Exposure to bromodichloromethane (BDCM), one of the most prevalent disinfection byproducts in drinking water, can occur via ingestion of water and by dermal absorption and inhalation during activities such as bathing and showering. The objectives of this research were to assess BDCM pharmacokinetics in human volunteers exposed percutaneously and orally to (13)C-BDCM and to evaluate factors that could affect disposition of BDCM. Among study subjects, CYP2E1 activity varied fourfold; 20% had the glutathione S-transferase theta 1-1 homozygous null genotype; and body fat ranged from 7 to 22%. Subjects were exposed to (13)C-BDCM in water (target concentration of 36 mug/l) via ingestion and by forearm submersion. Blood was collected for up to 24 h and analyzed for (13)C-BDCM by solid-phase microextraction and high-resolution GC-MS. Urine was collected before and after exposure for mutagenicity determinations in Salmonella. After ingestion (mean dose = 146 ng/kg), blood (13)C-BDCM concentrations peaked and declined rapidly, returning to levels near or below the limit of detection (LOD) within 4 h. The T(max) for the oral exposure ranged from 5 to 30 min, and the C(max) ranged from 0.4 to 4.1 ng/l. After the 1 h dermal exposure (estimated mean dose = 155 ng/kg), blood concentrations of (13)C-BDCM ranged from 39 to 170 ng/l and decreased to levels near or below the LOD by 24 h. Peak postdose urine mutagenicity levels that were at least twice that of the predose mean level occurred in 6 of 10 percutaneously exposed subjects and 3 of 8 orally exposed subjects. These results demonstrate a highly significant contribution of dermal absorption to circulating levels of BDCM and confirm the much lower oral contribution, indicating that water uses involving dermal contact can lead to much greater systemic BDCM doses than water ingestion. These data will facilitate development and validation of physiologically based pharmacokinetic models for BDCM in humans.

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Background Environmental, lifestyle, and occupational exposures on semen quality have been investigated in epidemiological studies with inconsistent results. Genetic factors involved in toxicant activation and detoxification have been examined in relation to the risk of outcomes such as cancer, cardiovascular, and neurologic disorders. However, the effect of common genetic variants in the metabolism of toxicants on semen quality parameters has rarely been evaluated. In this analysis, we evaluated functional SNPs of three genes of the glutathione-S-transferase (GSTM1, GSTT1, GSTZ1) enzyme family. Methods Participants were 228 presumed fertile men recruited as part of a community-based study. Semen outcome data from this study included total sperm count and concentration, sperm morphology, and sperm DNA integrity and chromatin maturity. DNA was obtained from 162 men from a mouth-rinse sample and genotyped for the presence of GSTT1-1 and GSTM1-1 null genotypes and the GSTZ1 SNPs at positions 94 (rs3177427) and 124 (rs3177429). We used multivariable linear regression to assess the relationship between each genotype and sperm outcomes. Results Overall, our results did not reveal a consistent pattern between GSTM1 and GSTZ genotypes and increased occurrence of adverse sperm outcomes. However, the GSTT1 non-null genotype yielded the coefficients with the largest magnitude for sperm count and sperm concentration (β= −0.528, 95% CI −1.238-0.199 and β= −0.353, 95% CI −0.708-0.001, respectively), suggesting that it might be adverse. Conclusions These results indicate that common polymorphisms in GST genes do not negatively impact sperm parameters in healthy men with good semen quality. Contrary to expectations, the GSTT1 non-null genotype was associated with reduced sperm concentration and count in semen. Further study with a larger study size and inclusion of gene-exposure interactions is warranted.

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Background: Wildland firefighters conducting prescribed burns are exposed to a complex mixture of pollutants, requiring an integrated measure of exposure. Objective: We used urinary mutagenicity to assess if systemic exposure to mutagens are higher in firefighters after working at prescribed burns versus after non-burn work days. Other biomarkers of exposure and oxidative stress markers were also measured. Methods: Using a repeated measures study design, we collected urine before, immediately after, and the morning after a work shift on prescribed burn and non-burn work days from 12 healthy subjects. Urines were analyzed for malondialdehyde (MDA), 8-isoprostane, 1-hydroxypyrene (OH-Pyrene), and mutagenicity in Salmonella YG1041 +S9. Particulate matter (PM2.5) and carbon monoxide (CO) measurements were collected by personal monitoring. Light-absorbing carbon (LAC) of PM2.5 was measured as a surrogate for black carbon exposure. Linear mixed-effect models were used to assess cross-work shift (pre- to post-work shift) changes in urinary biomarkers. Results: No significant differences occurred in creatinine-adjusted urinary mutagenicity across the work shift between burn days (48 samples) and non-burn day (21 samples). Firefighters lighting fires had a non-significant, 1.6-fold increase in urinary mutagenicity for burn- versus non-burn day exposures. Positive associations were found between cross-work shift (pre- to post-) changes in creatinine-adjusted urinary mutagenicity and MDA (p = 0.0010), OH-Pyrene (p = 0.0001), and mass absorption efficiency, which is the LAC/PM2.5 ratio (p = 0.2245), respectively. No significant effect of day type or work task on cross-work shift (pre- to post-) changes in MDA or 8-isoprostane was observed. Conclusion: Urinary mutagenicity may serve as a suitable measure of occupational smoke exposures among wildland firefighters, especially among those lighting fires for prescribed burns.

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Background: Deficiencies in microarray technology cause unwanted variation in the hybridization signal, obscuring the true measurements of intracellular transcript levels. Here we describe a general method that can improve microarray analysis of toxicant-exposed cells that uses the intrinsic power of transcriptional coupling and toxicant concentrationexpression response data. To illustrate this approach, we characterized changes in global gene expression induced in Salmonella typhimurium TA100 by 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), the primary mutagen in chlorinated drinking water. We used the co-expression of genes within an operon and the monotonic increases or decreases in gene expression relative to increasing toxicant concentration to augment our identification of differentially expressed genes beyond Bayesian-t analysis.

A systematic characterization of the cancerization field of esophageal carcinoma based on p53 protein accumulation has not been reported previously. The present report presents such a study based on 50 specimens of esophageal squamous‐cell carcinoma from northern China. To gain insight into the etiology of this disease among the 50 subjects, DNA was analyzed for a polymorphism of the aldehyde dehydrogenase‐2 (ALDH2) gene, which has been associated with increased risk for esophageal cancer among alcohol‐consuming patients in Japan. However, the frequency of this polymorphism among our subjects, 30% (15/50), was within published control frequencies for this allele, suggesting that this allele may not play a role in the etiology of esophageal cancer in this northern Chinese population. Immuno‐histochemical staining showed that 66% of the tumors were p53+. Of 420 pieces near or adjacent to p53+ tumors, p53+ cells were present among 64% of basal‐cell hyperplasia (BCH), 70% of dysplasia (DYS) and 88% of carcinoma in situ (CIS). Of 216 pieces near or adjacent to p53− tumors, p53+ frequencies were 25% of BCH, 25% of DYS and 0% of CIS. The proportion of BCH cells that were p53+ decreased at increasing distance from the tumor (p = 0.006). The sporadic distribution of p53+ cells and the distribution and frequency of p53+ precursor lesions support the view that accumulation of p53 protein is multifocal and occurs in precursor lesions in early stages of esophageal carcinogenesis. Int. J. Cancer 78:568–575, 1998. © 1998 Wiley‐Liss, Inc. + This article is a US Government work and, as such, is in the public domain in the United States of America.