About the Data: Blood Lead Surveillance

How the data is collected

CDC's Childhood Lead Poisoning Prevention Program compiles blood lead surveillance data. Data is collected from children <16 years of age who were tested at least once since January 1, 1997. The national surveillance system is composed of de-identified data from state and local health departments.

CDC applies nationally consistent standard case definitions and classifications for blood lead surveillance data from all states. In addition, CDC applies rigorous error-checking and validation algorithms to the data submitted. This process ensures only one test per individual per year is counted. Therefore, the information available from CDC will not match data reports from the individual states. Individual states may use different case definitions for clinical and environmental management.

State and local lead surveillance

State and local childhood lead poisoning prevention programs supported by cooperative agreements must provide childhood blood lead surveillance data to CDC. Other programs may provide data on a voluntary basis.

Most states have laws that require clinical laboratories to report all blood lead levels to the state health department. States maintain their own child-specific databases based on reports of blood lead tests from laboratories and health care providers. This allows duplicate or sequential test results from individual children to be identified and resolved.

These databases also contain information about clinical follow-up and environmental investigations into potential sources of lead exposure for children. Investigations occur when children have blood lead levels above the CDC's blood lead reference value (BLRV). States extract certain information from their child-specific surveillance databases. Identifying information is removed before the data extract is transferred to CDC for inclusion in the national surveillance database.

Blood lead surveillance data are collected for program management purposes and, therefore, have some limitations. Data collection methods vary across states and counties and are not generalizable or comparable at the national, state, or local level.

Blood lead reference value

In 2012, the Centers for Disease Control and Prevention (CDC) introduced a blood lead "reference value."

This value helps to identify children with higher levels of lead in their blood compared to most children. This level is based on the 97.5th percentile of the blood lead values among U.S. children ages 1-5 years from 2015-2016 and 2017-2018 National Health and Nutrition Examination Survey (NHANES) cycles. Children with blood lead levels at or above the BLRV represent those at the top 2.5% with the highest blood lead levels.

NHANES is a population-based survey to assess the health and nutritional status of adults and children in the U.S. and determine the prevalence of major diseases and risk factors for diseases. Every four years, CDC reanalyzes blood lead data from the most recent two NHANES cycles to determine whether the reference value should be updated.

The value of 3.5 μg/dL was derived from NHANES data from the 2015-2016 and 2017-2018 cycles. The Federal Advisory Committee, called the Lead Exposure and Prevention Advisory Committee (LEPAC), unanimously voted on May 14, 2021, in favor of recommending that CDC update the reference value to 3.5 μg/dL based on these NHANES data.

CDC's BLRV is a screening tool to identify children who have higher levels of lead in their blood compared with most children. The reference value is not health-based and is not a regulatory standard. States independently determine action thresholds based on state laws, regulations, and resource availability. CDC encourages healthcare providers and public health professionals to follow the recommended follow-up actions based on confirmed blood lead levels.

Previous terminology

Until 2012, children were identified as having a blood lead "level of concern" if the test result was 10 or more micrograms per deciliter (µg/dL) of lead in blood. CDC is no longer using this term and is instead using the blood lead reference value to identify children who have more lead in their blood than most children.

In 2012, the blood lead reference value for children corresponding to the 97.5 percentile was established to be 5 micrograms per deciliter (µg/dL) based NHANES data from 2007-2010. Prior to this current update, blood lead levels below 5 μg/dL may, or may not, have been reported to parents. The new lower blood lead reference value of 3.5 μg/dL means that more children could be identified as having lead exposure allowing parents, doctors, public health officials, and communities to act earlier to reduce the child's future exposure to lead.

Data definitions

CDC applies the following nationally consistent standard definitions and classifications for blood lead surveillance data from all states. A child may be screened in multiple years or even multiple times within a given year. However, in CDC data tables, a child is only counted once per each year based on their highest blood lead level.

These definitions are to be used for classifying blood lead surveillance data. However, decisions about the timing and sampling method for use in confirmatory and follow up testing should be made based on CDC's Recommended Actions Based on Blood Lead Level.

Test

Any blood lead draw (capillary, venous or unknown sample type) on a child <16 years of age that produces a quantifiable result and is analyzed by a Clinical Laboratory Improvement Amendments (CLIA)-certified facility or an approved (CLIA waived) portable device.

Test type

A blood lead test may be collected for screening, confirmation, or follow-up.

Sample type

A blood lead test may be collected as a venous, capillary, or unknown blood specimen type.

Screening test

A blood lead test for a child age <72 months who previously did not have a confirmed elevated BLL.

Confirmed BLL ≥ CDC's blood lead reference value

A child with one venous blood test ≥ 3.5 μg/dL or two capillary blood tests ≥ 3.5 μg/dL drawn within 12 weeks of each other.

Unconfirmed BLL ≥ CDC's blood lead reference value

A single capillary blood lead test ≥ 3.5 μg/dL or two capillary tests ≥ 3.5 μg/dL drawn more than 12 weeks apart.

Percent of children with BLLs ≥ CDC's blood lead reference value

The number of children less than 72 months of age with a blood lead level ≥ 3.5 µg/dL divided by the number of children less than 72 months of age tested for blood lead, multiplied by 100.

Percent of children tested

The number of children less than 72 months of age tested for blood lead divided by the total number of children less than 72 months of age within a geographic unit (i.e., county or state) based on annual intercensal estimates for the most recent U.S. Census data, multiplied by 100. (Also referred to as "screening penetrance.")

Resources

• Testing for lead poisoning in children–information on blood lead testing in children
• Recommended actions based on blood lead level–recommendations for follow-up and case management of children based on confirmed blood lead levels
• CDC's recommended terminology when discussing children's blood lead levels–guidance for interpreting and discussing children's blood lead levels
• CDC response to Advisory Committee on Childhood Lead Poisoning Prevention (ACCLPP) Recommendations in "Low Level Lead Exposure Harms Children: A Renewed Call of Primary Prevention"
• Recommendations of the Advisory Committee for Childhood Lead Poisoning Prevention (ACCLPP) "Low Level Lead Exposure Harms Children: A Renewed Call of Primary Prevention"

For information on adult blood lead surveillance data for individuals ≥16 years of age, please visit CDC's National Institute for Occupational Safety and Health (NIOSH) Adult Blood Lead Epidemiology & Surveillance (ABLES) Program.