Polycyclic aromatic hydrocarbons (PAHs) are common soil contaminants due to their lipophilic nature which limits partitioning to water or air. Soil properties such as organic carbon can affect PAH release from soil, and thus affect PAH bioavailability of ingested soil. Risk assessment of PAHs in soil generally assumes equal bioavailability of PAHs ingested in soil compared to PAHs ingested in reference dose media, leading to environmental cleanup guidelines that are potentially too conservative. This research intended to use the juvenile swine model to assess PAH bioavailability from impacted soil to better inform bioavailability estimates for risk assessment. This was done by assessing PAH bioavailability from single and repeated exposure to PAHs in different spiked exposure media, assessing PAH bioavailability from soil collected from PAH impacted sites, and assessing biomarkers of exposure and effect following PAH exposure. The effect of exposure duration on bioavailability was assessed because people are usually chronically exposed to PAHs, rather than acutely exposed, as most bioavailability studies are performed, and chronic exposure may lead to increases in xenobiotic metabolizing enzymes and transporters which may affect bioavailability. This research found that exposure duration did not significantly affect anthracene and benzo[a]pyrene bioavailability (p>0.075), but exposure media did (p<0.004). These results suggest that exposure medium has a more important effect on bioavailability than exposure duration, and also bioavailability calculated from a single exposure is appropriate for use in risk assessment. Bioavailability from 24 naturally impacted soils was assessed to determine which soil characteristics had the greatest effect on PAH bioavailability. Area under the curve (AUC) measurements for benzo[a]pyrene (BaP) and anthracene in swine blood after oral exposure from a soil matrix for benzo[a]pyrene and anthracene in soils had s very poor relationship with soil concentrations in soils collected from impacted sites (r2<0.15), but a very strong relationship with soil concentrations from spiked artificial soils (r2<0.95). As spiked soils had much higher concentrations of PAH, these results suggest there is a point of departure in soil concentrations where internal exposure becomes linearly related to soil concentration. Point of departure modeling indicates that this point occurs at soil PAH concentrations greater than 1,900 mg kg-1. Thus, risk assessment can assume a constant exposure to PAHs at soil concentrations lower than the point of departure. Comparison of terminal rate constants from intravenous (IV) exposure to PAHs and oral exposure to PAHs in a soilmatrix suggest that flip-flop kinetics occur in swine, where absorption occurs at a slower rate than elimination. Flip-flop kinetics likely explains the lack of relationship between real world soil concentrations and area under the curve measurements as absorption is the rate limiting step of elimination. Biomarkers of exposure and effect were assessed in swine liver and ileum tissue, as well as blood following single and subchronic exposure to PAHs to determine if relationships could be drawn between exposure magnitude and duration and biomarker formation. Biomarkers included cytochrome P450 (P450) 1A1, 1A2, and 1B1 expression and activity as biomarkers of exposure and DNA adducts, carbonylated proteins, and micronucleated reticulocytes as biomarkers of effect. Biomarkers of exposure were not affected by exposure magnitude or duration, indicating that they would serve best as exposure markers rather than indicators of bioavailability or other effects. However, DNA adduct and protein carbonyl formation was significantly affected by exposure duration (p<0.045), but micronuclei formation was not. The micronuclei results suggest the liver was effective at clearing PAHs to non-toxic metabolites at the study doses, while tissue biomarkers of effect may correlate more effectively with exposure iv length and magnitude of dose. This work indicates that PAH bioavailability from soil is lower than 100%, but additional work needs to be done to determine soil characteristics that affect bioavailability and to determine a bioavailability value relative to reference material.

