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CDC Reports Half a Million U.S. Kids Above New Threshold for Blood Lead Level

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May 8, 2013

The Centers for Disease Control and Prevention (CDC) announced that recent data analysis shows more than half a million U.S. children exceed the agency's current threshold for lead exposure. This report comes after the CDC reduced the "level of concern" by half last year and replaced it with a new reference value. Based on a recommendation from its Advisory Committee on Childhood Lead Poisoning Prevention (ACCLPP), the CDC lowered the blood lead level (BLL) indicative of exposure in young children from 10 micrograms per deciliter (mcg/dL) to 5 mcg/dL in May 2012. Upon further analysis, the CDC found that an estimated 535,000 children ages 1-5 had more than 5mcg/dL in their blood as of 2010, thus requiring a physician's supervision and follow-up testing.

The CDC lowered the threshold because of increasing evidence that suggests minute amounts of lead below the previously accepted 10 mcg/dL threshold, adopted in 1991, can have detrimental effects on children. These effects include developmental problems, learning disorders, and reduced IQ, as well as possible cardiovascular and hormonal effects that are currently under investigation. Many of these symptoms are irreversible, and as part of their response to the ACCLPP's recommendation, the CDC's strategy will have a greater focus on lead exposure prevention techniques.

Lead enters a child's bloodstream when it is absorbed from the surrounding environment, and children under the age of 6 are at greatest risk for lead poisoning because they grow rapidly and have a tendency to touch or put their mouths on objects. The CDC cites lead-based paint and lead-contaminated dust as the main sources for exposure, commonly present in houses built prior to 1978. While elevated lead levels do not necessarily present immediate symptoms, a doctor may advise a child to undergo screening between the ages of 1 and 2 and again between 3 and 6, depending on a child's risk of exposure.

Adopting 5 mcg/dL as the threshold allows the agency to more closely monitor children at risk for lead exposure in hazardous environments and improves the ability of health officials and primary care doctors to catch a possible life-threatening condition before it progresses further. The CDC does not have an accepted level at which lead is considered safe; rather, the current value (upper reference interval) represents a concentration of lead in the blood that is higher than the general population, defined as greater than 97.5% of U.S. children ages 1-5 years from two consecutive cycles of the National Health and Nutrition Examination Survey (NHANES).

Conducted by the CDC, the NHANES is a program of studies focused on the health and nutritional status of children and adults in the U.S. As part of the studies, blood samples are taken from 850 children ages 1-5 every two years. These samples were analyzed to estimate the number of children at risk of adverse health effects due to lead exposure and to evaluate the efficacy of prevention efforts. Analysis of data collected between 1999 and 2010 revealed that 2.6% of children surveyed had BLLs greater than 5 mcg/dL, translating to an estimated 535,000 U.S. children with elevated levels. According to NHANES, the average BLL for children ages 1-5 was 1.3 mcg/dL as of 2010. Notable differences exist in certain groups; the highest average lead levels are seen in children ages 1-2, children living in poverty, children enrolled in Medicaid, and children of African American descent.

Much progress has been made in reducing the overall BLLs of children ages 1-5 over the past 40 years, particularly in the groups with the highest recorded BLLs. An estimated 88% of young children in the 1976-1980 NHANES cycle had BLLs of 10 mcg/dL or more, as compared to 4.4% during the 1991-1994 NHANES cycle. The average BLL among young children has declined by nearly one-third in the last decade alone – from 1.9 mcg/dL in the 1999-2002 NHANES cycle to 1.3 mcg/dL as of 2007-2010. According to the CDC, these observed BLL declines are due to successful efforts at the national, state, and local levels, including better monitoring of high-risk populations and reduced lead content in vehicle emissions, paint hazards, air, water, and consumer products.

Prevention techniques, public education, and physician monitoring are the CDC's primary tactics for addressing lead exposure in high-risk geographical areas. For children already identified as having BLLs above 5 mcg/dL, responses include environmental assessments to determine lead sources, educating family members about lead poisoning, and instituting follow-up testing to monitor the condition. While progress is certainly being made to reduce the overall BLL of young children in the U.S., the CDC recognizes that there is more yet to be accomplished. The agency recommends that all houses and places where children are frequently present be examined for lead hazards to prevent children from ever being exposed.

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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.

Centers for Disease Control and Prevention. Blood Lead Levels in Children Aged 1-5 Years – United States, 1990-2010. MMWR. April 5, 2013. Available online at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6213a3.htm through http://www.cdc.gov. Accessed April 2013. 

Centers for Disease Control and Prevention. CDC Response to Advisory Committee on Childhood Lead Poisoning Prevention Recommendations. June 7, 2012. PDF available for download at http://www.cdc.gov/nceh/lead/ACCLPP/CDC_Response_Lead_Exposure_Recs.pdf through http://www.cdc.gov. Accessed April 2013.

Centers for Disease Control and Prevention. Lead Poisoning Prevention Tips. Updated June 25, 2012. Available online at http://www.cdc.gov/nceh/lead/tips.htm through http://www.cdc.gov. Accessed April 2013.

Centers for Disease Control and Prevention. National Health and Nutrition Examination Survey. Available online at http://www.cdc.gov/nchs/nhanes.htm through http://www.cdc.gov. Accessed April 2013.

Adler, Cara. Over Half a Million U.S. Children Have Risky Blood Lead Levels. Physician's First Watch. April 5, 2013. Available online at http://firstwatch.jwatch.org/cgi/content/full/2013/405/4 through http://firstwatch.jwatch.org. Accessed April 2013. 

Gever, John. CDC: Lead Levels in Half Million Kids Too High. MedPage Today. April 5, 2013. Available online through http://www.medpagetoday.com. Accessed April 2013. 

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