At a glance
As of October 28, 2021, CDC uses a blood lead reference value (BLRV) of 3.5 micrograms per deciliter (µg/dL) to identify children with blood lead levels that are higher than most children’s levels.
Overview
On October 28, 2021, CDC updated the blood lead reference value (BLRV) from 5.0 μg/dL to 3.5 μg/dL. A BLRV is intended to identify children with higher levels of lead in their blood compared with levels in most children.
The value is based on the 97.5th percentile of the blood lead distribution in U.S. children ages 1–5 years. Updating the BLRV to 3.5 μg/dL allows children within the range of 3.5–5 μg/dL to receive prompt actions. This helps mitigate health effects and remove or control exposure sources.
Updating the reference value encourages CDC, federal agencies, health departments, providers, communities, and other partners to take the following steps:
- Focus resources on children with the highest levels of lead in their blood compared with levels in most children in that age range
- Identify and eliminate sources of lead exposure
- Take more prompt actions to reduce the harmful effects of lead
The BLRV is a population-based measurement. It now indicates that 2.5% of U.S. children aged 1–5 years have BLLs at or above 3.5 μg/dL. It is not a health-based standard or a toxicity threshold. The BLRV should be used to guide to both determine recommended follow-up and prioritize communities with the need for exposure prevention.
Improving health equity and environmental justice
Updating the BLRV supports CDC's commitment to health equity and addressing environmental justice. The risk for lead exposure is not the same for all children. There are significant disparities in health outcomes across racial and ethnic groups and people with different socioeconomic status.
Higher blood lead levels are more prevalent among children from racial and ethnic minority groups and children from low-income households. Children who live in housing built before 1978 are also at risk.
Children from racial and ethnic minority groups are more likely to live in conditions where there is greater likelihood of exposure. Some of these conditions include poor housing and environmental exposures, such as lead in air, soil, and water.
CDC recommends that public health and clinical professionals focus screening efforts on neighborhoods and children at high risk. These factors are based on age of housing and socioeconomic risk factors:
- Public health and clinical professionals should collaborate to develop screening plans responsive to local conditions, using local data
- In the absence of such plans, universal BLL testing is recommended
- Jurisdictions should follow the Centers for Medicare & Medicaid Services requirement that all Medicaid-enrolled children be tested at ages 12 months and 24 months or at age 24–72 months if they have not previously been screened
Effects on lead in the blood
Protecting children from exposure to lead is important to lifelong good health. No safe BLL in children has been identified. Even low levels of lead in blood have been shown to have effect. Low levels of lead can reduce a child's learning capacity, ability to pay attention, and academic achievement.
Some effects of exposure to lead can be permanent. If caught early, however, parents, healthcare providers, and communities can take actions to prevent further exposure. The most important step that anyone can take is to prevent lead exposure before it occurs.
Frequently asked questions
What is CDC's blood lead reference value?
CDC has been involved in defining the criteria for interpreting blood lead levels in children for more than 40 years. In 2012, CDC introduced the concept of a blood lead reference value (BLRV) to identify children with higher levels of lead in their blood compared with levels in most children.
The BLRV is based on the 97.5th percentile of the blood lead distribution in U.S. children ages 1–5 years. In 2012, the BLRV in children was established to be 5 micrograms per deciliter (µg/dL). In 2021, CDC updated the BLRV in children to 3.5 μg/dL.
The BLRV is based on data from two consecutive cycles of the National Health and Nutrition Examination Survey (NHANES). The BLRV is updated periodically to reflect changes in the population. The current update is based on data from the 2015–2018 NHANES cycles.
Why did CDC update the blood lead reference value?
The blood lead reference value (BLRV) is based on the 97.5th percentile of blood lead distribution in children. This was determined from National Health and Nutrition Examination Survey (NHANES) data. The updated blood lead reference value is based on NHANES data from 2015–2016 and 2017–2018. CDC's Federal Advisory Committee, called the Lead Exposure and Prevention Advisory Committee, unanimously voted on May 14, 2021, in favor of updating the reference value to 3.5 μg/dL, based on data from the 2015–2018 NHANES cycles.
Updating the reference value allows CDC, healthcare providers, federal agencies, and health departments to focus resources on children with the highest exposure to lead compared with most children in that age range.
