMMONIA, Anhydrous with mercury, halogens, calcium hypochlorite, hydrogen fluoride
AMMONIUM NITRATE with acids, metal powders, flammable fluids,chlorates, sulfur nitrate
ANILINE with nitric acid and hydrogen peroxide
AZIDES with acids
BROMINE with ammonia, acetylene, butadiene, butane, hydrogen, sodiumcarbide, turpentine
CHLORATES with ammonium salts, acids, metal powders, sulfur, finelydivided organic and combustible materials
CHROMIC ACID with acetic acid, alcohol, camphor, flammable liquids,glycerol, naphthalene
CHLORINE with ammonia, acetylene, butadiene, benzene and otherpetroleum fractions, hydrogen, sodium carbides, powdered metals
COPPER SALTS with acetylene, hydrogen peroxide
CYANIDES with acids
ETHYLENEDIAMINE greater than 3 percent with methylene chloride(explosive)
FLAMMABLE LIQUIDS with ammonium nitrate, chromic acid, hydrogenperoxide, halogens, nitric acid, sodium peroxide
HYDROCARBONS (butane, propane, benzene) with halogens, chromicacid, peroxides
HYDROGEN PEROXIDE with copper chromium, iron, most metals andtheir salts, flammable fluids, aniline, and nitromethane
HYDROGEN SULFIDE with nitric acid and oxidizing gases
IODINE with acetylene, ammonia
MERCURY with acetylene, hydrogen
METHYLENE CHLORIDE with greater than 3 percent ethylenediamine(explosive)
NITRIC ACID with acetic, chromic and hydrochloric acids, aniline, carbon,hydrogen sulfide, flammable fluids, or gases which are readily nitrated
OXYGEN with oils, grease, hydrogen, flammable liquids, solids, and gases
OXALIC ACID with mercury, silver
PERCHLORIC ACID with acetic anhydride, alcohol, organic materials, e.g.,wood, paper, grease, and oils
PHOSPHORUS with air, alkalis, oxygen, reducing agents
PHOSPHORUS PENTOXIDE with water
SODIUM with carbon dioxide, carbon tetrachloride, water
SODIUM PEROXIDE with any oxidizable substances; acetic acid, aceticanhydride, benzaldehyde, carbon disulfide, glycerol, ethylene glycol, ethylacetate, methanol
SULFURIC ACID with potassium chlorate, potassium perchlorate,potassium permanganate
An annotated list of hazardous chemical reactions is available from the NFPA; a much longer compendium is provided by Bretherick.
Hazards of Some Common Hazardous Chemicals
Some hazards one may face when working with reactive chemicals are illustrated below; for specific information on distillation and extraction seeGENERAL SAFETY PRACTICES. Threshold Limit Values (TLV) areincluded for some agents as an indication of the upper limits of exposure thatare considered "safe." Values are either 8-hour time-weighted averages (TWA)or short term (usually 15 minutes) exposure limits (STEL). (See "Exposure"above for further information.) Note that some of these compounds are alsoregulated as carcinogens. This list is far from complete. Gloves, goggles, anda fume hood may be appropriate. If there are any questions, consult thedepartment head, laboratory supervisor or those responsible for environmentalhealth and safety.
The effect of exposure to CH3CN is due partially to the intact molecule and alsoto the cyanide ions released by metabolism. Acetonitrile is skin permeable.Ingestion, acute inhalation or contact exposures should be treated as forhydrogen cyanide exposure. The vapors are irritating to the eyes and skin.
Acetonitrile has a "etherish" odor detectible at 40 ppm but olfactory fatigue
occurs within 2 hours. A TWA of 40 ppm and a STEL of 60 ppm are recommended to protect against organic cyanide poisoning and injury to therespiratory tract.
Acrylamide is a potent neurotoxin. No data are available to evaluate the reproductive effects or prenatal toxicity of acrylamide to humans. The TLV is0.03 mg/m3. There is sufficient evidence for carcinogenicity of acrylamide toexperimental animals (IARC 2B). Purchase acrylamide in concentrated stocksolution. If dry acrylamide is absolutely necessary, wear gloves and weigh ina still area of the lab away from traffic, fume hoods and drafts.
Benzene is readily absorbed through intact skin, as well as through the respiratory tract. Do not handle carelessly. Poisoning can occur by inhalationof relatively small amounts causing white cell aberrations and possibly aplasticanemia. The TLV is 10 ppm (TWA) and 32 ppm (STEL). Benzene is a knownhuman carcinogen.7 Whenever possible toluene should be substituted forbenzene as a reagent.
Exposure to high concentrations and/or chronic exposure can result in disorientation, conjunctivitis, liver and kidney damage, and possiblesensitization of the heart to adrenaline, resulting in cardiac arrhythmias. Thereis sufficient evidence of carcinogenicity in experimental animals (IARC 2B).
Exposure of chloroform to heat or flame can results in generation of phosgenegas. In a few minutes phosgene may cause eye irritation and coughing at 5ppm, severe lung injury at 20 ppm, and death at 50 ppm. The odor detectionthreshold of chloroform is 200-300 ppm while the TLV without regard to itspotential carcinogenicity is 10 ppm (TWA).
Dichromate cleaning solution is an extremely corrosive agent. The TLV for chromium III is 0.5 mg/m3(TWA) and the TLV for chromium VI is 0.05mg/m3(TWA). Use alternatives for glassware cleaning such as MICROTM andrinse glassware with straight mineral acids if necessary to remove inorganicmetals. Alternatively, use 3:1 H2SO4:HNO3 in a fume hood.
