Comprehensive assessment of soil and dust heavy metal(loid)s exposure scenarios at residential playgrounds in Beijing, China

Abstract

Small playgrounds situated within residential communities are popular recreational areas. However, heavy metal(loid)s (HMs) in soil or equipment dust may pose a public health risk. This study provides a comprehensive assessment of the health risk associated with HMs exposure at residential playgrounds in cities, a field that has not been thoroughly investigated previously. 70 soil and 70 equipment dust samples were collected from 30 urban and 40 suburban playgrounds in Beijing. Results indicated significant enrichment of Cu, As, and Ni in the soil with Enrichment Factors (EFs) >5 from both anthropogenic and lithogenic sources. Correlation analyses showed that the levels of Be, Cr, Mn, Co, Ni in soil and Be, Mn, As, Cd in dust were positively correlated with the distance to the nearest highway, with p-values < 0.01. Enrichment and correlation analyses contributed to a better understanding of the sources and transport pathways of HMs in urban environment. Based on a site-specific Conceptual Site Model (CSM), the carcinogenic risks (CRs) and Hazard Quotients (HQs) were quantified for residents as the ratio of HMs exposure to reference doses. Risk assessment indicated the mean predicted CR for children and adults exposed to soil was 3.75 × 10−6 and 5.29 × 10−6, respectively, while that at dust exposure scenarios was lower, at 2.47 × 10−6 and 3.49 × 10−6, respectively, all of which were at the upper end of U.S. EPA's acceptable criteria of 1 × 10−6 to 1 × 10−4. Among the HMs, As and Ni were identified as the priority control contaminants due to significant contribution to CRs. Furthermore, the spatial distribution revealed an increasing trend in health risk from the urban center to the suburbs. This study emphasizes the need for effective measures to mitigate potential health risk and enhance the safety of recreational areas, particularly for susceptible individuals.