I. Measuring the Harm
There is no safe level of lead exposure in children. According to a preliminary 2012 report by the Centers for Disease Control and Prevention, current standards for measuring blood lead level (BLL) in children are inaccurate and misleading. Furthermore, addressing the harm retroactively is not nearly as important as preventing it. The report, which is subject to revision, contains significant insights and recommendations. This article highlights some of the CDC’s principal findings and proposals.
BLL is measured in micrograms per 1/10 liter of blood. Previously, a BLL of 10 was considered to be the “blood lead level of concern,” the point at which corrective interventions are triggered. In the very young, a BLL of 10 has been associated with attention deficits and learning problems. Recent studies, however, indicate that, even at lower levels, childhood lead exposure affects not only learning and IQ, but the functioning of the cardiovascular, immunological and endocrine (glands that secrete and release hormones into the bloodstream) systems.
The CDC now recommends elimination of the term, “blood lead level of concern.” Focusing on intervention after the exposure has occurred is an unproductive way to safeguard children’s health. Once the damage is done, it is likely irreversible. We can try to address learning problems in lead-exposed children through enrichment programs such as Head Start. But, since there is no safe threshold of exposure, the only acceptable strategy is to prevent the harm before it occurs. By use of a reference value, a BLL of 5 in children ages 1-5, we can measure lead exposure in specific populations and direct our public health and primary prevention efforts where they are needed most. The CDC proposes that this reference value be reevaluated every four years to assess changes in various populations.
There are approximately 450,000 U.S. children with BLL’s above 5. In recent decades, we have made progress in reducing childhood BLL’s. But racial and economic disparities persist. BLL’s continue to be higher in non-Hispanic black children. Differences in housing quality, nutrition, and environmental conditions dictate differing levels of lead exposure among U.S. children.
II. Sources of Exposure
The CDC describes lead as a “multi-media pollutant.” The principal source, lead-based paint, exists in 35 percent of all U.S, housing units. More than a fifth of these units contain significant hazards, and low income households are more likely to live in homes with lead paint than families with higher incomes. Although the use of lead paint was restricted in houses built after 1978, 3 percent of homes constructed 1978-1998 continue to have lead paint hazards.
Soil, dust and water can also be contaminated with lead. Further sources of exposure are 1) Lead mines, smelters and battery recycling plants. 2) Lead-glazed ceramic pottery 3) Folk remedies, medicines and herbs containing lead. 4) Cosmetics such as kohl, surma and certain spices. 5) Hobbies or work activities which use lead and track it into the home and 6) Lead-painted toys and children’s jewelry, usually imported from outside the U.S.
Home renovations often disturb painted surfaces and produce lead-containing dust and debris. In some communities, home renovations are responsible for one-third to one-half of childhood lead poisonings. The Environmental Protection Agency has certified 600,000 home renovators trained to understand the need to maintain paint in intact condition to prevent deterioration and dispersal. Certified abatement contractors are specialized in methods of enclosure, encapsulation and paint removal. Because lead-contaminated dust is invisible and can remain behind after building repairs, the CDC recommends additional testing after cleanup activities.
III. Lead and Children’s Health
Lead exposure can occur in utero. For pregnant and lactating women, the CDC recommends initial and follow-up screening. Further, immigrant, refugee and internationally-adopted children should be tested upon their arrival in the U.S. In their home countries, they may have been exposed to lead-contaminated medicines, folk remedies, toys, cosmetics and ceramic ware.
Maintaining a well-balanced diet with essential vitamins and minerals is vital to child health. Iron deficiency has been linked to higher BLL’s, and both conditions can contribute to lower IQ. Certain vitamins and minerals, notably calcium, iron and vitamin C, can actually minimize the absorption of ingested lead into the body.
Significant stores of lead can remain in the bone for decades and can be released back into the bloodstream. For this reason, blood testing alone will not measure whether lead abatement interventions have been successful. Environmental testing of soil and dust is a better indicator of effective intervention. Another troubling aspect of lead exposure is the role of epigenetic mechanisms in controlling how genes operate and express themselves. This new area of study examines how lead exposure can alter DNA and the regions that surround it. Although these alterations do not involve mutations to the DNA sequence itself, they can potentially be transferred to the next generation, affecting the development of the brain and other organ systems.
IV. Prevention Strategies
Primary prevention of childhood lead exposure is critical, and that means eradicating lead from home environments. Educating parents as to safe housing choices and renovation practices, as well as how to recognize and minimize lead hazards, is crucial. On the state and local levels, lead-safe housing laws and sanitary codes provide clear, objective standards for compliance. Property owners should be mandated to conduct annual visual inspections for signs of moisture problems, water damage and deteriorated paint. At the barest minimum, peeling paint and deteriorated building materials must be repaired in accordance with lead-safe work practices. Specifically, dust and debris must be contained, controlled, and cleaned up to remove any lingering threat of exposure to children.
One of the goals of CDC’s Healthy People 2010 Initiative is to eliminate childhood lead poisoning. As part of its ongoing effort, CDC has joined with agencies such as the Department of Housing and Urban Development and the Environmental Protection Agency. The key components of this interagency strategy include identifying and controlling lead paint hazards, identifying, treating and monitoring children with elevated BLL’s, and researching ways to continually improve prevention of childhood lead exposure.