Project Micropollutants

The previous problematic is studied by a systematic approach in order to construct the scientific questions. The target field is the agro-ecological system. The target compounds are the organic pollutants, which are in majority very persistent in the environment of the animals (water, soil, sediments) or in the animals themselves. The compounds able to be bioaccumulated in the tissues of the animals represent a priority.

Indeed, despite the fact that environmental concentrations on large agricultural areas can be considered as low, the concentrations reached in the body tissues might be of concern for Human health. Therefore, the compounds are classified as organic micropollutants.

The main exposure way is the not voluntary intake including not intentionally produced compounds (PAHS, PCDD/Fs), today forbidden synthetic compounds (PCBs, forbidden pesticides as organochlorinated ones) but also compounds which are not forbidden but coming into the animal as environmental contaminant (HBCDs, metabolites of pesticides) without a direct and authorized application (i.e. veterinary drugs are excluded).

In the contamination of food of animal origin, we distinguish two key processes: exposure of the animals but also the fate of the pollutant in the animal body. In each of these parts, different steps are the driving forces for the transfer. The scientific questions on which our team is looking for understanding are situated exactly on these levels. The exposure of the animals has two main aspects: on the one hand the ingestion of environmental matrices carrying the pollutant and on the other hand the accessibility of the pollutant during the digestive process (dependent of the specie) and depending on the vectorizing matrix. Then, the transfer across the animal is dependent of processes which are described here below.

Exposure

Concerning the pollutants in the field of interest of our research team, the oral exposure is the main exposure pathway for terrestrial animals and for aquatic animals shared with the branchial pathway. Therefore, the target matrices are plants, soil, preys, sediments and water. The first issue is to determine how many from each matrix the animals would ingest corresponding to the external exposure of the animal. Moreover, for some matrices as soil or sediments the question of their ability to retain these compounds should be asked as they are considered as a pollutant pit or accumulator. This corresponds to the term of bioaccessibility.

We developed methods to evaluate the relative bioaccessibility (express the retention capacity of a test matrix in comparison to this of a reference matrix considered as maximum retention). This would permit to determine the ability of the matrix to liberate (or not) the pollutant in the digestive tract. Two experimental strategies are enrolled to understand the relationship between the three elements pollutant-matrix-tract: a comparative and an explicative approach. Both are based on in vitro methods (isotherms of sorption-desorption, Physiologically Based Extraction Tests) ex vivo (cell culture, everted intestine) or in vivo. If the concentration of the pollutant in the matrix is known, the multiplication of the amount of ingested matrix and the bioaccessibility of the pollutant allow hierarchizing the exposure pathways of the considered animal. Finally, it remains to know his future in animals, with a crucial step the bioavailabilty.

Animal

The bioavailable fraction of a pollutant is frequently defined as the proportion to which the animal is exposed by external pathway and which reaches the systemic blood circulation. The issue of our research work is to determine this fraction but also its fate corresponding to its distribution in the tissues, its possible metabolism and its excretion. The entire process represents the approach ADME meaning Absorption-Distribution-Metabolism-Excretion. Our research aims to predict this process on a quantitative level and to identify the main variation sources in addition to the knowledge extracted from the literature.

Engineering

The work of understanding is completed by engineering proposals. Indeed, once the mechanisms have been identified and integrated, it becomes possible to think about solutions to modify the transfer into the Food products but also to build scenarios. Such an approach would significantly improve the assessment of sanitary risks of chemical origin and the management of such crises by changes in rearing practices or the use of technological innovations in animal husbandry.