OBJECTIVES. To evaluate trends in children's blood lead levels and the extent of blood lead testing of children at risk for lead poisoning from national surveys conducted during a 16-year period in the United States.
METHODS. Data for children aged 1 to 5 years from the National Health and Nutrition Examination Survey III Phase I, 1988–1991, and Phase II, 1991–1994 were compared to data from the survey period 1999–2004.
RESULTS. The prevalence of elevated blood lead levels, ≥10 μg/dL, among children decreased from 8.6% in 1988–1991 to 1.4% in 1999–2004, which is an 84% decline. From 1988–1991 and 1999–2004, children's geometric mean blood lead levels declined in non-Hispanic black (5.2–2.8 μg/dL), Mexican American (3.9–1.9 μg/dL), and non-Hispanic white children (3.1 μg/dL to 1.7 μg/dL). However, levels continue to be highest among non-Hispanic black children relative to Mexican American and non-Hispanic white children. Blood lead levels were distributed as follows: 14.0% were <1.0 μg/dL, 55.0% were 1.0 to <2.5 μg/dL, 23.6% were 2.5 to <5 μg/dL, 4.5% were 5 to <7.5 μg/dL, 1.5% were 7.5 to <10 μg/dL, and 1.4% were ≥10 μg/dL. Multivariable analysis indicated that residence in older housing, poverty, age, and being non-Hispanic black are still major risk factors for higher lead levels. Blood lead testing of Medicaid-enrolled children increased to 41.9% from 19.2% in 1988–1991. Only 43.0% of children with elevated blood lead levels had previously been tested.
CONCLUSIONS. Children's blood lead levels continue to decline in the United States, even in historically high-risk groups for lead poisoning. To maintain progress made and eliminate remaining disparities, efforts must continue to test children at high risk for lead poisoning, and identify and control sources of lead. Coordinated prevention strategies at national, state, and local levels will help achieve the goal of elimination of elevated blood lead levels.
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A New Slant on Pediatrics' Report of Falling Elevated Blood Lead Levels
A New Slant on Pediatrics’ Report of Falling Elevated Blood Lead Levels
Lelia M. Coyne, PhD, MST, NE-Certified Lead-based Paint Risk Assessor Independent Researcher April 2009
The recent Associated Press article by Lindsay Tanner1 (Based on a recent Pediatrics article by Jones, et al. March 10, 20092) has left some of us scratching our heads. This study reports and interprets demographic trends in testing and the national prevalence of elevated blood lead levels (EBLLs). Data were from National Health and Nutrition Examination Survey (NHANES)' "nationally representative samples" surveyed since 1988. In the article three statements are made which call for serious consideration both of their meaning as applied to any specific region, and also the implications of this meaning with respect to national lead poison prevention policy.
Two of the statements appear in the Abstract.
“The prevalence of elevated blood levels, greater than or equal to 10 micrograms/dL among children decreased from 8.6% in 1988-1991 to 1.4% in 1999-2004, which is an 84% decline.”
“Blood lead testing of Medicaid-enrolled children increased to 41.9% from 19.2% in 1988-1991.
The first sentence in the discussion states that:
“Blood lead levels (BLLs) in US children continue to decrease most likely as a result of an intense coordinated effort to control or eliminate lead sources in children’s environments by government officials, health care and social service providers, and the communities most at risk.”
The results reported are substantially inapplicable to conditions I know to exist, not just in my local community, but also my entire state.
For instance, in no part of Nebraska (NE), do the reporting statistics parallel the 41.9% stated in the Pediatrics article to describe the BLL testing level of Medicaid-enrolled children nationally. At its high point in 2005, NE, statewide, tested 14.6% of its children. Half of these tests were performed in one of our 93 counties. Six of these counties reported no screenings at all in 2005, and in another twenty- nine, less than 5% of children six and under were screened. The Medicaid status of these children was not, nor is now, systematically reported to the State. Examining the process of reporting of BLL levels here, it is not even clear how this could be practically retrospectively determined. Furthermore, in NE, because of the broad distribution of pre-1950 housing, it would be legitimate to question whether EBLLs are, in actuality, clustered among Medicaid children.