By updating the BLRV to 3.5 μg/dL, children with blood lead levels within the range of 3.5–5 μg/dL will now also be identified to receive prompt actions to mitigate health effects and control potential exposure sources.
Does CDC work with other groups that have a role in lead poisoning prevention?
Yes, CDC works with other federal agencies, CDC-funded lead grantees, and public health and medical partners to keep healthcare providers and the public informed.
What is a "reference value?"
No safe level of lead in children has been identified. Even low levels of lead in blood have been shown to reduce children's IQ, ability to pay attention, and academic achievement. Because any blood lead level can harm children, our focus is on eliminating exposure in the first place.
If a child has a blood lead level below the blood lead reference value (BLRV), it does not mean a child is free from harm caused by lead exposure. The reference value simply shows the value at which a child has more lead in their blood than most U.S. children (97.5% of children age 1–5 years).
The primary difference between the prior BLRV of 5 µg/dL and the current BLRV of 3.5 µg/dL is that children with a blood lead level within the 3.5–5 µg/dL range will now also be identified as having lead exposure greater than 97.5% of children. This can encourage prompt action to mitigate harmful health effects and removal or control of lead exposure sources.
CDC recommends that children with BLLs of 3.5 µg/dL and higher receive routine assessment of nutritional and developmental milestones, environmental exposure history to identify potential sources of lead exposure, nutritional counseling related to calcium and iron intake, and follow-up blood lead level testing at recommended intervals based on the child's age. CDC provides a summary of recommended actions based on blood lead level.
What is lead poisoning?
Lead poisoning or lead toxicity refers to exposures to lead that result in illness and require immediate medical attention. It is used to describe cases when there are severe health effects related to high blood lead levels. If blood lead levels are 45 micrograms per deciliter (μg/dL) or greater, healthcare providers may recommend medication to help remove lead from the body. However, children are highly sensitive to lead and exposure at lower levels has been shown to cause harm. CDC provides a summary of recommended actions based on blood lead level.
Many factors affect how different people's bodies handle exposure to lead. These factors include a person's age, nutritional status, source of lead exposure, amount of lead exposure, underlying health conditions, and length of exposure. Many children exposed to lead have no obvious symptoms. Some exposures, however, cause more obvious health effects that need urgent treatment.
No safe level of lead in children's blood has been identified. Even low levels of lead that were once considered safe have been linked to harmful changes in intelligence, behavior, and health. Children are most at risk because they are still developing physically and mentally.
A blood lead reference value (BLRV) of 3.5 micrograms per deciliter (µg/dL) can be used to identify children with blood lead levels higher than those of most U.S. children, determine appropriate follow-up actions, and prevent further exposure. The BLRV is simply the level at which a child has more lead in their blood than do most U.S. children (97.5% of children ages 1–5 years).
If you are concerned that your child has been exposed to lead, contact their healthcare provider to get a blood lead test. Based on the results of the test, actions can be taken to reduce further exposure to lead and connect them to recommended treatment and services. Lead exposure is preventable.
What are the benefits of updating the blood lead reference value for children age less than 6 years old from 5 µg/dL to 3.5 µg/dL?
There is no safe level of lead in blood. Updating the reference value encourages CDC, federal partners, and health departments to focus on young children, under age of 6 years, with the highest exposure to lead compared with most U.S. children. This is part of the nation's ongoing effort to reduce blood lead levels even further and identify sources of exposure to those young children at highest risk for continued exposures.
The primary difference between the previous blood lead reference value (BLRV) of 5 µg/dL and the updated BLRV of 3.5 µg/dL is that children with a blood lead level (BLL) within the 3.5–5 µg/dL range will also be prioritized for lead reduction action. With the updated BLRV, children with higher BLLs will continue to be eligible for the same targeted services as previously described.
CDC recommends that children with BLLs of 3.5 µg/dL and higher receive routine assessment of nutritional and developmental milestones, environmental assessment of detailed history to identify potential sources of lead exposure, nutritional counseling related to calcium and iron intake, and follow-up BLL testing at recommended intervals based on the child's age.
Despite the overall decline of blood lead levels over time, lead exposure remains a significant public health concern for some young children because of persistent lead hazards in the environment and hand to mouth activity that is common among this age group.
Sources of lead include lead-based paint, lead service lines, lead in household plumbing material, and soil contaminated by past sources, such as automobile gasoline and hazardous waste sites. Young children can also be exposed to lead in contaminated food, folk remedies, cultural products, and consumer products. Young children can also be exposed to lead secondhand if a parent or other adult they spend time with works or engages in recreational activities that involve lead or lead-based products.
