Eliminating Childhood Lead Poisoning in New York State by 2010
II. Needs Assessment
The toxicity of lead has been recognized for thousands of years, and more precisely described in medical literature since the 1920s.1 As knowledge about the effects of lead at various concentrations has grown, the defined level of intervention for children has been lowered steadily over the past four decades, and recent findings of harmful effects at blood lead levels even below the current "level of concern" of 10 mcg/dL have prompted discussion for potentially lowering acceptable blood levels even further. It is worth noting that standards for both blood lead levels and environmental lead sources (e.g. paint, residential dust, and drinking water) are not strictly health-based standards, but reflect ongoing consideration of toxicology, feasibility, and availability of effective intervention.2,3
|Year||Level of Concern|
|2004||Discussions underway at CDC to determine if level should be further decreased to 5 mcg/dL, in light of growing body of research demonstrating no "safe" threshold of exposure|
In the 1970s, in response to heightened recognition of the widespread health effects of environmental lead exposures from gasoline and residential paint, federal environmental standards for lead levels in air, food, and water, and restrictions on use of lead in industry, were increased substantially. In 1977 the maximum allowable level of lead in gasoline was lowered from 0.78 g/L to 0.026 g/L; in 1976 the allowable level of lead in residential paint was lowered to 0.06%.3 The combination of these and other lead-related regulations had dramatic impacts on lead levels in children: the median blood lead level (BLL) decreased from 14.6 mcg/dL in 1976 to 2.8 mcg/dL in 1990.1 While this is a marked success at the population level, lead poisoning remains epidemic in certain sub-populations in the U.S., in particular among young children living in the most socially and economically disadvantaged urban environments.
Current national data on the prevalence of elevated blood lead levels in children are drawn from the National Health and Nutrition Examination Survey (NHANES), conducted between 1988-1994 and 1999-2000, and from state child blood lead surveillance data for test results collected during 1997-2000 and submitted to CDC.
Based on NHANES data for 1999-2000 an estimated 434,000, or 2.2%, of children aged one to five years had blood lead levels (BLL) at or above 10 mcg/dL.4 This represents a decline from previous 1988-1994 data, which found 890,000, or 4.4% of children aged one to five years had BLL at or above 10 mcg/dL.3 A separate analysis of 1988-1994 data demonstrated that one in every four children (25.6%) had BLL at or above 5 mcg/dL, the concentration under consideration as a potential new designation for level of concern.5
State surveillance data submitted to CDC for 1997-2001 indicate that children's blood lead levels are declining throughout the U.S. Between 1997 and 2001, the number of reported lead test results increased from 1.7 million (in 39 states and municipalities) to 2.4 million (in 46 states and municipalities), while the number of children reported with elevated BLL at or above 10 mcg/dL decreased steadily from 130,512 to 74,887 in 2001. Despite this substantial progress, the year 2000 national goal of elimination of blood lead levels ≥ 25 mcg/dL was not achieved. A total of 8,723 children nationally had blood lead levels ≥ 25 mcg/dL in 2000.
New York State Data:i
Blood Lead Screening Rates:
Annual screening rates for children under six years of age in NYS remain high. The purpose of testing, or screening for blood lead levels, is to provide for the early identification of children with elevated blood lead levels, and, once identified, coordinate intervention services. NYS regulations require health care providers to screen all children for blood lead levels at age one and two years, and with a risk assessment history followed by blood lead test as indicated up to age six years. State analysis indicates that 62% of children born between 1994 and 1999 received a blood screen by twenty-four months of age. An additional 30% of children were screened with a blood lead level after age twenty-four months, for an overall screening rate of 92% by age six. In the year 2000, 76% percent of children enrolled in Medicaid Managed Care plans were screened for blood lead levels by twenty-four months of age. Of the children found to have non-elevated (<10 mcg/dL) blood lead levels on initial screen, approximately one-third were screened a second time. Among those screened a second time, 8% were found to have a newly elevated blood lead level at or above 10 mcg/dL on second screening, emphasizing the importance of a second screening test even when an initial screening test is negative.