This chemical is explosive in the solid state unless it is absolutely white. Keepbottles tightly stoppered. Vapors are highly irritating and very poisonous.Aqueous solutions of alkalies decompose cyanogen bromide to alkali cyanideand alkali bromide. The ceiling TLV is 0.3 ppm for cyanogen chloride.
This compound reacts with acetylcholinesterase and inactivates this enzyme, leading to the accumulation of acetylcholine. DFP can be absorbed byinhalation, ingestion or topical contact and can cause pinpoint pupils,lacrimation, rhinitis, weakness, wheezing, tachycardia. Severe intoxication is evidenced by ataxia, confusion, convulsions, and respiratory paralysis.
Sufficient 2 N NaOH should be on hand whenever DFP is being used in order to neutralize the entire amount of DFP. If exposed to DFP call for medicalassistance immediately. Treatment consists of administration of atropinefollowed by pyridine-2-aldoxime.
Repeated exposure via inhalation has caused loss of appetite, exhaustion, and headache. At a concentration of 3.6-6.5% in air general anesthesia occurs.Acute overexposure produces vomiting, irregular respiration, and low pulserates and body temperatures. The lethal oral dose is about 420 mg/kg. TheTLV is 400 ppm (TWA) and 500 ppm (STEL). No open flame is permitted inthe same room where ether is being used. Open bottles of ether should bestored in a fume hood or in a flammable storage refrigerator. Even vessels ofether containing an oxidation inhibitor, should not be kept more than a fewmonths to avoid the hazard of explosive peroxide formation. Do not disposeof ether by allowing it to evaporate in a fume hood or by pouring it down thedrain; arrange for proper chemical disposal.
DMF readily penetrates the skin and causes stomach pain, nausea, vomiting, epigastric cramps, and liver damage. The TLV is 10 ppm(TWA).
An extremely reactive material, especially when it comes in contact with the skin or mucous membranes, dimethyl sulfate was used as a war gas. A veryshort time of contact with the mucous membranes will result in painful burns.If it comes in contact with the eye, sight will be impaired if it is not removedimmediately; wash out the eye with a stream of water from an eyewash station.
In addition to the local effect, the inhalation of vapors will cause a very severetoxic effect which may be delayed up to 10 hours. The TLV is 0.1 ppm (TWA)and there is sufficient evidence of carcinogenicity in experimental animals(IARC 2A). In case of contact, wash the surface liberally with soap and wateror alcohol containing a little ammonia; then, cover the area with bicarbonatepaste. Seek medical assistance.
This substance decomposes violently on contact with a wide variety of active halogen compounds. Its toxicity is still unknown, but it is an excellent solventfor many compounds and does carry dissolved substances through the skin. Thick latexgloves should be worn when handling this substance.
Ethidium bromide is a potent mutagen and should be handled carefully; its carcinogenicity has not been sufficiently studied. Treatment with bleach mayproduce oxidation products that are also mutagenic. Dispose of ethidiumsolutions as chemical waste. Exposure to ultraviolet light (UV) fromtransilluminators used to examine ethidium bromide stained gels may causeserious eye and skin burns, the latter may make an individual more susceptible to skin cancer. Equipment shields, UV-rated face shields, a lab coat, andopaque gloves all increase protection.
Inhalation of vapors, 2-10 ppm, may result in severe irritation and edema of the
upper respiratory tract, burning and stinging of the eyes, headache, and has
been known to cause death. It is a skin sensitizer and severe eye irritant,
causing delayed effects that are not appreciably eased by eye washing. The
1982 TLV is 1 ppm (TWA) and 2 ppm (STEL). There is evidence of
carcinogenicity in animals (IARC 2A). Laboratory operations with formalin
in open vessels should be carried out in a hood. In addition, splash-proof
goggles and neoprene, butyl rubber, or polyvinyl gloves should be worn.
HYDRAZINE AND ITS SALTS
Acute exposure to vapors can cause respiratory tract irritation, convulsions,
cyanosis and a decrease in blood pressure. Hydrazine can cause fatty
degeneration of the liver, nephritis, and hemolysis and there is sufficient
evidence of carcinogenicity in experimental animals (IARC 2B). In addition,
hydrazine poses a significant fire hazard. Hydrazine has an ammonia-like odor
detectible at 3 ppm. The TLV for hydrazine is 0.1 ppm (TWA). Hydrazine is
volatile and readily absorbed through the skin. Nitrile rubber gloves are recom-
mended. Prompt washing with water effectively removes hydrazine from skin.
Hydrogen fluoride (HF) is a very serious hazard since both its gaseous and
liquid forms are toxic and it is rapidly absorbed through the skin and deep into
the body tissues causing long term excruciating pain and burns which are slow
to heal. It is difficult to contain because it attacks glass, concrete and some
metals, especially iron. It also attacks organic materials such as leather, natural
rubber, and wood. Because aqueous HF can cause formation of hydrogen in
metallic containers and piping, which presents a fire and explosion hazard,
potential sources of ignition should be excluded from an area in which it is
stored. It is crucial that this substance be used only in a fume hood to ensure
that the level considered safe (3 ppm) is not exceeded. All contact with the
vapor or liquid must be avoided by using protective equipment such as face
shields and neoprene or PVC gloves. This equipment should be washed after
each use to remove any HF.
