UPDATE: On May 16, 2012, the CDC announced acceptance of the ACCLPP's recommendation to replace "level of concern" for lead poisoning with a new reference value of 5 mcg/dL. To learn more, read the CDC's response.
Citing new data that lead causes harm to children at levels lower than previously thought, an advisory committee for the Centers for Disease Control and Prevention (CDC) urges that public health efforts focus on preventing lead exposure, a policy called "primary prevention," and also now recommends that the cutoff value for blood lead levels be lowered from 10 micrograms per deciliter (mcg/dL) to 5 mcg/dL. The January 4 report by the Advisory Committee on Childhood Lead Poisoning Prevention (ACCLPP) notes that even very low levels of lead can have long-term adverse health effects on children.
In emphasizing primary prevention, the committee aims to shift the focus of efforts to prevent lead exposure before children are harmed, rather than reacting to exposure that has already occurred. Their recommendations list ways that exposure from lead-tainted soil, water, dust and paint can be eliminated. For example, children should not be present when lead in old paint is exposed, such as when sanding or peeling paint, in homes built prior to 1978. They also advise prenatal counseling of mothers when possible. An assessment of the child's environment for potential sources of lead is encouraged even before screening for lead in the blood. For details from the CDC on how to prevent lead exposure, see web page Lead: Prevention Tips.
The recommendations in the report are based on a growing body of evidence from several studies that demonstrate harmful effects in children with blood lead levels less than the current limit of 10 mcg/dL. Up to now, this limit has been referred to as the "level of concern," but the ACCLPP recommends dropping that designation and putting the emphasis on prevention, noting there is no threshold level at which exposure to lead is considered safe. When testing blood lead levels, the committee favors using a lower 5 mcg/dL cutoff to notify public health officials when a child has been exposed to lead at a level greater than the general population (greater than 97.5% of all children in the U.S.).
A level above the established cutoff alerts doctors and public health officials to institute measures to reduce further harm. These actions usually include identifying the environmental source of the lead so as to eliminate it or minimize further exposure, providing education about lead poisoning, and establishing frequent testing and closer medical monitoring of those affected.
Over the years that U.S. children have been screened for lead, the limit has gradually been lowered as new evidence accumulates on the health problems from minute amounts, such as impaired development, lower IQ, learning disabilities, and behavioral disorders. Once a child has been affected, the problems are essentially irreversible. The committee's report also points to studies that are currently evaluating lead's influence on the health of the cardiovascular system and hormones (endocrine system). Young children are especially vulnerable to lead because they grow so quickly and are more likely to ingest or absorb lead from their environment.
Screening children for elevated blood levels has long been part of the strategy for minimizing their exposure to lead and preventing lead poisoning. Increased lead in the body does not always result in any immediate or obvious signs or symptoms, so an elevated level is often only detected through testing. Depending on children's risk of exposure, doctors may test them between 1 and 2 years old and again between 3 and 6 years old.
The ACCLPP recognizes the challenges that laboratories face in testing for lead at the new lower level. There is normally a certain amount of variation in results even when repeating the test on the same sample, and this variation can have greater impact when measuring very small amounts. Laboratories will have to ensure that the lead test is as precise and accurate as possible. To help ensure accuracy, the report states that all positive results are to be confirmed with repeat testing, and that results greater than 45 mcg/dL, or symptoms of lead poisoning, must be confirmed within 48 hours. Because the test can be contaminated from lead on a child's finger, a positive result from a fingerstick sample must be confirmed using a blood sample collected from a vein in the arm. Once lead exposure has been confirmed, activities to prevent further harm are set in motion.
Lowering the testing cutoff would increase the number of children identified as having lead exposure. Approximately 450,000 children in the U.S. have lead levels above the recommended revised limit, says the ACCLPP, compared to the 250,000 children estimated by the CDC using the current cutoff value. The lower threshold could impact efforts to address this public health problem, improving detection so that actions can be taken sooner.
Though the ACCLPP has proposed changes to the policy on lead along with the 5 mcg/dL cutoff value for lead testing, it may be some time before they are put into practice. The committee notes that the CDC and the Department of Health and Human Services will perform an internal review of the full report and will consider all the recommendations before deciding which to formally adopt and determining how those approved will be implemented.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
(January 4, 2012) Report of the Advisory Committee on Childhood Lead Poisoning Preventions of the Centers for Disease Control and Prevention, Low Level Lead Exposure Harms Children: A Renewed Call for Primary Prevention. PDF available for download at http://www.cdc.gov/nceh/lead/ACCLPP/Final_Document_011212.pdf through http://www.cdc.gov. Accessed Jan 31, 2012.
(June 1, 2009) Centers for Disease Control and Prevention. Lead. Available online at http://www.cdc.gov/nceh/lead/ through http://www.cdc.gov. Accessed Jan 31, 2012.