Predicting human plasma concentrations of persistent organic pollutants from dietary intake and socio-demographic information in the Norwegian Women and Cancer study

Abstract

<i>Background</i> - Concentrations of persistent organic pollutants (POPs) in humans are influenced by a large number of factors including birth year, reproductive history and diet. Accordingly, information on dietary habits and socio-demographic variables may predict plasma concentrations of POPs, thus enabling studies on health effects in large epidemiological studies, without performing time consuming and expensive chemical analyses on entire cohorts.<p>

<p><i>Aims</i> - To develop and evaluate statistical models for predicting concentrations of POPs in participants of the Norwegian Women and Cancer (NOWAC) study, using questionnaire information and measured plasma POP concentrations.<p>

<p><i>Materials and methods</i> - Information on estimated dietary intakes and socio-demographic variables from four different questionnaires (in 1991, 1994, 2004 and 2005) were obtained from participants in the NOWAC study. We measured POP concentrations in a total of 367 blood samples from 2005 and built multivariable linear regression models for <i>p,p′</i>-DDE, PCB-118, -138, -153, -180 and summed PCB concentrations in one subsample (N = 259) and evaluated the models in another subsample (N = 108). Measured and predicted values were compared using correlation coefficients and inter-method agreement was evaluated using weighted Cohen's κ for tertile categorization.<p>

<p><i>Results</i> - Median POP concentrations in the population ranged from 13 ng/g lipid to 162 ng/g lipid (lowest for PCB-118 and highest for <i>p,p′</i>-DDE). Common predictors for all POPs were birth year, breastfeeding and the weight-related variables (BMI or weight change), whereas influential dietary variables differed and were of varying importance. The predicted plasma concentrations were significantly correlated with the measured values (r_s = 0.24, 0.33, 0.41, 0.50, 0.56, and 0.54 for <i>p,p′</i>-DDE, PCB-118, -138, 153, -180 and summed PCBs, respectively). Tertiles of predicted plasma concentrations displayed significant, but varying agreement with measured concentrations (Weighted Cohen's κ = 0.19, 0.22, 0.33, 0.42, 0.45, and 0.50 respectively).<p>

<p><i>Conclusion</i> - Predicted plasma concentrations of certain PCBs showed good precision (Kw > 0.4) when compared to measured concentrations. Thus, the models can be used to classify NOWAC participants into high, medium and low PCB exposure groups.