Biological monitoring of persistent organic pollutants (POPs) in New Zealand : a thesis by publications presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Public Health, Centre for Public Health Research, Massey University, Wellington, New Zealand

Abstract

This thesis reports the results of a national research program investigating persistent organic pollutants (POPs) in New Zealanders. The research investigated human body burdens, and exposure sources, of the following POPs: • Polychlorinated dibenzo-p-dioxins (PCDDs) and furans (PCDFs) • Polychlorinated biphenyls (PCBs) • Organochlorine pesticides (OCPs) such as dichlorodiphenyltrichloroethane (DDT) • Brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) • Perfluoroalkyl substances (PFAS) such as perfluorooctanosulfonic acid (PFOS). Previous research has shown that POPs are toxic, and that they are found in the bodies of all humans and wildlife. This thesis builds on previous research by describing the results of recent studies of New Zealand human body burdens of POPs and comparing these results to previous New Zealand research and international studies. The research includes the second national survey of POPs in the serum of adult New Zealanders, and a related study of the importance of household dust as an exposure source for BFRs in breast-feeding infants. The POPs serum survey methodology was assessed, showing that younger adults, and those of Māori ethnicity, are less likely to participate in human biological monitoring surveys. The research found that the body burdens for the chlorinated POPs were higher for the older age groups. In contrast, the majority of BFRs showed higher serum concentrations in younger age groups. The observed positive association with age for the chlorinated POPs may be attributed primarily to a cohort effect (i.e. more recent cohorts having been exposed to lower levels of chlorinated POPs). The research also provides evidence that within the same cohort, chlorinated POPs body burdens have reduced over time, though some POPs appeared to have reached steady-state concentrations in individuals. In addition, burdens of BFRs and PFASs were found to be higher in men compared to women, possibly due to sex-related differences in human elimination of these POPs. In comparison to international results, New Zealand adults have (a) relatively low body burdens of PCDDs, PCDFs, and PCBs, and (b) similar body burdens of BFRs, PFASs, and OCPs (especially DDT compounds) to the rest of the world. Household dust is an important exposure source of BFRs in human milk. Over the past 15 years, human body burdens (measured in serum and breast milk) of chlorinated POPs have decreased in New Zealand and internationally, illustrating the effectiveness of measures to control POPs (e.g. the Stockholm Convention). The research provides the first reference point for human body burdens of BFRs and PFASs in the New Zealand adult population. In summary, the research outlined in this thesis provides insights into the distribution and dynamics of POPs in humans. The findings from the research, particularly the influence of age on the dynamics of POPs over time, and the exposure of children to POPs at a very early age, provide incentive for further research and public health initiatives. The research provides a resource to inform future biological monitoring programmes, and to aid in the assessment of human health risks from exposure to POPs.