Data and Statistics

Overview

CDC collaborated with the Council of State and Territorial Epidemiologists (CSTE) to develop a national surveillance system. This system monitors blood lead levels (BLLs) in the U.S.

In 1995, reporting of blood lead levels became the first non-infectious condition to be notifiable at the national level. This information is used to monitor individual case management and identify local program needs and high-risk areas to target preventive interventions.

State and local blood lead surveillance

At the state or local level, the primary source of blood lead surveillance data is usually the state-based Childhood Lead Poisoning Prevention Program (CLPPP) and/or the state-based Adult Blood Lead Epidemiology & Surveillance (ABLES) program. These programs are responsible for collecting, managing, and reporting data. This ensures that children and adults with lead in their blood receive appropriate follow-up and management. CDC supports development of the Healthy Homes and Lead Poisoning Surveillance System (HHLPSS) as a data management platform for blood lead surveillance.

Blood lead surveillance data are a valuable resource for program management. However, these data have limitations. First, data from these programs are restricted to individuals targeted for blood lead testing by health care providers. Health care providers usually test children and adults at a high risk for lead exposure. Because of this, the people tested are not representative of the entire U.S. population.

Additionally, state requirements for blood lead testing and reporting vary based on local conditions. Due to this, the data is not comparable across locations or generalizable at the national, state, or local level.

National Health and Nutrition Examination Survey (NHANES)

NHANES is another source of data for estimating the number of children and adults with lead in their blood. These surveys provide national estimates of the prevalence of lead in the blood among children and adults over time. However, it cannot provide information at the state or local level.

These surveys also do not directly measure incidence and the data cannot be used to follow short-term trends. NHANES blood lead data are used to monitor the nation's progress in meeting the Healthy People Objectives.

CDC’s childhood lead poisoning data

A blood lead test is the best way to measure lead exposure. Children are given a blood test to determine the level of lead in their blood.

The amount of lead in blood is referred to as blood lead level (BLL). BLLs are measured in micrograms of lead per deciliter of blood (μg/dL).

There is no known safe BLL. Exposure to lead can seriously harm a child's health. Millions of children are being exposed to lead in their homes, increasing their risks for:

• Damage to the brain and nervous system
• Slowed growth and development
• Learning and behavior problems (e.g., reduced IQ, ADHD, juvenile delinquency, and criminal behavior)
• Hearing and speech problems

CDC data collection

CDC began collecting childhood blood lead surveillance data in April 1995.

CDC funds 35 state and local health departments for lead surveillance. As part of their funding agreement, awardees (grantees) are required to report data to us on a quarterly basis. Data reporting is voluntary in states we don't fund. We do not have a contract or other mechanism to require reporting. In many of the states we don't fund, there are no staff to do this work.

• The 29 funded states are Arizona, Colorado, Connecticut, Delaware, Georgia, Illinois, Indiana, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, New Hampshire, New Jersey, New Mexico, New York State, North Carolina, Ohio, Oklahoma, Oregon, Rhode Island, Tennessee, Vermont, Washington, West Virginia, and Wisconsin.
• We also fund Washington, DC.
• The five cities are Chicago, Houston, Los Angeles, New York City, and Philadelphia.

CDC uses data from states to prepare the State Surveillance Data and the National Surveillance Data. These data are from funded states as well as states that volunteer to send us their data.

The summary data includes the number of addresses where multiple children have had confirmed elevated blood lead levels. Data from the 2000 census is also included.

About the data

The data is also broken down by highest BLL at or after confirmation. This chart represents data reported by state to the national surveillance system over the past several years. The chart represents only state-specific data and is not a population-based estimate. Therefore, we are not able to compare states against one another.

All states funded by CDC have state laws that require clinical laboratories to report all BLLs to their state health department. This excludes Indiana and Kentucky.

CDC grantees annually report:

• Data on blood lead testing and follow-up of children identified with high BLLs
• Lead hazard identification, control, and abatement activities in their jurisdictions
• Proposed interventions for high-risk areas

States collect the lead poisoning data through a variety of sources including:

• Both public and private labs
• State and local housing authorities
• State and local environmental protection agencies
• State and local education agencies

Limitations

Analyses and generation of surveillance reports require considerable time and human intervention. Therefore, data is not always sent to CDC in a timely manner. Even so, about 2.5 million blood lead tests are received by CDC each year. They are grouped into a reportable surveillance format after careful cleaning and deduplication to ensure only one test per individual.

Once CDC gets and cleans the data, we are able to look at it by county. Data collection methods vary among states, so CDC cannot accurately compare data across counties or states.

The childhood BLL data on CDC's website are not a population-based estimate. These data are not representative of a whole county or a whole state, they are designed to target the highest-risk areas. Programs work hard to test children most likely to have high BLLs.

Programs vary in the number of children tested and the number of children identified with high blood levels. This is due to a variety of factors. These data cannot be accurately compared between or among states and counties.

Percentage comparisons can be affected by:

• County size,
• Number of children tested within the counties, and
• Number of children in the counties who are reported to have high BLLs. For example, some counties may have a small number of children tested, but many of those tested have high BLLs.

Some statistics could underestimate the number of children with lead exposure because not all children are tested.

Use

Health agencies using CDC's surveillance system or another childhood lead poisoning surveillance and data collection system can:

• Identify remaining at-risk geographic areas
• Identify at-risk children to target testing and limited resources
• Identify emerging sources of exposure and inform strategic plans to remove or reduce sources
• Evaluate timeliness and efficacy of case management services available to children with lead poisoning and work with inspectors and risk assessors to ensure safe living environments
• Target pediatric health care provider education efforts

About NHANES

NHANES is a population-based survey. The survey is used to assess the health and nutritional status of adults and children in the United States. CDC's state-based data are not comparable to data in NHANES.

CDC analyzed data from NHANES from 1999–2002 to 2007–2010 to determine the 97.5th percentile of blood lead distribution in children. This helped to determine the reference value (currently 5 µg/dL). Using a reference value gives us a way to identify children with blood lead levels that are much higher than most.

Declining BLLs

BLLs have continued to decline in the last 30 years, even in the most high-risk areas. The overall declining in children detected with BLLs at or above the reference value is in keeping with the national population-based estimate from NHANES, which has also declined over time.

The decrease is most likely 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
• The communities most at risk

Additional resources

Blood Lead Levels in Children Aged 1–5 Years — United States, 1999–2010

CDC State Surveillance Data webpage showing county-level summary data

CDC National Surveillance Data webpage showing state summary data by year

CDC's Childhood Lead Poisoning Prevention Program