Agency for Toxic Substances and Disease Registry
Case Studies in Environmental Medicine (CSEM)
Benzene Toxicity
Standards and Regulations
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The current PEL for benzene is 1 ppm.
In 1987, OSHA instituted a PEL for benzene of 1 ppm, measured as an 8-hour TWA, and a short-term exposure limit of 5 ppm (Table 1). These legal limits were based on studies demonstrating compelling evidence of health risk to workers exposed to benzene. The risk from exposure to 1 ppm for a working lifetime has been estimated as 5 excess leukemia deaths per 1,000 employees exposed. (This estimate assumes no threshold for benzene's carcinogenic effects.) OSHA has also established an action level of 0.5 ppm to encourage even lower exposures in the workplace.
The National Institute for Occupational Safety and Health (NIOSH) recommends an exposure limit of 0.1 ppm as a 10-hour TWA. NIOSH also recommends that benzene be handled in the workplace as a human carcinogen. In 1997, the American Conference of Governmental Industrial Hygienists lowered its TWA-threshold limit value to 0.5 ppm to reflect the change in cancer classification to A1 (i.e., confirmed human carcinogen).
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EPA restricts benzene emissions from specific point sources.
Under section 112 of the Clean Air Act, benzene is a hazardous air pollutant. EPA has not promulgated a specific ambient air standard for benzene but has imposed restrictions designed to lower industrial emissions of benzene by 90% over the next 20 years. In addition, regulations have been proposed that would control benzene emissions from industrial solvent use, waste operations, transfer operations, and gasoline marketing. At gas stations, proposed rules would require new equipment restricting benzene emissions while dealers' storage tanks are being filled. Under the Clean Air Act Amendments of 1990, the use of clean ("oxygenated") fuels was mandated as a means of reducing motor vehicle emission-related air pollutants. EPA predicts that this clean fuels program will decrease ambient benzene levels by 33%.
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The maximum contaminant level of benzene in drinking water is 5 ppb.
The National Primary Drinking Water Regulations promulgated by EPA in 1987 set a maximum contaminant level for benzene of 0.005 ppm (5 ppb). This regulation is based on preventing benzene leukemogenesis. The maximum contaminant level goal, a nonenforceable health goal that would allow an adequate margin of safety for the prevention of adverse effects, is zero benzene concentration in drinking water.
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The Food and Drug Administration (FDA) prohibits the use of benzene in foods.
Effective April 1988, FDA mandated that benzene can only be an indirect food additive in adhesives used for food packaging.
| Agency |
Focus |
Level* |
Comments |
| American Conference of Governmental Industrial Hygienists |
Air (workplace) |
0.5 ppm |
Advisory; TWA†; confirmed human carcinogen |
| 2.5 ppm |
STEL (15-minute ceiling limit) |
| National Institute for Occupational Safety and Health |
Air (workplace) |
0.1 ppm |
Advisory; 10-hour TWA |
| 1.0 ppm |
15-minute ceiling limit |
| Occupational Safety and Health Administration |
Air (workplace) |
1 ppm |
Regulation; TWA |
| 5 ppm |
15-minute STEL ‡ |
| 0.5 ppm |
Action level TWA |
| U.S. Environmental Protection Agency |
Water (drinking) |
5 ppb |
Regulation; maximum contaminant level |
| Food and Drug Administration |
Food |
NA |
Regulation; may be used only as a component of packaging adhesives |
*ppb: parts per million; ppb: parts per billion.
†TWA (time-weighted average): concentration for a normal 8-hour workday or 40-hour workweek to which nearly all workers may be repeatedly exposed.
‡ STEL (short-term exposure limit): a 15-minute TWA exposure that should not be exceeded at any time during the workday. |
- The lawyer for the family of the patient in the case study approaches you and asks you to establish causality between the patient's condition and the benzene in the drinking water.
How would you do so?
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