GIS-based approach to generate the bioaccessibility of soil heavy metals for human risk assessments: case study in Changhua farmlands, Taiwan

Abstract

Considering the bioaccessibility of soil heavy metals for human health assessment can prevent overestimation for policymakers. However, the complexity of soil properties and heavy metal concentrations makes it challenging to establish a general dataset for bioaccessibility in assessments. Soil heavy metals commonly occur in agricultural regions due to both agricultural and industrial activities, posing high health risks for residents through soil exposure. In the past 10 years, the government in Taiwan has actively promoted soil remediation for agricultural heavy metal-polluted soils, completing remediation for more than 99% of polluted sites. However, conducting health risk assessments for remediated soils remains difficulty due to a lack of a general dataset for the bioaccessibility of common soil heavy metals. In this study, we conducted soil sampling from 98 sites located in agricultural regions with various soil properties. We first established regression relationships for the bioaccessibility of six common heavy metals: cadmium (Cd), lead (Pb), chromium (Cr), nickel (Ni), copper (Cu), and zinc (Zn), based on measured soil properties and heavy metal concentrations. Second, we performed GIS analysis to generate the bioaccessibility of heavy metals from a previous soil survey across all agricultural regions in Taiwan, using our established equations. Then, we conducted health risk assessments for residents at different stages of life (infants, children, teenagers, adults, and seniors) living in agricultural regions (i.e., Changhua farmlands) after soil remediation. Our results revealed high non-carcinogenic risks (hazard index > 1) for infants and children but high carcinogenic risks (total cancer risk index > 1e-4) for seniors. Our study established a GIS-based approach for estimating the bioaccessibility of soil heavy metals based on actual measurements, providing an easier way for health risk assessments of soil heavy metal pollution.   Keywords: SBET, human health, farmland, heavy metal pollution, GIS