Current concentrations, temporal trends and determinants of persistent organic pollutants in breast milk of New Zealand women

• New Zealand breast milk concentrations of PCDD/Fs and PCBs were low internationally
• Breast milk concentrations of PBDEs, dieldrin and DDTs were in the mid-range
• Age, urban/rural residency and BMI were determinants of POPs concentrations
• Between 1998 and 2008 POPs body burdens decreased by half in nursing women

Breast milk samples of 39 first time mothers aged 20–30 were collected in 2007–2010 from rural and urban areas of New Zealand, following the fourth World Health Organization coordinated survey protocol. Samples were individually analysed for persistent organic pollutants (POPs) including dioxins and furans (PCDD/Fs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs). The lipid adjusted concentrations of PCDD/Fs (mean toxic equivalent (TEQ): 3.54 pg/g) and PCBs (mean TEQ 1.29 pg/g) were low in comparison to those reported for other countries, and concentrations of dieldrin (10 ng/g) and p,p′-DDE (379 ng/g) and PBDEs were in the mid-range. Breast milk concentrations of PCDD/F-TEQ, PCB-TEQ, dieldrin and p,p′-DDE were significantly higher in rural compared to urban areas (+ 23%, 33%, 59%, and 44% respectively), while concentrations of several PBDEs and lindane were higher in urban areas. Concentrations of PCDD/Fs, PCBs and OCPs, but not PBDEs, increased with age, and higher body mass index was associated with lower concentrations of PCBs. Despite New Zealand's low body burdens of many chlorinated POPs in comparison to other countries, breast milk concentrations continued to decrease over time, with a decrease by half over the last 10 years for PCDD/F-TEQ (− 40%), PCB-TEQ (− 54%) and OCPs − 34 to − 90%), indicating that regulatory measures continue to have beneficial effects. Continued monitoring is needed particularly for the brominated POPs for which little New Zealand specific data is available.