Human populations are exposed to a variety of chemical substances through environmental pollution, ensuing in contamination by heterogeneous mixtures of substances. However, human health risk assessment is still carried out on a substance-by-substance basis.

In this context, the team has contributed to the development of a new methodological approach for assessing the chemical risk of heterogeneous contaminants mixtures. This methodology was applied to the French ContaLait survey, which measured several contaminants in breast milk. This initial theoretical assessment of combined risks suggests a high risk for neurodevelopmental processes including motor and cognitive functions. Thus, our study aims to generate experimental data to establish and improve this methodology by characterizing the effects of this human breast milk contaminants mixture on motor and cognitive processes. Eight-week-old C57BL6/J females were orally exposed to a mixture of breast milk contaminants containing the 5 “drivers” identified by the theoretical approach (PCB153, DDE, 2,3,7,8-TCDD, dieldrin, arsenic) at the estimated environmental dose and at doses 10 and 25 times more concentrated. Exposure was carried out two weeks before mating, then during gestation and lactation.

Our initial results show that, whatever the dose, the mixture has no effect on maternal weight, litter size or pup survival. A dose-dependant treatment effect was observed on body growth, developmental markers such as fur growth, eye opening and age at puberty in male and female offspring.

Finally, analyses are underway to determine the effects of exposure to human breast milk mix at different doses on locomotion, anxiety, as well as temporal and spatial memory in adult male and female offspring.