Therapeutic Study unfolds MWI emissions exposure increases pollutants in Mothers’ breast milk
Mothers living within 20 kilometres of waste incinerators may have a small increase in the total levels of two chemical pollutants in their body.
In an analysis led by researchers at Imperial College London, scientists have shown an association between women’s exposure to emissions from municipal waste incinerators (MWIs) and small increased levels of polychlorinated biphenyls (PCBs) and dioxins found in their milk.
The research was supported by funding from funded by the National Institute for Health and Care Research (NIHR) and the Medical Research Council (MRC).
The study, believed to be the largest of its kind in the UK, incorporates modelled emission patterns with analysis of breast milk samples from almost 200 first-time mothers living close to three incinerators across England, providing a nuanced picture of environmental exposure.
The researchers say that while diet is widely recognised as the main source of these chemicals in breast milk, their analysis suggests exposure to incinerator emissions may make a very small overall contribution to the total concentration of PCBs and dioxins in human tissue.
However, they explain the study is not able to prove that increased concentrations of dioxins and PCBs in human milk can be directly attributed to emissions from MWIs.
They also found that, of the women studied, those who lived closer to an incinerator were not more likely to have higher levels of the compounds in their milk.
Ruthie Parsons, from the School of Public Health at Imperial College London and first author of the study, said: “This study shows a complex picture of emissions exposure, but should ultimately be reassuring. PCBs and dioxins are ubiquitous and persistent pollutants.
“What we have found is the more exposure someone has to emissions from incinerators, the more likely they are to have a very small increase in the levels of these compounds in human milk. We cannot say that this translates to any increased health risk, but that more monitoring is needed to assess any potential health impacts over the long term.”
Persistent pollutants
Polychlorinated biphenyls (PCBs) and dioxins are common chemical pollutants which persist in the environment and human tissue and can be potentially toxic.
Their presence in human tissue is well established, with more than 90% of this concentration coming from eating meat, dairy, fish and shellfish. Evidence suggests infants may be vulnerable to certain effects linked to these pollutants, including impacts on their growth and neurodevelopment.
Burning household and commercial waste is known to be a potential source of the compounds, but modern municipal waste incinerators (MWIs) have operating procedures in place to minimise the risk.
Investigating exposure
In the latest study, a team led by researchers at Imperial College London and the UK Health Security Agency set out to investigate, for the first time, potential links between concentrations of dioxins and PCBs in breast milk and exposure to emissions from incinerators.
Between 2013 and 2016, the team recruited first-time mothers across England who lived within 20km of an incinerator.
Women provided breast milk samples which were analysed to show concentrations of several compounds (sub-types of dioxins and PCBs). In total, samples from 194 women were analysed for dioxins and samples from 150 were analysed for PCBs.
Increased concentrations
Researchers modelled emission patterns for MWIs to investigate the association between exposure to incinerator emissions based on their location and the concentration of compounds found in their breast milk.
The analysis found an association between exposure to emissions and small increases in the levels of dioxins and PCBs.
The team also modelled the concentration of small particles (PM10) at ground level closer to incinerators (within a 10km radius). This further analysis suggested that a doubling in the amount of PM10 was significantly associated with an increase (9.1%) in the concentration of dioxins alone in breast milk, as well as the concentration of dioxins and PCBs (9.7%).
However, the study could not show if emissions were the direct source of the increased level of PCBs and dioxins in breast milk, due to the persistent nature of the compounds in the environment and human tissues and the number of potential sources – including food.
Small contribution
The researchers say their findings are in line with previous European studies. Their study shows that overall, incinerators may make a small contribution to the overall total concentration of dioxins and PCBs found in breast milk, but enhanced monitoring and sampling would be needed to show any direct causal link between the two.
Professor Anna Hansell, one of the senior authors, and director of the Centre for Environmental Health and Sustainability at the University of Leicester, said: “We can’t say for certain using this type of study that the current operation of incinerators is responsible for the small increases of PCBs and dioxins we have seen. These compounds can last for years in the environment and in the body and may well come from other sources.
“However, we know that burning waste does have the potential to produce these compounds. While there is some monitoring of these compounds in the environment near incinerators, it’s very limited. We would recommend more environmental monitoring.”
Bigger picture
The researchers highlight that the findings do have some limitations as exposure to emissions were calculated solely on the participants postcode, there are demographic differences between the study population and the general population, and that and that the factors that contribute to the toxicity of pollutants are complex.
They add that the work did not assess PFAS (known as ‘forever chemicals’), and while there is increased public awareness of these compounds, they were outside of the scope of this study.
Previous research from the team into the health impacts of incinerators found no link between exposure to emissions from MWIs and infant deaths or reduced foetal growth.
The study did show that living closer to the incinerators themselves was associated with a very small increase in the risk of some birth defects, compared to the general population.
Similarly, they were unable to show whether this effect is directly related to the incinerator or not and that people living in industrial areas near MWIs may have increased exposure to pollutants from other sources, including industrial road traffic or other pollutants.
Professor Mireille Toledano, Director of the Mohn Centre in the School of Public Health at Imperial College London and principal investigator on the study, said: “While diet is generally recognised to be the main source of PCBs and dioxins in the human body, our study raises the possibility that MWI emissions do make a small additional contribution to the pollutants in breast milk. We would need improved pollutant monitoring near MWIs in order to conduct longer term analysis and accurately capture the potential effects on health.”