How might health departments use this new level?
Health departments may use the blood lead reference value (BLRV) in recommendations that involve follow-up evaluation of young children under 6 years, after blood lead level testing. They can use the reference value to identify high-risk populations and geographic areas most in need of lead exposure prevention.
Health departments can guide targeted interventions to reduce lead exposure in children by identifying hotspots for potential lead exposure and prioritizing where to focus blood lead screening, outreach, and community interventions.
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.
What might this new level affect laboratory reporting?
The Division of Laboratory Sciences in CDC's National Center for Environmental Health compiled and reviewed laboratory proficiency data through the Lead and Multi-element Proficiency Program. It concluded that current available laboratory tests for measuring blood lead can reliably measure blood lead levels of 3.5 μg/dL and greater.
CDC will continue to assist laboratories, healthcare providers, and health departments to overcome the challenges of measuring and managing lower levels of blood lead in children. CDC developed a template for clinical laboratories to report blood lead test results on the blood lead laboratory report. This reporting template identifies the BLRV and delineates risk-based intervals that represent escalating priorities for public health and medical intervention.
What does this mean for healthcare professionals?
Healthcare professionals should interpret the blood lead levels (BLLs) of their patients in accordance with the updated blood lead reference value (BLRV). They should then determine the need for follow-up testing and interventions for those children identified with BLLs at or above the BLRV. CDC has developed outreach materials to assist healthcare professionals.
What does this mean for parents of children who test above 3.5 μg/dL?
The primary difference between a blood lead reference value of 3.5 µg/dL and 5 µg/dL is that children with blood lead levels within the 3.5–5 µg/dL range will also be prioritized for lead exposure reduction actions. Even low levels of lead in blood have been shown to affect a child's intelligence, ability to pay attention, and academic achievement.
Who will pay for the testing and interventions needed? (Follow up tests for children with lower levels)
The blood lead reference value is based on a percentile of the population distribution of blood lead levels (BLLs). Because population growth has been relatively stable, the number of children with BLLs equal to or higher than 3.5 µg/dL today should be similar to the number of children with BLLs equal to or higher than 5 µg/dL in 2012. Therefore, overall national costs should not change much.
Children can be given a blood test to measure the level of lead in their blood. These tests are covered by Medicaid and most private health insurance. Costs associated with additional recommended actions will vary based on individual factors (e.g., health insurance status, recommended intervention, programs available in the jurisdiction).
If the child's BLL is 3.5 µg/dL or higher, CDC recommends that the child be referred for a follow-up venous blood test to assess the next steps. More information on follow-up can be found at recommended actions based on blood lead level.
What children should be tested or retested?
CDC recommends targeted screening efforts to focus on children having sociodemographic risk factors and those living in housing built before 1978. Public health and clinical professionals should collaborate to develop screening plans responsive to local conditions using local data. Lacking such plans, universal blood lead testing is appropriate.
Additionally, CDC recommends that jurisdictions follow the Centers for Medicare & Medicaid Services requirement that all Medicaid-enrolled children be tested at ages 12 months and 24 months, or at ages 24–72 months if not previously been screened.
How does the blood lead reference value fit in with CDC's lead poisoning prevention efforts?
CDC's lead poisoning prevention efforts and the updated blood lead reference value (BLRV) align well with the Federal Lead Action Plan's and CDC's goals to reduce children's exposure to lead. Updating the BLRV is a step in achieving health equity and environmental justice. The risk for lead exposure is not the same for all children. There are significant disparities in health outcomes across racial and ethnic groups and people with different socioeconomic status.
Higher blood lead levels are more prevalent among children from racial and ethnic minority groups, children from low-income households, and children who live in housing built before 1978. Also, children from racial and ethnic minority groups are more likely to live in conditions where there is greater likelihood of exposure. Some of these conditions include poor housing and environmental exposures, such as lead in air, soil, and water.
Additional resources
MMWR policy note: update of the blood lead reference value - United States, 2021
Press release: CDC updates blood lead reference value for children
Recommended actions based on confirmed blood lead level
Communication Briefs – information for CDC partners for implementing 3.5 μg/dL as the updated CDC Blood Lead Reference Value