EXPOSURE TO POLYCYCLIC AROMATIC HYDROCARBONS AND EXCRETION OF URINARY 3-HYDROXYBENZO[A]PYRENE: ASSESSMENT OF AN APPROPRIATE SAMPLING TIME

Biomonitoring of firefighting forces: a review on biomarkers of exposure to health-relevant pollutants released from fires

Occupational exposure as a firefighter has recently been classified as a carcinogen to humans by International Agency for Research on Cancer (IARC). Biomonitoring has been increasingly used to characterize exposure of firefighting forces to contaminants. However, available data are dispersed and information on the most relevant and promising biomarkers in this context of firefighting is missing. This review presents a comprehensive summary and critical appraisal of existing biomarkers of exposure including volatile organic compounds such as polycyclic aromatic hydrocarbons, several other persistent other organic pollutants as well as heavy metals and metalloids detected in biological fluids of firefighters attending different fire scenarios. Urine was the most characterized matrix, followed by blood. Firefighters exhaled breath and saliva were poorly evaluated. Overall, biological levels of compounds were predominantly increased in firefighters after participation in firefighting activities. Biomonitoring studies combining different biomarkers of exposure and of effect are currently limited but exploratory findings are of high interest. However, biomonitoring still has some unresolved major limitations since reference or recommended values are not yet established for most biomarkers. In addition, half-lives values for most of the biomarkers have thus far not been defined, which significantly hampers the design of studies. These limitations need to be tackled urgently to improve risk assessment and support implementation of better more effective preventive strategies.

Systematic review of prenatal exposure to endocrine disrupting chemicals and autism spectrum disorder in offspring

LAY ABSTRACT

Autism spectrum disorders comprise a complex group with many subtypes of behaviorally defined neurodevelopmental abnormalities in two core areas: deficits in social communication and fixated, restricted, repetitive, or stereotyped behaviors and interests each with potential unique risk factors and characteristics. The underlying mechanisms and the possible causes of autism spectrum disorder remain elusive and while increased prevalence is undoubtable, it is unclear if it is a reflection of diagnostic improvement or emerging risk factors such as endocrine disrupting chemicals. Epidemiological studies, which are used to study the relation between endocrine disrupting chemicals and autism spectrum disorder, can have inherent methodological challenges that limit the quality and strength of their findings. The objective of this work is to systematically review the treatment of these challenges and assess the quality and strength of the findings in the currently available literature. The overall quality and strength were "moderate" and "limited," respectively. Risk of bias due to the exclusion of potential confounding factors and the lack of accuracy of exposure assessment methods were the most prevalent. The omnipresence of endocrine disrupting chemicals and the biological plausibility of the association between prenatal exposure and later development of autism spectrum disorder highlight the need to carry out well-designed epidemiological studies that overcome the methodological challenges observed in the currently available literature in order to be able to inform public policy to prevent exposure to these potentially harmful chemicals and aid in the establishment of predictor variables to facilitate early diagnosis of autism spectrum disorder and improve long-term outcomes.

Human Biomonitoring of Selected Hazardous Compounds in Portugal: Part I-Lessons Learned on Polycyclic Aromatic Hydrocarbons, Metals, Metalloids, and Pesticides

Human biomonitoring (HBM) data provide information on total exposure regardless of the route and sources of exposure. HBM studies have been applied to quantify human exposure to contaminants and environmental/occupational pollutants by determining the parent compounds, their metabolites or even their reaction products in biological matrices. HBM studies performed among the Portuguese population are disperse and limited. To overcome this knowledge gap, this review gathers, for the first time, the published Portuguese HBM information concerning polycyclic aromatic hydrocarbons (PAHs), metals, metalloids, and pesticides concentrations detected in the urine, serum, milk, hair, and nails of different groups of the Portuguese population. This integrative insight of available HBM data allows the analysis of the main determinants and patterns of exposure of the Portuguese population to these selected hazardous compounds, as well as assessment of the potential health risks. Identification of the main difficulties and challenges of HBM through analysis of the enrolled studies was also an aim. Ultimately, this study aimed to support national and European policies promoting human health and summarizes the most important outcomes and lessons learned through the HBM studies carried out in Portugal.

