Harvard Health

People have used lead in innovative ways for centuries. The ancient Romans used this metal to construct water pipes, for example, while colonial New Englanders used it to make pewter pots and tableware. In the 1920s, U.S. fuel companies began adding lead to gasoline to boost octane levels.

But while lead is useful, it's also a poison that at sufficient levels can damage any organ in the body, including the brain. By the 1970s, a number of studies found that children with lead poisoning developed problems in learning, memory, and behavior.

The U.S. Environmental Protection Agency in 1973 issued the first in a series of regulations requiring the gradual phase-out of leaded gasoline. As a result of this and other public health initiatives, blood lead levels in the United States have fallen dramatically.

Several studies have raised concern that lead exposure may pose mental health risks, even at levels not previously considered dangerous.

Public health initiatives have produced a dramatic drop in U.S. blood lead levels since the 1970s, according to a series of reports from the National Health and Nutrition Examination Surveys.


The U.S. Centers for Disease Control and Prevention (CDC) defines blood levels of 10 micrograms (mcg) of lead or more per deciliter (dL) as high. Lead poisoning occurs once blood lead levels reach 15 mcg/dL. The CDC estimates that 250,000 U.S. children under age 5 have blood lead levels that are greater than 10 mcg/dL.

Exposure is most dangerous when it occurs prenatally and before age 6, because this is when the brain is developing rapidly and most vulnerable to long-term damage. Possible complications of lead poisoning in children include low IQ, slow growth, kidney damage, and learning and behavior problems.

A study published in Archives of General Psychiatry, however, suggested that mental health problems may develop even when blood lead levels are below the CDC thresholds. Researchers at the University of Montreal and the Harvard School of Public Health analyzed data from 1,987 people ages 20 to 39 who participated in the National Health and Nutrition Examination Survey between 1999 and 2004.

Participants provided blood samples and completed a standard diagnostic interview used to identify those who had major depression, panic disorder, or generalized anxiety disorder, according to criteria listed in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV).

The researchers found that participants whose blood lead levels were in the highest quintile -- 2.11 mcg/dL or more -- were twice as likely as those in the lowest quintile -- defined as less than 0.7 mcg/dL -- to develop major depression, and almost five times as likely to develop panic disorder. The study found no significant association between blood lead levels and generalized anxiety disorder.

The findings were alarming because, like two other observational studies, this analysis suggested that damage to the brain may occur even with low-level exposure to lead. However, none of these studies was designed to test for cause and effect, and in some cases the research had flaws.

For example, in this most recent study, the authors acknowledged that there was not always a linear relationship between blood lead levels and risk of developing mental health problems. That is, risk did not consistently increase as blood lead levels increased (at some blood levels, risk actually fell). And the investigators did not measure lead concentration in bones -- a more reliable indicator of long-term lead exposure than blood lead levels.

Although the discussion is likely to continue about what blood levels of lead should cause concern, most public health experts agree that too many American children have blood lead levels that are already high. Here's a brief review of ways to reduce lead exposure:

The best place to start lowering lead exposure is at home.


The major source of contamination for children in the United States comes from deteriorating lead paint. Although the government banned lead from house paint in 1978, any house built before then is likely to contain lead paint -- even if it has been repainted one or more times. Exposure can occur when paint chips or degrades.

Young children (especially toddlers, who put anything in their mouths) may eat paint chips or inhale it in house dust. Pregnant women living in houses with deteriorating lead paint not only expose themselves but also may transmit this toxic substance to the fetus.

Poor children living in urban areas are most at risk for lead poisoning because they are more likely to live in older, dilapidated buildings. But any child in an older home is at risk. A lead remediation expert in Rhode Island recounted the story of a young girl who developed lead poisoning after her middle-class parents decided to renovate their Victorian home on their own. They used a sander to remove old paint, filling the house with lead-contaminated dust -- which the child inhaled.

Federal and state agencies offer advice about how to properly remove lead paint and to perform ongoing maintenance, such as removing fallen paint chips on a regular basis or painting over deteriorated patches. People can also protect themselves by vacuuming frequently to eliminate lead dust and washing hands frequently, especially before eating anything. But such routines are hard to sustain.

Homeowners should contact local officials about how to safely undertake home renovations involving sanding and stripping of painted wood. As an extra precaution, many experts recommend that pregnant women and young children move out while any renovations are under way.


Although new building codes require lead-free solder to connect indoor pipes, many homes still have lead solder or other fixtures that may contaminate drinking water. Lead seeps into tap water when old fixtures corrode, or when water sits for more than six hours in pipes connected with lead solder.

There are some simple steps homeowners can take to reduce exposure. For example, when turning on a faucet in the morning (or whenever water has not been tapped for hours), run cold water for one to two minutes before drinking or cooking with it. This will help flush the line of any lead-contaminated water. (Avoid running hot water, as this may cause additional lead to leach out.)

An alternative (and one that may appeal more to conservatives) is to switch to bottled water for drinking or cooking, or install a filtering device.


Several U.S. agencies have published detailed information about how homeowners and parents can protect children by reducing common sources of lead exposure. It's important that people understand the hazards, because when it comes to lead exposure, prevention is the best medicine. For more information:

U.S. Centers for Disease Control and Prevention; 800-232-4636 (toll-free); www.cdc.gov/lead

Environmental Protection Agency; 800-424-5323 (toll-free); www.epa.gov/lead -- Harvard Mental Health Letter

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Health - Get the Lead Out: The Less Exposure to This Toxic Metal the Better