Cancer fumes
vehicular emission can pose some formidable health hazards. Everybody knows that. But only now, are scientists further cautioning that diesel fumes are perhaps more dangerous than what was previously thought. And according to a government draft report released recently by the Environmental Protection Agency ( epa ), usa, these fumes are carcinogenic, or, in layman's language, can cause cancer.
The preliminary report, which is still undergoing review by experts, states that "for carcinogenic hazard and risk of cancer over a lifetime, epa is recommending that exposure to diesel exhaust be viewed as likely to pose a risk at low levels, as well as high levels.'
Based on an overview analysis of dozens of animal and human-based studies, it explains that the particulate matter found in diesel fumes is very small in diameter and thus, it is able to penetrate deep into the lungs when we inhale.
The authors of the report also note that "light-duty diesel engines emit 50-80 times and heavy-duty engines 100-200 times more particulate matter than gasoline engines equipped with catalytic converters.' The epa experts speculate that at concentrations above five micrograms per cubic meter, airborne diesel particulate matter presents a significant lifetime cancer risk. They also point out that while air concentrations in most areas of the United States fall below this threshold, some previous studies have reported estimates of diesel particulate in the range four to 22 micrograms per cubic meter in some locations in and around California.
The report also notes that "some occupational settings may be prone to more frequent and higher exposures; such as in engine maintenance shops, heavy equipment operations, mining, or bus terminal operations.' The draft authors stress that all risk estimates remain "crude', and in a statement released recently, epa acting assistant administrator Richard Wilson cautioned a disclaimer that "this study is still undergoing peer review by independent scientists and is not final.'
Daniel Greenbaum, president of the Health Effects Institute, a nonprofit independent review agency co-funded by the epa and the industry, believes some of the results of animal studies cited in the draft report may not be applicable to humans. He says that some of the report's human-based studies, while more relevant, are based on the medical histories of workers who, in many cases, were exposed in the 1950s and 1960s to locomotive engines which were quite different than the engines today. Still, he believes the report contains enough reliable information to say that we should continue our efforts to reduce emissions, just as people have being doing now for a number of years.
This report becomes even more crucial as it comes close on the heels of a Japanese study published late last year which reported the discovery of a highly-carcinogenic chemical in the diesel exhaust fumes.
The researchers from the Kyoto University and National Institute of Public Health, Minato-Ku, Tokyo in Japan, isolated a compound called 3-nitrobenzanthone from the organic extracts of both diesel exhausts and airborne particles. This, they say, could be considered the strongest carcinogen known to man till now. They warned that the major source of the chemical is heavily-loaded diesel engines, and that it could be partly responsible for the large number of cancer cases in cities ( Environmental Science and Technology , Vol 31, No 10).
When the Ames test
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