Abstract D093: Who carries the excess cancer risk burden: Implications of disparities in polycyclic aromatic hydrocarbon exposure
Authors: Gearhart-Serna Larisa M , Tacam Moises , Slotkin Theodore A , Devi Gayathri R 
Published: September 2020

Polycyclic aromatic hydrocarbons (PAHs) are a toxic and ubiquitous class of environmental chemicals sourced from industrial practices, tobacco smoke, grilled and smoked meats, car exhaust, and other human and natural sources. Many PAHs are also considered carcinogenic. In this study, we sought to identify the most vulnerable populations for high PAH exposure in the U.S. and resultant excess cancer risk. Urinary biomarker data were collected from 2005-2014 by the U.S. CDC National Health and Nutrition Examination Survey for metabolites of four PAHs: naphthalene, fluorene, phenanthrene, and pyrene. We conducted reverse dosimetry modeling to estimate exposure to the four PAHs, singly and in sum, for each adult individual in the dataset, expressed as a daily intake rate. These were calculated using known excretion fractions and molecular weights specific to each PAH parent or metabolite compound, standardized adult urine output, and individual body weights. We then stratified these exposures by demographic factors (age, gender, race/ethnicity, education level, and family income), in addition to lifestyle factors (smoking status, exposure to secondhand smoke, and BMI). We analyzed these stratified demographic and lifestyle groups according to effect size, and analyzed subpopulations within each group by principal component analysis, so as to determine the most influential factors and the most vulnerable subpopulations for high PAH exposure. We then calculated lifetime excess cancer risk for subpopulations based on their PAH exposure using benzo(a)pyrene (BaP) toxic equivalency factors, BaP cancer slope factor, and a 70-year lifespan estimation. There were 8570 individuals in the final dataset, although smoking status information available for 3818 of these individuals. Unsurprisingly, smokers and those exposed to secondhand smoke had the highest total PAH intake rates. 36.9% of PAH exposure variance was explained by the demographic and lifestyle factors included in this analysis, with an additional 4.8% explained by smoking status and secondhand smoke exposure interactions with other demographic variables such as race/ethnicity. However, only 7.5% of the PAH exposure variance was explained when all smokers and those exposed to secondhand smoke were removed from the dataset, indicating the strength of association between tobacco smoke exposure and PAH intake. Demographic subpopulations such as those who did not complete high school, middle-income bracket ($45-75,000), and other Hispanic racial/ethnic identity had higher PAH exposure and resultant excess cancer risk, while higher income bracket (75,000+), those with a college degree, Asian identity, and females in general had lower PAH exposure levels and lower excess cancer risk. These results suggest that, in addition to smokers and those exposed to secondhand smoke, there are demographic subpopulations with disproportionately high PAH exposure and resultant excess cancer risk burden, which is a public health concern.

Citation Format: Larisa M Gearhart-Serna, Moises Tacam, Jr., Theodore A Slotkin, Gayathri R Devi. Who carries the excess cancer risk burden: Implications of disparities in polycyclic aromatic hydrocarbon exposure [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr D093.