Soil ingestion

Overall protectiveness Human health protection Direct contact/soil ingestion... 

Cap reduces direct contact risk and soil ingestion risk to less than 1 xlfb6... 

Apartment housing Soil ingestion by children 1.2xl05 Dt... 

The transfer of PBBs from soil to plants is so low, e.g., Table III and References (6,29), that the only important issue In the agricultural scenario appears to be soli ingestion (and possibly ingestion of groundwater) by cattle. Based on an estimated half-life, tj/2> in beef of 120 days (30) an estimated mass of fat per animal, M, of 67 kg and a soil Ingestion rate, Mg, of 0.72 kg/day (31), a reasonably conservative soll-to-fat bioconcentration factor can be obtained ... 

Where Cf FDA guideline for PBB concentration In fat (26), the SPPPLV for the soil ingestion pathway is then... 

The residential soil concentration PPLV is governed by children s soil ingestion, estimated at 10-4 kg/day (32). 

Bames RM. 1990. Childhood soil ingestion How much dirt do kids eat Anal Chem 62 1023-1033. 

Binder S, Sokal D, Maugham D. 1986. Estimating soil ingestion The use of tracer elements in estimating the amount of soil ingestion by young children. Arch Environ Health 41 341-345. 

Calabrese EJ, Stanek EJ III, Pekow P, et al. 1997. Soil ingestion estimates for children residing on a Superfund site. Ecotoxicol Environ Saf 36 258-268. 

Clausing P, Brunekreef B, van Wijen JH. 1987. A method for estimating soil ingestion by children. Int Arch Occup Environ Health 59 73-82. 

LaGoy P. 1987. Estimated soil ingestion rates for use in risk assessment. Risk Analysis 7 355-359. 

The US-EPA Exposure Factors Handbook (US-EPA 1997), first published in 1989, provides a summary of the available data on consumption of drinking water consumption of fmits, vegetables, beef, dairy products, and fish soil ingestion inhalation rates skin surface area soil adherence lifetime activity patterns body weight consumer product use and the reference residence (data that are available on residence characteristics that affect exposure in an indoor environment). 

The US-EPA Child Specific Exposure Factors Handbook (US-EPA 2006), first published in 2002, consolidates all children s exposure factors data into one document. The document provides a summary of the available and up-to-date statistical data on various factors assessing children s exposures. These factors include drinking water consumption soil ingestion inhalation rates dermal factors including skin area and soil adherence factors consumption of fruits, vegetables, fish, meats, dairy products, homegrown foods, and breast milk activity patterns body weight consumer products and life expectancy. 

The ingestion of soil is a potential source of human exposure to chemical substances. The exposure is usually expressed as an average amount of soil ingested per unit time (e.g., mg/day). 

WHO (1994) has specified the daily amount of soil ingested as 20 mg/day. This is a median value from Health and Welfare Canada (the national Department of Health of the Government of Canada). It has not been specified whether this standard value is valid for adults or for children. 

According to US-EPA (1997), data on soil ingestion rates for children who deliberately ingest soil (pica) are limited however, it does not appear to be a very common behavior. This conclusion is based on the seven key smdies used by US-EPA to estimate the daily soil intake in children, where only a single child, out of more than 600 examined, exhibited pica behavior directed toward sod. The results for this child are shown in Table 7.5. 

Table 7.6 summarizes soil ingestion recommendations in the Exposure Factors Handbook (US-EPA 1997). 

Recently, a U.S. study on daily soil ingestion estimates for children at a Superfund site has been published (Stanek and Calabrese 2000). The estimates are based on the results of an earlier investigation (Calabrese et al. 1997 - cited in ECETOC 2001), but with the use of improved methods. An average (mean) daily soil intake of 31 mg/day and a median of 17 mg/day were estimated. Furthermore 95th percentiles for soil intake during 7, 30, 90, and 365 days of 133, 112, 108, and 106 mg/day, respectively, were estimated. 

Stanek 111, E.J. and E.J. Calabrese. 2000. Daily Soil Ingestion Estimates for Children at a Superfund Site. Risk Anal. 20 627-635. 

As an alternative to the assumption of a one-time exposure for 1,000 h at the time of facility closure, permanent occupancy of a disposal site following loss of institutional control could be assumed (see Section 7.1.3.4). The assumption of chronic lifetime exposure would affect the analysis for hazardous chemicals that induce deterministic effects only if estimated intakes due to additional pathways, such as consumption of contaminated vegetables or other foodstuffs produced on the site, were significant. Based on the results for lead in Table 7.8, an intake rate from additional pathways of about 50 percent of the assumed intake rate by soil ingestion, inhalation, and dermal absorption would be sufficient to increase the deterministic risk index above unity. The importance of additional pathways was not investigated in this analysis, but they clearly would warrant consideration. The increase in exposure time during permanent occupancy does not otherwise affect the analysis for chemicals that induce deterministic effects, provided RfDs are appropriate for chronic exposure, because chronic RfDs incorporate an assumption that the levels of contaminants in body organs relative to the intake rate (dose) are at steady state. 

Van Wijnen JH, Clausing P, BrunekreefB. 1990. Estimated soil ingestion by children. Environ Res 51 147-162. 

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