Incorporating oral, inhalation and dermal bioaccessibility into human health risk characterization following exposure to Chromated Copper Arsenate (CCA)-contaminated soils.

Exposure to potentially toxic metal(loid)s (PTMs) in soil may happen via ingestion, inhalation, and dermal pathway. A more accurate risk characterization should consider PTM bioavailability. Using ten soil samples collected in the Montreal area (Canada) near CCA-treated utility poles, this study aims to characterize non-carcinogenic and carcinogenic human health risks associated with As, Cr, Cu, Pb, and Zn through a multi-pathway exposure approach. This innovative study incorporates, for the first time, the bioaccessible fraction of the metal(loid)s for three exposure routes and two different scenarios. For the residential and industrial scenarios, the oral and dermal pathways yielded a hazard index (HI) much higher than 1 with and without bioaccessibility considerations (range 1.7 - 349 without bioaccessibility and 0.8-134 with bioaccessibility), whereas the inhalation pathway caused a lower hazard (HI < 1). For the dermal pathway, the hazard quotient was higher when bioaccessibility of field-collected samples was considered due to inherent assumptions from the US EPA soil approach to calculate the dermal dose. For carcinogenic risk, As and Pb were the most significant contributors to risk for the oral pathway, followed by the same elements for the dermal pathway. The overall carcinogenic risk was higher than the acceptable risk ( > 10-4) with and without bioaccessibility considerations (range 1.9E-4 - 9.6E-3 without bioaccessibility and 6.8E-5 - 3.8E-3 with bioaccessibility). Bioaccessibility tests provide a more accurate assessment of exposure to PTMs compared to total concentrations in soils.

Using in vitro bioaccessibility to refine estimates of human exposure to PAHs via incidental soil ingestion.

PAH bioaccessibility in contaminated soil was determined using the organic physiologically based extraction test with the inclusion of a sorption sink. Silicone cord was incorporated into the assay in order to overcome the limited capacity of the in vitro medium to accommodate desorbable PAHs. Initially, silicone cord sorption efficacy was determined by assessing sorption kinetics using PAH-spiked sand (phenanthrene, pyrene and benzo[a]pyrene; 10-1000mgkg(-1)). Irrespective of PAH and concentration, >95% of the initial PAH mass partitioned into the silicone cord within 12h although rates were lower at higher concentration and with increasing hydrophobicity. When PAH bioaccessibility was assessed in contaminated soil (n=18), contamination source (i.e. pyrogenic versus petrogenic) influenced PAH bioaccessibility. Individual PAH bioaccessibility ranged up to 81.7±2.7% although mean values ranged from 2.1 (acenaphthalene) to 20.8% (benzo[k]fluoranthene) with upper 95% confidence intervals of the means of 4.5 and 28.3% respectively. Although a PAH in vivo-in vitro correlation is yet to be established, bioaccessibility approaches incorporating sorption sinks represent a robust approach for estimating PAH bioavailability as the desorbable fraction may be a conservative measure of the absorbable fraction.

Health assessment based on exposure to microplastics in tropical agricultural soil.

Microplastic (MP) pollution of agricultural soils has caused global alarm over its widespread distribution and potential risks to terrestrial ecosystems and human health. This study assessed human health based on exposure to soil MPs through a comprehensive investigation of the factors influencing their occurrence and spatial distribution on Hainan Island, South China. The results showed that the abundance of soil MPs was 1128.6 ± 391.5 items·kg-1, whereas the normalized abundance of MPs based on using a power-law function was 19,261.4 items·kg-1. Regarding the extent of population exposure to agricultural soil MPs, the average daily exposure dose (pADD) model revealed that using mass as an indicator to assess the health risks associated with MP intake is more reliable than using abundance. However, abundance-based exposure assessments are also relevant because MPs with smaller particle sizes are more harmful to human health. Moreover, for adults, the normalized pADD values based on abundance and mass were 1.68E-02 item MPs·kg BW-1·d-1 and 7.23E-02 mg MPs·kg BW-1·d-1, respectively. Although the multidimensionality of MPs should be further aligned and quantified, the preliminary findings of this study contribute to the development of human health risk assessment frameworks for soil MPs.