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Abstract
The first chapter of the thesis is a scientific literature review on PAHs. The descriptive and quantitative toxicokinetics (absorption, distribution, metabolism and excretion) of pyrene and of its metabolites are described. This update on pyrene metabolites enabled us to better develop our research objectives.
The second, third and fourth chapters of this thesis describe the steps followed to develop and validate the bioindicators of exposure to PAHs.
The first article identifies novel metabolites of pyrene by using an HPLC-ESI-MS system revealing the presence of pyrene-1,6-dione (P16D) and pyrene-1,8-dione (P18D) in the urine of rats that were exposed to pyrene. The quantification of these metabolites was carried out by their derivatization in the form of acetoxy, whose limits of instrumental detection (HPLC-fluorescence) were approximately 46 and 86 nmol/L for P16D and P18D, respectively. The intra-day and inter-day coefficients of variation of the method of analysis in urinary matrices of rats and humans were on average 7.4% and 12.5%, respectively. With this method, the presence of the P16D and of the P18D was then confirmed in the urine of subjects who were professionally and voluntarily exposed to PAHs. In the urine of rats, P16D was a major metabolite exceeding 64 to 121 times the levels of 1-hydroxypyrene (1-OHP) and 4 to 5 times the P18D levels. Moreover, the urine of individuals potentially exposed to PAHs (n = 4) showed levels of P16D exceeding 4 to 12 times 1-OHP levels and 6 to 10 times P18D levels.
In the second article, the urinary excretion kinetics of dioxided pyrene metabolites (P16D and P18D) was studied and compared with that of 1-OHP in two strains of rats (Sprague-Dawley and Wistar). After an intravenous injection of pyrene, a urinary collection at 48 hours demonstrated the following proportions of excreted metabolites in comparison with the dose of administrated pyrene: from 17 to 26% for P16D, from 6 to 9% for P18D and from 0.6 to 0.8% for 1-OHP in the Sprague-Dawley rats, as well as 10 to 15% for P16D, from 5 to 6% for P18D and from 0.3 to 0.4% for 1-OHP in the Wistar rats. Apparent half-lives for P16D, P18D and 1-OHP were 4, 6 and 4 hours in the Sprague-Dawley rats, as well as 5, 6 and 5 hours in the Wistar rats, respectively.
The third article presents a pilot study in a small group of human volunteers poorly exposed to PAHs (n = 16). Unfortunately, the analytical method did not appear to be sufficiently sensitive to monitor the exposure to PAHs in the general population with no occupational exposure to PAHs.
In conclusion, this work made it possible to develop an original method to analyze dioxidized pyrene metabolites, as well as obtain important data on the metabolism of pyrene in the rat. However, the use of the dioxidized pyrene metabolites as bioindicators of exposure to PAHs in the general population remains to be confirmed by improving of the above mentioned analytical techniques.
