National estimates of occupational exposure to animal bladder tumorigens

A prevention program for occupational bladder cancer should be based on an estimate of the number of workers previously and currently exposed to bladder carcinogens. The National Occupational Exposure Survey (NOES), which identified potential occupational exposures in approximately 5000 private sector firms in 1981 to 1983, is the best available source for recent hazard estimates; the National Occupational Hazard Survey (NOHS), conducted in 1972 and 1974, for past exposure estimates. The National Institute for Occupational Safety and Health Registry of Toxic Effects of Chemical Substances (RTECS) identified nearly 200 substances associated with animal bladder tumors. From NOES and NOHS, the numbers of workers with full time (greater than or equal to 4 hours/day) or any potential occupational exposure were estimated for the United States. About 60,000 workers were potentially exposed in the early 1970s and about 700,000 in the early 1980s on a full-time basis to the compounds on the RTECS list also appearing in NOES, and about 1.8 million workers in the 1970s and almost 3.5 million in the 1980s had some occupational exposure. Because matches were not found for many compounds and because NOES covers only part of the US work force, these are probably underestimates. The estimates for the number of exposed workers do not imply that these workers all have increased risk of developing bladder cancer, because some animal tumorigens may not be human carcinogens and our estimates are based on potential rather than measured exposures. The risk would depend on the potency, duration, and intensity of the actual exposures. Nevertheless these estimates are useful in estimating the approximate magnitude of the potential occupational exposure to animal bladder tumorigens.