Although immediate pain is felt from the concentrated acid, action of the acid
may be insidious and contact with a less concentrated solution may go
unnoticed for hours. In concentrations greater than 50%, the burn is felt
immediately and tissue destruction is apparent; in the 20 to 50% range, it may
take eight hours for a burn to become apparent; below 20% pain and erythema
can be latent for as long as 24 hours after exposure, sometimes delaying proper
treatment. After any contact, even if there is no immediate pain, obtain medical
aid. Prompt removal of contaminated clothing while the injured person is being
flushed with water under a safety shower is essential. Continuous flushing with
cool water is vital until any whitening of the tissue has disappeared. Simple
flushing with water does not remove HF deep in the tissues. Soak in ice water
or solution of benzalkonium chloride. Alternatively, apply 2.5% calcium
gluconate gel to the exposed area after a five minute shower or swab the area
with cotton moistened with 10% solution of 28% aqueous ammonia and
immerse area in a bath of water for a prolonged period. If HF is ingested, drink
a large quantity of water as quickly as possible, then drink milk or milk of
magnesia to sooth burning. Do not induce vomiting.
Commercial containers of this acid are labeled with a blue color code which
turns yellow when contaminated with the acid. The container then requires
continuous flushing with water until the blue color is restored. Spills should be
contained and diluted with water and the resulting solution neutralized with
lime before disposal.
HF Cleavage Operation
Commercially available HF systems utilizing a vacuum rather than positive
pressure to transfer reagents are preferred as the potential for escape of HF
is significantly less under negative pressure.
All HF system operators will receive formal and/or hands-on training on the
hazards presented by HF and the safe operating procedures for the unit
Detailed written operating protocols will be prepared and approved by those
responsible for environmental health and safety prior to the inauguration of
HF system use. Protocols to be posted at the HF fume hood, containing, at
- Guidelines for personal protective equipment (22 mil thick heavy-grade
neoprene gloves, chemically resistant sleeves and apron, and splash-proof
- Response to malfunctions such as occlusion of tubing, ports or control
valve associated with the reaction vessel, e.g., freezing with a Dry-Ice
alcohol bath and transferring vessel to an unused position on the
- Availability of HF specific spill absorbent pillows
- Emergency response and notification procedures
- First Aid procedures:
- 25% magnesium gluconate for skin exposure
- 1% calcium gluconate in a nebulizer and an eye dropper or squeeze bottle
for inhalation or eye exposure to HF
Hydrogen Cyanide (HCN) should always be used under a hood. Liquid
hydrogen cyanide is best kept over anhydrous calcium chloride. Formation of
a yellow color in the liquid indicates the lot should be destroyed. Hydrogen
cyanide and other cyanides are dangerous poisons which cause muscle
paralysis. The TLV has a ceiling of 10 ppm and an exposure to 200-500 ppm
can be fatal after 30 minutes. Aside from its high toxicity, HCN has a low flash
point and forms an explosive mixture with air over a wide range of
concentrations. When exposed to traces of base, detonation may result.
A solution is considered dangerous in concentrations over 3%. In contact with
the skin, it may cause severe burns. The TLV is 1 ppm (TWA). At a
concentration of 30% it may decompose violently if contaminated with iron,
copper, chromium, or other metals and their salts.
Mercuric compounds can be absorbed into the body by inhalation, ingestion, or
contact with the skin. The effects of mercury poisoning are cumulative and not
readily reversible. Chronic inhalation produces emotional disturbances,
inflammation of mouth and gums, memory loss, headaches, general fatigue, and
possible kidney damage. The TLV for exposure to vapor is 0.05 ppm (TWA).
Containers of mercury must be kept tightly closed and in well-ventilated areas.
Thick, high-density polyethylene bottles are useful for this purpose.
In the 1940s, CH2Cl2 was considered the safest of the chlorinated hydrocarbons
and a high exposure limit was thought to be adequate protection against
narcosis and liver injury. Subsequently the metabolism of methylene chloride
to carbon monoxide and production of carboxyhemoglobin was reported.
While the exposure limit was lowered to 50 ppm (TWA), the same as the TLV
for carbon monoxide, the exposure duration, peak concentration, and slow
metabolism make prediction of actual carboxyhemoglobin levels difficult.
Exposures to carboxyhemoglobin through processes generating carbon
monoxide, e.g., automotive exhausts, smoking should be considered additive.
The sweet odor, while distinctive, is a poor indicator of exposure since most
people can not detect less than 300 ppm. There is sufficient evidence of
carcinogenicity in experimental animals (IARC 2B). The carcinogenicity of this
compound is under extensive investigation and the literature as well as the
environmental health and safety office should be consulted for current
A fairly volatile and highly toxic agent useful to molecular biologists primarily
because it is a reversible denaturant of nucleic acids.
Alkyl mercury compounds pass through the blood brain barrier and the placenta
very rapidly, in contrast to inorganic mercury compounds. Major target organs
are the central and peripheral nervous systems and the kidneys. Work with
methyl mercury is very hazardous because of the difficulty of eliminating it from
the body. The human threshold for dangerous exposure levels is a urinary
concentration of between 10-15 g/L. Studies have shown that while 35% of
the compound is excreted in a few days, months are required to approach
complete excretion, and some organic mercury becomes incorporated into body
tissues. If the air concentration is greater than 0.03 mg/m3, one is considered
overexposed; over an 8-hour day one should not be exposed to an air
concentration greater than 0.01 mg/m3.
To guard against the major dangers posed by this compound, namely inhalation,
absorption through the skin, or ingestion, the following guidelines are
The stock solution of methyl mercuric hydroxide (1M) will be kept under a
fume hood at all times. All work involving use of the stock solution,
including dilutions, will be done in the hood.
All gels (methylmercury at 5-10 mM) will be diluted, poured and run in the
hood. After completion, any gels which require extensive handling, e.g.,
cutting out and eluting bands, will first be treated with 7 mM 2-mercapto-
ethanol, which converts the mercurial to a metallic, non-volatile form. Only
gels which must be autoradiographed may be removed from the hood
without being treated with 2-mercaptoethanol.
