Baseline Soil Dioxin Levels from Sites Where Municipal Solid Waste Incineration Construction Is Planned throughout China: Characteristics, Sources and Risk Assessment

The determination of baseline dioxins levels in soils is fundamental for the quantitative assessment of the net environmental and health impacts of municipal solid waste (MSW) incineration plants, which remains unexplored. Therefore, this study develops a Chinese baseline soil dioxins database (covering 918 soil samples from 292 pre-construction MSW incineration plants nationwide during 2016-2020) to thoroughly explore the baseline contamination characteristics and health risks of dioxins in soils. The empirical results show that (1) for concentration levels, the baseline international toxic equivalency (I-TEQ) concentrations vary from 0.0015 to 32 ng I-TEQ/kg, which are close to or even lower than those in most existing studies and show significant heterogeneity across provinces; (2) for dioxins homolog, highly chlorinated dioxins (i.e., PCDDs) are the dominant contributor to the total dioxins in soils (contributing 54.30% of the total I-TEQ concentrations), implying that dioxins in baseline soils often have an atmospheric fingerprint; and (3) for health risks, the carcinogenic risk and non-carcinogenic risk of dioxins in soils are mostly below acceptable levels, close to or even lower than the results of previous studies. Despite these results being considered as quite preliminary, they have certain implications for local authorities. Future studies can expand the size of the database and the generalizability of the results, and if necessary, establish a long-term dynamic monitoring of dioxins in soils for systematically evaluating the net impact of MSW incineration on environment and human health.