Arsenic soil ingestion

Ljung, K., Selinus, O., Otabbong, E., andBerglund, M. (2006). Metal and arsenic distribution in soil particle sizes relevant to soil ingestion by children. Appl. Geochem. 21, 1613—1624. 

Bioavailability and Risk of Arsenic Exposure by the Soil Ingestion Pathway... 

Incidental soil ingestion by children is an important pathway in assessing public health risks associated with exposure to arsenic-contaminated soils. Incidental ingestion of soil represents the principal direct pathway for exposure to nondietary sources of As in contaminated areas. The importance of soil ingestion by children as a health issue has been reported by numerous researchers and fully illustrates the importance of this pathway in terms of subsequent chemical exposure (4-8). 

METHODS FOR DETERMINING BIOAVAILABILITY OF ARSENIC FROM SOIL INGESTION... 

Chapters 4, 5, and 6 cover human exposure to arsenic ingestion, inhalation, and dermal absorption. Metabolism of arsenic in the body depends on the chemical species of arsenic absorbed. Association of arsenic in human urine is the most suitable biomarker to assess exposure to arsenic. Risk characterization and bioavailability of arsenic upon soil ingestion is critically evaluated. Arsenic occurrence in the United States is compared to that in Taiwan for health implications. Factors that may interfere with arsenic removal during water treatment, as well as significant diurnal and seasonal variations in arsenic concentration in U.S. surface water supplies, are thoroughly discussed. 

Of the metals considered, cadmium and mercury are the most toxic to humans and are also bioaccumulative historically, poisoning incidents by these metals has been via the contaminated foodstuffs pathway. Arsenic is less toxic than cadmium or mercury, as it is more easily eliminated from organisms, but is a more common contaminant and is often present at relatively high levels. In the developing world the most common pathway to humans is via drinking water, but in the UK soil ingestion is of more concern. Chromium is extremely mobile... 

Home uses of arsenic-treated lumber are being phased out in the United States, but it is estimated that approximately 60 billion board feet of arsenic-treated lumber is still in use in the United States as of 2002, about enough to cover half the state of California with a deck two inches thick. Several state agencies have recommended that treated lumber on which children may play should be coated periodically with paint or other sealer to reduce hand contact and subsequent ingestion of arsenic. Those who choose to remove arsenic-treated decks or other structures may want to test the soil underneath to see if levels exceed state standards. 

Okrent and Xing (1993) estimated the lifetime cancer risk to a future resident at a hazardous waste disposal site after loss of institutional control. The assumed exposure pathways involve consumption of contaminated fruits and vegetables, ingestion of contaminated soil, and dermal absorption. The slope factors for each chemical that induces stochastic effects were obtained from the IRIS (1988) database and, thus, represent upper bounds (UCLs). The exposure duration was assumed to be 70 y. Based on these assumptions, the estimated lifetime cancer risk was 0.3, due almost entirely to arsenic. If the risk were reduced by a factor of 10, based on the assumption that UCLs of slope factors for chemicals that induce stochastic effects should be reduced by this amount in evaluating waste for classification as low-hazard (see Section 7.1.7.1), the estimated risk would be reduced to 0.03. Either of these results is greater than the assumed limit on acceptable risk of 10 3 (see Table 7.1). Thus, based on this analysis, the waste would be classified as high-hazard in the absence of perpetual institutional control to preclude permanent occupancy of a disposal site. 

Study on the soil-to-carrot uptake rate of As 34 (hioavailahility). Inorganic arsenic species were prevalent in soil. The ingestion of the potentially toxic inorganic arsenic via consumption of carrots grown in soil contaminated at 30pgAsg was conservatively estimated at 37 pg per week... 

Bioaccessibility testing of metals using the physiologically based extraction test (PBET) or the simplified bioaccessibility extraction test (SBET) has gained popularity in recent years in the UK (Nathanail McCaffrey 2002). The aim of the tests is to simulate the extraction of metals into solution in the juices in the stomach, upper and lower intestine (PBET) and in the stomach (SBET). The empirical test results should only be applied to the ingestion of soil or dust pathways. The tests have been calibrated for lead, and to a lesser degree for arsenic. Risk assessors should be satisfied that the health criteria... 

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