Burden of Childhood Lead Poisoning:
In New York State, excluding New York City, the number of children with newly-identified blood lead levels of 10 micrograms per deciliter (mcg/dL) or higher decreased by 14% between the years 2000 and 2001, from 3,672 to 3,178 children. The incidence rate, or number of newly identified cases of 10 mcg/dL or greater per 100 children screened, declined from 1.98 per 100 in 2000 to 1.7 in 2001. While incidence reflects only new cases, prevalence reflects both new cases and previous cases with ongoing blood lead measurement. Over the period of 2000-2001, the prevalence of children with elevated blood lead levels (EBLL) of 10 micrograms per deciliter (mcg/dL) or greater decreased by 18%, from 6,385 children in the year 2000 to 5,258 children in the year 2001. Similar declines were accomplished in both incidence and prevalence of blood lead levels of 20 mcg/dL or greater.
Despite these significant gains in the struggle against childhood lead poisoning in New York State, elimination of this preventable condition has not yet been achieved. In 2001, 5,258 children, or 2.7% of all children under six years of age in New York State (excluding New York City) had elevated blood lead levels of 10 mcg/dL or higher.
Geographic Distribution of Lead Poisoning in Upstate New York:
Rates of children with elevated lead levels vary geographically across the state. Much of this variation can be attributed to the age of housing, use of leaded paint, poverty rates of communities, and property values.
Analysis of aggregate data in large geographic areas can mask smaller populations with relatively high rates of elevated blood lead levels. To more easily identify geographic areas with high rates of children with elevated blood lead levels, an analysis of zip code level data was conducted for all zip codes outside of New York City.ii In 2000-2001, thirty-six of the state's approximately 1,700 non-New York City zip codes were identified as having at least five new cases per one hundred children screened (or >5% incidence rate). These thirty-six high-incidence zip codes comprise only 2% of the state's zip codes outside of NYC, but account for 41% of all the children who were identified with EBLL outside of NYC. Among counties with one or more high-incidence zip codes, the high-incidence zip codes accounted for almost half of these counties' overall incidence rate. Not surprisingly, these thirty-six high-incidence zip codes have a substantially higher proportion of pre-1950 housing stock (59%) than the statewide (37%) and county figures.
- For a more complete review of recent NYS surveillance data, refer to the companion document: Promoting Lead Free Children in New York State: A Report of Lead Exposure Status Among New York State Children, 2000-2001
- Zip codes were selected because they are more universally understood than other measures, such as census tracts. Most children in the database had only one street addess associated with their record. In the cases with multiple addresses, the zip code associated with a child's initial screening test was used. Zip codes were validated against the street name and city, and if necessary, the zip code was corrected.
The U.S. Department of Health and Human Services has called for the elimination of lead poisoning (defined as blood lead level at or above 10 mcg/dL) among children aged six years and younger. In support of this goal, states and cities funded by CDC's lead poisoning prevention program — including New York State and New York City, which each receive CDC funding individually - are required to develop and implement plans to eliminate childhood lead poisoning by the year 2010.
As a first step toward addressing the CDC goal for elimination, statistical projections for New York State in the year 2010 were prepared. Based on historical data and knowledge of past and current relationships among factors related to lead poisoning rates, several statistical methods were used to predict future trends in childhood lead poisoning in NYS. Because this methodology assumes that influential factors will persist in the future, and because these contributing factors are complex and interrelated with other social, economic, and legal issues, the extent to which these factors and their interrelationships change over the next six years will influence the trends that are actually observed. The statistical models indicate that incidence rates in NYS, exclusive of NYC, will have decreased by the year 2010 to very low levels, as shown in Figure 1 and Table 2.
|Geographic Descriptor||Number of Children Screened in 2001||10-14 mcg/dL||15-19 mcg/dL||20+ mcg/dL|
|High IR Counties||41886||314||149||99|
|Low IR Counties||99303||199||99||99|
|Moderate IR Counties||45392||91||45||45|
|High IR Counties = Counties with incidence rates at or above 75th percentile; Low IR Counties = Counties with incidence rates at or below 25th percentile; Moderate IR Counties = Counties with incidence rates between 26th and 74th percentile. Includes all NY State exclusive of five New York City counties.
Projections based on number of children screened in 2001.
Several observations can reasonably be concluded from the projections.