Grill Workers Exposure to Polycyclic Aromatic Hydrocarbons: Levels and Excretion Profiles of the Urinary Biomarkers

Grilling activities release large amounts of hazardous pollutants, but information on restaurant grill workers’ exposure to polycyclic aromatic hydrocarbons (PAHs) is almost inexistent. This study assessed the impact of grilling emissions on total workers’ exposure to PAHs by evaluating the concentrations of six urinary biomarkers of exposure (OHPAHs): naphthalene, acenaphthene, fluorene, phenanthrene, pyrene, and benzo(a)pyrene. Individual levels and excretion profiles of urinary OHPAHs were determined during working and nonworking periods. Urinary OHPAHs were quantified by high-performance liquid-chromatography with fluorescence detection. Levels of total OHPAHs (∑OHPAHs) were significantly increased (about nine times; p ≤ 0.001) during working comparatively with nonworking days. Urinary 1-hydroxynaphthalene + 1-hydroxyacenapthene and 2-hydroxyfluorene presented the highest increments (ca. 23- and 6-fold increase, respectively), followed by 1-hydroxyphenanthrene (ca. 2.3 times) and 1-hydroxypyrene (ca. 1.8 times). Additionally, 1-hydroxypyrene levels were higher than the benchmark, 0.5 µmol/mol creatinine, in 5% of exposed workers. Moreover, 3-hydroxybenzo(a)pyrene, biomarker of exposure to carcinogenic PAHs, was detected in 13% of exposed workers. Individual excretion profiles showed a cumulative increase in ∑OHPAHs during consecutive working days. A principal component analysis model partially discriminated workers’ exposure during working and nonworking periods showing the impact of grilling activities. Urinary OHPAHs were increased in grill workers during working days.

Exposure of nursing mothers to polycyclic aromatic hydrocarbons: Levels of un-metabolized and metabolized compounds in breast milk, major sources of exposure and infants' health risks

In this study, biomonitoring of nursing Portuguese mothers to polycyclic aromatic hydrocarbons (PAHs) exposure and assessment of potential health risks of their infants were performed through determination of 18 PAHs and 6 major metabolites (OH-PAHs) in breast milk. Concentrations of total PAHs ranged between 55.2 and 1119 ng/g fat, being naphthalene, dibenz(a,h)anthracene, benzo(g,h,i)perylene, and phenanthrene the most abundant compounds (68.4% of ∑PAHs). Benzo(a)pyrene, known carcinogenic, was not detected. Total levels of OH-PAHs ranged from 6.66 to 455 ng/g fat with 1-hydroxyphenanthrene, 1-hydroxynaphthalene and 1-hydroxyacenaphthene as major compounds (96% of ∑OH-PAHs). Concentrations of ∑PAHs and ∑OH-PAHs were strongly correlated between each other (r = 0.692; p ≤ 0.001) and moderately-to-strongly associated with individual compounds (0.203 < r < 0.841; p ≤ 0.001). The attained data suggest increased levels of PAHs in older nursing mothers (>30 years) and in those whose child had lower weight (up to 3.0 kg). Breast-fed infant presented a median PAHs daily intake of 1.41 μg/kg body weight (total benzo(a)pyrene equivalents of 0.0679 μg/kg) and were exposed to 0.024 μg/kg body weight of ∑PAH4 [benz(a)anthracene, benzo(b)fluoranthene, benzo(j)fluoranthene, and chrysene]. Although breast milk is a secure food for newborns, un-metabolized and metabolized PAHs should be included in biomonitoring surveillance studies during breastfeeding to prevent potential health risks for infants.

Firefighters exposure to fire emissions: Impact on levels of biomarkers of exposure to polycyclic aromatic hydrocarbons and genotoxic/oxidative-effects

Firefighters represent one of the riskiest occupations, yet due to the logistic reasons, the respective exposure assessment is one of the most challenging. Thus, this work assessed the impact of firefighting activities on levels of urinary monohydroxyl-polycyclic aromatic hydrocarbons (OHPAHs; 1-hydroxynaphthalene, 1-hydroxyacenaphthene, 2-hydroxyfluorene, 1-hydroxyphenanthrene, 1-hydroxypyrene, 3-hydroxybenzo(a)pyrene) and genotoxic/oxidative-effect biomarkers (basal DNA and oxidative DNA damage) of firefighters from eight firehouses. Cardiac frequency, blood pressure and arterial oxygen saturation were also monitored. OHPAHs were determined by liquid-chromatography with fluorescence detection, while genotoxic/oxidative-effect biomarkers were assessed by the comet assay. Concentrations of total OHPAHs were up to 340% higher (p ≤ 0.05) in (non-smoking and smoking) exposed workers than in control subjects (non-smoking and non-exposed to combat activities); the highest increments were observed for 1-hydroxynaphthalene and 1-hydroxyacenaphthene (82-88% of ∑OHPAHs), and for 2-hydroxyfluorene (5-15%). Levels of biomarker for oxidative stress were increased in non-smoking exposed workers than in control group (316%; p ≤ 0.001); inconclusive results were found for DNA damage. Positive correlations were found between the cardiac frequency, ∑OHPAHs and the oxidative DNA damage of non-smoking (non-exposed and exposed) firefighters. Evidences were raised regarding the simultaneous use of these biomarkers for the surveillance of firefighters' health and to better estimate the potential short-term health risks.

