Exposure to chemicals in plastic during the fetal stage is linked with a lower IQ

Bisphenol F chemical (found in plastics) may cause changes in a gene that is crucial for neurological development. Researchers from the Swedish universities of Uppsala and Karlstad have made this discovery.

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The process could explain why exposure to this chemical during the fetal stage is associated with a lower IQ at seven years of age, as previously observed by the same research community. The findings of the research have been published in the scientific journal Environment International.

We’ve previously shown that bisphenol F (BPF for short) may be connected with children’s cognitive development. However, with this study, we can now begin to understand which biological mechanisms may explain such a link, which is unique for an epidemiological study.”

Carl Gustaf Bornehag, Professor and Head, Public Health Sciences, Karlstad University

He is the project manager for the Swedish Environmental Longitudinal Mother and Child, Asthma, and Allergy (SELMA) research, which provided the data.

Changes in gene activity may be caused by external factors through an “epigenetic” process. This suggests the human genes are altered by a process known as “methylation.” Methylation in a DNA fragment makes it more challenging for the cellular machinery to interpret that specific part. Thus, the expression of methylated genes is often affected.

The researchers tested BPF levels in urine from pregnant women during their first trimester and then followed up monitoring with their children after birth. At the age of seven, the children’s DNA methylation was assessed, and their cognitive capacity was examined. The fetus is exposed to chemicals in the mother’s body when it encounters the mother’s blood through the placenta.

The findings show that in fetuses exposed to higher levels of BPF, methylation rises in a particular region of the GRIN2B gene, which plays an important neurological role. Furthermore, higher methylation was linked to lower IQ in infants.

The research did discover, however, that there seems to be a gender difference in these children’s vulnerability to BPF. Only in boys was an epigenetic correlation between BPF and cognition discovered.

The fact that we’ve been able to identify DNA methylation as a potential mechanism behind BPF's effect on IQ adds an important piece of evidence in work to understand how environmental chemicals affect us on a molecular level.”

Elin Engdahl, Study Lead Author and Researcher, Environmental Toxicology, Uppsala University

In a previous study, the researchers discovered that 25% of seven-year-olds exposed to the highest maternal levels of bisphenol F during week 10 of pregnancy had a 2-point reduction in full-scale IQ relative to 25% of children exposed to the lowest levels. This is a minor difference that is imperceptible in a single child but becomes apparent in a population.

Source:
Journal reference:

Engdahl, E, et al. (2021) DNA methylation at GRIN2B partially mediates the association between prenatal bisphenol F exposure and cognitive functions in 7-year-old children in the SELMA study. Environment International. doi.org/10.1016/j.envint.2021.106617.

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