Percutaneous uptake, distribution, and excretion of pyrene in rats

Mineral oil in food, cosmetic products, and in products regulated by other legislations

For a few years, mineral oils and their potential adverse health effects have been a constant issue of concern in many regulatory areas such as food, cosmetics, other consumer products, and industrial chemicals. Analytically, two fractions can be distinguished: mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH). This paper aims at assessing the bioaccumulative potential and associated histopathological effects of MOSH as well as the carcinogenic potential of MOAH for consumer-relevant mineral oils. It also covers the absorption, distribution, metabolism, and excretion of MOSH and MOAH upon oral and dermal exposures. The use and occurrence of consumer-relevant, highly refined mineral oils in food, cosmetics and medicinal products are summarized, and estimates for the exposure of consumers are provided. Also addressed are the challenges in characterizing the substance identity of mineral oil products under REACH. Evidence from more recent autopsy and biopsy studies, along with information on decreasing food contamination levels, indicates a low risk for adverse hepatic lesions that may arise from the retention of MOSH in the liver. With respect to MOAH, at present there is no indication of any carcinogenic effects in animals dermally or orally exposed to highly refined mineral oils and waxes. Such products are used not only in cosmetics but also in medicinal products and as additives in food contact materials. The safety of these mineral oil-containing products is thus indirectly documented by their prevalent and long-term use, with a simultaneous lack of clinical and epidemiological evidence for adverse health effects.

Polycyclic Aromatic Hydrocarbons: Part II, Urine Markers

There has been increasing demand for simple, rapid, highly sensitive, inexpensive yet reliable method for detecting predisposition to cancer. Human biomonitoring of exposure to the largest class of chemical carcinogen, polycyclic aromatic hydrocarbons (PAHs) that are rapidly transformed into detectable metabolites (eg, 1-hydroxypyrene), can serve as strong pointers to early detection of predisposition to cancer. Given that any exposure to PAH is assumed to pose a certain risk of cancer, several biomarkers have been employed in biomonitoring these ninth most threatening ranked compounds. They include metabolites in urine, urinary thioethers, urinary mutagenicity, genetoxic end points in lymphocytes, hemoglobin adducts of benzo(a)pyrene, PAH-protein adducts, and PAH-DNA adducts among others. In this chapter, the main focus will be on the urine metabolites since urine samples are easily collected and there is a robust analytical instrument for the determination of their metabolites.

Polycyclic Aromatic Hydrocarbons: Part I. Exposure

Polycyclic aromatic hydrocarbons (PAH) comprise the largest class of cancer-causing chemicals and are ranked ninth among chemical compounds threatening to humans. Although interest in PAH has been mainly due to their carcinogenic property, many of these compounds are genotoxic, mutagenic, teratogenic, and carcinogenic. They tend to bioaccumulate in the soft tissues of living organisms. Interestingly, many are not directly carcinogenic, but act like synergists. PAH carcinogenicity is related to their ability to bind DNA thereby causing a series of disruptive effects that can result in tumor initiation. Thus, any structural attribute or modification of a PAH molecule that enhances DNA cross linking can cause carcinogenicity. In part I, we review exposure to these dangerous chemicals across a spectrum of use in the community and industry.

Determination of polycyclic aromatic hydrocarbons in milk samples by high-performance liquid chromatography with fluorescence detection

This paper describes a high-performance liquid chromatographic (HPLC) method for the determination of polycyclic aromatic hydrocarbons (PAHs) in milk samples. The method involves a liquid-liquid extraction procedure after saponification of milk samples with sodium hydroxide. Reproducible determination with highly sensitive detection was attained by HPLC with fluorescence detection using 1,2-bis(9-anthryl)ethane as an internal standard. The detection limits of 12 kinds of PAHs ranged from 1.3 to 76 ng/kg milk at a signal/noise ratio of 3. By the proposed method, the presence of 12 and 11 kinds of PAHs could be confirmed in commercial milk and human milk samples, respectively. The average concentrations of total PAHs (mean+/-SD, micro g/kg) were found to be 0.99+/-0.37 for commercial milk (n=14), 2.01+/-0.30 for infant formula (n=3) and 0.75+/-0.47 for human milk (n=51). High correlation coefficients between the concentrations of total PAHs and triglyceride were observed for commercial milk (r=0.659) and human milk (r=0.645).

Biological versus ambient exposure monitoring of creosote facility workers

Traditional methods for monitoring occupational creosote exposure have focused on inhalation. However, there is evidence that dermal exposure contributes importantly to total systemic dose, as measured by biological monitoring methods. This study was conducted to further characterize the relationships between inhalation and dermal exposures to creosote, and to compare traditional ambient exposure monitoring versus biological monitoring in 36 creosote-exposed wood treatment workers. Full-shift personal air samples were obtained, along with post-shift and next-day urine measurements for 1-hydroxypyrene. There was little or no correlation between airborne measures and urinary 1-hydroxypyrene (r2 = 0.05 to 0.35). More than 90% of 1-hydroxypyrene could be attributed to dermal exposure. These data indicate that traditional monitoring methods may be inappropriate for creosote workers, raising concerns about the adequacy of methods currently mandated by the Occupational Safety and Health Administration.