Towards a recommended biomonitoring strategy for assessing the occupational exposure of roofers to PAHs

The aims of this work were to assess the PAH exposure among roofers and to identify relevant biomarkers for monitoring occupational exposure. Several campaigns were conducted between 2004 and 2017, with 28 individual air samples and 240 urinary samples collected from 73 roofers. Seventeen parent PAHs and 14 urinary biomarkers, metabolites of pyrene (1-OHP), benzo(a)pyrene (3-OHBaP and TetraolBaP), naphthalene (1- and 2-naphtols), fluorene (1- 2- 3- 9-fluorenols) and phenanthrene (1- 2- 3- 4- 9-phenanthrols), were analysed. Three exposure groups were considered: soft-applied roofing using polymer-modified bitumen ("PMB"), hot-applied roofing using oxidized bitumen ("OB") and the tearing off of old roof coatings containing coal tar ("CT"). The PAHs containing 2-3 rings were much more abundant, and the highest airborne levels were observed in the "CT" group. The biomonitoring results were consistent with these results, with a large predominance of 2-3 ring PAH metabolites. 1-OHP, 3-fluorenol and 2-phenanthrol were better correlated with airborne levels and less influenced by smoking than the other metabolites. Conversely, 1-/2-naphtol levels were heavily influenced by smoking and not correlated with airborne naphthalene levels. Moreover, 3-OHBaP and TetraolBaP levels were very low when applying bitumen membranes, and much higher exposures were observed during tear-off activities. In this context, the recommended strategy for roofer biomonitoring should include 1-OHP, fluorenols and phenanthrols, as well as carcinogenic BaP metabolites (3-OHBaP or TetraolBaP) when evaluating the occupational exposure of roofers that are tearing off old roof coatings.

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 90^e 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.

Maintenance of Low-Pressure Carburising Furnaces: A Source of PAH Exposure

Objectives

Low-pressure carburising is a new technology used to harden steel; the process has been shown to be a source of considerable polycyclic aromatic hydrocarbons (PAH) pollution. Some PAH are carcinogenic, and activities such as furnace maintenance may thus represent a risk to workers. Occupational exposure during these operations should therefore be assessed.

Methods

In this study, the PAH-related carcinogenic risk associated with furnace maintenance was assessed by monitoring atmospheric levels of benzo[a]pyrene (BaP), a representative marker, alongside urinary levels of 3-hydroxybenzo[a]pyrene (3-OHBaP), one of its metabolites. PAH exposure levels were monitored during seven sampling campaigns in four different factories specialized in heat-treatment of mechanical workpieces for the automotive and helicopter industries. Two types of furnace were studied, and 37 individuals were monitored.

Results

Values up to 20-fold the French regulatory value of 150 ng/m3 for atmospheric BaP, and, for urinary 3-OHBaP values up to 40-fold the French biological limit value (BLV) of 0.35 nmol/mol of creatinine were detected. Very high concentrations of BaP, close to or even exceeding those found in coal-tar pitch (up to about 20 g/kg), were measured in residues (tars, dusts) deposited inside the furnace. Even when adequate and suitable personal protective equipment was used, urinary 3-OHBaP values often exceeded the BLV. We hypothesize that this exposure is linked to insidious and fortuitous dermal contamination through contact with factory equipment and staining.

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.

