Exposure to persistent organic pollutants (POPs) and pesticides via consumption of sport-caught Great Lakes fish and risk of prostate cancer and melanoma
Green, Joseph William, Jr.
MetadataShow full item record
Fish from the Great Lakes are a potential source of persistent organic pollutants, including polychlorinated biphenyls (PCBs) and organochlorine pesticides (e.g., Mirex and DDT). However, fish are also a source of micro- and macro- nutrients hypothesized to have chemopreventive properties. I investigated the consumption of sport-caught fish from Lake Ontario and the incidence of prostate cancer and melanoma in the New York State Angler Cohort (NYSAC), a prospective cohort of 17,110 anglers and their spouses aged 18 to 40 years old at enrollment. Participants completed a mailed self-administered questionnaire upon enrollment in 1991. The questionnaire queried the number of years that fish from Lakes Ontario and Erie were consumed in addition to potential confounders. As of December 31, 2008 fifty-eight first primary incident prostate cancers and 51 melanoma cases were identified via the New York State Cancer Registry. Vital status was determined by linkage the Social Security Administration Death file. Of those enrolled at baseline, 6 % (1,075) were lost to follow-up. Poisson regression was used to calculate rate ratios (RR) and 95% confidence intervals, adjusting for age, and annual household income. Consumption of Lake Ontario fish was inversely associated with prostate cancer risk (RRadjusted=0.54; 95% CI=0.31-0.95). Moreover, subjects who reported greater than 10 years of consumption of L. Ontario fish demonstrated a 50% reduction in risk compared with never consumers (RR adjusted =0.49; 95% CI=0.23-0.99). Consumption of Lake Erie fish was not associated with prostate cancer risk (RR adjusted = 1.0; 95% CI= 0.6- 1.7). Results from the melanoma analysis provide suggestive evidence of an increased incidence of melanoma among ever consumers of L. Ontario fish (RR adjusted = 2.13; 95% CI= 0.55- 8.22). Additionally, those participants consuming L. Ontario sport-caught fish for greater than 13 years had an increase in the incidence of melanoma (RR adjusted = 1.67; 95% CI= 0.64- 4.44). Persistent organic pollutants in fish are not a likely explanation for an inverse association with prostate cancer. Rather, the results are consistent with experimental evidence suggesting that fatty acids found in fish are chemopreventive. External adjustment for missing covariates determined that the observed measures of association could be biased due to the effect of unmeasured confounding. For prostate cancer, however, the confounding was minor and analyses demonstrated that an inverse relationship persisted. Accurate assessment of exposure is desirable, but often challenging, for epidemiologic studies in environmental contexts. Biomarkers are an objective method to assess exposure, but also have important limitations. Trichloro-2-pyridinol (TCPy) is a urinary metabolite specific to chlorpyrifos (CPF) and has been used as a biomarker of CPF exposure in occupational settings. The goal of this research is to examine the validity and reliability of a single, or small number of, urinary samples necessary to estimate average TCPy concentrations among a group highly exposed applicators. Data were collected as part of an occupational study of cotton field workers in Menofia, Egypt during a 9-17 day application of CPF in 2008. Spot urine samples were collected daily at the beginning and end of the work shift and subsequently analyzed for TCPy. Using the mean of all urine samples, measures of validity and reliability were calculated for a single sample chosen from the beginning, middle and end of the study. The results demonstrated that a single urinary sample taken at day 27, representing the midpoint of the study period, performed best for the estimation of average TCPy concentration (Spearman correlation= 0.97; sensitivity =1.00; specificity=0.70, Kappa =0.68). Further, two samples taken at the midpoint (day 27 and day28) increased measures of reliability (sensitivity =1.00; specificity=0.77, Kappa =0.73). No further improvement was seen with three sample days. This research demonstrates that for a larger epidemiologic study, the selection of one or two days for urine sampling at the midpoint of the CPF application period may perform best at estimating mean TCPy concentration and reduce burden on participants as well as investigators.