Disposable pipettes will be used to draw from any methylmercury-containing
solution and a solid waste container will be maintained for used pipettes and
gels to be discarded. This waste will be disposed of along with other
chemical waste; arrange for disposal as chemical waste.
All workers using methylmercury will wear gloves and lab coats.
Buffer solutions used in gel electrophoresis have been found to leach
approximately 0.6 g/ml of methylmercury out of gels. This is, of course,
a fairly low concentration, and could probably be washed down the drain.
To insure against unintentional accumulation in the plumbing system,
however, liquid waste should be accumulated and disposed of through the
chemical disposal service.
Osmium tetroxide is a volatile chemical with a disagreeable chlorine-like odor.
The toxic vapors cause lacrimation, eye and respiratory irritation and coughing,
blurred vision and headache, following acute exposure. It should be used only
in a functioning fume hood and stored in tightly sealed containers. The TLV
is 0.0002 ppm (TWA) and 0.0006 ppm (STEL).
Explodes at 100C and decomposes at lower temperatures with the generation
of oxygen. It reacts vigorously with organic materials. In addition, it is an
irritant affecting skin, eyes, and upper respiratory tract. Rubber gloves and
apron should be worn and, in the absence of a fume hood, an appropriate
Cold perchloric acid, 70% or weaker, is not considered to have significant
oxidizing power. The oxidizing power, however, increases rapidly as the
concentration increases above 70%. Temperature rises will also increase the
oxidizing power of perchloric acid solutions. Aqueous perchloric acid can
cause violent explosions if misused or used in concentrations greater than 72%.
Anhydrous perchloric acid is unstable even at room temperature and ultimately
decomposes spontaneously with violent explosion. Therefore, perchloric acid
should be segregated from dehydrating agents such as concentrated sulfuric
acid, phosphorus pentoxide, or acetic anhydride. Should only be used in
laboratories with specially designed perchloric acid hoods. These hoods feature
duct work of stainless steel and a wash-down facility to prevent the collection
of explosive perchlorate compounds in the duct system. Dried spills on wooden
or asphalt surfaces can ignite spontaneously with friction or impact.
Perchlorate esters have the same shattering effect as nitroglycerine. Do not use
magnesium perchlorate as a desiccant, except in the standard procedure for the
determination of carbon and hydrogen.
Phenol is highly corrosive. Inhalation or skin contact can result in serious or
fatal poisoning. When phenol is dissolved in organic solvents it is readily
absorbed into the blood stream. If phenol is accidentally spilled, flush all
contaminated parts with water. Phenol vapors are toxic, and the TLV is 5 ppm
(TWA) and 10 ppm (STEL). Purchase ultrapure phenol; if phenol must be
redistilled, see warnings under "Distillation" in GENERAL SAFETY
Classified as a high explosive, it is particularly dangerous when in a dry or
crystallized state (containing less than 20% water); do not store for more than
two years. Weigh bottle before and after each use and record use. Picric acid
that is old or dried out is shock sensitive; careless handling or removing the cap
can cause detonation. Arrange for chemical disposal. Picric acid dust,
solutions, and fumes are potent skin and eye irritants. The STEL is 0.3 mg/m3.
Acute exposure can produce dizziness, eye and nasal irritation, nausea, and
anorexia. Chronic exposure has produced serious liver, kidney, and bone
marrow damage and possible central nervous system effects. Transient
symptoms of overexposure are nausea, headache, insomnia and nervousness,
and low back or abdominal discomfort with urinary frequency. Exposure to
heat or flame with pyridine vapors can be explosive. It reacts violently with
sulfuric acid, nitric acid, maleic anhydride, chromic acid; cyanides can be
liberated on decomposition. The TLV is 5 ppm (TWA) and 10 ppm (STEL).
The odor threshold is below 1 ppm.
Acute exposure primarily affects the central nervous system, but the mildness
of the irritation which produces headache, fatigue, and irritability does not
provide sufficient warning to protect against overexposure, and coma and death
have been reported following severe intoxication. The TLV is 50 ppm (TWA)
and 200 ppm (STEL). The odor recognition level is 20 ppm.
In addition to the hazards of flammability, xylene can present a broad range of
neurological and gastrointestinal symptoms and possible injury to heart, liver,
and kidneys. The TLV is 100 ppm (TWA) and 150 ppm (STEL).
The following can be disposed of as trash or into the sanitary sewer system
without special handling:
Acetates: Ca, Na, NH4, and K
Amino acids and their salts
Citric acid and salts of Na, K, Mg, Ca, and NH4
Lactic acid and salts of Na, K, Mg, Ca, and NH4
Bicarbonates: Na, K
Borates: Na, K, Mg, Ca
Bromides: Na, K
Carbonates: Na, K, Mg, Ca
Chlorides: Na, K, Mg, Ca
Iodides: Na, K
Oxides: B, Mg, Ca, Al, Si, Fe
Phosphates: Na, K, Mg, Ca, NH4
Silicates: Na, K, Mg, Ca
Sulfates: Na, K, Mg, Ca, NH4
When in doubt about the disposal of chemicals, consult your supervisor or
CHEMICAL WASTE PREPARATION AND LABELING
Chemical wastes should be treated as follows:
Collect, identify, and label the containers of all chemical waste. "Unknowns"
are unacceptable. Make sure that the label contains the full chemical
name(s) and percentages of mixtures, the waste volume, and its location.
