Biomarkers For Monitoring Coke Oven Workers Exposure To Coke Oven Emissions

Coke oven emissions (COEs) are formed when coal is pyrolysed at high temperature into coke. The emissions are complex mixtures of dusts, vapors, and gases that include numerous nocuous chemicals, such as polycyclic aromatic hydrocarbons (PAH), nitrosamines, coal tar, arsenic compounds, and benzene which are known carcinogens or potentially carcinogenic chemicals. Long-term COEs exposure of humans can result in many health problems, and cancer is the major concern for the public exposed to COEs. United States Environmental Protection Agency classified COEs as a known human carcinogen. Coke oven workers have a high risk of possible exposure to COEs during coking process. Identification of biomarkers of exposure, effect, and susceptibility for occupational COEs exposure may provide technical support for regularly monitoring the exposure levels of COEs and the extent of health damage in coke oven workers, and provide scientific reference for reducing exposure to COEs and related adverse effects.A molecular epidemiology study of seventy-eight male workers selected from a coke oven plant in northern China was carried out. The aim of the study is to investigate the biomarkers related to COEs exposure in coke oven workers. All the workers were classified into two groups, namely COEs exposure group and control group, based on historic exposure data from mandatory regular air sample analysis. The exposure group consisted of 47 coke oven workers and the control group consisted of 31 subjects who were from the distillery, maintenance sections and offices. The participants aged 36 to 44years and employed for at least 10 years were currently working in the coke oven plant. General information of workers was collected by questionnaire. As an important way of assessing COEs exposure, atmospheric PAH concentrations were determined at various locations in the coking area (topside area and cokeside area) and in the non-coking area (distillery area administrative area) using high performance liquid chromatography with diode array detector / fluorescence detector (HPLC-DAD/FLD). As internal exposure of PAH, urinary 1-hydroxyrene (1-OHP) was also determined simultaneously by alkaline hydrolysis and HPLC. As candidates of biomarker of effect for COEs exposure, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), serum malondialdehyde (MDA), serum glutathione S-transferase (GST), micronucleated binucleated cells (BNMN) and silver-staining nucleolar organiser regions (AgNORs) in peripheral blood lymphocyte were measured using high performance liquid chromatography with electrochemical detection (HPLC-ECD), MDA colorimetric activity assay kit, GST colorimetric activity assay kit, cytokinesis-block micronucleus method (CBMN), and silver staining the cultured lymphocytes, respectively. In addition, genetic polymorphisms of cytochrome P4501 A1 (CYP1A1), glutathione S-transferase Ml (GSTM1) and glutathione S-transferase T1 (GSTT1), which are candidates of biomarker of susceptibility for COEs exposure, were identified using the method based on polymerase chain reaction (PCR).The results showed: (1) The concentrations of PAH in the air determined on the coking area were higher than at the non-coking workplaces. As the parameter of external exposure of PAH, the concentrations of carcinogenic benzo (a) pyrene (B [a] P) were 0.33μg/m~3 on the topside and 0.1μg/m~3 at the cokeside. These concentrations were 8.25 and 2.50 times of that measured at the office place (0.04μg/m~3), respectively. The concentration of urinary 1-OHP was markedly increased in the exposed [5.7(1.4-12.0) umol/mol creatinine] than in the controls [3.0(0.5-6.4)] (P < 0.05). After categorizing by smoking status, significant increase of urinary 1-OHP was found only in smokers among coke oven workers compared to control workers (P = 0.029). (2) The levels of urinary 8-OHdG, BNMN in lymphocytes, and serum GST were markedly increased in the exposed [1.9(1.4-15.4) umol/mol creatinine, 6(2-8) ‰, and 22.1(14.9-31.2) U/1, respectively] than in the controls [1.3(1.0-4.0), 2(0-4), and 13.1(9.5-16.7), respectively](P < 0.001, P < 0.05, P < 0.05). AgNORs (I/S) in lymphocytes was significantly decreased in the exposed [0.064(0.054-0.063)] than in the controls [0.079(0.070-0.083)] (P < 0.001). The above results appeared to be modified by smoking. Statistically significant differences between exposure group and control group existed only in smokers for BNMN (P = 0.002), AgNORs (P < 0.001) and GST (P < 0.001), and in non-smokers for 8-OHdG (P = 0.005). No significant difference of serum MDA level was found between coke oven workers [2.56(1.84-3.63) nmol/ml] and control subjects [2.99(2.44-4.27)] (P > 0.005). (3) There are significantly positive correlations between serum GST activity and urinary 1-OHP (r_s = 0.31, P = 0.005, n = 78), as well as serum GST activity and lymphocytic BNMN (r_s = 0.296, P = 0.009, n = 78), and significantly negative correlations between AgNORs (I/S) in lymphocytes and urinary 1-OHP (r_s = -0.507, P < 0.001, n = 50), as well as AgNORs (I/S) in lymphocytes and serum GST activity (r_s= -0.527, P < 0.001, n = 50). (4) In 78 subjects, genotype frequencies of GSTM1 null and GSTTl null were 32.89 % and 15.79 % respectively, the frequencies of CYP1A1 MspI (T/T), CYP1A1 MspI (T/C), and CYP1A1 MspI (C/C) genotypes were 36.51 %, 42.86 %, and 20.63 % respectively, and the frequencies of CYP1A1 Ile/Val (A/A) and CYP1A1 Ile/Val (A/G) genotypes were 77.14 % and 22.86 %, respectively. We found no subjects with CYP1A1 Ile/Val (A/G) genotype. (5) The median levels of 1-OHP, 8-OHdG, GST, BNMN and AgNORs were 4.27 μmol/mol creatinine, 1.8 μmol/mol creatinine, 16.72 U/ml, 4‰ and 0.063, respectively. Multivariate logistic regression was used to estimate the odds ratios (OR) and corresponding 95 % confidence intervals (CI) for related variables of biomarkers, which have higher levels than the median level. The multivariate logistic regression analysis showed that coke oven workers were at the higher risk of having elevated levels of 1-OHP (OR = 3.03; 95% CI, 1.00-9.09), 8-OHdG (OR = 4; 95% CI, 1.02-16.67), GST (OR = 14.28; 95% CI, 2.38-50), BNMN (OR = 3.57; 95% CI, 1.08-12.5) and AgNORs (OR = 0.03; 95% CI, 0.003-0.25). High body mass index (BMI) is independent factor of having reducing effects on the 8-OHdG levels. No effects of GSTM1, GSTTl, and CYP1A1 genotype on the levels of urinary 1-OHP, urinary 8-OHdG, serum GST, lymphocytic BNMN, and lymphocytic AgNORs were found.The present study suggested: (1) COEs exposure led to increase in internal andexternal PAH burden. The exposure level of PAH can be used as indication of the extent of COEs exposure in the workplace of coking, but cannot directly replace the monitoring for exposure to COEs. It is necessary to monitor the exposure levels of other constituents derived from COEs. Serum GST and lymphocytic AgNORs might be considered as biomarkers of PAH exposure according to their high correlation. (2) COEs exposure led to elevated oxidative stress and genetic damage, as well as decreasing cell immunity function. Lymphocytic MN, urinary 8-OHdG, and lymphocytic AgNORs might be used as biomarkers of effect for monitoring occupational exposure to COEs, and the consequences of the changes in these biomarkers, such as risk of cancer, shoud be paid more attention in health damage monitoring and prevention for coke oven workers. (3) Whether genetic polymorphism of GSTM1, GSTT1, and CYP1A1 genes could be used as biomarkers of susceptibility for occupational exposure to COEs needs further study.Compared with the reported molecular epidemiology studies on COEs exposure, the current study design had two outstanding traits: (1) Age and employment time of subjects had been strictly restricted to reduce the effect of viables (age and employment time) on study results and to increase chance of observing mild damage, which is difficult to detect under the condition of short-term COEs exposure. (2) Three new indexes to estimate COEs exposure were introduced, of which serum GST and lymphocytic AgNORs have not been reported as indexes of evaluation of COEs exposure and effect. Only one paper tried to evaluate the health risk of COEs exposure by measuring the urinary 8-OHdG. In addition, three meaning results were obtained in the study: (1) The health damage of COEs exposure and subsequently likely increasing cancer risk were evaluated from aspects of genetic damage, oxidative stress and cell immunity function. (2) Through analyzing the association between PAH exposure and body damage of workers, a viewpoint was introduced that the monitoring for COEs exposure cannot directly be replaced by evaluation of PAH exposure and it is necessary to monitor the exposure levels of other constituents derived from COEs. (3) Serum GST and lymphocytic AgNORs could be used as biomarkers for monitoring PAH exposure or COEs exposure, and their use as biomarkers in evaluation of other occupational contaminations exposure warrants study.