Office of Research

VI. Hazardous Substances

Many of the chemicals encountered in the laboratory are known to be toxic or corrosive or both.  New and untested substances that may be hazardous are also frequently encountered. Thus, it is essential that all laboratory workers understand the types of toxicity, know the routes of exposure, and recognize the major classes of toxic and corrosive chemicals.

When considering possible toxicity hazards while planning an experiment, it is important to recognize that the combination of the toxic effects of two substances may be significantly greater than the toxic effect of either substance alone. Because most chemical reactions are likely to contain mixtures of substances whose combined toxicities have never been evaluated, it is prudent to assume that mixtures of different substances (i.e., chemical reaction mixtures) will be more toxic than the most toxic ingredient contained in the mixture. Furthermore, chemical reactions involving two or more substances may form reaction products that are significantly more toxic than the starting reactants. This possibility of generating toxic reaction products may not be anticipated by the laboratory worker in cases where the reactants are mixed unintentionally. For example, successive treatments of a surface or an object with aqueous ammonia and then with sodium hypochlorite or other positive-halogen reagents may generate hydrazine, a substance that poses both acute and chronic toxicity hazards. Similarly, inadvertent mixing of formaldehyde (a common tissue fixative) and hydrogen chloride could result in the generation Of bis(chloromethyl) ether, a potent human carcinogen.

derivatives) and some of the common solvents (benzene) are cumulative poisons that can produce body damage through exposure to small concentrations over a long period of time.

or that becomes evident only after a long latency period. Hydrogen cyanide, hydrogen sulfide, and nitrogen dioxide are examples of acute poisons. Chronic poisons include all carcinogens and many metals and their compounds (such as mercury and lead and their derivatives). Chronic toxins are particularly insidious because of their long latency periods. The cumulative effects of low exposures may not be apparent for many years. Some chemicals, (e.g., vinyl chloride), can be either acutely or chronically toxic, depending on the degree of exposure. All new and untested chemicals should be regarded as toxic until proven otherwise.


Embryotoxins are substances that act during pregnancy to cause adverse effects on the fetus. These effects include embryo lethality (death of the fertilized egg, the embryo, or the fetus), malformations (teratogenic effects), retarded growth, and postnatal functional deficits.

Women of child bearing age, particularly women who are pregnant, must not be subjected to increased risk of exposure to possible or known teratogenic agents while employed or in training at Clemson University. In those circumstances where a risk exists, the woman is responsible for reporting pregnancy (in writing) to her supervisor so that appropriate action can be taken.

A few substances have been demonstrated to be embryotoxic in humans. These include organomercurials, lead compounds, and the formerly used sedative, thalidomide. Maternal alcoholism is probably the leading known cause of embryotoxic effects in humans, but the exposure to ethanol encountered in laboratories is unlikely to be embryotoxic. Many substances, some common (e.g., sodium chloride), have been shown to be embryotoxic to animals at some exposure level, but usually this is at a considerably higher level than is met in the course of normal laboratory work. However, some substances do require special controls because of embryotoxic properties. One example is formamide; women of child-bearing potential should handle this substance only in a hood and should take precautions to avoid skin contact with the liquid because of the ease with which it passes through the skin.

Because the period of greatest susceptibility to embryotoxins is the first 8-12 weeks of pregnancy, which includes a period when a woman may not know she is pregnant, women of child-bearing potential should take care to avoid skin contact with and inhalation of all chemicals. The following procedures are recommended to be followed routinely by women of child-bearing potential in working with chemicals requiring special control because of embryotoxic properties:

1.    Each use should be reviewed for particular hazards by the research supervisor, who will decide whether special procedures are warranted or whether warning signs should be posted. Consultation with appropriate Environmental Health and Safety personnel may be desirable. In cases of continued use of a known embryotoxin, the operation should be reviewed annually or whenever a change in procedures is made.

2.    Embryotoxins requiring special control should be stored in an adequately ventilated area. The container should be labeled in a clear manner such as the following: EMBRYOTOXIN: READ SPECIFIC PROCEDURES FOR USE.  If the storage container is breakable, it should be kept in an impermeable, unbreakable secondary container having sufficient capacity to retain the material should the primary container accidentally break.

3.    Women of child-bearing potential should take all possible precautions to guard against spills and splashes. Operations should be carried out using impermeable containers and in adequately ventilated areas. Appropriate safety apparel, especially gloves, should be worn. All hoods, glove boxes, or other essential engineering controls will be known to be operating at required efficiency before work is started.

4.    Supervisors should be notified of the pregnancy of an employee who is working with or could be required to work with any embryotoxic chemical. This notification should be made by the employee in writing as soon as possible after positive test results for pregnancy have been received.

5.    Supervisors should be notified of all incidents of exposure or spills of embryotoxins requiring special control. A Redfern Health Center physician will be consulted about any exposures of women of child-bearing potential where exposure of any type has occurred.

6.    No live virus vaccine should be administered to a pregnant employee. If a pregnant employee is required to receive a live virus vaccine to perform her duties, she should be excluded from these duties during her pregnancy 

7.    Since no information on the potential teratogenic effects of most microorganisms is available, the risk of laboratory infection with any microorganisms should be kept to a minimum during pregnancy. Those viruses to which the woman is known to be immune (that is, by serologic testing) can be safely worked with. Viruses or other microorganisms to which the woman is not known to be immune should be handled only under generally acceptable safe conditions (that is by inoculation of invitro cultures, etc.). Depending on the agent involved, work with such microorganisms which involves animal inoculation or infectious aerosols should be kept to a minimum or entirely eliminated.

