| ObjectivesThe aims of the present study were to perform the mornitoring of levels of di (2-ethylhexyl) phthalate (DEHP) in the water samples and 5 PAEs in the soil samples which were collected from the exposure region and the control region; to measure the levels of oxidative stress and the extent of DNA oxidative damage by the biomarkers including levels of MDA, SOD and GSH-Px in sera samples and 8-OHdG in the urine samples from the workers who engaged plastic recycle and plastic reclaim, and to analyze the risk factors relating to these biomarkers.Methods1. The study population:The exposure region was a plastic recycling centers in the Southern city where has had over 20 years in plastics recycle and the control region was 50 km far away from exposure region where is without known sources of pollution-related. The 157 workers in exposure region and 157 residents in control region were selected based on gender and age matched, and the basic information was collected by uniform questionnaire, i.e., the name, age, alcohol and cigarette consumption, living habits or behaviors, occupational career and other related generic information.2. Sample collection and DEHP analysis in water and soil samples: In summer of 2008, the multiple mixture sampling method was used to collect the 10 separate farming layer soil samples from 0 to 20cm in exposure and control regions. The column chromatography and gas chromatography technique were applied to determine the concentrations of DEHP and other PAEs in soil samples. In autumn of 2009, multiple mixture sampling method was used to collect water samples from surface layer of river bank, and raw water, product water and end use of water supply system in this city. In the villages in exposure and control regions, the 3 household well water samples were randomly collected and mixture into 1 sample, separately, and the total is 15 water samples. The 3 to 10 water samples were collected from un-control effluence in exposure and control regions. The total is 45 water samples. The eTrex Venture GPS navigation instrument was applied to locate sampling site and geological data. The concentrations of DEHP in water samples were analysed by solid-phase extraction and gas chromatography technique.3. Oxidative damage analysis on stress index: The chemical colorimetry was used to determine serum malondialdehyde (MDA), glutathione peroxides (GSH-Px) and superoxide dismutase (SOD) in exposure and control population, which is served as an oxidative stress index of DNA damage. The Electrochemical-High Performance Liquid Chromatography was applied to test the level of urinary 8-OHdG, which is served as an index of the extent of DNA oxidative damage.4. Database establishment and statistical analysis: The spatial database was established by using ArcGIS9.2 software, with linkage between the water quality data and geological data. The GIS topology technique was used to map sampling sites and protract specific map on DEHP determination. The demography data and related medical index in exposure and control were analyzed by using significance test. Logistic regression was performed to analyze the DNA damage.Results1. Concentrations of DEHP in water samples: The different DEHP levels in water samples were identified. The average DEHP concentrations in water samples from the polluted river section (2.05μg/L) were 6.4 times of that from the control section (0.32μg/L). Average DEHP concentrations in the pond water (135.68μg/L) and the well water (14.20μg/L) water samples from the exposure region were 18 times and 215 times of those (0.79μg/L and 0.37μg/L) in the control region, respectively. The DEHP concentrations in un-control effluent samples ranged from 0.36 to 161.86μg/L. The concentrations of DEHP from samples of waterworks in raw water, product water and water in end point of use ranged from 0.23 to 2.36μg/L.2. Concentrations of DEHP in soil samples: The DBP (0.94-24.09 mg/kg) and DEHP (0.85-37.23 mg/kg) were indentified in all soil samples from exposure and control regions. In five PAEs determined, the DEHP and dibutyl phthalate (DBP) concentration is the highest one, following by diethyl phthalate (DEP), di-n-octyl phthalate (DnOP) and dimethyl phthalate (DMP). The average of 5 PAEs in soil of exposure region was 1-19 times of that in control region. The contents of DBP (mean: 9.46 mg/kg) and DEHP (mean: 13.07 mg/kg) in exposure region soil were the 19 and 16 times of that in control region. The detection rate of DBP (range: 0.94-24.09 mg/kg) and DEHP (range: 0.85-37.23 mg/kg) in the exposed soil are 100 percent.3. The level of oxidative stress in population: the medians of serum SOD in exposed population and control population were 111.80 U/ml (range: 31.71-167.69 U/ml) and 124.16 U/ml (range: 78.88-181.46 U/ml) respectively, with a significant difference between the two groups (P<0.01). The medians of serum GSH-Px in exposed population and control population were 252.41 U (range: 140.49-386.53 U) and 225.58 U (range: 68.12-359.94 U), respectively, with a significant difference between the two groups (P<0.01). The medians of serum MDA in exposed people and the control people were 3.85 nmol/ml and 3.19 nmol/ml, respectively, with a significant difference between the two groups (P<0.01). The results from multivariate logistic regression showed that occupational exposure were a risk factor of serum SOD decreasing. The risk of serum SOD of increasing in women was 1.717 times that of men (95% CI: 1.088-2.711, P<0.05). The risk of serum GSH-Px increasing in occupational exposure was 2.06 times that of generic population (95% CI: 1.312-3.224, P<001); the risks of serum MDA increasing of alcohols consumption and occupational exposure were 2.13 times (95% CI: 1.057-4.275, P<0.05) and 2.50 times of (95% CI: 1.554-4.022, P<0.01) non-drinkers and non-occupational exposure. The results from multiple indicate that these three compound levels in body were affected by occupational exposure, and mean that the oxidative DNA damage may presented in exposure population.4. Oxidative DNA damage state in population: the medians of urinary 8-OHdG in exposed and control population were 366.84μmol/mol Cr and 254.09μmol/mol Cr, separately, with a significant difference in two group (P<0.01). Logistic regression analysis showed that occupational exposure was an important factor impacting urinary 8-OHdG level. The risk of increasing urinary 8-OHdG in occupational exposure was 2.610 times that of in non-occupational exposure (95%CI: 1.639 - 4.156, P<0.01).ConclusionThe study results showed that DEHP exposure concentrations in water and soil samples in plastic recycling centers where occupational workers lived were higher than that where the control residents live. The demological study results showed that the occupational exposure were the main factor which affects the levels of serum SOD, MDA, GAH-Px and urine 8-OHdG Although Urine 8-OHdG levels may be affected by other pollutants from plastic recycling center, the exposure population has shown the oxidative DNA damage. |
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