DIESEL EXHAUST AND LUNG-CANCER IN THE TRUCKING INDUSTRY - EXPOSURE-RESPONSE ANALYSES AND RISK ASSESSMENT

Background Diesel exhaust is considered a probable human carcinogen by the International Agency for Research an Cancer (IARC). The epidemiol ogic evidence rests an studies of lung cancer among truck drivers, bus drivers, shipyard workers, and railroad workers. The general public i s exposed to diesel exhaust in ambient air Two regulatory agencies are now considering regulating levels of diesel exhaust: the California E PA (ambient levels) and the Mine Safety Health Administration (MSHA) ( occupational levels). To date, there have been few quantitative exposu re-response analyses of diesel exhaust and lung cancer based on human data. Methods We conducted exposure-response analyses among workers in the trucking industry, adjusted for smoking. Diesel exhaust exposure was estimated based on a 1990 industrial hygiene survey. Past exposure s were estimated assuming that they were a function of 1) the plumber of heavy duty trucks on the road, 2) the particulate emissions (grams/ mile) of diesel engines over time, and 3) leaks from trucks' exhaust s ystems for long-haul drivers. Results Regardless of assumptions about past exposure, all analyses resulted in significant positive trends in lung cancer risk with increasing cumulative exposure. A male truck dr iver exposed to 5 mu g/m(3) of elemental carbon (a typical exposure in 1990, approximately five times urban background levels) would have a lifetime excess risk of lung cancer of 1-2%, above a background risk o f 5%. Conclusions We found a lifetime excess risk ten times higher tha n the 1 per 1,000 excess risk allowed by OSHA in setting regulations. There are about 2.8 million truck drivers in the U.S. Our results depe nd on estimates about unknown past exposures, and should be viewed as exploratory. They conform reasonably well to recent estimates for dies el-exposed railroad workers done by the California EPA, although those results themselves have been disputed Am. J. Ind. Med. 34:220-228, 19 98. (C) 1998 Wiley-Liss, Inc.