Asphyxiants are substances that interfere with the transport of an adequate supply of oxygen to vital organs of the body. The brain is the organ most easily affected by oxygen starvation, and exposure to asphyxiants leads to rapid collapse and death. Simple asphyxiants are substances that displace oxygen from the air being breathed to such an extent that adverse effects result. Acetylene, carbon dioxide, argon, helium, ethane, nitrogen, and methane are common asphyxiants. Certain other chemicals have the ability to combine with hemoglobin, thus reducing the capacity of the blood to transport oxygen. Carbon monoxide, hydrogen cyanide, and certain organic and inorganic cyanides are examples of such substances.
Neurotoxic chemicals induce an adverse effect on the structure or function of the central or peripheral nervous system, which can be permanent or reversible. The detection of neurotoxic effects may require specialized laboratory techniques, but often they are inferred from behavior such as slurred speech and staggered gait. Many neurotoxins are chronically toxic substances with adverse effects that are not immediately apparent. Some chemical neurotoxins that may be found in the laboratory are mercury (inorganic and organic), organophosphate pesticides, carbon disulfide, xylene, tricholoroethylene, and n-hexane. (For information about reducing the presence of mercury in laboratories, see Chapter 5, section 5.B.8.)
4.C.3.4 Reproductive and Developmental Toxins
Reproductive toxins are defined by the OSHA Laboratory Standard as substances that cause chromosomal damage (mutagens) and substances with lethal or teratogenic (malformation) effects on fetuses. These substances have adverse effects on various aspects of reproduction, including fertility, gestation, lactation, and general reproductive performance, and can affect both men and women. Many reproductive toxins are chronic toxins that cause damage after repeated or long-duration exposures with effects that become evident only after long latency periods. Developmental toxins act during pregnancy and cause adverse effects on the fetus; these effects include embryo lethality (death of the fertilized egg, embryo, or fetus), teratogenic effects, and postnatal functional defects. Male reproductive toxins in some cases lead to sterility.
When a pregnant woman is exposed to a chemical, generally the fetus is exposed as well because the placenta is an extremely poor barrier to chemicals. Embryotoxins have the greatest impact during the first trimester of pregnancy. Because a woman often does not know that she is pregnant during this period of high susceptibility, women of childbearing potential are advised to be especially cautious when working with chemicals, especially those rapidly absorbed through the skin (e.g., formamide). Pregnant women and women intending to become pregnant should seek advice from knowledgeable sources before working with substances that are suspected to be reproductive toxins. As minimal precautions, the general procedures outlined in Chapter 6, section 6.D, should be followed, though in some cases it will be appropriate to handle the compounds as PHSs.
For example, among the numerous reproductive hazards to female laboratory scientists, gestational exposure to organic solvents should be of concern (HHS/CDC/NIOSH, 1999; Khattak et al., 1999). Some common solvents in high doses have been shown to be teratogenic in laboratory animals, resulting in developmental defects. Although retrospective studies of the teratogenic risk in women of childbearing age of occupational exposure to common solvents have reached mixed conclusions, at least one such study of exposure during pregnancy to multiple solvents detected increased fetal malformations. Thus, inhalation exposure to organic solvents should be minimized during pregnancy. Also, exposure to lead or to anticancer drugs, such as methotrexate, or to ionizing radiation can cause infertility, miscarriage, birth defects, and low birth weight. Certain ethylene glycol ethers such as 2-ethoxyethanol and 2-methoxyethanol can cause miscarriages. Carbon disulfide can cause menstrual cycle changes. One cannot assume that any given substance is safe if no data on gestational exposure are available.
Specific hazards of chemical exposure are associated with the male reproductive system, including suppression of sperm production and survival, alteration in sperm shape and motility, and changes in sexual drive and performance. Various reproductive hazards have been noted in males following exposure to halogenated hydrocarbons, nitro aromatics, arylamines, ethylene glycol derivatives, mercury, bromine, carbon disulfide, and other chemical reagents (HHS/CDC/NIOSH, 1996).
Information on reproductive toxins can be obtained from LCSSs, MSDSs, and by consulting safety professionals in the environmental safety department, industrial hygiene office, or medical department. Literature sources of information on reproductive and developmental toxins include the Catalog of Teratogenic Agents (Shepard and Lemire, 2007), Reproductively Active Chemicals: A Reference Guide (Lewis, 1991), and “What Every Chemist Should Know About Teratogens” in the Journal of Chemical Education (Beyler and Meyers, 1982). The State of California maintains a list of chemicals it