Annals of Occupational Hygiene Advance Access originally published online on October 17, 2006
Annals of Occupational Hygiene 2007 51(1):27-34; doi:10.1093/annhyg/mel069
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DNA Adducts among Asphalt Paving Workers
1 Boston University School of Public Health, Boston MA, USA
2 University of California, San Francisco CA, USA
3 Harvard School of Public Health Boston, MA, USA
*Author to whom correspondence should be addressed. Tel: +1-617-638-7755; fax: +1-617-638-4857; e-mail: mmcclean{at}bu.edu
Objective: Asphalt is used extensively in the highway construction industry and contains a complex mixture of polycyclic aromatic hydrocarbons, some of which are known or suspected to be human carcinogens. Though numerous epidemiologic studies have described an excess cancer risk among asphalt workers, a causal relationship has not been established. Accordingly, the primary objective of this study was to use DNA adducts as a biomarker of biologically effective dose and determine whether DNA damage resulted from occupational exposure to asphalt among paving workers. Methods: Over a 12 month period, four peripheral blood samples (spring, summer, fall and winter) were obtained from 49 asphalt paving workers (169 samples) and 36 non-paving construction workers (103 samples). The spring, summer and fall samples were collected during the work-season, whereas the winter samples were collected during the off-season (due to the seasonality of paving work). Mononuclear white blood cells were isolated and analyzed for DNA adducts via the 32P-postlabeling assay and generalized linear models were used to evaluate the DNA adduct data. Results: Among paving workers during the work-season, DNA adducts increased during each day of the workweek such that mean adduct levels were lowest on Mondays (3 adducts per 1010 nucleotides) and highest on Fridays (46 adducts per 1010 nucleotides). Additionally, a 3-fold difference in adduct burden was observed by paving task such that mean adduct levels were lowest among roller operators (7 adducts per 1010 nucleotides) and highest among screedmen (23 adducts per 1010 nucleotides). Using adducts as a measure of biologically effective dose, these findings (weekday trend and task-based differences) were consistent with a previous evaluation of absorbed dose in the same population. Adduct levels were not, however, higher among paving workers than among non-pavers. Adducts were also highest during the winter months, suggestive of a seasonal effect that has been observed in previous studies. Conclusion: These findings indicate that adduct burden increased throughout the workweek among paving workers, suggesting that DNA damage may be associated with occupational exposure to hot-mix asphalt. However, the lack of contrast with non-paving workers, as well as the seasonal variation warrants additional investigation.
Keywords: asphalt • biomarkers • DNA adducts • polycyclic aromatic hydrocarbons • 32P-postlabeling assay