Harmful chemicals were found in the organs of fetuses conceived decades after the substances were banned. In a study on 20 stillborn babies published in the journal Chemosphere, researchers at Karolinska Institutet in Sweden found chemicals linked to cancer, infertility and other adverse health conditions. In many cases, the concentrations exceeded those found in maternal blood and placenta. Some chemicals were present in the fetuses even when they couldn’t be detected in the mother.
“These are alarming findings that call for urgent development of better health risk assessments for chemicals,” says first author Richelle Duque Björvang, PhD student at the Department of Clinical Science, Intervention and Technology at Karolinska Institutet. “Importantly, regulators need to consider the collective impact of exposure to multiple chemicals rather than evaluating just one chemical at a time.”
The researchers studied concentrations of 22 persistent organic pollutants (POPs). These are toxic chemicals that remain in the environment for long periods of time and accumulate in humans through food, drinking water and air particles.
At least 15 of 22 chemicals in every organ
In samples of fetal fat tissue, liver, heart, lung and brain from 20 pregnancies that ended in stillbirth in the third trimester in 2015-2016, the researchers identified at least 15 of the 22 POPs in every organ. Four chemicals were found in all tissues in all fetuses. The most pervasive chemicals were:
- HCB, a pesticide previously used to protect food crops from fungi;
- DDE, a metabolite of DDT, an insect killer used in the mid-1900s;
- Variants of PCBs, chemicals formerly used in a range of electrical products.
Some pesticides-PeCB, α-HCH, γ-HCH and oxychlordane-were detected in fetal tissue even when they were not quantified in maternal blood samples or the placenta.
Most current methods for estimating fetal exposure to chemicals rely on maternal blood and placenta samples as proxies. However, these latest findings suggest that this approach may give a misleading picture on the diversity and concentration of chemicals that babies are exposed to during early development.
Linked to health risks
Several previous studies have linked early life exposure to POPs to adverse health outcomes such as low birth weight, gestational diabetes, ADHD, infertility, obesity and reduced sperm production. POPs have also been linked to hormonal disruption, which in turn may be associated with various cancers.
“Getting an accurate picture of chemical exposure in early human development is critical to assessing both short and long-term health consequences for future generations,” says last author Pauliina Damdimopoulou, researcher in the same department at Karolinska Institutet. “Therefore, we believe today’s approaches estimating fetal chemical exposure, for example in birth cohort studies, need to be updated to better reflect the likelihood that for some chemicals, fetal exposure is actually greater than what the blood and placenta samples show.”
Thirteen of the pregnancies also had data from an earlier study on PFAS (chemicals used in frying pans, food packaging and firefighting foam). By combining these data, the researchers were able to assess the proportion of chemicals in each type of tissue. While pesticides and PCBs were significantly overrepresented in fat tissue, more than half of the chemicals in the fetal lung, brain, liver and heart was due to PFAS. Overall, the highest concentration of a mix of chemicals were found in fat tissue and the lowest in the brain.
The study has some limitations, including a relatively modest sample size and that it only included fetuses who died in the womb late in the pregnancy. Thus, it may not be fully representative of babies born alive.
The tissue samples were collected from the Stockholm Medical Biobank, which in part stores tissue samples for cause-of-death investigations of stillbirths.
The researchers have received funding from the Swedish Research Council for Sustainable Development (FORMAS), Jane & Aatos Erkko Foundation, and Women’s Department in Sundsvall Development Fund.
Facts on POPs
- Persistent organic pollutants (POPs) are toxic human-made chemicals that once released into the environment remain intact for exceptionally long periods of times and become widely distributed through air, soil and water.
- Currently, there are 30 POPs listed under the so-called Stockholm Convention on Persistent Organic Pollutants, an international environmental treaty initiated by the United Nations to eliminate or restrict the production and use of POPs.
- The list includes pesticides, industrial chemicals and by-products, many of which were long banned by countries around the world but continue to affect the environment and animal and human health.
“Mixtures of persistent organic pollutants are found in vital organs of late gestation human fetuses,” Richelle D. Björvang, Marie-Therese Vinnars, Nikos Papadogiannakis, Sebastian Gidlöf, Linn Salto Mamsen, Daniel Mucs, Hannu Kiviranta, Panu Rantakokko, Päivi Ruokojärvi, Christian H. Lindh, Claus Yding Andersen, and Pauliina Damdimopoulou, Chemosphere, online June 8, 2021, doi: 10.1016/j.chemosphere.2021.131125