Oral Bioavailability, Bioaccessibility, and Dermal Absorption of PAHs from Soil—State of the Science

Abstract

This article reviews the state of the science regarding oral bioavailability, bioaccessibility, and dermal absorption of carcinogenic polycyclic aromatic hydrocarbons (cPAHs) in soil by humans, and discusses how chemical interactions may control the extent of absorption. Derived from natural and anthropomorphic origins, PAHs occur in a limited number of solid and fluid matrices (i.e., PAH sources) with defined physical characteristics and PAH compositions. Existing studies provide a strong basis for establishing that oral bioavailability of cPAHs from soil is less than from diet, and an assumption of 100% relative bioavailability likely overestimates exposure to cPAHs upon ingestion of PAH-contaminated soil. For both the oral bioavailability and dermal absorption studies, the aggregate data do not provide a broad understanding of how different PAH source materials, PAH concentrations, or soil chemistries influence the absorption of cPAHs from soil. This article summarizes the existing studies, identifies data gaps, and provides recommendations for the direction of future research to support new default or site-specific bioavailability adjustments for use in human health risk assessment.

Particle-Size Distribution and Bioaccessibility of Metals-Loaded in Street Dust of Urban Center in Southwest Nigeria

“…The relative oral bioavailability (bio accessibility) of each metal in dust particles was determined using the In vitro method as described by Ruby et al [16] and Oomen et al [23]. The method is a two-step physiological based extraction test that investigates the solubility of metals in laboratory test.…”

“…According to Ruby et al [15], some metals and their compounds are not readily soluble; therefore toxicity tests based on their solubility may overestimate the health risk associated with them. Bioaccessibility is a closely related term which refers to the fraction of contaminant that is dissolved in the digestive fluids and assumed to be available for absorption and bioavailable [16]. Similarly, it has also been reported that total concentration of metals can reflect the pollution level of dust, but cannot predict its bioavailability [17].…”

“…It is therefore imperatively necessary to investigate speciation of metals in dust; this is to enable us determine accurately the bioaccessibility and risks posed by individual metals. To date, a lot of investigators have studied human bioaccessibility of metals using several methods and tools; including in vivo and in vitro digestion models of [16,[18][19][20][21][22][23]. The in vivo methods (animal models) depend on the toxico-kinetic profile of the chemical of interest, chemical concentrations in dust and sensitivity of analytical methods.…”

Management Options for Contaminated Urban Soils to Reduce Public Exposure and Maintain Soil Health

“…Although these screening levels are exceeded, multiple research studies suggest that PAHs in soil have soil ingestion bioaccessibility <50%, and this finding indicates that bioaccessibility assessment may be included in site‐specific risk assessments rather than relying on total contamination concentration only (Ruby et al, 2016). Bioaccessibility refers to the amount of contaminant extracted in a laboratory test (in vitro) that can be used to estimate the contaminant uptake that would occur in an animal study (Ruby et al, 2016). Bioavailability refers to the amount of contaminant measured in an animal uptake study (in vivo), and this contaminant amount can be described in absolute concentration or a concentration relative to a standard contaminant material (Ruby et al, 2016).…”

“…Bioaccessibility refers to the amount of contaminant extracted in a laboratory test (in vitro) that can be used to estimate the contaminant uptake that would occur in an animal study (Ruby et al, 2016). Bioavailability refers to the amount of contaminant measured in an animal uptake study (in vivo), and this contaminant amount can be described in absolute concentration or a concentration relative to a standard contaminant material (Ruby et al, 2016). With well‐established regression equations between bioaccessibility and bioavailability data, bioaccessible tests can be used to help predict contaminant uptake in a variety of new soils without conducting in vivo studies for each new soil.…”