Urinary trans-anti-7,8,9,10-tetrahydroxy-7,8,9,10-tetrahydrobenzo(a)pyrene as the most relevant biomarker for assessing carcinogenic polycyclic aromatic hydrocarbons exposure.

Polycyclic aromatic hydrocarbons (PAH) are ubiquitous pollutants present as complex mixtures in the environment. Among them, benzo(a)pyrene (BaP) is classified as carcinogenic to humans by the International Agency of Research on Cancer. Taking into account all absorption ways, human biomonitoring allows PAH exposure assessment, but biomarkers both specific to carcinogenic effect and sufficiently sensitive are lacking. In this work, we proposed the urinary 7,8,9,10-tetrahydroxy-7,8,9,10-tetrahydrobenzo(a)pyrene (7,8,9,10-OHBaP) stemming from hydrolysis of BaP-7,8-diol-9,10-epoxide, the ultimate carcinogenic BaP metabolite, as biomarker of PAH exposure. A simple and highly sensitive analytical method, with a limit of quantification (LQ) reaching 0.06pmol/L (0.02ng/L), was described and validated. The relevance of urinary 7,8,9,10-OHBaP concentrations adjustment by creatinine was demonstrated. In a group of 24 non-occupationally PAH exposed subjects, only 15% of 7,8,9,10-OHBaP levels was below the LQ and the last daily void has been found as the best sampling time. Tobacco consumption had a significant positive effect on 7,8,9,10-OHBaP concentrations with a 90e percentile equal to 0.05nmole/mole creatinine (nmol/mol) and 0.03nmol/mol for smokers and non-smokers, respectively. In case of occupational PAH exposure, all the pre- and post-shift urinary 7,8,9,10-OHBaP levels of 7 non-smoking workers in a prebaked electrodes production plant were above the LQ. Concentrations ranged from 0.05 to 0.91nmol/mol and accumulation of 7,8,9,10-OHBaP into organism of workers during the working week was clearly observed. The best sampling time was the post-shift at the end of week but samples should also be collected at pre-shift the beginning of week to assess the background level. Finally, the urinary 7,8,9,10-OHBaP elimination kinetic through the weekend was studied using non-linear mixed effect modelling. Mean apparent urinary half-life was 31.5h with low inter-individual variability. Describing key characteristics of urinary 7,8,9,10-OHBaP as PAH exposure biomarker, this work should promote its use for future large-scale biomonitoring campaigns.

Comparison of gaseous polycyclic aromatic hydrocarbon metabolites according to their specificity as biomarkers of occupational exposure: Selection of 2-hydroxyfluorene and 2-hydroxyphenanthrene.

Exposure to Polycyclic Aromatic Hydrocarbons (PAHs) occurs by respiratory, digestive and dermal absorption. Biomonitoring takes all pathways into account but sensitive and specific biomarkers are required. Different gaseous PAHs metabolites were used due to their abundance in the atmospheric mixtures but none of them were selected as better biomarker than the others. To identify the best candidates for assessing occupational airborne exposure, relation between atmospheric levels of Naphtalene, Fluorene and Phenanthrene and urinary metabolites concentrations was studied in a carbon electrode workers group. Linear mixed effects models were built to select explanatory variables and estimate variance component. Urinary creatinine was a predictor of metabolites levels confirming the importance of diuresis for interpreting results. High significance of pre-shift sampling time combined with positive coefficients of post-shift indicated that urine should be sampled at the end of the workday in association with pre-shift urine to avoid misinterpretations. Among the 10 metabolites studied, urinary 2-hydroxyfluorene and 2-hydroxyphenanthrene showed the highest increase of variance explained by models after inclusion of individual atmospheric levels as explanatory variable. Priority could be given to 2-hydroxyfluorene due to higher excretion levels than 2-hydroxyphenanthrene.

Urinary elimination kinetics of 3-hydroxybenzo(a)pyrene and 1-hydroxypyrene of workers in a prebake aluminum electrode production plant: Evaluation of diuresis correction methods for routine biological monitoring.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous carcinogenic pollutants emitted in complex mixtures in the ambient air and contribute to the incidence of human cancers. Taking into account all absorption routes, biomonitoring is more relevant than atmospheric measurements to health risk assessment, but knowledge about how to use biomarkers is essential. In this work, urinary elimination kinetic of 1-hydroxypyrene (1-OHP) and 3-hydroxybenzo(a)pyrene (3-OHBaP) were studied in six electrometallurgy workers after PAHs exposure. Spot samples were collected on pre- and post-shift of the last workday then the whole urinations were separately sampled during the weekend. Non-linear mixed effects models were built to study inter- and intra-individual variability of both urinary metabolites toxicokinetic and investigate diuresis correction ways. Comparison of models confirmed the diuresis correction requirement to perform urinary biomonitoring of pyrene and BaP exposure. Urinary creatinine was found as a better way than specific gravity to normalize urinary concentrations of 1-OHP and as a good compromise for 3-OHBaP. Maximum observed levels were 1.0 µmol/mol creatinine and 0.8nmol/mol creatinine for 1-OHP and 3-OHBaP, respectively. Urinary 1-OHP concentrations on post-shift were higher than pre-shift for each subject, while 3-OHBaP levels were steady or decreased, and maximum urinary excretion rates of 3-OHBaP was delayed compared to 1-OHP. These results were consistent with the sampling time previously proposed for 3-OHBaP analysis, the next morning after exposure. Apparent urinary half-life of 1-OHP and 3-OHBaP ranged from 12.0h to 18.2h and from 4.8h to 49.5h, respectively. Finally, inter-individual variability of 1-OHP half-life seemed linked with the cutaneous absorption extent during exposure, while calculation of 3-OHBaP half-life required the awareness of individual urinary background level. The toxicokinetic modeling described here is an efficient tool which could be used to describe elimination kinetic and determine diuresis correction way for any other urinary biomarkers of chemicals or metals exposure.

Occupational exposure to polycyclic aromatic hydrocarbons: relations between atmospheric mixtures, urinary metabolites and sampling times.

PURPOSE: Occupational exposure to polycyclic aromatic hydrocarbons (PAHs) can be assessed by either air monitoring or biomonitoring using urinary 1-hydroxypyrene (1-OHP) or 3-hydroxybenzo(a)pyrene (3-OHBaP). The aim of this study was to understand the links between atmospheric PAHs and urinary metabolites, in order to improve the biomonitoring strategy for assessing carcinogenic risk. METHODS: Personal air sampling for pyrene and BaP measurements, and urines for 1-OHP and 3-OHBaP analyses of seven workers from electrode production plant were collected every day of the working week. RESULTS: High variability of atmospheric levels between activities and between days was observed, especially for gaseous pyrene. No correlation was found between urinary metabolites: 1-OHP maximum levels occurred for "electrode extrusion" activity; those of 3-OHBaP occurred for "raw materials dispatcher." Sixty percentage of 3-OHBaP maximum levels were observed in urines collected at the beginning of shift the last workday. Those of 1-OHP occurred at different sampling times, depending on the gaseous pyrene levels (not stopped by P3 respirators). Dermal absorption of PAHs was confirmed by significant effect of particulate pyrene on 1-OHP in the samples collected the morning of the following day (p < 0.02, n = 25). CONCLUSIONS: Lack of correlation between metabolites concentrations emphasizes the non-relevance of 1-OHP, from a non-carcinogenic gaseous and particulate compound, and the great interest of 3-OHBaP, from carcinogenic BaP. Its slower urinary elimination prevents the risk of exposure underestimation, and urinary analysis should be performed at the beginning of shift the end of working week, especially in case of high exposure variability.