Quantitative analysis of 3-OHB[a]P and (+)-anti-BPDE as biomarkers of B[a]P exposure in rats

The aim of this study was to develop an analytical method for the determination the levels of metabolites of benzo[a]pyrene (B[a]P), 3-hydroxybenzo(a)pyrene (3-OHB[a]P) and (+)-anti-benzo(a)pyrene diol-epoxide [(+)-anti-BPDE, combined with DNA to form adducts], in rat blood and tissues exposed to B[a]P exposure by high-performance liquid chromatography with fluorescence detection (HPLC/FD), and to investigate the usefulness of 3-OHB[a]P and (+)-anti-BPDE as markers of intragastrical exposure to B[a]P in rats. The levels of 3-OH-B[a]P and B[a]P-tetrol I-1 released after acid hydrolysis of (+)-anti-BPDE in the samples were measured by HPLC/FD. The calibration curves were linear (r(2) > 0.9904), and the lower limit of quantification ranged from 0.34 to 0.45 ng/mL for 3-OHB[a]P and from 0.43 to 0.58 ng/mL for (+)-anti-BPDE. The intra- and inter-day stability assay data suggested that the method is accurate and precise. The recoveries of 3-OHB[a]P and (+)-anti-BPDE were in the ranges of 73.6 ± 5.0 to 116.5 ± 6.3% and 73.3 ± 8.5 to 141.2 ± 13.8%, respectively. A positive correlation was found between the concentration of intragastrical B[a]P and the concentrations of 3-OH-B[a]P and (+)-anti-BPDE in the blood and in most of the tissues studied, except for the brain and kidney, which showed no correlation between B[a]P and 3-OHB[a]P and between B[a]P and (+)-anti-BPDE, respectively. A sensitive, reliable and rapid HPLC/FD was developed and validated for analysis of 3-OHB[a]P and (+)-anti-BPDE in rat blood and tissues. There was a positive correlation between the concentration of 3-OHB[a]P or (+)-anti-BPDE in the blood and the concentration of 3-OHB[a]P or (+)-anti-BPDE in the most other tissues examined. The concentration of 3-OHB[a]P or (+)-anti-BPDE in the blood could be used as an indicator of the concentration of 3-OHB[a]P or (+)-anti-BPDE in the other tissues in response to B[a]P exposure. These results demonstrate that 3-OHB[a]P and (+)-anti-BPDE are potential biomarkers of B[a]P exposure, which would also be useful to assess the carcinogenic risks from B[a]P exposure.

Effects of intravenous benzo[a]pyrene dose administration on levels of exposure biomarkers, DNA adducts, and gene expression in rats

The effects of benzo[a]pyrene (BaP) administration on biomarkers of exposure and early effects were studied in male Sprague-Dawley rats intravenously injected with doses of 0.4, 4, 10, or 40 μmol BaP/kg . Blood, tissues, and excreta were collected 8 and 24 h posttreatment. BaP and several of its metabolites were simultaneously measured in blood, tissues and excreta by ultra-high-performance liquid chromatography (UHPLC)/fluorescence. DNA adducts of BaP diol epoxide (BaPDE) in lungs were quantified using an ultrasensitive immunoassay with chemiluminescence detection. Expression of selected genes in lungs of treated rats (lung RNA) compared to control rats was also assessed by quantitative real-time polymerase chain reaction. There was a dose-dependent increase in blood, tissue, and excreted levels of BaP metabolites. At 8 and 24 h postinjection, BaP and hydroxyBaP were found in higher concentrations in blood and tissues compared to other analytes. However, diolBaP were excreted in greater amounts in urine and apparently more rapidly than hydroxyBaP. Mean percentages (± SD) of injected dose excreted in urine as 4,5-diolBaP during the 0-8 h and 0-24 h period posttreatment were 0.16 ± 0.027% and 0.14 ± 0.083%, respectively. Corresponding values for 3-OHBaP were 0.0045 ± 0.0009% and 0.026 ± 0.014%. BaP-diones were not detectable in blood, tissues, and excreta; 7,8-diolBaP and BaPtetrol were found to be minor metabolites. There was also a dose-dependent increase in DNA adduct formation in lung. Analysis of gene expression further showed a modulation of Cyp1a1, Cyp1b1, Nqo1, Nrf2, Fos, and Ahr expression at 10- and 40-μmol/kg doses, but not at the lower doses. This study provided a better assessment of the influence of absorbed BaP doses on biological levels of diolBaP and OHBaP exposure biomarkers and association of the latter with early biological alterations, such as DNA adducts and gene expression.

