Childhood Blood Lead Levels — United States, 2007–2012

Please note: An erratum has been published for this article. To view the erratum, please click here.

Jaime Raymond, MPH

Mary Jean Brown, ScD

Division of Emergency and Environmental Health Services, National Center for Environmental Health, CDC

Corresponding author: Jaime S. Raymond, Division of Emergency and Environmental Health Services, National Center for Environmental Health, CDC. Telephone: 770-488-3627; e-mail: zvu0@cdc.gov.

Preface

This report provides data concerning childhood blood lead levels (BLLs) in the United States during 2007–2012. These data were collected and compiled from extracts sent by state and local health departments to CDC's Childhood Blood Lead Surveillance (CBLS) system. The numbers of children aged <5 years reported to CDC for 2007–2012 with BLLs ≥10 μg/dL are provided by month, geographic location, and age group in tabular form (Tables 1–3). The number of children who received a new diagnosis of BLLs ≥70 μg/dL during the same time period is summarized (Figure). This report is a part of the first-ever Summary of Notifiable Noninfectious Conditions and Disease Outbreaks, which encompasses various surveillance years but is being published in 2015 (1). The Summary of Notifiable Noninfectious Conditions and Disease Outbreaks appears in the same volume of MMWR as the annual Summary of Notifiable Infectious Diseases (2).

Background

In 1991, CDC recommended that identification of children with BLLs ≥10 μg/dL should prompt public health action by state or local health departments with follow-up testing (3). In 1995, in collaboration with CDC, the Council of State and Territorial Epidemiologists designated elevated blood lead levels as the first noninfectious condition to be added to the list of conditions designated as reportable at the national level (4).

In May 2012, the Advisory Committee on Childhood Lead Poisoning Prevention (ACCLPP) recommended the use of a reference range for blood lead. ACCLPP recommended that clinical and public health-care providers use the upper value of the reference range to identify children with elevated BLLs, on the basis of the 97.5th percentile of the National Health and Nutritional Examination Survey (NHANES)–generated BLL distribution in children aged 1–5 years (currently 5 μg/dL) (5).

Permanent neurological damage and behavioral disorders have been found to be associated with lead exposure at blood levels at or below 5 μg/dL (6–9). Previous studies have shown that high BLLs (≥70 μg/dL) can cause severe neurologic problems such as seizures, comas, and even death (10).

In 2007, a total 38 states identified and reported 37,289 children aged <6 years with BLLs ≥10 μg/dL (11). In 2012, approximately 122,000 children aged <6 years were reported with BLLs ≥5 μg/dL (11). For the period 2007–2012, CDC examined reported BLLs of children aged <5 years in three categories: children with BLLs ≥10 μg/dL, children with new reports of BLLs ≥10 μg/dL, and children with new reports of BLLs ≥70 μg/dL.

Data Sources

Results of blood lead tests for children from state and local health departments were sent to CDC's Healthy Homes and Lead Poisoning Prevention Program (HHLPPP) quarterly. At the end of each quarter, state health departments verify the data collected for blood lead testing. The test results compiled and analyzed by state health departments and submitted to CDC comprise the CBLS database.

State and local childhood blood lead surveillance systems contain the results of blood lead tests of children reported to state health departments by private laboratories as well as state and local government laboratories. The reporting criteria of BLLs from the laboratories to the state are set by each state and vary across jurisdictions. CDC and participating states have established a set of core data variables that should be collected for every child at the time of the blood lead test. These variables include identification and demographic information (e.g., date of birth, race, or ethnicity), laboratory information (e.g., venous or capillary blood test), date of blood lead test, address information (e.g., city and zip code), and test result. Records are de-identified and de-duplicated; the child associated with each record is assigned a unique identifier that is sent to CDC along with the collated core data. CDC checks each state-submitted record for correct formatting, coding, and content. Records not meeting CDC criteria are summarized in file processing reports that are sent to states for correction. Certain errors, if not corrected, prevent the record from being entered in the CBLS database.

