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Deposition of inhaled carcinogens in ETS

Institution: University of California, Irvine
Investigator(s): Michael Oldham, M.S.
Award Cycle: 2001 (Cycle 10) Grant #: 10KT-0003 Award: $210,446
Subject Area: General Biomedical Science
Award Type: New Investigator Awards

Initial Award Abstract
The goals of this project are to determine the particle size(s) of four of the major carcinogens in environmental tobacco smoke (ETS), verify predicted local airflow patterns within airways and then estimate carcinogen doses for adults and children. To obtain realistic estimates various daily activity profiles for both adults and children are used to cover all exposure conditions. The proposed research generates scientific information for risk assessment including potential carcinogenic doses to children and adults.

Epidemiology studies have found associations between high exposure to environmental tobacco smoke and increased respiratory diseases. To estimate the risk, accurate predictions of the amount of inhaled sidestream smoke that deposits in the respiratory tract are required. The main factors that determine deposition in the respiratory tract are particle size and airborne concentration. One assumption used in such predictions has been that all of the chemicals in ETS have the same particle size. Preliminary studies of one carcinogen in sidestream tobacco smoke, benzo(a)pyrene, found that the particle size of benzo(a)pyrene is statistically significantly smaller than that for the rest of sidestream tobacco smoke. This particle size difference leads to a 10% increase in deposition efficiency for infants and children (0 – 6 years) while resulting in less than a 1% increase for adults. It is not known if particle sizes are also smaller for other carcinogens that have been identified in ETS. However, if true, this would result in a significantly greater projected risk from carcinogens for children than currently predicted.

The proposed research will determine the particle sizes of several carcinogenic polyaromatic hydrocarbons and the most potent N-nitrosamine carcinogen in ETS. In order to see how much of these compounds deposit in the respiratory tract dosimetry, predictions will be done using different activity pattern assumptions that cover all potential exposure conditions. By using carcinogen-specific particle size data, enhancement factors, age-specific lung airway size data and breathing patterns, more accurate estimates of doses and risk can be established.