Asphalt Fumes

Over a half-million workers are exposed to fumes from asphalt, a petroleum product used extensively in road paving, roofing, siding, and concrete work. When hot asphalt is applied in a molten state, it generates toxic fumes. Workers exposed to asphalt fumes are at risk of developing headaches, rashes, cough, and possibly cancer. There is no OSHA standard for asphalt fumes. OSHA is developing an action plan to reduce worker exposures to this hazard but is not initiating rulemaking at this time.

Hazard Description

NIOSH estimated that over 500,000 workers were potentially exposed to asphalt fumes (1). OSHA estimated in 1992 that over 300,000 construction workers were exposed primarily in road-paving and roofing operations (2). Exposures vary considerably between different types of asphalt work (i.e. roofing vs. paving) and the different worker jobs (i.e. kettle operator vs. paver operator.) More research needs to be performed to determine and control important factors which cause increased worker exposures (i.e. application temperatures, type of equipment used, environmental conditions, workplace practices, and asphalt constituents.)

The acute effects of exposure to asphalt fumes include headache, skin rash, fatigue, reduced appetite, throat and eye irritation, and cough. Asphalt paving workers, for example, have reported breathing problems, asthma, bronchitis, and skin irritation (6). A recent study has shown that some of these effects occur at exposures of 0.5 to 1.3 mg/m3 (3).

Human studies have reported lung, stomach, and skin cancers following chronic exposures to asphalt fumes. However, these studies have been inconclusive, and the possible chronic effects to workers following exposures to asphalt fumes are areas of continuing investigations. One recent summary analysis of the available human studies found a nearly twofold increase in risk of lung and stomach cancer among roofers. Increased risks were also noted for other asphalt workers for lung, stomach, and bladder cancer, and for leukemia (4).

Laboratory studies have shown chemical extracts of asphalt fumes to have cancer-causing and mutagenic properties. For example, painting of asphalt extracts on mouse skin produces tumors that increase with dose (7). Other laboratory studies show DNA changes in mouse lung and skin cells (8) and in human fetal cells exposed to asphalt fume extracts (9). Urinalysis of exposed workers shows mutations in laboratory tests (10).

Current Status

OSHA does not have a standard for asphalt fumes although it proposed a 5 mg/m3 permissible exposure limit (PEL) in 1992 (5). OSHA's quantitative risk assessment estimated a significant risk of lung cancer among exposed workers at levels as low as 0.2 mg/m3.

The American Conference of Governmental Industrial Hygienists (ACGIH) currently recommends a Threshold Limit Value (TLV) of 5 mg/m3 as an 8-hour time weighted average. In 1977, the National Institute for Occupational Safety and Health (NIOSH) recommended a 5 mg/m3 15 minute short-term exposure limit. NIOSH is developing a new Criteria Document for asphalt fumes and expects to make new recommendations for exposure limits within six months.

The International Agency for Research on Cancer (IARC) found:

  • "There is sufficient evidence for the carcinogenicity of extracts of steam-refined bitumens, air-refined bitumens and pooled mixtures of steam- and air-refined bitumens in experimental animals."
  • There is limited evidence for the carcinogenicity of undiluted steam-refined bitumens and for cracking-residue bitumens in experimental animals.
  • There is inadequate evidence for the carcinogenicity of undiluted air-refined bitumens in experimental animals.
  • There is inadequate evidence that bitumens alone are carcinogenic to humans."

Rationale

Asphalt fume exposure meets several of the criteria for designation as an OSHA priority. In particular, the known and potential health effects are serious and a large number of workers are potentially exposed, especially considering high industry turnover rates. Although the human studies of workplace cancer have limitations, there is considerable experimental evidence of cancer risk. There is also evidence of acute health effects among workers exposed to asphalt fumes.

References

  1. NIOSH; National Occupational Exposure Survey; 1981-1983.
  2. Federal Register, vol. 57, no. 114, June 12, 1992. Air Contaminants; Proposed Rule. pp. 26001-26602.
  3. Chase, R.M., Liss, G.M., Cole, D.C., and Heath, B. 1994. Toxic health effects including reversible macrothrombocytosis in workers exposed to asphalt fumes. Am. J. Indus. Med. 25:279-289.
  4. Partanen, T. and Boffetta, P. 1994. Cancer risk in asphalt workers and roofers: review and meta-analysis of epidemiologic studies. Am. J. Indus. Med. 26:721-740.
  5. Federal Register vol. 57, June 12, 1992. Air Contaminants; Proposed Rule. p. 26182-26190 deals specifically with asphalt fume.
  6. Norseth T, Waage J, and Dale I. Acute Effects and Exposure to Organic Compounds in Road Maintenance Workers Exposed to Asphalt. Am J Ind Med; 1991; 20:737-44.
  7. "Assessment of the Cocarcinogenic/Promoting Activity of Asphalt Fumes;" U.S. Department of Health and Human Services, National Institute for Occupational Safety and Health; Contract 200-83-2612; December 1989.
  8. Schoket B, Hewer A, Grover PL, Phillips DH; Covalent binding of components of coal-tar, creosote and bitumen to the DNA of the skin and lungs of mice following topical application. Carcinogenesis; vol. 9, no. 7, pp. 1253-1258; 1988.
  9. Schoket B, Hewer A, Grover PL, Phillips DH; Formation of DNA Adducts in Human Skin Maintained in Short-Term Organ Culture and Treated with Coal-Tar, Creosote or Bitumen. Int. J. Cancer; 42:622-626; 1988.
  10. Pasquini R, et al.; Urinary excretion of mutagens, thioethers and D-glucaric acid in workers exposed to bitumen fumes. Int Arch Occup Environ Health; 61:335-340; 1989.
  11. International Agency for research on Cancer 1985. IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans: Polynuclear Aromatic Compounds, Part 4, Bitumens, Coal-tars and Derived Products, Shale-oils and Soots. Vol. 35 Lyon, France:IARC.

 

 

 

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