Chemical substances: their neurotoxic effects accumulate

Food, water, air… Chemicals are omnipresent and enter our body when we eat, drink, breathe or even when we use cosmetic products. Although numerous regulations exist concerning the maximum concentrations that these chemical substances must not exceed, they do not take into account their potential cumulative effect. “Environmental and water studies show that the effects of chemicals are additive when present at low concentrations in complex mixturesexplains Professor Beate Escher, head of the Department of Cellular Toxicology at the UFZ and professor at the University of Tübingen. [Mais] it has not yet been sufficiently studied whether this is also the case in the human body. This is precisely where our study comes in.”

294 chemicals found in the plasmas of 624 pregnant women

“In our daily lives, we are exposed to a wide variety of chemicals that disperse and accumulate in our bodies. These are extremely complex mixtures that can affect bodily functions and our health”, begins by explaining the specialist in toxicology to present her work published in the journal Science.

Together with her colleagues, she analyzed more than 600 blood samples from pregnant women from the LiNA mother-child cohort in Leipzig, coordinated by the UFZ since 2006. First, the researchers individually analyzed the chemicals present in the samples. “We wanted to know what chemicals were contained in blood plasma and at what concentrations. We used a two-step extraction process to isolate the most diverse chemical mixtures possible”, specifies Georg Braun, postdoctoral researcher in the working group of Professor Beate Escher and first author of the study.

Using mass spectrometry analysis, they looked for 1,000 different chemicals that could be present in the environment, ingested by humans and have harmful effects on human health. “Of these, we were able to quantify approximately 300 chemicals in several plasma samples”, says the researcher.

“Our study allowed us to prove for the first time that what we know about the effects of chemical mixtures in the environment also applies to humans”

With this basis, the research group then used a prediction model to calculate the neurotoxic effects of the chemical mixtures. Tests to indicate potential neurotoxic effects were carried out using a cellular bioassay established on human cells.

“We analyzed individual chemicals as well as almost 80 different self-made chemical mixtures in realistic concentration proportions. Extracts from plasma samples were also tested”, relates Prof Braun.

These laboratory experiments confirmed the model’s predictions: “the effects of
chemical substances add up in complex mixtures”, says Professor Escher.

“Even if the individual concentrations of neurotoxic substances are so low that they are all below the effect threshold, there is still an effect on nerve cells in complex mixtures with many other chemicals” she adds. “Our study allowed us to prove for the first time that what we know about the effects of chemical mixtures in the environment also applies to humans. It is therefore imperative to rethink risk assessment. Indicator substances alone are far from sufficient. In the future, we must learn to think in terms of mixtures.”

Allergies, obesity, immune system disorders… What impact on health?

According to environmental immunologist Gunda Herberth, “It is becoming increasingly clear that many diseases such as allergies, immune system disorders, obesity or nervous system development are linked to exposure to chemicals in the womb or in early childhood”. In new work, scientists would therefore like to refine their analysis method in order to study the effects of chemical mixtures on other health-related parameters, such as immunotoxicity or possible links between exposure to products. chemicals and developmental disorders in children.