Pediatrics’ attributes the improvement to “an intense coordinated effort to control or reduce exposures to lead in children’s environments….” This statement controverts strong divergence of emphases by public health units on lead poison prevention programs even between the two most populous counties in this state. In one, the Pediatrics’ attribution is accurate to an awe-inspiring degree as the result of combined efforts between an EPA Superfund cleanup of industrially contaminated soil, and broadly based community attention to multicultural outreach, education about prevention of exposure risks, and remediation of old housing and public schools. The other stoutly maintains lack of a significant incidence of lead poisoning, in spite of a similarly large stock of pre-1950 housing and unabated public school facilities. Yet, both have mirrored the stunning national decrease in the prevalence of EBLLs (albeit considerably larger in the one relative to the other).
The Pediatrics’ attribution for the extended national decline in EBLLs cannot be reconciled with disparate NE policies. I therefore searched for an over-arching explanation for the broadly observed decline in EBLL prevalence that might amalgamate exposure prevalences in our “polyglot” society.
An EPA Document3 was compiled which supported the need for a dramatically lowered acceptable standard for airborne lead. A lowered standard was recently adopted, in response. Figure 2.8 on page 2-81 may provide an explanation for numerous disparities that is worthy of more general consideration. Airborne Pb emissions dropped by 98% between 1970 and 2003. However, the figure caption points out that 5% of this decrease occurred between 1993 and 2002, well after the complete phase-out of leaded fuel, which occurred in 1986.
Is it possible that during the period of the NHANES surveys and the NE surveillance data collection that decreasing national airborne Pb emissions have remained the dominating factor in lowering BL levels?
If so, rather than being in the midst of “an intense coordinated effort to control or eliminate lead sources in children’s environments by government officials, health care and social service providers, and the communities most at risk” can we, as a nation, not just NE, be still in very early stages of a widely neglected effort to control exposures of our children to multitudinous sources of lead? As a society, have we been falsely cheered by results from a study designed neither to quantify the degrees of lead poisoning that are being suffered regionally, nor to evaluate comprehensively the extent of local effectiveness in addressing specific regional risk factors? Is it the exceptional, rather than the typical community that is paying serious attention to minimizing the economic and social consequences of early childhood lead poisoning?
Examination of several other recently published articles4,5,6, which conduct additional analyses just of the most recent of the NHANES studies, complicated my consideration of these questions, rather than clarifying it. Although these articles delineate a number of risk factors, the data analysis is very complex and hard for all but a very few experts to use. This is because inferential statistical modeling procedures are employed, which, fundamentally, are of a different nature from statistical data presentation methods familiar to most scientists and public health officials.
The NHANES nationally representative sample found the national prevalence of BLLs elevated above 10 μg/dL to be 1.4%. In many specific regions, overall prevalences are acknowledged to be much higher.
How extended can these specific regions be? What is an expected range of variability about the national figures? How dissimilar do the local demographic factors have to be from those described by the “nationally representative sample” to signal existence of a specific local risk factor, more importantly, to warn that the national figure does not likely reflect the regional prevalence? How extensive must the testing coverage be to give a reliably representative picture?
It is difficult even to absorb the meaning of the caution that “estimates can be generalized only to the US population." Respecting this, it remains problematic to grasp how these studies can then have applicable local descriptive or predictive value, and to discern what this might be.
The Pediatrics article states:
“Since 1997, the Center for Disease Control (CDC) has recommended that states develop plans to target testing to children at high risk.”
Other Federal Agencies also have long advised us to design and apply strategies targeted for specific high-risk populations in our own locales. All of the recent articles restate this directive.
I note that, in spite of the reiterated caution that "nationally representative samples do not identify or characterize local risks," public officials at all levels cite the NHANES national EBLL prevalence as if it were regionally applicable, even in the absence of such programs.
How many communities are aware of their overall prevalence of EBLLs? Of those who are, how many have explored the uniformity of this prevalence throughout their community, and sought to identify vulnerable clusters within it? How many have tried to correlate EBLL prevalence in their own community with their prevalences of academic and behavioral problems that are well proven to be associated with even lower levels of lead exposures?