Kinetics of Diol and Hydroxybenzo[a]pyrene Metabolites in Relation to DNA Adduct Formation and Gene Expression in Rats

Benzo[a]pyrene (BaP) is a human carcinogen, but there are no validated biomarkers of exposure and the relationship of carcinogenesis with early biological alterations is not fully documented. This study aimed at better documenting the toxicokinetics of diolBaP and hydroxyBaP metabolites as potential biomarkers of exposure to BaP in relation to DNA adduct formation and gene expression. Rats were intravenously (iv) injected with 40 μmol/kg BaP. BaP and several metabolites were measured in blood, tissues, and excreta collected at frequent intervals over 72 h posttreatment. BaP diol epoxide (BaPDE)-DNA adduct formation and gene expression were assessed in lungs. 3-HydroxyBaP (3-OHBaP) and 4,5-diolBaP were the most abundant measured metabolites, and differences in time courses were apparent between the two metabolites. Over the 0-72 h period, mean proportions of BaP dose recovered in urine as 3-OHBaP and 4,5-diolBaP (±SD) were 0.017 ± 0.003% and 0.1 ± 0.03%. Corresponding values in feces were 1.5 ± 0.5% and 0.42 ± 0.052%. BaPDE-DNA adducts were significantly increased in lungs and a correlation was observed with urinary 3-OHBaP and 4,5-diolBaP. Analysis of gene expression showed a modulation of expression of metabolic genes (Cyp1a1, Cyp1b1, Nqo1, Ahr) and oxidative stress and repair genes (Nrf2, Rad51). However, BaPDE adducts formation did not exhibit any significant correlation with expression of genes, except a negative correlation with Rad51 expression. Similarly, there was no significant correlation between urinary excretion of OHBaP and diolBaP and expression of genes, except for urinary 7-OHBaP excretion, which was negatively correlated with Rad51 expression. Results indicate that concomitant measurements of diolBaP and OHBaP may serve to better assess the extent of exposure as compared to single metabolite measurements, given kinetic differences between metabolites. Further, although some urinary metabolites were correlated with BaPDE adducts, links with gene expression need to be further investigated.

Factors and Trends Affecting the Identification of a Reliable Biomarker for Diesel Exhaust Exposure

The monitoring of human exposures to diesel exhaust continues to be a vexing problem for specialists seeking information on the potential health effects of this ubiquitous combustion product. Exposure biomarkers have yielded a potential solution to this problem by providing a direct measure of an individual's contact with key components in the exhaust stream. Spurred by the advent of new, highly sensitive, analytical methods capable of detecting substances at very low levels, there have been numerous attempts at identifying a stable and specific biomarker. Despite these new techniques, there is currently no foolproof method for unambiguously separating diesel exhaust exposures from those arising from other combustion sources. Diesel exhaust is a highly complex mixture of solid, liquid, and gaseous components whose exact composition can be affected by many variables, including engine technology, fuel composition, operating conditions, and photochemical aging. These factors together with those related to exposure methodology, epidemiological necessity, and regulatory reform can have a decided impact on the success or failure of future research aimed at identifying a suitable biomarker of exposure. The objective of this review is to examine existing information on exposure biomarkers for diesel exhaust and to identify those factors and trends that have had an impact on the successful identification of metrics for both occupational and community settings. The information will provide interested parties with a template for more thoroughly understanding those factors affecting diesel exhaust emissions and for identifying those substances and research approaches holding the greatest promise for future success.

Use of physiologically-based pharmacokinetic modeling to simulate the profiles of 3-hydroxybenzo(a)pyrene in workers exposed to polycyclic aromatic hydrocarbons

Biomathematical modeling has become an important tool to assess xenobiotic exposure in humans. In the present study, we have used a human physiologically-based pharmacokinetic (PBPK) model and an simple compartmental toxicokinetic model of benzo(a)pyrene (BaP) kinetics and its 3-hydroxybenzo(a)pyrene (3-OHBaP) metabolite to reproduce the time-course of this biomarker of exposure in the urine of industrially exposed workers and in turn predict the most plausible exposure scenarios. The models were constructed from in vivo experimental data in rats and then extrapolated from animals to humans after assessing and adjusting the most sensitive model parameters as well as species specific physiological parameters. Repeated urinary voids from workers exposed to polycyclic aromatic hydrocarbons (PAHs) have been collected over the course of a typical workweek and during subsequent days off work; urinary concentrations of 3-OHBaP were then determined. Based on the information obtained for each worker (BaP air concentration, daily shift hours, tasks, protective equipment), the time courses of 3-OHBaP in the urine of the different workers have been simulated using the PBPK and toxicokinetic models, considering the various possible exposure routes, oral, dermal and inhalation. Both models were equally able to closely reproduce the observed time course of 3-OHBaP in the urine of workers and predicted similar exposure scenarios. Simulations of various scenarios suggest that the workers under study were exposed mainly by the dermal route. Comparison of measured air concentration levels of BaP with simulated values needed to obtain a good approximation of observed time course further pointed out that inhalation was not the main route of exposure for most of the studied workers. Both kinetic models appear as a useful tool to interpret biomonitoring data of PAH exposure on the basis of 3-OHBaP levels.