To assist state health departments with tracking children who have received a blood lead test, CDC developed a computer software program, Healthy Homes Lead Poisoning Surveillance System (HHLPSS). Some states have adopted this system, while others have developed their own system.

Interpreting Data

In this report, state surveillance data are presented for children aged <5 years who were tested for lead at least once during 2007–2012. Confirmed BLLs ≥10 μg/dL are defined as having one venous blood lead test ≥10 μg/dL or two capillary blood tests ≥10 μg/dL drawn within 12 weeks of each other (12). Incidence data are presented by the date of the confirmed blood lead test. Data are reported by the jurisdiction of the child's residence at the time of the confirmed blood lead test. State health departments check for duplicate laboratory reports for children as well as for completeness of the laboratory report before sending the data to CDC. After data are sent, CDC has its own checks for the data to ensure its completeness and accuracy.

The data provided in this report are useful for analyzing childhood blood lead trends and determining relative morbidity numbers. However, reporting practices affect how these data are interpreted. Childhood blood lead reporting is likely incomplete, and completeness of the records might vary depending on state, laboratory, or BLL range (e.g., some states might not require reporting of BLLs <10 μg/dL). Independent of the actual incidence of disease, factors such as changes in the methods of surveillance or introduction of new diagnostic tests (e.g., portable handheld analyzer) can cause changes in the reported blood lead levels. Only states funded by CDC are required to report.

Methods for Identifying Childhood Lead Exposure

Each state has laws and regulations regarding blood lead tests reported to the state health department. Most states require electronic reporting. Some states have laws that require laboratories to send all blood lead tests, regardless of the BLL, while other states only require laboratories to send blood lead tests with BLLs ≥10 μg/dL. Blood lead test reporting has been a notifiable condition since 1995 (4). CDC asks that state health departments report all blood lead test data for children to HHLPPP. In May 2012, CDC adopted the ACCLPP recommendation to replace the "level of concern" (10 μg/dL) with a reference value based on the distribution of BLLs in U.S. children aged 1–5 years, the upper value of which is 5 μg/dL (5). However, because this change was not made until mid-2012, in this report, an elevated blood lead level (EBLL) is defined as ≥10 μg/dL.

Publication Criteria

Reports of children (aged <5 years) with confirmed BLLs ≥10 μg/dL during 2007–2012.

Highlights

Lead exposure in children can cause permanent neurologic damage (6). Behavioral disorders are associated with lead exposure even at detectable blood levels at or below 5 μg/dL (6–9). The most common highly concentrated source of lead for children is lead paint. When paint containing lead deteriorates into flakes, chips, or fine dust, it is easily inhaled or ingested by small children In 2007, a total of 38 states* and New York City submitted BLL data to CDC; however, by 2012, that number was reduced to 29 states† and New York City submitting data (a 24% reduction in contributors). One state, California, provided a substantial amount of BLL data during 2007–2011 but did not submit any data for 2012. The other states not submitting data to CDC in 2012 did not contribute a substantial number of BLLs ≥10 μg/dL. Among the states that reported data to CDC for all 6 years, the number of children with confirmed BLLs ≥10 μg/dL declined (Table 2), a trend which is consistent with national data reporting for 2007–2012 (11).

During the four warm-weather months (June–September), 40%–50% of cases are identified, more than would be expected (33%) if identification rates were distributed evenly over the year (Table 1). In warm weather, windows possibly painted with lead-based paint are opened and closed, creating lead dust in the air and on the ground. Also, repainting and renovation activities are more common in summer. Increased presence and activity of children in and around the home might lead to children having more contact with contaminated dust, surfaces, and soil.

