In many large institutions, the environmental health and safety department has developed a generic Chemical Hygiene Plan, but the plan must be modified to include detailed protections that are specific to each laboratory and its workers. This approach allows considerable flexibility in achieving the performance-based goals of the Laboratory Standard. Model Chemical Hygiene Plans are available from the OSHA consultation service, from the American Chemical Society, and from some professional associations or commercial sources.
Several points about the OSHA Laboratory Standard deserve special mention. The intention of the standard is to supersede existing OSHA health standards, but other OSHA rules on topics not specifically addressed in the standard remain applicable. The so-called "general duty" clause of the Occupational Safety and Health Act, which requires an employer to "furnish to each of his employees ... a place of employment ... free from recognized hazards that are likely to cause death or serious physical harm ... " and requires an employee to "comply with occupational safety and health standards and all rules ... issued pursuant to this chapter which are applicable to his own actions and conduct" continues to be applicable and, indeed, is one of the most commonly cited sections in cases of alleged OSHA violations. Other OSHA standards relating to possible eye or skin contact must continue to be observed. There are dozens of chemicals in this category. They are listed in 29 CFR 1910 as well as in specific standards following Section 1910.1000, such as the vinyl chloride standard, 29 CFR 1910.1017, which prohibits direct contact with liquid vinyl chloride.
Other OSHA standards setting forth permissible exposure limits (PELs) apply to the extent that they require limiting exposures to below the PEL and, where the PEL or "action level" is routinely exceeded, the Laboratory Standard's provisions require exposure monitoring and medical surveillance. The requirements for exposure monitoring and medical surveillance are found in Appendix A, sections (d) and (g) of the Laboratory Standard.
OSHA's permissible exposure limits were directly adopted, in 1970, from the similar list of threshold limit values (TLVs), a nonregulatory consensus document prepared by the American Conference of Governmental Industrial Hygienists (ACGIH). Quoting the TLV booklet (ACGIH, 1994), "Threshold Limit Values (TLVs) refer to airborne concentrations of substances and represent conditions under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse health affects." TLVs are average concentrations over a normal 8-hour work day and a 40-hour work week. The existence of a "time-weighted average (TWA) exposure" approach to control of airborne contaminants indicates that exposures may be somewhat higher or lower than the average at various times of the day, which is typical of work with chemicals.
ACGIH also recommends, for some compounds, a short-term exposure limit (STEL), which establishes a safe exposure limit of no more than four 15-minute periods a day. STELs are published only for compounds where toxic effects have been reported from high short-term exposures in either humans or animals. STELs typically are no more than 25 to 200% above the associated TLV. Some compounds have a "C" preceding the numerical TLV designation. This indicates that the TLV is a ceiling level concentration that should not be exceeded during any part of the working exposure. Ceiling limits have generally been applied to compounds that are fast acting. For compounds that include neither a STEL nor a C notation, a limit on the upper level of exposure should still be imposed. According to the TLV booklet, "Excursions in worker exposure levels may exceed 3 times the TLV-TWA for no more than a total of 30 minutes during a work day, and under no circumstances should they exceed 5 times the TLV-TWA, provided that the TLV-TWA is not exceeded."
The "action level" is an OSHA regulatory term occurring in a few substance-specific regulations. It is an airborne concentration (lower than the associated PEL) that, when exceeded, requires certain activities, such as exposure monitoring or medical surveillance. If the researcher is working with one of the listed substances, it is important to understand when air monitoring and/or medical surveillance are required.
There are special provisions in the Laboratory Standard regarding work with "particularly hazardous substances," a term that includes "select carcinogens," "reproductive toxins," and "substances with a high degree of acute toxicity.'' A select carcinogen is defined in the standard as any substance (1) regulated by OSHA as a carcinogen, (2) listed as "known to be a carcinogen" in the Annual Report on Carcinogens published by the National Toxicology Program (NTP), (3) listed under Group 1 ("carcinogenic to humans") by the International Agency for Research on Cancer (IARC) Monographs, or (4) in certain cases, listed in either Group