Refining health risk assessment by incorporating site-specific background concentration and bioaccessibility data of Nickel in soil

Abstract

Risk assessment of Nickel (Ni) in a brownfield site contaminated was refined by incorporating the site-specific background level (SSBL) derived using multiple lines of evidence technology and bioaccessibility measured by the Unified Bioaccessibility Method (UBM) and Inhalation Bioaccessibility Method (IBM). The results revealed that the SSBL was 80mg/kg, which was much higher than the general soil screening value (GSSL) (50mg/kg) and more than two times regional background level reported for Tianjing (33mg/kg). The average bioaccessibility for the gastric and intestinal phases was 24.2% (8.6%-54.4%) and 12.6% (7.7%-17.1%), respectively. In simulated lung fluid, only 2.1% (1.0%-4.6%) of Ni in the soil particle was bioaccessible. The amount of samples exceeding the acceptable level was reduced by 50% when SSBL, other than GSSL, was used as the screening value. Moreover, the site-specific target level (SSTL) under acceptable risk level was increased from 94mg/kg to 283mg/kg when bioaccessibility was considered, and the amount of samples above SSTL was reduced to 10%. The study indicated that incorporating site-specific background levels and bioaccessibility data of contaminants in a given site has the potential to support health risk assessment decisions and can reduce the remediation cost greatly.

Keywords: Background level; Health risk; Multiple lines of evidence technology; Oral bioaccessibility; Respiratory bioaccessibility.