Physiologically-based pharmacokinetic modeling of pyrene in the rat

The objective of the present study was to develop a physiologically-based model to simulate the oral and i.v. pharmacokinetics of pyrene in the rat. The physiologically-based pharmacokinetic (PBPK) model for pyrene consisted of the following tissue compartments: liver, lungs, adipose tissue, slowly perfused tissues, and richly perfused tissues interconnected with arterial and venous blood pools. The tissue:blood partition coefficients required for the pyrene PBPK model were estimated by equilibrium dialysis. Using perfusion-limited descriptions for tissue uptake and previously determined in vitro-derived hepatic metabolism rate constants (V(max) and K(m)), the PBPK model predicted a faster clearance of pyrene than that suggested by the experimental data. The biological basis of PBPK model then provided an opportunity to refine the estimate of V(max), and to explore and uncover additional mechanistic determinants of pyrene disposition in vivo. Accordingly, the in vitro V(max) had to be lowered by about a factor of 10 to adequately simulate experimental data on pyrene pharmacokinetics. Further, the model simulations could be matched with the experimental data on tissue concentrations of pyrene only with the considerations of (i) diffusion-limited uptake in slowly perfused tissues and adipose tissue, and (ii) binding to proteins in metabolizing tissues (lungs and liver). The present study successfully integrated the available data on oral and i.v. pharmacokinetics of pyrene using a physiological model framework, and identified several mechanistic data gaps that should be addressed by future research efforts.

Methods for routine biological monitoring of carcinogenic PAH-mixtures

The ability of a biomarker to provide an assessment of the integrated individual dose following uptake through multiple routes is especially valuable for mixtures of polycyclic aromatic hydrocarbons (PAH), due to methodological and practical difficulties of collecting and analysing samples from the various environmental compartments like air, water and soil and various media such as diet, cigarette smoke and workroom air. Since 1980, a large variety of novel approaches and techniques have been suggested and tested, e.g. urinary thioethers, mutagenicity in urine, levels of PAH or PAH-metabolites in blood and urine and methods for determination of adducts in DNA and proteins. Two approaches are more frequently reported: PAH-DNA-adduct monitoring in blood cells and urinary 1-hydroxypyrene monitoring. A large research effort has been made to use the extent of binding of PAH to DNA as a biomarker of exposure. The 32P-post-labeling assay detects the total of aromatic DNA-adducts and the adduct level in white blood cells is claimed to be an indicator of the biological effect of the PAH-mixture. However, the levels of aromatic DNA-adducts may be subject to appreciable analytical and biological variation. The present technical complexity of the method makes it more convenient for research applications than for routine application in occupational health practice. Pyrene is a dominant compound in the PAH mixture and is mainly metabolised to the intermediary 1-hydroxypyrene to form 1-hydroxypyrene-glucuronide, which is excreted in urine. Since the introduction of the determination of 1-hydroxypyrene in urine as a biomarker for human exposure assessment in 1985, many reports from different countries from Europe, Asia and America confirmed the potential of this novel approach. The conclusion of the first international workshop on 1-hydroxypyrene in 1993 was that urinary 1-hydroxypyrene is a solid biological exposure indicator of PAH. Studies with a comparison of several biomarkers confirmed that 1-hydroxypyrene in urine is a valid and sensitive indicator of exposure. Periodical monitoring of 1-hydroxypyrene appears to be a powerful method in controlling occupational PAH-exposure in industries. The reference level and the biological exposure limit of 1-hydroxypyrene in urine are discussed.

Pharmacokinetics of inhaled pyrene in rats

Male Wistar rats were exposed to micronized aerosol concentrations of a 14C-labeled model polycyclic aromatic hydrocarbon (pyrene) at 200, 500, and 800 mg/m3 for a period of 95 min. Both the 14C label and free pyrene were monitored in the blood, urine, and feces. At the termination of the blood sampling, three of the six rats per dose group were killed and the distribution of [14C]pyrene to eight major tissues was analyzed. The analysis of blood concentration data using a one-compartment pharmacokinetic model revealed that the uptake and elimination kinetic parameters were dose dependent, for both total radioactivity (pyrene plus metabolites) and for pyrene per se, over the range of exposures used in this study. The ratio of the percent excreted via the urinary and fecal routes, collected over a 5-d period postexposure was about 1.0 at each exposure level.