Exposure to chemical mixtures during pregnancy linked to language delay
Åke Bergman och Eewa Nånberg
Mixtures of chemicals entail a higher risk for women to have children with delayed language development, as shown in a study published in Science.
“We are exposed to a cocktail of chemicals. Meanwhile, maximum exposure levels are determined to protect us from overexposure to individual chemicals. The system currently in use for evaluating risks and regulating the use of chemicals is not sufficient,” says Åke Bergman, who together with his Örebro colleague Eewa Nånberg has participated in the EU project EDC-MixRisk.
It is unusual for researchers to link epidemiological population studies with experimental cell and animal models. But that is exactly what they have done in this EU project, EDC-MixRisk.
The study was conducted in three phases. First, a mixture of chemicals were identified in blood and urine from pregnant women in the SELMA study, managed from Karlstad University. The mixture could be linked to delayed language development in the children. This critical mixture contained a number of phthalates, bisphenol A (BPA) and perfluorinated substances (PFAS).
Second, experimental research was conducted to study the association between chemical mixtures that we are exposed to and hormone disruption or other biological mechanisms.
In the third and concluding phase, the findings from the experimental research were drawn on to develop new principles for risk assessment of chemical mixtures.
There is today increasing support in research that a wide range of chemicals in our environment may be endocrine – or hormone – disruptive and therefore constitute a health hazard to humans and wildlife. This even if exposure levels to single chemicals involved are below the existing threshold.
“The multidisciplinary approach in this study is unique and will offer great opportunities for improved risk assessment of chemicals,” says Åke Bergman, visiting professor at Örebro University and coordinator of EDC-MixRisk.
Researchers have followed almost 2,000 mothers and children from early pregnancy, through birth, up to school age. This allowed researchers to examine the impact of exposure to hormone disruptive chemicals during early pregnancy on the child’s health and development later in life.
“We are talking about ordinary children and mothers. They are not in high-risk jobs or move in particularly high-risk environments. They are simply exposed to the chemicals that we all come across on a day-to-day basis – in furniture, clothing, building material, hygiene products, drinking water and food, for example,” says Eewa Nånberg, professor of biomedical laboratory science at Örebro University.
Researchers have identified a mixture of chemicals in the women’s blood and urine, which in turn could be linked to a delay in language development in some of the children.
“In Sweden, the majority of children are tested in terms of language development at around 2.5 years of age. We could see that there statistically was an association between exposure to common levels of some identified chemicals and delayed language development,” says Eewa Nånberg.
Experimental studies – at cell level and in animal models – confirm the results from the epidemiological research. In the lab, researchers could see an effect on genes linked to ADHD and autism spectrum disorders (ASD), conditions where language development is often impeded.
In the next step, researchers used the combined research data to develop methods for risk assessment of chemical mixtures at a population level.
“The associations found say nothing about individual risks, but they do show that early exposure to combinations of chemicals may pose a risk at population level, and by extension an increased risk of developing ASD or ADHD. These conditions develop as a result of a complex combination of risk factors, and it is fair to say that this study identifies a risk factor,” says Eewa Nånberg.
“It pinpoints that when examining risks and determining statutory maximum exposure levels, we need to consider the fact that we are exposed to numerous chemicals. We need to assess the total risk, not the individual chemicals. This is a major challenge if we are to create a sustainable future,” says Åke Bergman.
This is a collaborative study with contributions from seven higher education institutions in Sweden (Uppsala University, Karlstad University, Gothenburg University, Karolinska Institute, Lund University, Stockholm University, Örebro University), five partners in the EU and one in the US.
Carl-Gustaf Bornehag is professor at Karlstad University and project leader of the SELMA study. He leads the epidemiological research in EDC-MixRisk. Joëlle Rüegg is professor in environmental toxicology at Uppsala University and leads the experimental research in EDC-MixRisk.