Health risks of typical soil and groundwater organic pollutants in greenhouse vegetables growing area

Nine groups of groundwater samples and two groups of soil samples were collected in greenhouse areas in Shijiazhuang and analyzed for organic pollutants. Two groups of groundwater samples were sampled from drinking water wells and seven groups from irrigation wells. Soil samples were surface soils inside greenhouse and farmland outside greenhouse respectively. About 20 organic pollutants were detected in the surface soil, 8 of which also occurred in groundwater with PAEs as the main pollutant. There were obvious differences in the pollutant species and content from surface soils between outside and inside greenhouse. There were more OCPs in farmland soils than inside greenhouse soils and the reverse was the general trend for PAEs and PAHs. Based on standard health risk assessments, the target pollutants for health risk were dieldrin, benzo a-anthracene, benzo a-pyrene, indeno 1,2,3-cd-pyrene, dimethyl phthalate and dibutyl phthalate. The test results showed that the characteristics of the above organic pollutants in surface soils and groundwater systems in studying area posed health risks to greenhouse farmers and sensitive population. The exploration assessment of cultivated greenhouse soils followed the four steps of Health Risk Assessment certified by US EPA. The steps include data collection and evaluation, toxicity assessment, exposure assessment and risk attribute. The major exposure pathways included oral ingestion of soil and drinking groundwater. Then oral ingestion of soil was subdivided into oral ingestion of greenhouse surface soil and that of surface soil of farmland outside greenhouse. The results of the health risk assessment showed that in this area, both non-carcinogenic risk and carcinogenic risk of greenhouse farmers were at acceptable levels. The contribution rate of dibutyl phthalate to non-carcinogenic risk, which was the most dangerous non-carcinogenic risk contaminant, was nearly 84.2%, while that of dieldrin was only 15.8%. Also the contribution rate of dieldrin to carcinogenic risk, which was the most dangerous carcinogenic contaminant, was 51.35%. That of benzo a-pyrene, the second largest rate, was about 39.75%. Then those of benzo a-anthracene and indeno 1,2,3-cd-pyrene were the least, with contribution rates of only 4.89% and 4.01%. Drinking groundwater was the main pathway for non-carcinogenic risk, with a contribution rate of about 94.42%. The contribution rates of the other two exposure pathways (oral ingestion of greenhouse surface soil and that of surface soil in farmland outside greenhouse) to non-carcinogenic risk were 5.578% and 0.002%, respectively. Oral ingestion of surface soil in farmland outside greenhouse was the main pathway for carcinogenic risk, with a contribution rate of about 47.14%. The contribution rates of the other two exposure pathways (drinking groundwater and oral ingestion of greenhouse surface soil) to carcinogenic risk were 33.2% and 19.66%, respectively.