Do not pour any flammable, water immiscible, water reactive, or highly toxic
chemicals down the drain. Small amounts (e.g., <100 ml) of neutralized
acids, alkalies, and water miscible alcohols may be disposed of by slowly
flushing them down the laboratory drain with large amounts of water.
Caution: Acids and alkalies react vigorously and exothermically with
water. Always add acid or alkali to water, not the reverse.
Use a waste container with a volume as close to that of the waste as
possible. If plastic containers are used, make sure that they are compatible
with the chemical to be stored.
Generally, wastes should not be combined. Each container of waste should
have only one component unless mixtures are a necessary part of the process
that produces the waste, e.g., solid state peptide synthesis. Machine- or
should be segregated and labeled according to the type of machine. For
example, Peptide Synthesis ABI 430A waste should be labeled as such and kept
separate from DNA Synthesis ABI 380A waste. A detailed description of the
composition of machine-generated waste should be obtained from the
manufacturer and given to those responsible for waste disposal.
Combining waste solvents is permissible ONLY if the quantities of individual
components are small, i.e., < 2 L/week, and if the solvents are from the same
categories, e.g., all halogenated solvents. This eliminates the need to have
dozens of waste containers in a synthesis lab. If solvents are combined, a
record of the approximate composition of each waste must be kept. If the
quantity of combined solvent waste exceeds 2 L per week, other
arrangements must first be made with those responsible for chemical waste
Contaminated labware should be placed in the clear plastic bags provided.
No more than 1 kg of waste and NO liquid should be put into the bag.
Do not dispose of volatile chemical waste by allowing it to evaporate in a
NOTE: The presence of any radioactivity must be indicated on the hazardous
waste labels. These materials must be treated as radioactive waste (see waste
handling procedures in The Radiation Safety Manual.
When ordering hazardous gases, consider factors such as handling and storage,
compatibility of gas regulators, eye and skin absorption, and chemical
properties. Remember that some gases are corrosive, e.g., ammonia, chlorine,
hydrogen chloride, hydrogen fluoride; flammable, e.g., acetylene, butane,
hydrogen, methane, propane; oxidizers, e.g., oxygen, chlorine; or toxic, e.g.,
carbon monoxide, ethylene oxide; and cryogenic, e.g., nitrogen, carbon dioxide,
Cylinders of compressed gases should be handled as high energy sources and
therefore as potential explosives. The following rules apply:
When storing or moving a cylinder, have the cap securely in place to protect
the valve stem.
When moving large cylinders, they should be strapped to a properly
designed wheeled cart to ensure stability.
Cylinders of all sizes must be restrained by straps, chains, or a suitable stand
to prevent them from falling.
Cylinders of toxic, flammable, or reactive gases should be used in fume
hoods and, when possible, stored in fume hoods.
Do not expose cylinders to temperatures higher than 50C. Some rupture
devices on cylinders will release at about 65C. Some small cylinders
including lecture bottles are not fitted with rupture devices and may explode
if exposed to high temperatures.
Never use a cylinder that cannot be positively identified. Do not rely on the
color of the cylinder to identify its contents.
Use the appropriate regulator on each gas cylinder. Adaptors or homemade
modifications can be dangerous.
Use only, correct, pressure-rated tubing.
Never lubricate, modify, force or tamper with a cylinder valve. Do not
loosen or remove the safety plug or rupture disc.
Leaks can be monitored by pressurizing the system, turning off the cylinder
stem valve and looking for a drop in the discharge pressure. The location
of leaks can be identified by painting all fittings and joints with soapy water
and watching for bubble formation. When using toxic gases, it is advisable
to use a toxic gas detector or indicator for detection and warning. Wrapping
the thread with Teflon tape may be necessary to stop the leaks.
When corrosive gases are being used, the cylinder stem valve should be
worked frequently to prevent its freezing.
Keep cylinders containing liquified gases upright. Note that it is often
difficult to determine the contents of a cylinder containing liquified gas,
except by weighing. As long as a liquid is present, the cylinder or vapor
pressure will remain constant. The cylinder pressure for liquified carbon
dioxide does provide an indication of cylinder content.
Oil or grease on the high pressure side of an oxygen cylinder can lead to an
Care should be exercised when compressed air or gas is used to blow away
dust or dirt, since the resultant flying particles are dangerous.
Rapid release of a compressed gas will cause an unsecured gas hose to whip
dangerously and also may build up a static charge which could ignite a
Do not extinguish a flame involving a highly combustible gas until the source
of gas has been shut off as it can re-ignite causing an explosion.
Never bleed a cylinder completely empty. Leave a slight pressure to keep
contaminants out. In case of nitrogen cylinders, leave approximately 10 psi.
This prevents contamination of the cylinder.
When not in use, cylinder and bench valves should be closed tightly.
Remove the regulators from empty cylinders and replace the protective caps.
Mark the cylinder "Empty" or "MT" and return to the distributer.
Do not keep cylinders filled with corrosive, explosive, or highly toxic gases
more than 6 months; do not keep cylinders with oxygen or liquids or
flammable gases more than 3 years.
If a cylinder begins to leak move it outdoors and contact the supplier.
Damaged or corroded cylinders and cylinders with a test date more than 5
years old stamped on the shoulder should be returned to the vendor.
Do not order a surplus of cylinders. Besides presenting a safety hazard,
there usually is a daily rental fee.
Precautions for Cryogenic Gases
Avoid contact, both the liquid and the gases can cause frostbite. Do not
touch uninsulated piping.
Wear loose-fitting thermal gloves, goggles and/or face shield, closed shoes.
Work in a well ventilated area. Liquified gas can rapidly expand, e.g.,
nitrogen expands almost 700-fold.