- Elimination is possible
- Additional efforts are needed statewide to achieve elimination
- Some communities will need to do more than others to reach elimination
Associated Risk Factors:
Children's blood lead levels typically rise rapidly between six and twelve months of age and peak between eighteen and thirty-six months of age, before gradually declining.3 This pattern reflects active exploration of environment, increased mobility, high hand-to-mouth activity, and highly efficient gastrointestinal absorption of lead, which is estimated to be five to ten times higher than in adults.1,3 Older children with developmental delays may continue to be at high risk for lead exposure, for example through persistence of mouthing behaviors.
In the U.S., African American children are at the highest risk for elevated lead levels nationwide. NHANES III data demonstrated prevalence of BLL at or above 10 mcg/dL of 11.2 % of African American children ages one to five, compared to 2.3% of white children in the same age group; Hispanic children have prevalence rates intermediate to these.6 When levels at or above 5 mcg/dL were assessed, 47% of African American children, 28% of Mexican American children, and 19% of non-Hispanic white children age one to five had elevated blood lead levels.2
Socioeconomic status (SES) is a powerful predictor of lead exposure. NHANES III data found that 13% of Medicaid recipients had BLL at or above 10 mcg/dL, and 42% had levels at or above 5 mcg/dL. Poor children are more likely to live in lead-contaminated environments, including older and dilapidated housing and deposits of lead from years of leaded gasoline, hazardous waste disposal, and lead-related industry.1 Furthermore, there is accumulating evidence in both human and animal studies that socially and economically disadvantaged children may be more vulnerable to the effects of a given level of lead exposure.7
Lead-based residential paint is the most significant source of high-level lead exposure for children in the U.S. The highest risk is for pre-1946 housing, with continued high risk for all housing built before the federal ban on high-lead paint in 1977. Nationally, tens of millions of existing housing units were built prior to the ban, and many of these units are in increasingly dilapidated condition.1 Multiple studies have demonstrated household lead dust as the major source of lead exposure for young children.8 Regional differences in prevalence of elevated lead levels, with highest prevalence rates in the Northeast and Midwest, reflect differences in housing stock. Lead paint can also be disturbed during renovation of older housing if lead-safe work practices are not followed. 9
Children with iron or calcium deficiencies have been shown to have increased absorption of lead, and to be at significantly higher risk for development of elevated blood lead levels.4,10 However, there is currently no solid evidence that supplementation with calcium or iron prevents elevated blood lead levels in children.3
While more data are needed, several studies have suggested that immigrants to the U.S., including foreign-born adopted children, appear to have an increased prevalence of elevated lead levels, reflecting a variety of environmental exposures in their countries of origin and/or a variety of cultural practices. Continued use of leaded gasoline, industrial emissions, cottage industries, traditional folk medicines, cosmetics, ceramics, and foods all have been noted as sources of lead exposure among immigrant populations.11-13
Pregnant women and fetuses may represent a unique population in terms of demographics and exposure pathways to lead. Women can carry lead from any lifetime exposure stored in their bones for decades, or may be exposed to lead during pregnancy from environmental, occupational, or other sources.7 During pregnancy, maternal lead may be mobilized from bone stores into the bloodstream and then cross the placenta or enter breast milk. Various reports have estimated the prevalence of elevated blood lead levels among adult women to be between three and nineteen percent.14 Dramatic increases in the population of immigrant women in some communities may mean that the prevalence of elevated BLL among pregnant women is higher than previous estimates.
Routes of Exposure:
The primary route of lead absorption in children is ingestion and absorption through the gastrointestinal tract. Only a small amount of ingested lead is needed to raise child's blood lead level. Because lead accumulates in the body, toxicity depends on the amount of lead one is exposed to and the duration of the exposure. Lead readily crosses the placenta, thus a developing fetus may be exposed to lead in the mother's bloodstream. Once absorbed, lead is carried in the blood and absorbed by all other tissues of body. The half-life of lead is approximately thirty-five days in blood, approximately two years in the brain, and decades in bone. Blood lead levels are primarily an indicator of recent exposure, although they can remain elevated longer due to mobilization of internal stores.
Sources of Lead:
Dusting, flaking and peeling residential lead paint is by far the most significant source of lead exposure to children.1,3 Even in well-maintained housing units, some deterioration of paint occurs. As paint deteriorates, it is converted into dust-sized particles. Children living in dilapidated older houses or an older house undergoing renovations are at particular risk for lead poisoning due to lead contaminated dust and debris. Deteriorated exterior paint poses a similar threat to children who regularly play outside in soil near the structure.
