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. 2020 May 20:718:134639.
doi: 10.1016/j.scitotenv.2019.134639. Epub 2019 Nov 22.

Ingestion and inhalation of metal(loid)s through preschool gardening: An exposure and risk assessment in legacy mining communities

Affiliations

Ingestion and inhalation of metal(loid)s through preschool gardening: An exposure and risk assessment in legacy mining communities

Iliana Manjón et al. Sci Total Environ. .

Abstract

Children residing in mining towns are potentially disproportionately exposed to metal(loid)s via ingestion and dust inhalation, thus, increasing their exposure when engaging in school or home gardening or playing outside. This citizen science study assessed preschool children's potential arsenic (As), cadmium (Cd), and lead (Pb) exposure via locally grown produce, water, incidental soil ingestion, and dust inhalation at four sites. Participants were trained to properly collect water, soil, and vegetable samples from their preschools in Nevada County, California. As, Cd, and Pb concentrations in irrigation sources did not exceed the U.S. EPA's maximum contaminant and action levels. In general, garden and playground As and Pb soil concentrations exceeded the U.S. EPA Regional Screening Level, CalEPA Human Health Screening Level, and California Department of Toxic Substances Control Screening Level. In contrast, all Cd concentrations were below these recommended screening levels. Dust samples (<10 μm diameter) were generated from surface garden and playground soil collected at the preschools by a technique that simulated windblown dust. Soil and dust samples were then analyzed by in-vitro bioaccessibility assays using synthetic lung and gastric fluids to estimate the bioaccessible fraction of As, Cd, and Pb in the body. Metal(loid) exposure via grown produce revealed that lettuce, carrot, and cabbage grown in the preschool gardens accumulated a higher concentration of metal(loid) than those store-bought nation-wide. None of the vegetables exceeded the respective recommendation maximum levels for Cd and Pb set by the World Health Organization Codex Alimentarius Commission. The results of this study indicate that consumption of preschool-grown produce and incidental soil ingestion were major contributors to preschool-aged children's exposure to As, Cd, and Pb. Traditionally, this level of site- and age-specific assessment and analyses does not occur at contaminated sites. The results of this holistic risk assessment can inform future risk assessment and public health interventions related to childhood metal(loid) exposures.

Keywords: Arsenic; Bioaccessibility; Cadmium; Children exposure assessment; Incidental soil ingestion; Inhalation; Lead; Mining waste; Plant uptake; Preschool gardening; Risk characterization.

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Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Figure 1.
Figure 1.
Schematic of a child’s multi-route exposure considered in this study.
Figure 2.
Figure 2.
Map of abandoned gold mines in Western Nevada County, CA. (Original map source: US Geological Survey). Approximate location of preschools are indicated.
Figure 3.
Figure 3.
Process of determining particle size distribution by ImageJ. (A) Environmental Scanning Electron Microscopy image of S1 playground dust sample viewed at 2,500× magnification. Yellow box indicates analyzed area. (B) Contrast and brightness adjustment for selected area. (C) Particle area analyzed. (D) Outlines of analyzed particles.
Figure 4.
Figure 4.
Garden irrigation water metal(loid) concentrations (μg L−1).
Figure 5.
Figure 5.
Metal(loid) concentrations (µg g−1) measured from garden and playground soil samples (< 63 μm). Note: The box represents the 25% to 75% range, the line in the box is the median, the whiskers are the 5% and 95%, and outliners are represented with circles.
Figure 6.
Figure 6.
Atmospheric metal(loid) concentrations (µg m−3) estimated from garden and playground dust samples (< 10 μm effective diameter).
Figure 7.
Figure 7.
As, Cd, and Pb concentrations in preschool garden produce (fresh weight – FW, µg g−1), Significant differences (p < 0.05) in mean metal(loid) concentrations between plants are denoted by different letters (e.g. mean As concentration in cilantro was only significantly different to that in carrot and lettuce).
Figure 8.
Figure 8.
Site-specific median Bioconcentration factors of metal(loid) per plant type.
Figure 9.
Figure 9.
Median bioconcentration factor of metal(loid) per plant type (across all sites).
Figure 10.
Figure 10.
Bioaccessible fraction (BAF) of metal(loid) determined by gastric (A) and lung (B, logarithmic scale) IVBA. Asterisk signifies significant difference at p-value < 0.05.
Figure 11.
Figure 11.
Percent contribution of exposure media to average daily dose (ADD) of As, Cd, and Pb for children of different exposure age groups: (A) 1 to < 2 yrs, (B) 2 to < 3 yrs, and (C) 3 to < 6 yrs. The value below each bar is the cumulative exposure to As, Cd, and Pb (mg kg−1 d−1) for a child of that age group.

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