Lead Exposure: A primer on its scope and related developments
Lead exposure in the United States has been declining since lead was banned from many products in the 1970s. Lead has been banned from paint, plumbing and gasoline, three of the primary historical sources of exposure. Far from being a public health crisis or epidemic, lead exposures are at their lowest level in modern times.
Lead exposure is assessed by measuring the concentration in blood. Prior to 1980 average blood lead levels in the U.S. were greater than 10 micrograms per deciliter (µg/dL). Now average blood lead levels in children are less than 2 µg/dL, and fewer than 2.5% of the nation’s children have blood lead levels greater than 5 µg/dL, the reference blood lead level at which the Centers for Disease Control and Prevention (CDC) recommends initiating public health actions. Despite these significant reductions, efforts to reduce exposure continue, because a safe level of lead exposure has not been identified.
Public health specialists focus on lead exposure prevention. Lead exposure reduction efforts focus on young children because they are more susceptible to the effects of lead and also have the highest exposures. Medical treatment is only recommended when blood lead levels exceed 45 µg/dL; however, whenever high blood lead levels are confirmed, actions can be taken to identify and remove any previously unrecognized sources of lead present in homes.
Screening methods for blood lead have large error rates at lower blood lead levels. For that reason, any screening value over 5 µg/dL needs to be verified by testing at a doctor’s office. So if a child has a screening blood lead level greater than 5 µg/dL, the first step to take is to re-test the blood.
If the high blood lead level is confirmed after the re-test, the next step is to conduct a home assessment. Most children with these levels were exposed in their home, but there are many possible sources. Typically, a questionnaire is administered to the parents, and the home may be tested for the presence of lead paint.
The water may also be tested. Even though lead has been banned from paint and plumbing, many homes still have lead-based materials present.
Paint and Other Potential Exposure Sources
Lead paint is of particular concern if it is in poor condition, allowing lead-containing particles to flake off. Even if the paint is in good condition, it can still come into contact with a child’s mouth, such as through windowsills. Lead pipes and lead-containing plumbing fixtures may also still be present in older homes.
Household products that may contain lead include traditional folk medicine and cosmetics, candies imported from Mexico, lead-glazed ceramic containers, cookware or tableware, some kinds of old venetian blinds, imported toys and toy jewelry.
Adult hobbies and activities may also bring lead sources into a home. These include casting lead fishing sinkers, bullets, lead solder used in making stained glass and recycled lead batteries. Adults may also bring lead-containing dust into a house on work clothes or clothes worn at a shooting range.
The CDC provides information about lead toxicity and tips for preventing lead exposures at http://www.cdc.gov/nceh/lead/. Specific recommendations include testing homes built before 1978 for lead; using wet paper towels often to clean up lead dust; regularly washing children’s hands and toys; and making sure that children and pregnant women stay away from areas being renovated that have lead paint. For additional information see a CDC fact sheet here.
Lead in Soil
In some cases, there may be lead in soil around homes that comes from past industrial activities. The U.S. Environmental Protection Agency or state environmental agencies are responsible for investigating these situations and will use health risk assessments to decide what actions may be needed to reduce exposures from industrial lead sources. The health risk assessment considers how people contact the soil, how much soil a person might actually ingest accidentally, and how much of the lead in the soil that someone ingests will actually be absorbed into the body.
Ramboll Environ recently completed a study that examines the effectiveness of community-wide remediation and a metals abatement program in reducing lead exposure in a community with high soil lead from historical mining activity. This study demonstrated the importance of considering all sources of lead exposure rather than just focusing on one source.
About the Author: Dr. Rosalind A. Schoof, Principal – Ramboll Environ, is a board certified toxicologist with more than 25 years’ experience assessing human health effects and exposures from chemicals substances. Ramboll Environ is a leading global environmental and health consulting firm.
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