Relevance of urinary 3-hydroxybenzo(a)pyrene and 1-hydroxypyrene to assess exposure to carcinogenic polycyclic aromatic hydrocarbon mixtures in metallurgy workers

OBJECTIVES

In metallurgy, workers are exposed to mixtures of polycyclic aromatic hydrocarbons (PAHs) in which some compounds are carcinogenic. Biomonitoring of PAH exposure has been performed by measuring urinary 1-hydroxypyrene (1-OHP), a metabolite of pyrene which is not carcinogenic. This study investigated the use of 3-hydroxybenzo(a)pyrene (3-OHBaP), a metabolite of benzo(a)pyrene (BaP) which is the main carcinogenic component in PAHs, to improve carcinogen exposure assessment.

METHODS

We included 129 metallurgy workers routinely exposed to PAHs during working hours. Urinary samples were collected at three sampling times at the beginning and at the end of the working week for 1-OHP and 3-OHBaP analyses.

RESULTS

Workers in anode production showed greater exposure to both biomarkers than those in cathode or silicon production, with respectively, 71, 40, and 30% of 3-OHBaP concentrations exceeding the value of 0.4 nmol mol(-1) creatinine. No difference was observed between the 3-OHBaP levels found at the end of the penultimate workday shift and those at the beginning of the last workday shift. Within these plants, the 1-OHP/3-OHBaP ratios varied greatly according to the workers' activity and emission sources. Using linear regression between these two metabolites, the 1-OHP level corresponding to the guidance value for 3-OHBaP ranged from 0.7 to 2.4 µmol mol(-1) creatinine, depending on the industrial sector.

CONCLUSIONS

This study emphasizes the interest of monitoring urinary 3-OHBaP at the end of the last workday shift when working week exposure is relatively steady, and the irrelevance of a single guideline value for 1-OHP when assessing occupational health risk.

Modeling of the internal kinetics of benzo(a)pyrene and 3-hydroxybenzo(a)pyrene biomarker from rat data

Measurements of 3-hydroxybenzo(a)pyrene (3-OHBaP) in urine has been proposed for the biomonitoring of exposure to benzo(a)pyrene (BaP) in workers. To allow a better understanding of the toxicokinetics of BaP and its key biomarker, a multicompartment model was developed based on rat data previously obtained by this group. According to the model, iv injected BaP is rapidly distributed from blood to tissues (t₁/₂ = 3.65 h), with particular affinity for tissue lipid components and liver and lung proteins. BaP is then rapidly distributed to lungs, where significant tissue uptake occurs, followed by the skin, liver, and adipose tissues. Once in liver, BaP is readily metabolized, and 3-OHBaP is formed with a t₁/₂ of 3.32 h. Lung metabolism of BaP was also accounted for, but its contribution to the whole kinetics was found to be negligible. Once formed, 3-OHBaP is distributed from blood to the various organs almost as fast as the parent compound (t₁/₂ = 2.26 h). In kidneys, 3-OHBaP builds up as a result of the smaller rate of 3-OHBaP urinary excretion (t₁/₂ = 4.52 h) as compared with its transfer rate from blood to kidneys (t₁/₂ = 27.8 min). However, overall clearance of 3-OHBaP from the body is driven by its biliary transfer from liver to the gastrointestinal tract (t₁/₂ = 3.81 h). The model provides a great fit to independent sets of published data on 3-OHBaP urinary excretion time course (χ² = 0.019). This model proves useful in establishing the main biological determinants of the overall kinetics of these compounds.