Other important sources of childhood lead exposure include soil contaminated by industry or traffic, and contaminated drinking water systems. However, children can be exposed to lead from countless sources, including imported pottery and ceramics, imported foods, toys, or cosmetics, folk medicines, leaded weights and fishing sinkers, parent occupational exposures, and exposure to maternal lead stores during pregnancy or through breast milk.
A solid and growing body of scientific evidence demonstrates that lead is a systemic toxin, resulting in adverse health effects in virtually all body systems. Lead exposure has been associated with anemia, hearing loss, diminished skeletal growth, delayed pubertal development, dental caries, cognitive and behavioral deficits, hypertension, osteoporosis, and a range of non-specific constitutional symptoms. In pregnant women, lead toxicity has been linked with pregnancy-induced hypertension/ toxemia, spontaneous abortion, preterm birth, and low birth weight. Lead is a potent neurotoxin and is especially detrimental to the vulnerable developing nervous system of babies and young children.3,7 Most children with elevated blood lead levels are asymptomatic. Effects of lead on cognition and behavior may be insidious and lag behind the actual period of lead ingestion, even after blood lead levels have declined.1,7
Lead exposure has been associated with significant, dose-dependent declines in IQ and a range of other measurable cognitive, social-emotional, and behavioral deficits in children.,3,7,15-18 A systematic review of published research demonstrates that an aggregate increase in blood lead levels from 10 to 20 mcg/dL is associated with an average decline of 2.6 IQ points in young children.16 This finding is consistent across a range of study populations, and holds when important social and demographic co-variates are controlled.
Over the past several years, at least four peer-reviewed scientific studies have demonstrated an association between lead exposure and cognitive impairments at blood lead concentrations below 10 mcg/dL, the current "level of concern" as defined by the CDC.7,16,19,20 The most rigorous of these studies, a prospective longitudinal analysis of blood lead levels and IQ between the age of 6 and 60 months, found an average decline of 7.4 IQ points over the first 10 mcg/dL of lifetime average blood levels, an observation consistent with other previous research.20 Collectively, these findings demonstrate that there is no discernible threshold for the toxic effect of lead, and that in fact incremental negative effects on cognition may be highest at concentrations below the current "level of concern".7,21 Perhaps most importantly, research increasingly demonstrates that the harmful effects of lead on cognition and behavior are not reversible.
While the observed average declines in IQ may appear small, the public health implications of such effects are likely to be significant. At a population level, a shift in the population curve even a few IQ points to left will notably increase the number of children at risk for problematic outcomes, and in need of special services, while concurrently decreasing the number of children at the other end of the curve whose intellectual potential and productivity is optimized.21 Such shifts may have substantial public health and financial implications. For example, a 1994 cost-benefit analysis reportedly estimated that lowering the population average of children's BLL by only 1 mcg/dL would result in savings of $6.9 billion nationally.1
Equally important, average declines in IQ mask the susceptibility or resilience of individual children, which is likely to be quite variable.7 In fact, several studies have demonstrated an effect-modifying relationship between lead exposure and poverty, suggesting that the most socially disadvantaged children may in fact be more vulnerable to a given lead exposure dose, thereby compounding the detrimental effects of lead in at-risk populations. Thus average group effects likely underestimate the effect on some individual children, and studies that statistically control for the effects of poverty or other socio-economic contextual factors may actually obscure the most potent effects of lead exposure on high-risk populations.7,22
The assessment summarized above makes clear several related findings: 1) lead exerts harmful effects at concentrations commonly observed among young children, including at levels below 10 mcg/dL, perhaps without any identifiable threshold of safety; 2) a large proportion of the population of young children currently have BLL between 5-10 mcg/dL; 3) the cognitive effects of lead toxicity are believed to be irreversible; 4) children already at high risk for a range of health and developmental problems due to socio-economic disadvantage are the most likely to be exposed to lead, and may be most vulnerable to its debilitating effects. Based on this collective evidence, there is consensus among researchers, health care providers, and policymakers that comprehensive prevention strategies, and especially primary prevention strategies, must be strengthened to achieve elimination of childhood lead poisoning.