Comparison between personal sampling methodologies for evaluating diesel particulate matter exposures in mines: submicron total carbon corrected for the adsorption of vapor-phase organic carbon vs. respirable total carbon.

In the mining industry, personal measurements of elemental and total carbon are frequently used as surrogates of diesel particulate matter (DPM) exposure, and the respirable or submicron fractions are usually measured. However, vapor-phase organic carbon (OC) can be adsorbed in the filters, interfering with total carbon results. This study presents a comparative evaluation between the submicron fraction of DPM concentrations corrected for the adsorption of the vapor-phase OC (dynamic blank), and the respirable fraction of DPM corrected for a field blank. Respirable and submicron fractions of total carbon (TCR and TC1) and elemental carbon (ECR and EC1) concentrations were sampled in parallel, in the workers' breathing zone, in an underground gold mine. A total of 20 full-shift personal samples were taken for each size fraction. Field blanks were collected each day for both the submicron and respirable fractions, while dynamic blank correction was also applied for the submicron fraction. TCR presented a larger and statistically different geometric mean concentration compared to TC1 (98 µg/m3 vs. 72 µg/m3; p = 0.01), while the concentrations of ECR and EC1 were not statistically different (58 µg/m3 vs. 54 µg/m3; p = 0.74). Average TCR/ECR ratio was 1.7, while the TC1/EC1 ratio was 1.3. In addition, 93% of EC had an aerodynamic size lower than 1 µm, while the proportion of TC particles in the submicron fraction was lower (73%). Finally, a similar quantity of OC was found when analyzing the dynamic and field blanks of the filters with the submicron fraction selective size (24 µg and 22 µg, respectively). In conclusion, the correction for the vapor phase OC by the dynamic blank was not a significant correction in our study design compared to the field blank samples. This study suggests that the differences in TC may be explained by the different aerodynamic fractions of DPM collected. In addition, elemental carbon measurements did not seem to be extensively affected by the aerodynamic size of the particles collected.

Detailed Urinary Excretion Time Courses of Biomarkers of Exposure to Permethrin and Estimated Exposure in Workers of a Corn Production Farm in Quebec, Canada.

Permethrin is a synthetic pyrethroid insecticide widely used in agriculture. Farm workers are thus regularly exposed during spraying season. To help interpret routine biomonitoring results, a proper knowledge of the time courses of biomarkers of exposure is necessary. The kinetics of biomarkers of exposure to permethrin has recently been documented in volunteers exposed to permethrin under controlled conditions but there is a lack of detailed time profiles following real exposure conditions. This study aimed at obtaining data on the excretion time courses of permethrin metabolites in agricultural workers following typical exposure conditions in the field. Twelve workers exposed to permethrin were recruited from a corn production farm in the Montérégie, Quebec, Canada. They provided all their urine voided over a period of 3 days following the onset of a spraying episode of permethrin or work in a treated area. Three major metabolites of permethrin, trans- and cis- 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-l-carboxylic acid metabolites (trans-DCCA, cis-DCCA), and 3-phenoxybenzoic acid (3-PBA), were analyzed. For the applicator, a progressive rise in excretion values was observed with a single peak being reached 29h following the onset of the 3.5h exposure and ensuing elimination with a half-life of 6.4h for trans-DCCA and 8.7h for 3-PBA. In the other workers (supervisor and corn pickers), excretion profiles were generally more compatible with multiple entries in the treated area during the 3-day sampling period and rapid elimination between exposure episodes. In general, 3-PBA was found in slightly higher levels than trans-DCCA, except for the applicator and a harvester. For both trans-DCCA and 3-PBA in a given worker, excretion values expressed as creatinine-normalized concentrations were less variable than those expressed as excretion rates per kilogram body weight. Time-dependent variability in excretion values of workers confirms the need for serial urine sampling of at least two biomarkers of exposure, with minimally pre-exposure, end-of-shift sample the day of onset of exposure, and following morning void.

Correlation between biomarkers of polycyclic aromatic hydrocarbon exposure and electrophilic tissue burden in a rat model.