Except for 2010 and 2012, the number of BLL cases reported in January exceeds other months in that year (15% of cases). Various reasons might account for this finding. Increases in illness acquired during the holidays might account for increased visits to pediatrician offices and increased lead screening tests. Insurance changes at the beginning of the calendar year also might cause an increase in child testing. Another possible contributor to this observation is delayed reporting of BLL data from the latter half of December, when many businesses (laboratories and physician offices) are closed.

States in the Mid-Atlantic region reported the largest number of cases in 2007 (Table 2). This same region also shows the largest reduction in reported cases, with a decrease of >50% in reported cases during 2007–2012. In the East North Central states, elevated BLLs decreased 33%. In the East South Central states, where the fewest cases were reported, the number of cases decreased 22% and no clear trend was evident over time (Table 2).

The number of incidence cases (defined as cases among children aged <5 years with a first confirmed BLL ≥10 μg/dL) decreased 50% during 2007–2012 (Table 3). The percentage of children aged 1–4 years with BLLs ≥10 μg/dL was higher than that for children aged <1 year across all years, possibly because of increased hand-to-mouth activity and mobility for older children. However, the number of children with BLLs ≥70 μg/dL remains persistent with no clear trend emerging (Figure). Although CDC funding for state and local programs ended in 2012, a total of 21 states§ and New York City still have Healthy Homes and Childhood Lead Poisoning Prevention Programs and continue to send screening and elevated blood lead data to CDC quarterly.

More detailed annual summaries describing the number of children tested for lead by state, county, and BLL are published periodically by CDC. A summary of childhood lead exposure in 2013, the most recent year for which data are available, is available at http://www.cy118119.com/nceh/lead.

References

1. CDC. Summary of notifiable noninfectious conditions and disease outbreaks—United States. MMWR Morb Mortal Wkly Rep 2013;62(54).
2. CDC. Summary of notifiable infectious diseases—United States. MMWR Morb Mortal Wkly Rep 2013;62(53).
3. CDC. Preventing lead poisoning in young children: a statement by the Centers for Disease Control. Atlanta, GA: US Department of Health and Human Services, CDC; 1991.
4. CDC. Changes in national notifiable diseases data presentation. MMWR Morb Moral Wkly Rep 1996;45:41–2.
5. CDC. Low level lead exposure harms children: a renewed call for primary prevention. Report of the Advisory Committee on Childhood Lead Poisoning Prevention of the Centers for Disease Control and Prevention. Atlanta, GA: US Department of Health and Human Services, CDC; 2012. Available at http://www.cy118119.com/nceh/lead/ACCLPP/Final_Document_030712.pdf.
6. Bellinger DC, Stiles KM, Needleman HL. Intellectual impairment and blood lead levels. N Engl J Med 2003;349:500–2.
7. Bellinger DC, Stiles KM, Needleman HL. Low-level lead exposure, intelligence and academic achievement: a long-term follow-up study. Pediatrics 1992;90:855–61.
8. Dietrich K, Ris M, Succop P, Og B, Bornschein R. Early exposure to lead and juvenile delinquency. Neurtoxicol Teratol 2001;23:511–8.
9. Needleman H, McFarland C, Ness R, Fineberg S, Tobin M. Bone lead levels in adjusted delinquents: a case control study. Neurtoxicol Teratol 2002;24:711–7.
10. National Research Council. Measuring lead exposure in infants, children, and other sensitive populations. Washington, DC. National Academy Press; 1993.
11. CDC. Healthy homes and lead poisoning prevention: CDC's National Surveillance Data (1997–2010). Atlanta, GA: US Department of Health and Human Services, CDC; 2012. Available at http://www.cy118119.com/nceh/lead/data/StateConfirmedByYear1997-2010.htm.
12. Council of State and Territorial Epidemiologists. CSTE position statement 09-OH-02. Atlanta, GA: Council of State and Territorial Epidemiologists; 2009. Available at http://c.ymcdn.com/sites/www.cste.org/resource/resmgr/PS/09-OH-02.pdf.