Tuesday, August 09, 2005

Money Tox - Cambridge Envronmental Against Diesel

BrooklynDodger found this abstract when looking up precedents for Cambridge Environmental. But the comparison of cigarette smoke and diesel particulate matter instructs.

The effect level for lung cancer for diesel in a rat bioassay is around 5 mg/m3. For tobacco smoke it's upwards of 100 mg/m3. Cigarette smoke is virtually impotent compared to occupational agents and air pollution in general.

Cigarette carcinogenesis has been framed as a mutagenicity effect. Here, likely hired by the diesel engine manufacturers, Cambridge demonstrates that mutagenicity is about equal. Nevertheless, diesel is way more potent in the bioassay, and, if you believe the epidemiology of truck drivers and train drivers, way more potent in people.

It follows that mutagenic potential is not the driving force, and particles are.

Inhal Toxicol. 1999 Mar;11(3):215-28.

Comparative mutagenic dose of ambient diesel engine exhaust.

Valberg PA, Watson AY.
Cambridge Environmental, Inc.,
58 Charles Street, Cambridge, MA 02141, USA.


Diesel engine exhaust contains carbon-based particles that can be inhaled and deposited on lung surfaces. Concern about the carcinogenic potential of diesel engine exhaust derives in part from the mutagenic activity of organics that can be extracted from exhaust particles. However, the lung cancer risk is controversial, and diesel exhaust is a candidate for further evaluation. A comparative potency approach can be used to rank the mutagenic risk of diesel exhaust with other combustion products. We compared the specific mutagenic activities of cigarette smoke condensate (CSC) and diesel exhaust particle extract (DEPE) and estimated "mutagenic dose" to the lungs. Although the specific mutagenic activities of CSC and DEPE are similar in magnitude, it is the dose reaching the lungs that is more relevant for comparing mutagenic potential. We calculated that, depending on the source of CSC and DEPE, a person would have to inhale approximately 63 to 181 mg of particulate from diesel engine exhaust to match the mutagenic dose of 1 cigarette. We also calculated that a person would have to breathe diesel exhaust (1.5 microg/m(3), estimated total personal exposure) for 6 to 16 yr to equal the mutagenic dose of 1 cigarette. Although instructive, comparative potency results should be used cautiously due to the need for simplifying assumptions. For example, the type of mutagenic assay and the source of cigarettes and diesel engine exhaust could affect dose estimates to some degree; however, the extent to which diesel particle mutagens are bioavailable would have an even greater effect on estimates of relative risk. For both cigarette smoke and diesel exhaust particles, we assumed that the organic mutagens are 100% bioavailable. In summary, our analysis showed a larger mutagenic dose-to-target-tissues in the smoke of one cigarette as compared to a year of exposure to diesel exhaust particulate at ambient levels.

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