Highly sensitive routine method for urinary 3-hydroxybenzo[a]pyrene quantitation using liquid chromatography-fluorescence detection and automated off-line solid phase extraction

Many workers and also the general population are exposed to polycyclic aromatic hydrocarbons (PAHs), and benzo[a]pyrene (BaP) was recently classified as carcinogenic for humans (group 1) by the International Agency for Research on Cancer. Biomonitoring of PAHs exposure is usually performed by urinary 1-hydroxypyrene (1-OHP) analysis. 1-OHP is a metabolite of pyrene, a non-carcinogenic PAH. In this work, we developed a very simple but highly sensitive analytical method of quantifying one urinary metabolite of BaP, 3-hydroxybenzo[a]pyrene (3-OHBaP), to evaluate carcinogenic PAHs exposure. After hydrolysis of 10 mL urine for two hours and concentration by automated off-line solid phase extraction, the sample was injected in a column-switching high-performance liquid chromatography fluorescence detection system. The limit of quantification was 0.2 pmol L(-1) (0.05 ng L(-1)) and the limit of detection was estimated at 0.07 pmol L(-1) (0.02 ng L(-1)). Linearity was established for 3-OHBaP concentrations ranging from 0.4 to 74.5 pmol L(-1) (0.1 to 20 ng L(-1)). Relative within-day standard deviation was less than 3% and relative between-day standard deviation was less than 4%. In non-occupationally exposed subjects, median concentrations for smokers compared with non-smokers were 3.5 times higher for 1-OHP (p<0.001) and 2 times higher for 3-OHBaP (p<0.05). The two urinary biomarkers were correlated in smokers (ρ=0.636; p<0.05; n=10) but not in non-smokers (ρ=0.09; p>0.05; n=21).

Evaluation of DNA adducts, DNA and RNA oxidative lesions, and 3-hydroxybenzo(a)pyrene as biomarkers of DNA damage in lung following intravenous injection of the parent compound in rats

Biomarkers of exposure and effect were assessed in 40 male Sprague-Dawley rats injected intravenously with 40 micromol/kg of benzo(a)pyrene (BaP) to determine which biomarkers are more representative of BaP-induced DNA damage in lung. Lung, liver, blood, and urine were collected at t = 2, 4, 8, 16, 24, 33, 48, 72, and 360 h postdosing. Specific BaP-diol epoxide (BPDE)-DNA adducts, 8-hydroxy-7,8-dihydro-2'-deoxyguanosine (8-OHdGuo), were measured in lung, liver, and mononucleated blood cells by high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). Urinary 8-OHdGuo and 8-hydroxy-7,8-dihydroguanosine (8-OHGuo) were also determined by HPLC-MS/MS, and urinary 3-hydroxybenzo(a)pyrene was measured by HPLC/fluorescence. Between 2 and 72 h postdosing, BPDE-DNA adducts were significantly increased in lung, liver, and mononucleated blood cells of BaP-treated rats as compared to controls, with the highest levels found in lung. 8-OHdGuo levels also increased in lung of BaP-treated rats with values reaching statistical significance at 2, 8, and 16 h postinjection. No influence of BaP treatment was found on 8-OHdGuo and 8-OHGuo urinary excretions. BPDE-DNA adducts in lung were strongly correlated to urinary 3-OHBaP (r = 0.936 and p < 0.001) and to a lesser extent to blood BPDE-DNA adducts (r = 0.636 and p < 0.001), the latter of which were correlated to each other (r = 0.573 and p = 0.002). Urinary 3-OHBaP and BPDE-DNA adducts in mononucleated blood cells appear as relevant biomarkers of BaP genotoxic exposure and are highly promising for health risk assessment in humans.

Amounts and proportion of administered pyrene dose excreted as urinary 1-hydroxypyrene after dietary exposure to polycyclic aromatic hydrocarbons

Although urinary 1-hydroxypyrene (1-OHP) is the most relevant parameter for assessing exposure to polycyclic aromatic hydrocarbons, the inability to further elucidate the intra- and inter-individual variability, specificity and kinetics makes it difficult to enhance its value as an exposure predictor. Therefore, this human control study examined the excretion kinetics of urinary 1-OHP after consuming barbecued meat. Two feeding experiments were conducted, with doses of 15 and 30 g of barbecued meat per kg of body weight for experiments 1 and 2, respectively. All voided urine was collected for 7 days and analyzed for 1-OHP. In both experiments, the amounts of urinary 1-OHP excreted was significantly increased (P < 0.05) at 12 h post exposure but not at 12-24 h post exposure. Mean percentages of administered pyrene doses excreted as urinary 1-OHP at 0-12 h and 12-24 h post exposure were 3.80 and 0.61% in experiment 1 and 1.66 and 0.38% in experiment 2. Excretion ratio was inversely related to dose. A pattern of diurnal fluctuation (P < 0.05) in 1-OHP excretions was also identified. That is, 1-OHP excretions were smaller in the first half of the day (~0:00-12:00) than in the last half of the day (~12:00-24:00). This study demonstrated that, even at large dietary doses, most of the total urinary excretion of 1-OHP occurs within 12 h. Thus, subjects of occupational or environmental studies need only recall their diets for the current or previous day to diminish the influence from dietary pyrene.

