Human health risk-based soil generic assessment criteria of representative perfluoroalkyl acids (PFAAs) under the agricultural land use in typical Chinese regions

Exposure risk assessment of representative phthalate acid esters and associated plastic debris under the agricultural land use in typical Chinese regions

Phthalate acid esters (PAEs) are frequently detected in the global environment and can cause potential health hazards. In this study, quantitative exposure risk assessment was undertaken to derive soil generic assessment criteria (GAC) for six representative PAEs under the agricultural land use in the evaluated Chinese regions, which coupled multi-media transport and human exposure models based on multiple exposure pathways including vegetables consumption, dermal absorption, ingestion of soil and dust, and the exposure from non-soil sources. It is identified that the PAEs in agricultural soil are dominated by DEHP and DnBP representing 72-96% of the total PAEs. The GAC for BBP and DEHP, calculated on the basis of region-specific exposure parameters and soil properties in various locations, are stringent, signifying greater potential health risks from exposure to them, warranting more rigorous contamination management. The proposed soil GAC for plastic debris are 100, 107, 73 and 88 mg kg-1 for Heilongjiang Province, Beijing City, Jiangsu and Guangdong Provinces respectively. Additionally, the potential risks of 1.68 × 10-6 and 7 × 10-6 are identified for BBP and DEHP in Guangdong Province as indicated by the exceedance of target risk level of 1 × 10-6, with the consumption of vegetables being the dominant contributor to the total estimated PAEs exposure. Overall, this methodology based on the coupled contaminant transport and exposure models incorporating region-specific data provides a technical framework to derive science-based soil GAC for representative PAEs for maintaining and assessing soil quality and food safety under the agricultural land use.

Coexisting ions and long-chain per- and polyfluoroalkyl substances (PFAS) inhibit the adsorption of short-chain PFAS by granular activated carbon

We assessed the competitive adsorption between long-chain and short-chain PFAS and the impact of coexisting ions to understand the mechanisms leading to the early breakthrough of short-chain PFAS from granular activated carbon (GAC) filters. Three pairs of short-chain and long-chain PFAS representing different functional groups were studied using GAC (Filtrasorb 400) in batch systems. In bisolute systems, the presence of long-chain PFAS decreased the adsorption of short-chain PFAS by 30-50% compared to their single solute adsorption capacity (0.22-0.31 mmol/g). In contrast to the partial decrease observed in bisolute systems, the addition of long-chain PFAS to GAC pre-equilibrated with short-chain PFAS completely desorbed all short-chain PFAS from GAC. This suggested that the outermost adsorption sites on GAC were preferentially occupied by short-chain PFAS in the absence of competition but were prone to displacement by long-chain PFAS. The presence of inorganic/organic ions inhibited the adsorption of short-chain PFAS (up to 60%) but had little to no impact on long-chain PFAS, with the inhibitory trend inversely correlated with Kow values. Study results indicated that the displacement of short-chain PFAS by long-chain PFAS and charge neutralization are important mechanisms contributing to the early breakthrough of short-chain PFAS from GAC systems.