Selective Soil Particle Adherence to Hands: Implications for Understanding Oral Exposure to Soil Contaminants

Abstract

Over the last 30 years, there has been extensive research designed to quantify the extent of oral bioavailability and bioaccessibility of organic and inorganic contaminants in soil. One aspect of this research is the soil particle size selected to represent environmental exposures, which may affect study results and comparability across studies. Different research groups have studied soil particle sizes ranging from <45 μm to <2000 μm. This article reviews the historical and technical considerations that pertain to the selection of an appropriate particle size fraction for evaluating the relative oral bioavailability of chemicals from soil, which include (1) how the resultant data will be used in human health risk assessment, (2) soil fractions historically used in oral bioavailability studies, (3) studies of soil adherence to human hands, (4) the distribution of contaminants in soils as a function of particle size, and (5) the effect of differential bioavailability as a function of soil particle size and geochemical matrix. These factors are first discussed from a general perspective, applicable to all contaminants in soil, and then more specifically for polycyclic aromatic hydrocarbons (PAHs) in soil. Based on this review, a specific soil particle size of <150 μm is recommended for future studies on the oral bioavailability and bioaccessibility of PAHs in soil.

Comparison of arsenic bioaccessibility in housedust and contaminated soils based on four in vitro assays

“…For soils, the b250 μm particle fraction has been used in bioaccessibility analysis because this fraction most likely adheres to children's hands (USEPA, 2007). However, in this study, particle size b 150 μm was used for housedust (Ruby and Lowney, 2012). In short, difference in contamination source, higher TOC, lower Fe content, and particle size all contributed to higher As bioaccessibility in housedust.…”

Estimating Children’s Soil/Dust Ingestion Rates through Retrospective Analyses of Blood Lead Biomonitoring from the Bunker Hill Superfund Site in Idaho

“…U.S. EPA’s in vitro assay measures the solubility, or bioaccessibility, of lead in soil and dust samples to estimate ( in vivo ) bioavailability. The 80 mesh sieve for both soil and dust was initiated at the BHSS in 1974 and focuses analyses on particle sizes more likely to adhere to hands and other surfaces and be ingested by children (Panhandle District Health Department et al 1986; Ruby and Lowney 2012). Archived soil and dust samples collected between 1986 and 2002 were retrieved from storage.…”

‘Towards a unified approach for the determination of the bioaccessibility of organic pollutants’

“…b 250 μm (Calabrese et al, 1996;Stanek, 2000), b50 μm (Ljung et al, 2006) and b 45 μm (Siciliano et al, 2010). After a comprehensive review of data from the last 30 yrs Ruby and Lowney (2012) proposed a value of b150 μm, this incorporated the fraction most likely to adhere to hands and that containing the majority of the sorbed pollutant.…”