In a study which has implications for occupational health, European researchers have found that certain non-toxic substances can have a negative impact on neuronal development when mixed with other substances.

The in-vitro research project conducted by the European Commission’s Joint Research Centre (JRC) examined this “cocktail effect” by using chemical products belonging to different classes, such as pesticides and other synthetic products known to contaminate human beings and associated with cognitive deficits among children.

The substances selected were: lead(II) chloride; chlorpyrifos; polybrominated diphenyl ether-47 or PBDE-47; ethanol and bisphenol A.

These cocktails were tested in vitro on a nervous system cell culture enabling the key brain development processes to be observed. Brain development takes a long time, starting at the fetal stage and extending to adulthood. During this period, the developing nervous system is particularly vulnerable to chemical exposures.

Certain chemical cocktails were found to have neurotoxic effects. The effects observed reflect cell changes similar to those observed in the brains of autistic children. The research confirms the hypothesis that cocktails of substances considered to be non-toxic when analyzed alone can however have negative effects on development when combined with other substances, even at low levels of exposure.

The researchers recommends further studies to determine whether these findings can be extrapolated to in vivo situations, i.e. when people are actually exposed.

Workplace safety advocates say the research highlights the current limits of European Union regulations of chemical risks. “The mandatory tests need to be adapted to take account of these effects”, said Laurent Vogel, senior researcher at the European Trade Union Institute (ETUI). “In many cases, workplace exposures are multiple exposures. And prevention rules need to be tightened up, giving precedence to the substitution of hazardous substances,” he concluded.

The study’s findings were presented by Ana Bal-Price in September 2019 at the 47th European Teratology Conference and published in the September 2019 issue of the Reproductive Toxicology journal.

Read the article in the Reproductive Toxicology journal.