National Institute for Occupational Safety & Health
Report on Diesel Exhaust Fume Exposure
Several studies over the past five years indicate that workers exposed to diesel exhaust over a number of years are more likely to contract lung cancer in addition to other maladies.
Earlier studies had only identified irritation of eyes and temporary breathing problems as being related to inhalation of diesel smoke, due to the difficulty of isolating the many other factors which contribute to other, more serious ailments. These include asbestos exposure and cigarette smoking. More recent studies controlled these factors and found a statistically significant number of cancers and tumors among such workers. Also, recent experiments in which rats and mice were exposed “confirm an association between the induction of cancer and exposure to whole diesel exhaust.” The consistency in the findings of the worker histories and the animal experiments “suggests that a potential occupational carcinogenic hazard exists in human exposure to diesel exhaust.”
Not only is the particulate matter associated with cancer: the gases in diesel exhaust are suspect as well. According to NIOSH Current Intelligence Bulletin 50, “The emissions from diesel engines consist of both gaseous and particulate fractions. The gaseous constituents include carbon dioxide, carbon monoxide, nitric oxide, nitrogen oxide, oxides of sulfer, and hydrocarbons (e.g., ethylene, formaldehyde, methane, benzene, phenol, 1, 3-butadiene, acrolein, and polynuclear aromatic hydrocarbons). Particulates (soot) in diesel exhaust are composed of solid carbon cores that are produced during the combustion process and that tend to form chain or cluster aggregates. More than 95% of these particulates are less than one micrometer in size. Estimates indicate that as many as 18,000 different substances from the combustion process can be absorbed onto diesel exhaust particulates. The absorbed material constitutes 15% to 65% of the total particulate mass and includes such compounds as polynuclear hydrocarbons (PAHs) several of which are carcinogens.”
On the basis of these studies, NIOSH recommends that whole diesel exhaust be regarded as “a potential occupational carcinogen.” Although current experimental data is not sufficient to quantify the risk one runs of contracting cancer from diesel exhaust, NIOSH assumes that reductions in exposure to diesel exhaust in the workplace would reduce the excess risk.” NIOSH recommends that users of diesel-powered equipment inform their workers and that professional and trade associations and unions inform their members of the new findings of potential carcinogenic hazards of exposure to diesel engine emissions, and that all available preventitive efforts be vigorously implemented to minimize exposure of workers to diesel exhaust.”
Those interested in receiving Current Intelligence Bulletin 50, entitled “Carcinogenic Effects of Exposure to Diesel Exhaust” may contact NIOSH at 513-533-8287 from 8:30 am – 4:40 pm (EST).