[Show abstract][Hide abstract] ABSTRACT: Nitrotoluenes, such as 2-nitrotoluene, 2,4-dinitrotoluene (24DNT), and 26DNT, are carcinogenic in animal experiments. Humans are exposed to such chemicals in the workplace and in the environment. It is therefore important to develop methods to biomonitor people exposed to nitrotoluenes to prevent the potential harmful effects. For the present study, workers exposed to high levels of these chemicals were investigated. The external dose (air levels), the internal dose (urine metabolites), the biologically effective dose [hemoglobin (Hb) adducts and urine mutagenicity], and biological effects (chromosomal aberrations and health effects) were determined. Individual susceptibility was assessed by determining genetic polymorphisms of enzymes assumed to function in nitrotoluene metabolism, namely glutathione S-transferases (GSTM1, GSTT1, GSTP1), N-acetyltransferases (NAT1, NAT2), and sulfotransferases (SULT1A1, SULT1A2). The levels of urinary metabolites did not correlate with the air levels. The urinary mutagenicity levels determined in a subset of workers correlated with the levels of a benzylalcohol metabolite of DNT. The Hb-adducts correlated with the urine metabolites but not with the air levels. The frequency of chromosomal aberrations (gaps included) was increased (P < 0.05) in the exposed workers in comparison with a group of factory controls and correlated with the level of 24DNT Hb-adducts in young subjects (<31 years). The GSTM1-null genotype was significantly more prevalent in the controls than in the exposed group, which probably reflected an elevated susceptibility of the GSTM1-null genotype to adverse health effects of DNT exposure, such as nausea (odds ratio, 8.8; 95% confidence interval, 2.4-32.2). A statistically significant effect was seen for SULT1A2 genotype on a 24DNT Hb-adduct; GSTP1 genotype on a 2,4,6-trinitrotoluene Hb-adduct; and SULT1A1, SULT1A2, NAT1, GSTT1, and GSTP1 genotypes on chromosomal aberrations in the exposed workers.
[Show abstract][Hide abstract] ABSTRACT: Chloronitrobenzenes (CNBs) are important intermediates for the production of dyes, pesticides, rubber chemicals, and drugs. 2CNB and 4CNB are possible human carcinogens. Therefore, it is important to develop methods to biomonitor people exposed to these occupational and environmental pollutants. We developed a method to determine hemoglobin (Hb) adducts of CNBs. Nitrobenzenes and the resulting arylamines yield the same sulfinamide adducts. Therefore, after base hydrolysis of the isolated Hb the corresponding arylamines are released and quantified by GC-MS. The method was applied to monitor 39 Chinese workers exposed to CNB and 15 control workers from the same factory. The determined Hb adduct levels were compared to the measured air levels, the clinical blood and urine parameters, and health effects identified in the workers. The median Hb adduct levels resulting from exposure to 2CNB and 4CNB were 82.9 and 1013 pg/mg of Hb, respectively. The median air concentrations determined from personal samplers were 0.37 and 0.87 mg/m3 for 2CNB and 4CNB, respectively. The air levels did not correlate with the Hb adduct levels. The median Hb adduct levels were higher in workers with fatigue, eye irritation, splenomegaly, and cardiovascular effects. Most negative urinary clinical parameters were present at higher median Hb adduct levels. The clinical blood parameters decreased at higher adduct levels. The daily dose was estimated from the Hb adduct levels and used to estimate the cancer risk.
[Show abstract][Hide abstract] ABSTRACT: 2,4,6-Trinitrotoluene (TNT) is an important occupational and environmental pollutant. In TNT exposed humans, the notable toxic manifestations have included aplastic anemia, toxic hepatitis, cataract, hepatomegaly and liver cancer. Therefore, we developed methods to biomonitor workers exposed to TNT. The workers were employed in a typical ammunition factory in China. The controls were recruited from the same factory. We determined hemoglobin (Hb) adducts and urine metabolites of TNT. Hb-adducts of TNT, 4-amino-2,6-dinitrotoluene (4ADNT) and 2-amino-4,6-dinitrotoluene (2ADNT), and the urine metabolites of TNT, 4ADNT and 2ADNT were found in all the workers and in a few controls. 4ADNT was the main product. Although the levels of 2ADNT correlated well with 4ADNT, 2ADNT was not found in all the samples. Therefore, 4ADNT was the best marker of exposure for Hb-adducts and urine metabolites. The levels of the urine metabolites and Hb-adducts were related to the health status of the workers. The Hb-adduct 4ADNT was statistically significantly associated with risk of hepatomegaly, splenomegaly and cataract. The odds ratio (OR) for cataract, splenomegaly and hepatomegaly were 6.4 [95% confidence interval (CI) = 1.4-29.6], 9.6 (1.1-85.3) and 7.6 (1.3-43.7), respectively. No correlation was found between urine metabolites and health effects. These results were tested for confounding factors like age, workyears, smoker status, smoke years, cigarettes per day and hepatitis B status using stepwise forward logistic regression analysis. In the case of splenomegaly, hepatitis B status is a confounder. In the case of cataract, age is a confounder. The Hb-adduct, 4ADNT, is a good biomarker of exposure and biomarker of biological effect.
[Show abstract][Hide abstract] ABSTRACT: Nitrotoluenes are important intermediates in the chemical industry. 2,6-Dinitrotoluene (26DNT), 2,4-dinitrotoluene (24DNT) and 2-nitrotoluene are carcinogenic in animals and possibly carcinogenic in humans. It is therefore important to develop methods to biomonitor workers exposed to such chemicals. Hemoglobin (Hb) adducts of nitroarenes are established markers of the biological effective dose. We developed a method to measure Hb adducts in biological samples. Hb adducts were measured in rats after a single exposure (0.5 mmol/kg) of 24DNT, 26DNT, 2,4-toluenediamine (24TDA) and 26TDA. Hydrolysis of Hb from rats dosed with 24DNT yields, 4-amino-2-nitrotoluene (4A2NT) (16.3 nmol/g Hb), 24TDA (4.3 nmol/g Hb) and 4-acetylamino-2-aminotoluene (4AA2AT) (0.51 nmol/g Hb). Hydrolysis of Hb from rats dosed with 26DNT yields three amines, 2-amino-6-nitrotoluene (2A6NT) (2.5 nmol/g Hb), 26TDA (1.2 nmol/g Hb) and 2-acetylamino-6-aminotoluene (2AA6AT) (0.17 nmol/g Hb). A similar Hb adduct pattern was found in Chinese workers exposed to nitrotoluenes. With respect to 24DNT, 4A2NT was the predominant adduct, and the amount was approximately 24-fold higher than 24TDA. With respect to 26DNT, 2A6NT was the predominant adduct, and the amount was approximately 20-fold higher than 26TDA. With respect to the mononitrotoluenes, the Hb adduct of 2NT was present in the highest concentrations. Each worker was examined for adverse health effects linked to exposure to DNT. The health effects were compared with the Hb adduct levels using logistic regression analysis. The odds of suffering from inertia were 3.2 times higher [95% confidence interval (CI) = 1.8-5.8] when the level of 4A2NT Hb adducts increased by one log-unit. Similar odds ratios were observed with somnolence (3.1, CI = 1.4-6.9), nausea (2.4, CI = 1.3-4.3) and dizziness (5.5, CI = 1.3-24.2). These results inferred that quantification of DNT-Hb adducts provided an effective biomarker of toxicity and could be used to estimate the risk associated with a particular exposure to DNT.