We have control to alter (and responsibility to do so) local exposure sources by our community efforts, but in the absence of local surveillance data we can remain oblivious even of their existence, and certainly are unable to quantify their direct consequences on the intellectual, behavioral, and physical health of our citizenry, because the NHANES surveys do not supply such data. NHANES models, even if their implications are correctly interpreted, offer only generic guidance to parents and concerned citizens about specific types of high-risk sources that may exist in local communities, and the relative risks that they impose.
Even the national prevalence of 1.4% remains unacceptably high and this, very possibly, is a serious underestimate of the actual national prevalence, because many likely scenarios for exposure are not included explicitly in the survey design. More specific guidance is needed to inform design of local strategies to reduce lead exposure and to stimulate us to push for their adoption. To acquire this guidance, we need a means to identify and quantify risk factors specific to our own localities, via their measured contribution on local lead exposure prevalences.
Such evidence is provided only via comprehensive, publicly reported testing. Current surveillance data are most sparse, and results are essentially inaccessible to any but professional public health specialists. Most BLL sampling now being done is at the discretion of private providers, and, for most part, is timed in compliance with rigid age-based screening intervals. These are prescribed by diverse, loosely coordinated organizations such as CDC, Medicaid, the American Academy of Pediatrics, or State Early Childhood Lead Poison Prevention Programs (ECLPPPs). Their advisories vary widely. Parent compliance with any of them is subject to widely varying individual accessibility to and affordability of health care. Physician compliance varies with their personal diligence actually to provide recommended testing, and then reliably to report test results to a common database that includes a modicum of demographic information. Few physicians include responses to lead exposure questionnaires as a standard component of medical history on patient intake, or draw BLL samples when a patient complains of vague symptoms after a household remodeling project, if the activity were even to be mentioned.
Age-based testing is more apt to capture ongoing chronic, rather than acute exposures, and thus can be far removed in time and conditions from the onset of actual exposure of the child, such as from an unsafely conducted home improvement project or a move. Thus, timely warnings, or evidence of harm may or may not be provided to primary caregivers and the broader health community in a way useful to promoting immediately needed changes of behavior, even among tested children.
Perhaps it is time to get a truly descriptive profile of the incidence of EBLLs. To do this would require mandated universal screening over at least the first 7 1/2 years of life using reevaluated and uniformly applied screening criteria that are designed to capture the bulk both of chronic and acute exposures. Minimally, EBLL data summaries by zip code need to be reported to the public. Both parents and concerned citizens deserve to know how many of our small ones are being subjected to lead poisoning, when and where it is being acquired, and what they need to see done to eliminate it. In the lack of surveillance data, continued NHANES surveys will remain overly restrictive mirrors of the societal price of lead poisoning.
Lead poisoning in the 21st century remains a weighty problem!
1 Tanner, Lindsay. “Study: Fewer kids have high lead levels. Lincoln Journal Star, Monday March 2, 2009 (based on a recent Pediatrics article by Jones Robert L, et al.2). 2. Jones, Robert L., Homa, David M., et al. Trends in blood lead levels and blood lead testing among U.S. children aged 1 to 5 years, 1988 2004. Pediatrics [serial online]. 2009;123:e376-e385. Available from: American Academy of Pediatrics, 141 Northwest Point Boulevard, Elk Grove Village, Illinois, 60007. Accessed March 10, 2009.
2. U.S. Environmental Protection Agency (EPA). “Air Quality Criteria – Lead” October 2006. Available from: National Center for Environmental Assessment Research, Triangle Park, NC 27111.
3. Levin Ronnie, Brown, Mary Jean et al., Lead exposures in U.S. Children, 2008: implications for prevention. Environmental Health Perspectives. 2008;116(10): 1285-1292.
4. Gaitens, Joanna M., Dixon, Sherry L., et al., Exposure of U.S. children to residential dust lead, 1999-2004 I. Environmental Health Perspectives [serial online]. March 2009;117(3):461-467.
5. Dixon, Sherry L, Gaitens, Joanna M., et al., Exposure of U.S. children to residential dust lead, 1999-2004 II. Environmental Health Perspectives [serial online]. 2009;117(10): 468-474).
Conflict of Interest:
None declared