8.   Laboratory exposure to radioactive materials should be kept “as low as reasonably achievable” during pregnancy. Contact the Institutional Radiation Safety Officer (656-7165) for training on Nuclear Regulatory Commission’s Reg. Guide 8.13 “Instruction Concerning Prenatal Radiation Exposure”.



Chemicals can affect both adult male and female reproductive systems. Reproductive hazards affect people in a number of ways, including mental disorders, loss of sexual drive, impotence, infertility, sterility, mutagenic effects on cells, teratogenic effects on the fetus, and transplacental carcinogenesis. Consult the Safety Data Sheet and other information available on possible reproductive hazards. Handle these materials in a properly functioning chemical hood with appropriate PPE and indicated by the SDS, product label, etc.



A wide variety of substances can produce skin and lung hypersensitivity. Examples include such common substances as diazomethane, chromium, nickel, bichromates, formaldehyde, isocyanates, and certain phenols. Because of this variety and because of the varying response of individuals, suitable gloves should be used whenever hand contact with products of unknown activity is probable.



The major classes of corrosive chemicals are strong acids and bases, dehydrating agents, and oxidizing agents. Some chemicals, e.g., sulfuric acid, belong to more than one class. Inhalation of vapors or mists of these substances can cause severe bronchial irritation. These chemicals erode the skin and the respiratory epithelium and are particularly damaging to the eyes. Special care should be taken to select the appropriate glove material. Safety goggles and in many case a face shield should be worn when handling corrosive chemicals. 



All concentrated strong acids can damage the skin and eyes. Exposed areas should be flushed promptly with water. Nitric, chromic, and hydrofluoric acids are especially damaging because of the types of burns they inflict. Hydrofluoric acid, which produces slow-healing, painful burns should be used only after thorough familiarization with recommended handling procedures. Ensure that the proper glove material is selected. Safety goggles with a face shield and any other PPE as described by the SDS, label, etc. These materials should be handled only in a chemical hood. (see Appendix F for handling Hydrofluoric acid).



The common strong bases are potassium hydroxide, sodium hydroxide, and ammonia. Ammonia is a severe bronchial irritant and should always be used in a well-ventilated area. The metal hydroxides are extremely damaging to the eyes. Should exposure occur, the affected areas should be washed at once with copious quantities of water and an opthalmologist should evaluate the need for further treatment. Use appropriate PPE as described by the SDS, product label, etc.



The strong dehydrating agents include concentrated sulfuric acid, sodium hydroxide, phosphorus pentoxide, and calcium oxide. Because much heat is evolved on mixing these substances with water, mixing should always be done by adding the agent to water to avoid violent reaction and spattering. Because of their affinity for water, these substances cause severe burns on contact with the skin. Affected areas should be washed promptly with large volumes of water.



In addition to their corrosive properties, powerful oxidizing agents such as perchloric, nitric, and chromic acids, present fire and explosion hazards on contact with organic compounds and other oxidizable substances. The hazards associated with the use of perchloric acid are especially severe; it should be handled only after thorough familiarization with recommended procedures. Strong oxidizing agents should be stored and used in glass or other inert containers (preferably unbreakable), and corks and rubber stoppers should not be used. Reaction vessels containing significant quantities of these reagents should be heated by using fiberglass mantles or sand baths rather than oil baths. Use in a chemical hood. Use proper gloves, goggles, and face shield, lab coat (and possibly apron).



Recommendations for handling procedures for chemicals begin with the admonition that, even for substances of no known significant hazard, it is prudent to observe good laboratory practice, minimizing exposure by working in an exhaust hood and wearing eye and hand protection and laboratory coat or apron. For the case of substances that present special hazards, we call attention to the following procedures for minimizing risk for toxic substances, the procedures fall into two groups:

OSHA has published detailed procedures (29 CFR 1910; also 45 Fed. Reg. 5002-5296) for working with substances that have classified as carcinogens. Anyone contemplating work with materials on this list should consult the regulations to be advised of the necessary approvals, training, working conditions, monitoring, record-keeping, and medical surveillance. In addition, if a worker anticipates that an OSHA-regulated carcinogen might be a product or an impurity, the regulations should be consulted (e.g., N-phenyl-1,4-benzenediamine (semidine) can contain substantial benzidine impurity).


1.   Procedure A should be followed in laboratory operations using substances for which infrequent, small quantities do not constitute a significant carcinogenic hazard but which can be dangerous to those exposed to high concentrations or repeated small doses. A substance that is not known to cause cancer in humans, but which has shown statistically significant, but low, carcinogenic potency in animals, generally should be handled according to Procedure A. 

2.    Procedure B should be followed in laboratory operations using those substances believed to be moderately to highly toxic, even when used in small amounts. A substance that has caused cancer in humans or has shown high carcinogenic potency in test animals (but for which a regulatory standard has not been issued by OSHA) will generally require the use of Procedure B. However, before choosing Procedure A, other factors, such as the physical form and volatility of the substance, the kind and duration of exposure, and the amount to be used should also be considered. A substance is deemed to have moderate to high carcinogenic potency in test animals if it causes statistically significant tumor incidence (a) after inhalation exposure of 6-7 hours per day, 5 days per week, for a significant portion of a lifetime to dosages of less than 10 mg/ml, or (b) after repeated skin application of less than 300 (mg/kg of body weight) per week, or (c) after oral dosages of less than 50 (mg/kg of body weight) per day.