Never attempt to prevent vapors from escaping from cylinders of liquified,
cryogenic gases. Since they are not at thermal equilibrium, vapor is
produced as the liquid boils and, if not vented to the atmosphere, could
produce excessive pressures.
Use only the special (usually metal) tubing designed for use with these gases.
Do not improvise with plastic or rubber tubing.
Be aware that oxygen enrichment and a fire hazard can result from the
condensation of oxygen (boiling point -183C) from the air onto piping
cooled by liquid nitrogen (boiling point -196C).
If skin contacts liquified cryogenic gases, thaw burned area slowly in cold
water. Do not rub.
The valve outlet connection connects to pressure and/or flow-regulating
equipment. Specific connections are provided to prevent interchange of
equipment for incompatible gases. They are identified by a CGA number; for
example, CGA 350 is used for hydrogen, carbon monoxide, methane and some
other flammable gases. For information on valve and regulator fittings, consult
the manufacturer or those responsible for environmental health and safety.
A pressure relief device prevents a fully charged cylinder from bursting in
case of exposure to high heat.
The cylinder collar holds the cylinder cap which protects the cylinder valve
from mechanical or weather damage. It should be removed from the
cylinder only when the cylinder is supported and ready to be attached to
pressure-reducing and/or flow control equipment for use.
The DOT number signifies that the cylinder conforms to DOT specifications
and that the service pressure for which the cylinder is designed is 2265 psi
at 21C with an exception indicated by the + sign following the last test
date, which allows a 10% overfilling.
The cylinder serial number is registered with the DOT, and can be used to
verify the contents of the cylinder by querying the manufacturer.
The cylinder test date indicates the month and year of initial hydrostatic test.
Thereafter, hydrostatic tests are performed on a cylinder at intervals
specified by the DOT (usually every 5 years), or when the supplier feels they
are necessary, to determine whether the cylinder is fit for further use. For
each hydrostatic test, the new test date is stamped into the cylinder shoulder.
The encircled insignia is that of the original inspector.
Cylinder size is important to consider when purchasing compressed gas,
especially flammable gases. The National Fire Protection Association has
recommended that laboratories using flammable gas contain no more than
a single tank of 0.59 cu. ft. water volume as long as the presence of other
combustible items in the room is minimal. For example, a tank of 0.59 cu.
ft. water volume is a Matheson Company size 2 cylinder (8" diameter x 27"
length) or Ohio size 30.
The proper choice of a regulator depends on the delivery-pressure range
required, the degree of accuracy of delivery pressure to be maintained, and the
required. There are two basic types of pressure regulators, single-stage and
two-stage. The single-stage type will show a slight variation in delivery
pressure as the cylinder pressure drops. It will also show a greater drop in
delivery pressure than a two-stage regulator as the flow rate is increased. In
addition, it will show a higher "lock-up" pressure (pressure increase above the
delivery set-point necessary to stop flow) than the two-stage regulator. In
general, the two-stage regulator will deliver a more constant pressure under
more stringent operating conditions than will the single-stage regulator.
A regulator should be attached to a cylinder without forcing the threads. If the
inlet of a regulator does not fit the cylinder outlet, no effort should be made to
try to force the fitting. A poor fit may indicate that the regulator is not intended
for use on the gas chosen. The following steps should be taken for delivery of
1. After the regulator has been attached to the cylinder valve outlet, turn the
delivery pressure-adjusting screw counterclockwise until it turns freely.
2. Open the cylinder valve slowly until the tank gauge on the regulator registers
the cylinder pressure. At this point, the cylinder pressure should be checked
to see if it is at the expected value. A large error may indicate that the
cylinder valve is leaking.
3. With the flow-control valve at the regulator outlet closed, turn the delivery
pressure-adjusting screw clockwise until the required delivery pressure is
reached. Control of flow can be regulated by means of a valve supplied in
the regulator outlet or by a supplementary valve installed in a pipeline
downstream from the regulator. The regulator itself should not be used as
a flow control by adjusting the pressure to obtain different flow rates. This
defeats the purpose of the pressure regulator and in some cases where higher
flows are obtained in this manner, the pressure setting may be in excess of
the design pressure of the system.
Acetylene is the most thermodynamically unstable common gas, has a very wide
explosive range (from 2% to 80% in air), and under pressure and certain
conditions can decompose with explosive force. To allow safe handling of
acetylene in cylinders, suppliers use a porous packing material saturated with
a solvent in which the acetylene dissolves. The combination of porous filling
and solvent markedly enhances the stability of acetylene. Acetylene is
authorized for shipment only as a dissolved gas in cylinders marked DOT-8 or
-8AL, and cylinders so designated may be used only for acetylene.
ARGON, CARBON DIOXIDE, HELIUM AND NITROGEN
These gases are inert, colorless, odorless, and tasteless but can cause
asphyxiation and death in confined, poorly ventilated areas. Do not lean into
or place your head into a freezer. In addition these gases can cause severe
frostbite to the eyes or skin. Some carbon dioxide cylinders contain an eductor
tube and are intended for liquid withdrawal. These cylinders are specially
marked; be sure you are using equipment appropriate to the application. Air
will condense on exposed helium liquid or cold-gas surfaces, such as vaporizers
and piping. Nitrogen, having a lower boiling point than oxygen, will evaporate
first, leaving an oxygen-enriched condensation on the surface. To prevent
possible ignition of grease, oil, or other combustible materials, care must be
taken that equipment is free of these materials.
Hydrogen is a flammable gas. A mixture of hydrogen and oxygen or air in a
confined area will explode if ignited by a spark, flame or other similar source.
