Study on internal exposure of three typical halogenated hydrocarbons in blood of children near a chemical industrial park

Objective To investigate the internal exposure of trichloromethane, carbon tetrachloride, and trichloroethylene in school-age children near a chemical industrial park, and to analyze their effect on hematological indices.

Methods In 2016, a middle school located 1 km upwind of a chemical industrial park was selected as the exposure group, and a middle school located 25 km upwind of the chemical industrial park was selected as the control group. Students in the exposure group who met the inclusion and exclusion criteria were selected as the exposure group, and students of the same age and gender in the control group, according to the principle of 1∶1 matching, were selected as the control group by the cluster random sampling method. A total of 184 students were included. Ambient air, drinking water, and venous blood samples of students were collected to measure the concentrations of trichloromethane, carbon tetrachloride, and trichloroethylene, and the hematological indices of blood.

Results The detection rates of trichloromethane, carbon tetrachloride, and trichloroethylene in drinking water were significantly higher in the exposure group than those in the control group(P < 0.05). The internal exposure levels and detection rates of trichloromethane and carbon tetrachloride in blood samples in the exposure group were significantly higher than those in the control group(P < 0.05). The monocyte count and the concentrations of hemoglobin, albumin, and alanine aminotransferase in the exposure group were significantly lower than those in the control group, while the platelet count in the exposure group was significantly higher than that in the control group(P < 0.05). The detection risk of trichloromethane in blood samples in the exposure group was 3.13 times that in the control group(OR=3.13, 95% CI: 1.20, 8.15), and the detection risk of carbon tetrachloride was 7.02 times that in the control group(OR=7.02, 95% CI: 1.44, 34.34). After adjusting for age, gender, body mass index, and passive smoking, trichloromethane had a nonlinear effect on monocyte count, and carbon tetrachloride had a nonlinear effect on hemoglobin concentration(P < 0.05).

Conclusion The internal exposure levels and detection rates of trichloromethane and carbon tetrachloride in blood samples in the exposure group are significantly higher than those in the control group. Meanwhile, trichloromethane exposure is related to monocyte count, and carbon tetrachloride exposure is related to hemoglobin concentration.