The Precautionary Principle and Chemical Exposure Standards for the Workplace

  • Date: Jan 01 1996
  • Policy Number: 9606

Key Words:

The American Public Health Association,

Understanding that the "precautionary principle" that was adopted internationally as a starting point for environmental policy in 1992 at the global United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro, Brazil, states that "where there are threats of serious or irreversible environmental damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent degradation,"1 that chemicals that are carcinogenic or genotoxic and those that have toxic effects on reproduction have potentially serious or irreversible effects and thus must be considered in the application of the precautionary principle to the workplace environment; and

Recognizing that 75% of current occupational exposure limits (OELs) were established 15 to 40 years ago; that historically, these values have been set near the maximum acutely tolerable level, with little regard for the risks of long-term serious or irreversible damage for men, women, and children such as cancer or reproductive health effects, effects on growth and development, and toxic illnesses;2 and that for many substances to which millions of workers are exposed, working at current exposure limits is expected to cause death rates from occupational cancer greater than 1 per 100;3 and

Knowing that in the United States and other countries, since 1946, workplace chemical exposure limits have been substantially based on the threshold limit values (TLVs) established by a private organization (the American Conference of Governmental Industrial Hygienists or ACGIH); that TLVs historically have tended to represent long-existing levels of exposure to toxic substances in industry, rather than guidelines to control exposures to levels below those shown to cause harm;4 that the minutes of the TLV committee show that, starting in 1970, employees of various multinational chemical companies have played central roles as committee members in developing TLVs for over 120 chemicals;5 and that this company role was not balanced by those representating of workers' interests, such as union representatives; and

Recognizing that an alternative approach to setting standards for occupational exposure to chemicals has been proposed, which reverses the burden of proof in that every chemical is considered potentially dangerous until the extent of toxicity is sufficiently known;6 that this alternative approach reflects an attitude of risk avoidance, instead of the attitudes of risk regulation or risk acceptance implicit in the TLV concept; that for substances with adequate available experimental toxicological data, a precautionary exposure limit is derived from the lowest observed effect level, by the use of a defined set of safety factors (for example, by the use of existing environmental airborne reference concentrations as a starting point);7 that these health-based exposure levels' (HBELs)may be derived from existing environmental risk values published by governmental agencies, where available and that (for example, about 100 chemical compounds have California Office of Environmental Health Hazard Assessment [OEHHA] cancer potency numbers; that there are over 40 USEPA Airborne Reference Concentrations (RfCs); and that OEHHA is currently developing chronic reference exposure levels for 120 substances); If no such toxicological data are currently available, an interim precautionary occupational exposure limit of 0.1 mg/m3 is established;6 therefore

  1. Finds that current US workplace chemical-exposure limits often fail to adequately protect the health of workers;
  2. Encourages the development of a workplace chemical-exposure, including pesticide-exposure, prevention policy based on the UNCED precautionary principle; and
  3. Encourages regulatory agencies responsible for setting workplace health standards to evaluate the effects on more sensitive populations not previously considered in standard development.


  1. United Nations Conference on Environment and Development (UNCED). Principle 15. Declaration of Rio. Rio de Janeiro, Brazil: United Nations, 1992.
  2. Stijkel A, van Dijk F. Developments in reproductive risk management. Occup Environ Med. 1995;52:294-303.
  3. Alvanja MCR, et. al. Risk assessment for carcinogens: a comparison of approaches of the ACGIH and the EPA. Appl Occup Environ Hyg. 1990;5:510-519.
  4. Tarlau ES. Industrial hygiene with no limits. Am Ind Hyg Assoc J. 1990;51:A-9.
  5. Ziem GE, Castleman BI. Threshold limit values: historical perspectives and current practice. J Occup Med. 1989;31:910-918.
  6. Stijkel A, Reijnders L. Implementation of the precautionary principle in standards for the workplace. Occup Env Med. 1995;52:304-312.
  7. World Health Organization. Environmental Health Criteria 170: Assessing Human Health Risks of Chemicals: Derivation of Guidance Values for Health-Based Exposure Limits. Geneva, Switz: World Health Organization; 1994.
  8. Cunningham K. A Comparison of PEL's and TLV's to Health-Based Exposure Limits Derived from the IRIS Data Base. Report to OSHA by the New Jersey Department of Health. October 5, 1988. (Annual updates of these HBELs are published by the Santa Clara Center for Occupational Safety and Health, 720 N 1st. St, San Jose, CA 95112, and on the internet: [].)

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