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Bioaccessibility of heavy metals in soils of contaminated sites and its application on health risk assessment for children

Absrtact	Harmful substances in soil and dust may enter into human body through direct inhalation, digestion, and dermal contact causing adverse health effects. Owing to the difference in physical and physiological behaviors, infants and toddlers are not only easier to expose to toxic substances in soil, but also less tolerant to toxic substances than adults. Therefore, toxic substances will pose higher risk to children. We have already acquired the soil/dust ingestion data of 0~6 years old children and some parameters pertaining to dermal contact in the past programs, as well as establishing a good communication channel with the US Environmental Protection Agency (USEPA). This year, the program will focus on supplementing the data of localized exposure parameters, such as bioaccessibility of metals in soil; therefore, we plan to collect soil samples in twenty four soil contaminated sites. To assess the suitability of in vitro assays to predict Cd bioavailability in contaminated soils by correlating Cd bioaccessibility with Cd- relative bioavailability in contaminated soils. Then, apply in the bioaccessibilities of different hazardous elements in contaminated soil for estimating the health risk of containment soil. In this study, the range of pH value, broad ranges in the contents of organic matter and clay of soil samples were shown among the 53 contaminated soils. The pH value ranged from 4.24 to 7.38. The content of organic matter ranged from 0.48 to 6.06%. The content of clay ranged from 6.48 to 42.3%. Based on the in-vitro digestion method, i.e., simple bioaccessibility extraction test (SBET), the average bioaccessibility of Cd, Cr, Cu, Ni, Pb, and Zn is 63%, 17%, 66%, 23%, 50%, and 35%, respectively.Cd-RBA was comparable at 34.46±18.87% based on mouse kidney. The results of multiple linear regression model showed that the types and motilities of the metals, pH, organic matter content, and clay content of soil had significant impacts on the SBET bioaccessibility of metals. SBET had better correlated with 0.1 N HCl extraction and PBET. Our data suggested that inexpensive SBET assay might be useful in estimating the metals bioaccessibility in contaminated soils.
Keyword	Local exposure factors, Bioaccessibility, Bioavailability, Health risk assessment

Absrtact

Harmful substances in soil and dust may enter into human body through direct inhalation, digestion, and dermal contact causing adverse health effects. Owing to the difference in physical and physiological behaviors, infants and toddlers are not only easier to expose to toxic substances in soil, but also less tolerant to toxic substances than adults. Therefore, toxic substances will pose higher risk to children. We have already acquired the soil/dust ingestion data of 0~6 years old children and some parameters pertaining to dermal contact in the past programs, as well as establishing a good communication channel with the US Environmental Protection Agency (USEPA). This year, the program will focus on supplementing the data of localized exposure parameters, such as bioaccessibility of metals in soil; therefore, we plan to collect soil samples in twenty four soil contaminated sites. To assess the suitability of in vitro assays to predict Cd bioavailability in contaminated soils by correlating Cd bioaccessibility with Cd- relative bioavailability in contaminated soils. Then, apply in the bioaccessibilities of different hazardous elements in contaminated soil for estimating the health risk of containment soil. In this study, the range of pH value, broad ranges in the contents of organic matter and clay of soil samples were shown among the 53 contaminated soils. The pH value ranged from 4.24 to 7.38. The content of organic matter ranged from 0.48 to 6.06%. The content of clay ranged from 6.48 to 42.3%. Based on the in-vitro digestion method, i.e., simple bioaccessibility extraction test (SBET), the average bioaccessibility of Cd, Cr, Cu, Ni, Pb, and Zn is 63%, 17%, 66%, 23%, 50%, and 35%, respectively.Cd-RBA was comparable at 34.46±18.87% based on mouse kidney. The results of multiple linear regression model showed that the types and motilities of the metals, pH, organic matter content, and clay content of soil had significant impacts on the SBET bioaccessibility of metals. SBET had better correlated with 0.1 N HCl extraction and PBET. Our data suggested that inexpensive SBET assay might be useful in estimating the metals bioaccessibility in contaminated soils.

Keyword

Local exposure factors, Bioaccessibility, Bioavailability, Health risk assessment