Study of persistent organic pollutants in breast milk and blood

Woman breastfeeding with child next to her

Since 1996, the Swedish Food Agency has been regularly collecting samples of breast milk and blood from first-time mothers in Uppsala County, with co-financiers including the Swedish Environmental Protection Agency as part of its environmental monitoring remit. The study is called Persistent Organic Pollutants in Uppsala Primiparas (POPUP). Since 2008, the study has also followed up the children of these mothers. The main aim with the POPUP study is to investigate how exposure to persistent organic pollutants changes over time in Swedish first-time mothers and their children.

How are samples collected?

Between 30 and 50 first-time mothers giving birth at Uppsala University Hospital and who are resident in Uppsala County are recruited to the study each year. The participating women collect breast milk during the third week after childbirth and provide blood, hair and urine samples. The mothers also respond to questionnaires on subjects such as lifestyle and dietary habits.

Research reports from other countries have raised suspicions that high levels of certain persistent organic pollutants may affect the health of children, with certain pollutants increasing the risk of developing allergies while others appear to reduce the risk. To investigate this among other things, a follow-up study is being conducted of children to the mothers who have participated in POPUP, at approximately 4, 8 and 12 years of age. The follow-up study includes a questionnaire on the children’s health. Where possible we also take blood and urine samples from both mother and child.

The study was approved by the Regional Ethical Review Board in Uppsala.

What are the samples used for?

Milk and blood samples are primarily analysed for persistent organic pollutants, including polychlorinated biphenyls (PCBs), organochlorine insecticides (DDT and others), dioxins and brominated flame retardants (BFRs). These analyses are performed by the Swedish Food Agency.

Among other things, the results are used to monitor changes in levels of persistent organic pollutants over time. The results are also very important in following up the Swedish Food Agency’s advice on the consumption of fish contaminated with PCBs and dioxins. So far, the results have shown a decrease in levels of many persistent organic pollutants in breast milk.

Per- and polyfluoroalkyl substances (PFAS) are among the environmental pollutants analysed in blood from first-time mothers and their children at 4, 8 and 12 years of age. Mercury has been analysed in hair samples, while urine samples have been found to contain phenolic compounds, including bisphenols and phthalate metabolites used as plastic softeners.

A non-toxic environment

The Swedish Riksdag has adopted 16 environmental quality objectives.  The work conducted by the Swedish Food Agency on persistent organic pollutants in breast milk and blood is the basis for one of the indicators for the environmental quality objective a non-toxic environment.

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Reviewed 2023-06-21