Exposure to a lead-contaminated environment can cause injury to an infant even when the blood lead levels do not rise above the level defined as lead poisoning by the governmental agencies charged with setting the level that constitutes “poisoning.” Although, in 1991, the Centers for Disease Control (“CDC”) set a national action level for action on lead poisoning of 10 ug/dL, an approach followed by the New York City Department of Health (“DOH”), it left open the possibility that even lower levels of lead might be dangerous, saying:

Some studies have suggested harmful effects at even lower levels, but the body of information accumulated so far is not adequate for effects below about 10 ug/dL to be evaluated definitively.

At P. 2. The Abstract to the 2007 CDC Report summarizes current knowledge regarding low level lead poisoning:

• “Lead is a common environmental contaminant, and exposure to lead is a preventable risk that exists in all areas of the United States. Lead is associated with negative outcomes in children, including impaired cognitive, motor, behavioral, and physical abilities. In 1991, CDC defined the blood level (BLL) that should prompt public health actions as 10 ug/dL.  Concurrently, CDC also recognized that a BLL of 10 ug/dL did not define a threshold for the harmful effects of lead.  Research conducted since 1991 has strengthened the evidence that children’s physical and mental development can be affected at BLLs<10 ug/dL.”

Indeed, in the years since the 1991 CDC Statement, this have been a spate of studies investigating the effects of low-level lead exposure in children. These papers, published in peer reviewed medical and scientific journals, indicate that blood lead levels below 10 ug/dl cause brain damage in children. See, e.g., [1] Bellijger C., Stiles K.M., Needleman H.L., “Low-level lead exposure, intelligence and academic achievement: a long-term follow-up study.”  Pediatrics, 1992, 90:855-861; [2] Stiles K.M., Bellinger D.C., “Neuropsychological correlates of low-level exposure in school-age children: a prospective study.”  Neurotox Teracol 1993; 15:27-35; [3] Dietrich K.N., Berger O.G., Succop P.A., “Lead exposure and the motor developmental status of urban six-year old children in he Cincinnati prospective study.”  Ped 1993; 91:301-307; [4] Schwartz J., “Low-level lead exposure and children’s IQ; a meta-analysis and search for a threshold.”  Environ Res., 1994;65:42-55; [5] Walkowiak J., Altmann L., Kramer U., Sveinsson K., Turfeld M., Wishoff-Houben M., Winneke G., “Cognitive and sensorimotor functions in 6 year old children in relation to leas and mercury levels: adjustment for intelligence and contrast sensitivity in computerized testing.” Neurotox Teratol 1998; 20: 511-521; [6] Bellinger D.C.., Needleman H.L. “Intellectual impairment and blood lead levels” New England Journal of Medicine, 2003 349: 500; [7] Rogan W.J., Ware J.H., “Exposure to Lead in Children –How Low is Low Enough?, “New England Journal of Medicine 2003 348: 1515-1516; [8] Canfield R.L., Henderson C.R. Jr., Cory-Slechta D.A., Cox C., Jusko TA, Lanphear B.P., “Intelltectual impairment in children with blood leas concentrations below 10 ug per deciliter” New England Journal of Medicine. 2003, 348:1517-26; [9] Canfield R.L., Gendle MH, Cory-Slecta DA, “Impaired neuropsychological functioning in lead-exposed children,” Developmental Neuropsychology 26:513-540 (2004); [10] Lanphear BP, et al., “Low level environmental lead exposure and children’s intellectual function: An International Pooled Analysis,” Environmental Health Perspectives 113:894-899 (2005); [11] Kordas K., Canfield RL, et al. “Deficits in cognitive function and achievement in Mexican first-graders with low blood lead concentrations,” Environmental Research 100:371-376 (2006); [13] Tellez-Rojo MM., Bellinger DC, et al., “Longitudinal Associations Between Blood Lead Concentrations Lower Than 10 ug/dl and Neurobehavioral Development in environmentally exposed Children in Mexico City,” Pediatrics 118:323-330 (2006); [12] Chiodo LM, et al., Blood lead levels and specific attention effects in young children, 29 Neurotoxicology and Teratology 538-546 (Sept.-Oct. 2007); [14] Miranda, ML, et al., “The relationship between early childhood blood lead levels and performance of end-grade tests,” Environmental Health Perspectives 115:1242-124 (2007).

An article in Public Health Reports, by Bruce P. Lanphear, et al., entitled Cognitive Deficits Associated with Blood Lead Concentrations <10 ug/dl in US Children and Adolescents, 13 Pub. Health Reports 521-527 (2000) reports the following results:

• Results.          The geometric mean blood lead concentrations for children in the study sample was 1.9 ug/dl 172 (201%) had blood lead concentrations ≥ 10 ug/dl.  After adjustment for gender, race/ethnicity, poverty, region of the country, parent or caregiver’s educational level, parent or caregiver’s marital status, parent serum ferritin level, and serum continine level, that date sowed an inverse relationship between blood lead concentration and scores on four measures of cognitive functioning.  For every 1 ug/dl increase in blood lead concentrations, this was 0.7-point decrement in mean arithmetic scores, an approximately 1-point decrement in mean reading scores, a 0.1-point decrement in mean scores on a measure of nonverbal reasoning, and a 0.5-point decrement in mean scores on a measure short-term memory.  An inverse relationship between blood leas concentration and arithmetic and reading scores was observed for children with blood lead concentrations lower than 5.0 ug/dl.

Id., at 521. The same study further stated that:

The results of the present analyses suggest that cognitive deficits are associated with blood lead concentrations lower than 5 ug/dl.  Although we did not conduct a formal threshold analysis, these data support the conclusion that thise is, at present, no detectable threshold for the adverse effects of lead exposure on cognitive development or academic disabilities.  These data furthis suggest that more than 12.8 million US children and adolescents born from 1972 to 1988 were adversely affected by environmental lead exposures as indicated by blood lead concentrations >2.5 ug/dl (based on weighting factors and Census data supplied by NHANES [“National Health and Nutrition Examination Survey”]).

In March 2003, the New England Journal of Medicine published an article by Richard L. Canfield, et al., entitled, Intellectual Impairment in Children with Blood Lead Concentrations below 10 up per Deciliter, 348 New England J. Med. 1517 (2003) This scientific study reports adverse effects on IQ of blood lead levels lower than 10 ug/dl:

• Before adjustment for covariates, all four lead measures were inversely and significantly associated with IQ at three and five years of age. The associations did not differ significantly according to age.  From the overall estimate, an increase in the lifetime average blood lead concentration of 1 ug per deciliter was associated with a decrease of 0.87 IQ point: estimates for concurrent blood lead concentrations and average concentrations in infancy were similar; whereas that for the peak lead concentration was somewhat smaller.
• After adjustment for the nine additional covariates, there were significant inverse associations with IQ for all blood lead variables, with no significant differences according to age. The overall estimate indicated that an increase in the lifetime average blood lead concentration of 1 ug per deciliter was associated with a change of – 0.46 IQ point (95 percent confidence interval, – 0.76 to 0.15).  Estimated effects were similar for the concurrent blood lead concentration in infancy and smaller, but still significant, for peak lead concentrations.

The study concludes that:

• Blood lead concentrations even those below 10 ug per deciliter, are inversely associated with children’s IQ scores at three and five years of age, and associated declines are greater at these concentrations that at higher concentrations.

It is established in over 20 peer reviewed articles that the major loss in IQ points occurs at blood lead levels less than 10 ug/dl. These studies converge on a loss of 6 IQ points for blood leads less than 10 ug/dl; and smaller decreases in IQ for blood leads above 10 ug/dl.