Soil, lead concentrations

Outdoor lead dust was found to be a more potent contaminant of children s hands than indoor lead dust at day care centers in New Orleans boys, in general, had higher hand lead levels than girls. The conclusions were based on lead analysis of hand wipe samples taken before and after children played outdoors at four different day care centers (a private inner-city site, a private outer-city site, a public inner-city site, and a public outer-city site). The private inner-city site had a severely contaminated outdoor play area with measured soil lead concentrations ranging from 287 to 1,878 mg/kg. The outdoor play area at the public inner-city site, where children exhibited the lowest hand lead measurements of any site in the study, had been completely paved over with concrete or rubberized asphalt and had well-maintained equipment (Viverette et al. 1996). 

Baltrop D, Strehlow CD, Thorton I, et al. 1974. Significance of high soil lead concentrations for childhood lead burdens. Environ Health Perspect 7 75-82. 

Schmitt MDC, Trippler DL, Wachtler JN, et al. 1988. Soil lead concentrations in residential Minnesota as measured by ICP AES. Water Air Soil Pollut 39 157-168. 

Pbs=soil lead concentration PbD=dust lead concentration Pbw=water lead concentration PbA0=outside air lead concentration PbAI = inside air concentration PbF=food lead concentration T=relative time spent... 

In soils, lead concentrates in organic-rich surface horizons (NRCC 1973). In one instance, only 17 mg of soluble Pb/kg was found in soils 3 days after the addition of 2784 mg of lead (as lead nitrate)/kg (NRCC 1973). The estimated residence time of lead in soils is about 20 years complete turnover in topsoil is expected every few decades (Nriagu 1978a). In forest litter, however, the mean residence time of lead is lengthy estimates range from 220 years (Turner et al. 1985) to more than 500 years (Friedland and Johnson 1985). 

Soil lead concentrations have been observed to be associated with children s blood lead concentrations using multiple study designs - cross-sectional, ecological spatial, ecological temporal, prospective soil removal and isotopic (Laidlaw Filippelli, 2008). 

Ericson, J.E. Mishra, S.I., 1990. Soil lead concentrations and prevalence of hyperactive behavior among school children in Ottawa, Canada. Environment International, 16, 247-256. 

United Retek Corporation s asphalt emulsion stabilization process was used at an active paper company in Pawtucket, Rhode Island. The company wanted to expand its facility at the site however, lead contamination was discovered in the proposed 43,000-fU expansion area. Soil lead concentrations were in excess of 100 ppm at some locations within the area. Asphalt emulsion stabilization was used over 5 days to treat 2000 yd of soil. Total treatment costs were 80,000, or 2000 yd of soil treated at 40/yd. It was estimated that excavation and removal costs at the site would have been 200 to 250/yd of soil (D21950L, pp. 2, 3). 

Barltrop D (1966) The prevalence of pica. Am J Dis Child 112 116-123 Barltxop D, Strehlow CD, Thorton I, Webb JS (1974) Significance of high soil lead concentrations for childhood lead burden. Environ Health Perspect 7 75-82 Beloian A (1982) Use of a food consumption model to estimate human contaminant intake. Environ Monitor Assess (in press)... 

U.S. EPA (2001) holds ICP-AES or ICP-MS to be the soil lead measurement methods of choice. Detection hmits are on the order of 40 parts per bU-hon (ppb) which are quite adequate for an environmental medium where even background, i.e., uncontaminated soil lead, concentrations are on the order of 10—20 ppm. 

Limits on lead in soil have also been established. In the USA, for instance, the regulatory authorities recommend limits of between 500-1000 ppm, though some states have set lower levels. Soil lead concentrations are a function of various complex factors, related to host rocks, humus content, etc, and their direct impact on lead exposure amongst the population is probably limited. 

Soil lead concentrations greater than 10,000 mg/kg -1 (milligrams/deci-gram) of soil are commonly reported at shooting ranges around the world, in-... 

The study of ambient air lead concentrations has also shown the significant correlation between the combustion of leaded gasoline and soil lead concentrations. The EPA has noted that air lead concentration decreases as you travel from the center of a city and that soil lead levels are a direct function of the deposition of ambient air lead (see EPA reports for 1986). The contribution of leaded gasoline emissions and soil lead levels to interior house dust is evident in studies showing that lead in house dust is related to exterior lead levels (Chaney, 1989). 

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