Escaping hydrogen cannot be detected by sight, smell or taste and, because of
its lightness, it has a tendency to accumulate in the upper portions of confined
Oxygen supports and can greatly accelerate combustion; keep combustibles
away from oxygen and eliminate ignition sources. Oxygen is colorless,
odorless, and tasteless and as a liquid or cold gas may cause severe frostbite to
the eyes or skin. Many materials, especially some non-metallic gaskets and
seals, constitute a combustion hazard when in oxygen service, although
they may be acceptable for use with other gases. Before attaching regulator to
cylinder, be certain that the regulator and inlet filter are free of oil, grease, or
other contaminants, and crack the cylinder valve momentarily to blow out any
dust or dirt that might have accumulated in the cylinder valve outlet.
When using an oxygen torch remember to turn on the natural gas (in
sufficient quantity) first and off last and wear UV absorbing eye
Gas Cylinder Disposal
When compressed gas tanks are empty, label the cylinders with the letters
When compressed gas tanks are empty or no longer needed, contact those
responsible for chemical waste disposal to return the cylinders to the
Never dispose of gas cylinders, even small propane canisters, lecture
bottles, or chemical aerosol cans, in the general trash.
American Chemical Society, Committee on Chemical Safety. 1989. Chemical
Safety Manual for Small Businesses. Washington DC: American Chemical
American Chemical Society, Committee on Chemical Safety. 1990. Safety in
Academic Chemistry Laboratories. Washington, DC: American Chemical
American Industrial Hygiene Association. 1989. Odor Thresholds for
Chemicals with Established Occupational Health Standards. Akron, OH:
Braker, W., and A.L. Mossman. 1980. Matheson Gas Data Book, 6th ed.
Lyndhurst, NJ: Matheson.
Bretherick, L. 1990. Handbook of Reactive Chemical Hazards, 4th ed.
London, England: Butterworths. ISBN
Bretherick, L. (ed.). 1986. Hazards in the Chemical Laboratory, 4th ed. Port
Washington, NY: Royal Soc. Chem.
Compressed Gas Association. 1990. Handbook of Compressed Gases, 3rd ed.
New York, NY: Van Nostrand
Reinhold. ISBN 0-442-25419-9.
Fawcett, H.H., and W.S. Wood. 1982. Safety and Accident Prevention in
Chemical Operations, 2nd ed.
New York, NY: Wiley and Sons. ISBN 0-471-02435-X.
Foa, V. 1987. Occupational and Environmental Chemical Hazards: Cellular
and Biochemical Indices for
Monitoring Toxicity. New York, NY: Wiley and Sons.
Ho, M.H., and H.D. Dillon (eds.). 1987. Biological Monitoring of Exposure
to Chemicals: Organic Compounds. New York, NY: Wiley and Sons.
International Agency for Research on Cancer. 1979. Handling Chemical
Carcinogens in the Laboratory: Problems of Safety. IARC Scientific
Publications No. 33. Geneva,
Switzerland: WHO Publications
International Agency for Research on Cancer. 1972-. Monographs on The
Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva,
Switzerland: WHO Publications
Center. ISBN 92-832-1417-X.
Klaasen, C.D., Amdur, M.O., and J. Doull. 1986. Casarett and Doull's
Toxicology, 3rd ed. New York, NY:
Macmillan Publishing Co. ISBN 0-02-364650-0.
Manufacturing Chemists Association. 1973. Guide for Safety in the Chemical
Laboratory, 2nd ed. New York, NY: Van Nostrand Reinhold. ISBN 0-442-
National Fire Protection Association. Quincy, MA: NFPA.
1991. NFPA 49: Hazardous Chemicals Data
1991. NFPA 321: Basic Classification of Flammable and Combustible
1991. NFPA 325M: Fire Hazard Properties of Flammable Liquids, Gases
and Volatile Solids
1991. NFPA 491M: Hazardous Chemical Reactions
1986. NFPA 704: Fire Protection Guide on Hazardous Materials
National Institute of Occupational Safety and Health (NIOSH). 1985-86.
Registry of Toxic Effects, 14th ed. Washington, DC: U.S. Govt. Printing
National Research Council. 1981. Prudent Practices for Handling Hazardous
Chemicals in Laboratories.
Washington, DC: National Academy Press. ISBN 0-309-03390-X.
National Toxicology Program. Most recent. Annual Report on Carcinogens.
Research Triangle Park, NC: NIEHS.
Office of Science and Technology Policy. 1985. Chemical Carcinogens: A
Review of the Science and Its Associated Principles. Federal Register
Pipitone, D.A. (ed.). 1991. Safe Storage of Laboratory Chemicals, 2nd ed.
New York, NY: Wiley and Sons.
Searle, C.E. 1984. Chemical Carcinogens, 2nd ed. Washington, DC: American
Chemical Soc. ISBN 0-8412-0869-7.
Shepard, T.H. 1983. Catalog of Teratogenic Agents, 4th ed. Baltimore, MD:
Johns Hopkins University Press. ISBN 0-8018-3027-3.
Sittig, M. 1985. Handbook of Toxic and Hazardous Chemicals and
Carcinogens, 2nd ed. Park Ridge, NJ: Noyes Publications. ISBN 0-8155-
United States Coast Guard. 1974. A Condensed Guide to Chemical Hazards.
Washington, DC: U.S. Dept. of Transportation. CG-4461-1.