Le chlordécone est un pesticide organochloré, qui a été utilisé dans les Antilles françaises pour lutter contre le charançon du bananier Cosmopolites sordidus. Ce pesticide a été interdit en 1993 en raison de sa toxicité et de sa persistance dans l'environnement. Cependant des études ont montré que la population antillaise continue d'être exposée (lait maternel et sang contaminés, transfert de chlordécone mère-jeune, retard du développement cognitif, risque de cancer de la prostate) en particulier via l'alimentation. Depuis 2008, la réglementation européenne n°396/2005 est appliquée sur le territoire antillais (limite maximale fixée à 10 et 20 µg chlordécone /kg poids frais repsectivement dans le foie et l'oeuf et de 100 µg/kg de matière grasse dans le gras). Il s'avère que la contamination des denrées au chlordécone est due au fait que les sols d'anciennes bananeraies autrefois traités au chlordécone (principalement des andosols, des nitisols et des ferrisols) demeurent contaminés. L'andosol contient de l'argile allophane, structure qui confère une microporosité élevée par l'enchevêtrement de motifs particulaires répétés à plusieurs échelles. Le chlordécone de l'andosol a été potentiellement piégé par ce réseau de micropores et est supposé être fortement retenu. Au contraire, le nitisol contient de l'argile halloysite, dont la structure correspond à une superposition de couches et ménage une faible porosité. Notre hypothèse est que le chlordécone est moins retenu par le nitisol que par l'andosol. Les animaux monogastriques élevés en plein air (porcin, volaille) sont susceptibles d'ingérer du sol de manière involontaire. Chez la poule pondeuse, les niveaux d'ingestion de sol peuvent atteindre 25 % de la ration alimentaire journalière dans le cas d'une réduction du couvert végétal et/ou d'un rationnement alimentaire. L'ingestion de sol pour le porcin a été peu étudiée. Nous avons cherché à déterminer les aptitudes d'un andosol et d'un nitisol à retenir le chlordécone durant le processus digestif. Pour cela nous avons évalué la biodisponibilité relative du chlordécone d'un andosol et d'un nitisol chez l'animal monogastrique. La détermination de la biodisponibilité relative repose sur la comparaison des pentes entre la réponse (concentration de chlordécone dans les matrices animales) obtenue lors des doses croissantes de chlordécone ingérées via la matrice testée (l'andosol ou le nitisol) à la réponse obtenue lors des mêmes doses de chlordécone ingérées via une matrice de référence (huile). Les résultats obtenus chez la poule pondeuse et le porcelet ont indiqué que l'andosol et le nitisol n'affectent pas la biodisponibilité du chlordécone. Ainsi, la biodisponibilité relative du chlordécone des sols étudiés a été identique et considérée égale à 100% aussi bien chez la poule que chez le porcelet. Le chlordécone du sol a donc été extrait durant le processus digestif et absorbé par l'animal monogastrique à l'identique du chlordécone dissous dans de l'huile. Le chlordécone du sol est donc assimilable par l'animal d'élevage. Ainsi, les sols contaminés en chlordécone présentent un réel risque pour la filière animale. Les teneurs en chlordécone des produits (foie, gras, oeuf) ont dépassé les limites maximales acceptables dès lors que les animaux monogastriques ont ingéré 6,8 µg chlordécone /jour/kg de poids vif. Sachant que 10% des sols cultivables contiennent au moins 1 mg chlordécone /kg, dès lors qu'un animal monogastrique (poule pondeuse ou porcelet) ingère 17 % de sol dans sa ration alimentaire quotidienne, les teneurs en chlordécone des produits dépasseront les limites maximales et seront « impropres » à la consommation. Il convient ainsi d'identifier les pratiques d'élevage à risques pour préconiser des mesures limitant la contamination des produits animaux au chlordécone / Chlordecone (CLD) is an organochlorine pesticide used in the French West Indies against black weevil Cosmopolites sordidus. This pesticide was banned in 1993, because of the toxicity and persistence of this compound in the environment. However, several studies indicated that the population is already exposed to chlordecone (contaminated blood and maternal milk, chlordecone transfer to the mother from the child, memory delay in child and risk to the prostate cancer) particularly by food ingestion. Since 2008, European Regulation °396/2005 is applied in French West Indies (maximal limit fixed at 10 and 20 µg chlordecone/kg of fresh weight in liver and egg and at 100 µg chlordecone /kg of fat in fat). Soils of banana crops previously treated by chlordecone (mainly andosols, nitisols, ferrisols) are still contaminated and are the major source of contamination of food products. Andosol contains allophane clay structure which allows a high microporosity with the formation of particle aggregates in a pattern repeated at different scales. chlordecone would be strongly trapped by this micropores structure and supposed to be strongly retained. Nitisol contains halloysite clayed structure composed to the clay layers superposition with a low porosity. Our hypothesis is that chlordécone is less retained by nitisol than by andosol. Monogastric animals reared outside (pig, poultry) may involuntary ingest soil. It has been shown that hen can ingest soil amounts corresponding to 25 % of the daily ration in the case of vegetation reduction and of nutritional imbalance. Soil ingestion by pig was less studied. In the frame of this research work, we determined andosol and nitisol capacities to retain chlordecone during the digestive process. The relative bioavailability of soil-bound chlordecone in monogastric farm animals (laying hen and juvenile swine) was established. The relative bioavailability determination consists to the slope comparison between the response (concentrations of chlordecone in animal matrices) obtained with increasing chlordecone doses via andosol or nitisol and the response obtained with the same chlordecone ingestion doses via a reference matrix (oil). Results showed that andosol and nitisol did not reduce the chlordecone bioavailability. Thus, relative bioavailability of soil-bound chlordecone was considered to be equal to 100% in laying hen and in juvenile swine. chlordecone was extracted during the digestive process and was absorbed by the monogastric animals. Thus, soil-bound chlordecone is directly assimilated by monogastric farm animals. Concentrations of chlordecone in animal products (liver, fat, egg) exceeded maximal limits for a chlordecone ingestion at least equal to 6.8 µg chlordecone/day/kg of body weight. Since 10% of agricultural soils are contaminated with at least 1 mg/kg, the ingestion of 17% of soil in the daily food ration will result in animal products not acceptable for human consumption. Therefore, it is important to characterize the risk livestock farming practices in order to limit the contamination of food products