3-Hydroxybenzo(a)pyrene as a biomarker of dermal exposure to benzo(a)pyrene

The aim of this study was to determine the percutaneous absorption flux of BaP (20 microg/cm(2) in ethanol) and the usefulness of urinary 3-OHBaP as a bio-indicator of dermal exposure to BaP. The percutaneous absorbed dose and absorption flux were estimated by comparison with intravenous administration of BaP (0.01 and 0.05 mg/kg in Cremophor) as reference way. A percutaneous absorption flux of 0.37 microg/cm(2)/h was determined by killing groups of rats, following exposure time of 4.5 and 24 h. [(14)C] skin content was 3.1 microg/cm(2), after 24 h exposure to BaP. Total urinary 3-OHBaP accounted for 0.4% of the real absorbed dose, which was fourfold higher than the percentage of an intravenous dose excreted as 3-OHBaP. This finding reveals that percutaneous absorption of BaP, based on the ratio of urinary excretion of 3-OHBaP following percutaneous exposure compared to percutaneous absorption following intravenous administration of BaP, is overestimated in the rat. In vitro, BaP was intensively metabolised by rat skin. Unchanged BaP and 3-OHBaP in receptor fluid accounted for 50 and 30% of the total radioactivity. This percutaneous first past effect of BaP in rats could, in part, explain the higher urinary excretion ratio of 3-OHBaP compared to the value based on intravenous administration of BaP. Conversely, BaP was largely lower metabolised as 3-OHBaP during percutaneous absorption by humans, so BaP absorption flux should be overestimated to a lesser extent in humans than in rats.

Evaluation of a battery of Salmonella typhimurium tester strains for biomonitoring of mutagenic polycyclic aromatic hydrocarbons, nitroarenes and aromatic amines

Various combinations of Salmonella typhimurium tester strains and S9 mix for bioactivation (TA98+S9 mix, TA98S; YG1041+S9 mix, YG1041S) and strain YG1041 in the absence of S9 mix (YG1041) were used to evaluate the mutagenic activity of eight polycyclic aromatic hydrocarbons (PAHs), seven nitroarenes (NAs) and seven aromatic amines (AAs). Three cigarette smoke extracts and two extracts of smokers' urine (SUE) were also included. Urinary mutagenicity was then determined on 31 individuals, potentially exposed to PAHs, for 0 h, 7 h, 12 h and 24 h. Concentrations of urinary 1-hydroxypyrene (1OHP) and 3-hydroxybenzo[a]pyrene (3OHBaP), the levels of atmospheric pyrene (Py) and benzo[a]pyrene (BaP), and particulate concentrations in air (AP) were also measured. PAHs could be detected by TA98S and YG1041S, with TA98S being more sensitive than YG1041S. While NAs could be detected by all combinations, YG1041 and YG1041S were more sensitive than TA98S. Although both YG1041S and TA98S could detect AAs, YG1041S was more sensitive than TA98S. Cigarette smoke extract contained mutagenic AAs and NAs, but AAs were the only mutagenic compounds detected in the extracts of smokers' urine. The concentrations of 1OHP (7 h and 12 h) were significantly higher than those at 0 h, but no difference could be detected with 3OHBaP. Correlations were found between Py and 1OHP (7 h and 24 h) and between BaP and 3OHBaP concentrations (7 h, 12 h and 24 h). A significantly elevated urinary mutagenicity was detected with YG1041S at 7h in the group of smokers. A good correlation was determined between AP and the test results with TA98S (7 h) and with YG1041 (0 h and 7 h). Urinary 1OHP correlated with the test results with YG1041S (0 h, 7 h and 12 h) while 3OHBaP correlated with those obtained with YG1041S (7 h). Overall, 21/31 individuals were occupationally exposed to AAs, 15/31 individuals were exposed to NAs, and 2/31 were exposed to PAHs as indicated by the Salmonella mutagenicity assay. The urine mutagenicity test was not effective at monitoring occupational exposure to PAHs. However, the correlation with AP implied the presence of unknown mutagenic atmospheric substances that could modulate the urinary mutagenicity.