Published June 23, 2021 at 10.15
Science. Researchers at Karolinska Institutet have found industrial chemicals in fetal organs for decades after the substances had been banned in many countries. In a study published in the journal Chemosphere, researchers urge decision-makers to take into account the mix of chemicals that accumulate in humans and nature.
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– These are important findings that point to the need to weigh the overall effect of exposure to several chemicals, rather than evaluating one at a time, says the study's lead author Richelle Duque Björvang, doctoral student at the Department of Clinical science, intervention and technology at Karolinska Institutet.
The researchers studied concentrations of 22 so-called persistent organic pollutants (abbreviated POPs). These are different types of toxic chemicals that are difficult to break down and therefore remain in nature for a long time. They are spread to humans and animals via food, water and air particles, among other things. EU member states and several other countries have signed agreements banning or restricting their production and use.
In the study, the researchers examined samples of adipose tissue, liver, heart, lungs and brain from 20 fetuses that had died of various causes in the third trimester during the years 2015–2016. They identified at least 15 of the 22 analyzed chemicals in each organ. Four of the chemicals were found in all tissues in all fetuses. The most common were:
– HCB, a pesticide previously used to protect food crops from fungi;
– DDE, a substance produced in the degradation of DDT, an insecticide used in the middle of 20th century;
Variants of PCBs, chemicals previously used in various electronic products.
The usual way to estimate fetal exposure to chemicals is to measure the level in the mother's blood and placenta. In the current study, the concentration of certain chemicals was often higher in fetal adipose tissue than in blood and placenta samples from the mother. This can be explained by the fact that the structure of the chemicals means that they accumulate in adipose tissue. But the levels in the fetus' liver and lungs also exceeded the levels in the mother. Some pesticides – PeCB, α – HCH, γ – HCH and oxychlordane – were found in the fetus even though they could not be measured in the mother's blood sample or placenta. According to the researchers, the findings indicate that blood and placenta measurements underestimate the diversity and concentration of chemicals to which the fetus is exposed prematurely in development.
The now published study examined only the presence of the chemicals in fetal tissue, not connections to possible health risks. However, the researchers point out that other studies have linked early exposure to POPs to health risks such as low birth weight, gestational diabetes, ADHD, infertility, obesity and reduced sperm production. For example, the European Food Safety Authority (EFSA) recently revised its risk assessment of dioxins and dioxin-like PCBs and concluded that dietary intake in Europe is currently at a level that could interfere with male fertility.
– It is important that we get a true picture of the chemical exposure in the early stages of development. Only then can we evaluate the health consequences for future generations in the short and long term. Today's approach to estimating fetal chemical exposure, for example in birth cohort studies, needs to be updated to take into account the probability that for certain chemicals the fetal exposure is actually greater than the blood and placenta samples show, says the study's final author Pauliina Damdimopoulou, researcher at the Department of Clinical Medicine. science, intervention and technology at Karolinska Institutet.
13 of the pregnancies had data from a previous study on PFAS (chemicals that to some extent are still used in frying pans, food packaging and fire foam). By combining these data, the researchers were able to analyze the proportion of chemicals in different types of tissue. Pesticides and PCBs were significantly overrepresented in adipose tissue, while more than half of the chemicals in the fetus' lungs, brain, liver and heart consisted of PFAS. Overall, the highest concentration of a mix of chemicals was found in adipose tissue and the lowest in the brain. Boys 'relative exposure was higher compared to girls'.
– Studies conducted in the 1960s and 1970s, when there was a widespread use of POPs, found clearly higher levels. This shows that policy measures that lead to restrictions on the use of chemicals have an impact on the population's exposure, even if it takes long-lived chemicals several generations to get rid of the exposure, says Richelle Duque Björvang.