Walters, D.B. (ed.). 1980. Safe Handling of Chemical Carcinogens, Mutagens,
Teratogens and Highly Toxic Substances. Ann Arbor, MI: Ann Arbor
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SUBSTANCES SPECIFICALLY REGULATED BY OSHA UNDER THE
This list includes compounds regulated by OSHA under 1910.Subpart Z,1
compounds considered to be "Known Carcinogens" by the NTP,2 and the IARC
designated carcinogens and suspect carcinogens.3 Those compounds included
in the IARC lists are shown with their IARC Group; those from Subpart Z and
the NTP lists are shown with the appropriate footnote.
Aluminum production 1
Analgesic mixtures containing phenacetin2
Androgenic steroids 2A
Arsenic and arsenic compounds1,2
Auramine, manufacture of 1
Benzidine-based dyes 2A
Benzyl violet 4B 2B
Beryllium compounds 2A
Betel quid with tobacco 1
Bischloroethyl nitrosourea (BCNU) 2A
Bis(chloromethyl) ether1,2 1
Bitumens, extracts of steam-refined & air-refined
Boot and shoe manufacture and repair
Bracken fern 2B
1,4-Butanediol dimethanesulfonate ("Myleran")2 1
Butylated hydroxyanisole (BHA) 2B
Cadmium compounds 2A
Carbon-black extracts 2B
Carbon tetrachloride 2B
Carpentry and joinery 2B
Carrageenan, degraded 2B
Chlordecone ("Kepone") 2B
-Chlorinated toluenes 2B
Chlorophenoxy herbicides 2B
Chromium VI compounds2 1
Citrus Red No. 2 2B
Coal gasification operations 1
Coal tar pitches1 1
Coal tars1 1
Coke production1 1
Cotton dusts1 --
Diethyl sulphate 2A
Diglycidyl resorcinol ether 2B
Dimethyl sulphate 2A
Ethyl acrylate 2B
Ethylene dibromide 2A
Ethylene oxide1 2A
Ethyl methanesulphonate 2B
Furniture and cabinet making 1
Hematite mining, underground, with exposure to radon
IQ (2-Amino-3-methylimidazo[4,5-f]quinoline) 2B
Iron-dextran complex 2B
Iron and steel founding
Isopropyl alcohol manufacture, strong-acid process
Lead compounds (inorganic)1 2B
Magenta, manufacture of
8-Methoxypsoralen & UV light2
Methylazoxymethanol and its acetate
Methyl chloromethyl ether1 1
4,4'-Methylene bis(2-chloroaniline) (MOCA)
Methyl methanesulphonate 2B
N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) 2A
Mineral oils 1
Mitomycin C 2B
MOPP and combined chemotherapy preparations
Mustard gas2 1
Nickel compounds 1
Nitrofen (technical-grade) 2B
Nitrogen mustard 2A
Nitrogen mustard N-oxide 2B
Oestrogen replacement therapy
Oestrogens, non-steroidal 1
Oestrogens, steroidal 1
Oil Orange SS 2B
Oral contraceptives, combined
Oral contraceptives, sequential
Panfuran S (containing dihydroxymethylfuratrizine) 2B
Phenacetin & analgesics 2A
Phenoxybenzamine hydrochloride 2B
Polybrominated biphenyls 2B
Polychlorinated biphenyls 2A
Ponceau MX 2B
Ponceau 3R 2B
Potassium bromate 2B
Procarbazine hydrochloride 2A
1,3-Propane sultone 2B
Propylene oxide 2A
The rubber industry 1
Shale oils 1
Silica, crystalline 2A
Styrene oxide 2A
Talc containing asbestiform fibers 1
Thorium dioxide2 --
Tobacco products, smokeless
Tobacco smoke 1
Toluene diisocyanates 2B
Toxaphene (polychlorinated camphenes)
Tris(1-aziridinyl)phosphine sulphide (Thiotepa) 2A
Tris(2,3-dibromopropyl) phosphate 2A
Trypan blue 2B
Uracil mustard 2B
Vinyl bromide 2A
Vinyl chloride1,2 1
1 OSHA Standard, Subpart Z - Toxic and Hazardous Substances (29 CFR
1910 Subpart Z) as of 19 January 1989.
2 National Toxicology Program (NTP), Substances "Known to be
Carcinogenic". NTP. 1989. Fifth Annual Report on Carcinogens. Report
3 International Agency for Research on Cancer (IARC).1987. IARC
Monographs on the Evaluation of Carcinogenic Risks to Humans: Overall
Evaluations of Carcinogenicity. Supplement 7. Lyons, France.
4 IARC Carcinogen Groups: 1 = known carcinogenicity; 2A = probable; 2B =
possible; 3 = not classifiable due to insufficient or conflicting data.
TABLE 3. Relative Hazard Levelsa
Relative Hazard 1
Relative Hazard 2
Relative Hazard 3
Relative Hazard 5
0.5 ml causes no
0.005 ml causes
no severe injury
0.0005 ml or > 40%
solution causes severe
> 5% solution
> 1% solution
8 hrs fatal < 50%
2-4 hrs fatal < 66%
1/4-1 hrs fatal < 66%
2-5 min fatal <
2 min fatal < 83%
LD50 > 20 ml/kg body
LD50 2-20 ml/kg
LD50 0.2-1.99 ml/kg
ml/kg body weight
LD50 < 0.02
Undiluted solution causes
erythema & slight edema
LD50 > 10 g/kg body
LD50 1-10 g/kg
LD50 100-999 mg/kg
LD50 10-99 mg/kg
LD50 < 10 mg/kg
aHandbook of Laboratory Safety, 2nd Ed, 1984, ed. Norman V. Steere. Boca Raton, FA: CRCPress, Inc., 680-682.
Total pages 854.
bStudies performed on male albino rabbits
cStudies performed on male albino rats