Dioxins/furans and PCBs in Canadian human milk: 2008 – 2011 (Lay summary)

Rawn DFK , Sadler AR, Casey VA, Breton F, Sun WF, Arbuckle TE, Fraser WD. Science of the Total Environment  2017 Apr 3;595:269-278. doi: 10.1016/j.scitotenv.2017.03.157. 

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) that accumulate in environmental compartments. These pollutants have been monitored over the past several decades worldwide. PCDDs and PCDFs mostly originate as by-products of industrial activities (e.g. waste incineration, smelting and coal-burning power plants), whereas PCBs were used in a wide range of products including paints and industrial oils. Humans are exposed to these contaminants via dietary intake, particularly foods of animal origin (e.g., fish).

As part of the Maternal-Infant Research on Environmental Chemicals (MIREC) study, human milk was collected from participants in ten urban centres across Canada and analysed for these persistent compounds. Human milk samples were collected between two and ten weeks post-delivery.

Levels of PCBs and PCDD/Fs in human milk were very low, with PCBs measured in parts per billion (ppb) and PCDD/Fs in parts per trillion (ppt).  PCB levels in human milk of European–born women were statistically significantly higher compared to women born in North America. Higher PCDD/Fs levels were detected in the human milk of women who were older than 30, and in those giving birth for the first time.  PCDD/Fs and those PCB congeners having dioxin-like activity have been studied to determine their relative toxicity and toxic equivalent factors have been developed for them.  These factors are used in the determination of overall toxic equivalent concentrations (TEQ).  No association was found between individuals’ level of education or pre-pregnancy body mass index and toxic equivalency concentrations (TEQ) observed in the human milk.

The results showed that overall levels of PCBs and PCDDs/PCDFs in human milk have been decreasing since 1992.