This study was aimed at investigating the correlation between biomarkers of exposure to polycyclic aromatic hydrocarbons and, more specifically, at examining the role of urinary 1-hydroxypyrene (1-OHP) as a reliable measure of internal dose linked to the electrophilic tissue burden (ETB), assessed as covalent binding of the ultimate carcinogen benzo( a)pyrene diolepoxide (BaPDE) with cellular proteins in target organs. The protocol included experimental verification of a previously proposed algorithm for adjustment of reference values for urinary 1-OHP with exposure to different mixtures of polycyclic aromatic hydrocarbons in a rat model. Hence, the relationships between ETB in liver, lung, and heart as well as the BaPDE-haemoglobin adducts level on the one hand, and urinary/faecal 1-OHP or urinary/faecal 3-hydroxybenzo( a)pyrene (3-OHBaP) on the other hand have been examined. Male Sprague-Dawley rats received intraperitoneally, once daily for 10 consecutive days, binary mixtures of benzo( a)pyrene (BaP) and pyrene (P) in three different exposure scenarios corresponding to BaP/P ratios of 0.2, 1 and 5, with three doses of BaP (2, 6 and 20 mg/kg) for each scenario. The ETB levels were measured as the ultimate analyte benzo( a)pyrene tetrol (BaPTeT) obtained after mild acid hydrolysis of BaPDE adducts with proteins. It was experimentally confirmed that: (1) urinary 1-OHP is a reliable biomarker linked to the ETB in tissues that are targets for carcinogenicity, such as lung, for the BaP/P ratios of 0.2 and 1 (linear regression p=0.0099 and 0.0293, respectively); (2) urinary 3-OHBaP is correlated with the BaPDE-haemoglobin adducts for all three exposure scenarios ( p=0.0011 for BaP/P=0.2, p<0.0001 for BaP/P=1 and p=0.0099 for BaP/P=5). The experimental relationship between ETB and urinary 1-OHP was used to interpolate biological limit values for the urinary metabolite assuming three arbitrary critical levels of ETB. These were compared with the values calculated from the algorithm using the BaP/P ratio 1 mixture as a reference. The ratios of calculated to observed values varied from 1.0 to 1.6 for the BaP/P 0.2 mixture, and from 1.9 to 3.0 for the BaP/P 5 mixture. The results obtained in the present study indicate that the algorithm mentioned above applies well for two of the three exposure scenarios corresponding to realistic occupational BaP/P ratios of 0.2 and 1. This suggests that, using ETB as an endpoint, the proposed algorithm will reasonably predict the critical value of urinary 1-OHP for mixtures having different BaP/P ratios. Stronger linear relationships between ETB in all chosen tissues and 1-OHP or 3-OHBaP excretion were obtained with urinary metabolites than with their faecal analogues. Thus urinary 1-OHP and 3-OHBaP are more reliable biomarkers in biological monitoring strategies.

Urinary excretion kinetics of 1-hydroxypyrene in rats subchronically exposed to pyrene or polycyclic aromatic hydrocarbon mixtures.

The urinary excretion kinetics of 1-hydroxypyrene (1-OHP) were studied in male Sprague-Dawley rats exposed orally, on Tuesdays and Fridays for 10 consecutive weeks, to 0.046 mg/kg/d of pyrene or 0.3, 1 or 3 mg/kg/d of polycyclic aromatic hydrocarbon (PAH) mixtures containing pyrene (0.046, 0.15, and 0.46 mg/kg/d, respectively). During the subchronic exposure, 24-h urine samples were collected on Mondays (prior to exposure) and Tuesdays (after exposure) for all exposure groups. During a 14-d period following last exposure in rats treated with 3 mg/kg/d of PAH mixture, 24-h urine samples were collected at frequent time intervals (0-24, 48-72, 96-120, 144-168, 193-217, 313-338 h). Whatever the administered dose, repeated exposures to pyrene and PAH mixtures resulted in a progressive time-dependent increase in the daily urinary excretion of 1-OHP. After 10 wk of treatment, daily excretion rates were on average 5 times higher than those observed after the first administration. Following the subchronic exposure to 3 mg/kg/d of PAH mixture, the time profile of 1-OHP excretion in rat urine showed a multiphasic elimination. An average first-order apparent elimination half-life of 26.5 h could be estimated for the 48-168 h period following the end of the exposure. The observed time-dependent increase in 1-OHP excretion values upon repeated exposures to PAHs does not appear to result from a PAH enzyme induction effect of pyrene metabolism to 1-OHP. Rather, the slow release of residual pyrene accumulated in a long-term compartment and/or the enterohepatic recirculation of 1-OHP and other pyrene metabolites may play significant roles in the observed urinary excretion kinetics of 1-OHP. Furthermore, the absence of mixture effect on the urinary excretion of 1-OHP suggests that 1-OHP is a good bioindicator of exposure to complex PAH mixtures, in the dose range used in this study.