Rennes (AFP)

Created in 2010 to meet new environmental health challenges, the Rennes Institute for Health, Environment and Work (Irset) is today seeking to understand the role of environmental factors on human health throughout life, says "exposome" in scientific language.

"At the start we were interested in molecules like glyphosate, atrazine or Bisphenol A, then little by little we came to study their mixture, because real life is to be exposed to mixtures, it's a cocktail, "summarizes the director of Irset, Michel Samson.

The institute, which has 260 employees, publishes several hundred studies each year on the impact of environmental pollution on health, from pesticides to industrial compounds, including medicines.

Its main asset: bringing together formerly confined approaches, each in their field of research (molecular biology, epidemiology, toxicology, genetics, modeling, etc.).

The Covid-19 epidemic has brought the health effects of environmental degradation back to the fore: people with chronic diseases (obesity, diabetes, Alzheimer's, Parkinson's, cancer, etc.), to which the environmental factor is pointed out, were thus more likely to develop a serious form of Covid-19.

To carry out their research, the researchers work with fragments of human embryonic organs from voluntary termination of pregnancy and data from epidemiological cohorts, including "Pelagie" in Brittany, which has followed some 3,000 adolescents since birth.

- "Cocktail effects" -

In 2017, an Irset team specializing in "cocktail effects" showed for the first time, on human tissue, that a mixture of molecules with endocrine disrupting properties could have a multiplied effect on the organism, with a factor ranging from 10 to 1,000.

"We look at whether molecules alter the formation of an organ. To do this, we expose these organ fragments to molecules at very high concentrations which will kill the cells, then we test increasingly low concentrations to get closer of those observed in the environment, "explains Séverine Mazaud-Guittot, researcher at Inserm.

"Finally, we test different mixtures of these molecules at low concentrations to see if they have an effect together, while only not," she adds.

Since the creation of a dedicated chair in 2016, Irset has been working on the chemical "exposome" of the fetus, namely the influence of hundreds or thousands of exposures to organic pollutants before birth on the appearance of chronic diseases .

"It is the logical continuation of the study of the cocktail effect. Today we are the only ones, in the field of human health, to treat + the exposome + in this way with the latest technologies", congratulates Michel Samson.

In September 2019, France published its second "national strategy on endocrine disruptors" to reduce exposure to these substances.

- "Chemical fingerprints" -

"The challenge is the increase in chronic diseases because we realized, after having sequenced the genome, that DNA was not enough to explain their occurrence," recalls Arthur David, professor at EHESP.

"There has been a technological revolution for five years. We are able to detect a wide spectrum of substances present in our organism, with chemical fingerprints containing up to 10,000 signals," continues the researcher.

On the "high resolution mass spectrometer", peaks corresponding to molecules appear ... It is still necessary to identify what they correspond to.

"We are facing a major challenge, because even if the technology is there, we need a methodology to decrypt information, especially since around 100,000 chemical substances are currently used", adds Arthur David.

According to André Cicolella, president of the association "Réseau environnement Santé", highly publicized cases like that of "babies born without forearms", or pediatric cancers show more than ever the need for research.

"Environmental health is not yet considered a major policy and we are mainly interested in the disease when it occurs. However if we want to prepare for the next epidemic waves, with 21 million chronically ill people in France, we must act on all risk factors, "adds the chemist.

© 2020 AFP