DEVELOPMENT OF HEALTH CRITERIA FOR SCHOOL SITE RISK ASSESSMENT PURSUANT TO HEALTH AND SAFETY CODE SECTION 901(g): CHILD-SPECIFIC BENCHMARK CHANGE IN BLOOD LEAD CONCENTRATION FOR SCHOOL SITE RISK ASSESSMENT

Executive Summary This document establishes a new child-specific health guidance value (HGV) for lead, for use in health risk assessment at school sites pursuant to Health and Safety Code Section 901(g). This HGV is a benchmark incremental change in blood lead concentration (ΔPb B) of 1 microgram lead per deciliter (µg/dl) of blood. More specifically, this HGV identifies lead exposures from a specific location that cause a rise in a child's blood lead level by more than 1 µg/dl as significant for purposes of risk assessment. A change in blood lead of 1 µg/dl does not represent an absolutely safe exposure level, since no safe level has been definitively established. One µg/dl is the estimated incremental increase in children's Pb B that would reduce IQ by up to 1 point. Since 1991, the U.S. Centers for Disease control has recommended that primary prevention activities in children should begin when blood lead levels exceed 10 µg/dl. At that time, it was not clear whether the effects trend extended to blood Pb levels below 10 µg/dl. Numerous epidemiology studies and meta-analyses over the past three decades have firmly established that there is an inverse relationship between blood lead concentrations in infants and children and several health and developmental indicators. As a consequence of declining blood lead concentrations in children in several countries, the more recent of these studies have included significant numbers of children with Pb B levels less than 10 µg/dl. It is becoming increasingly clear that the inverse relationship between blood lead concentrations and these health and developmental effects extends well below 10 µg/dl. Since a clear no-effect concentration has not been established, our assessment used a dose-response slope characterizing the relationship between Pb B and full-scale IQ scores rather than a more traditional no-effect level with uncertainty factors. As a basis on which to develop such a dose-response slope, we selected a pooled analysis of seven epidemiology studies conducted in four countries. This study involved a large number of preschool to school-age children with relatively low Pb B and therefore has sufficient statistical power to define the relationship between blood lead and cognitive function at lower Pb B levels within reasonably tight confidence limits. U.S. EPA (2006) also selected this study for their pilot risk assessment. We used the upper confidence limit on the slope to estimate an incremental increase in Pb B that would cause a decrease in …