Research update: Lead poisoning continues to pose threat
Despite recent efforts to reduce the amount of lead in the environment, lead poisoning remains one of the most common environmental health problems for children in the United States today.
The Centers for Disease Control (CDC) and the American Academy of Pediatrics have both called for universal screening of children ages 6 months to 6 years in an effort to ward off the physical and developmental problems associated with even relatively low blood levels for lead.
In addition, the CDC recently lowered the acceptable blood lead level from 25 to 10 micrograms per deciliter (ug/dl) — the lowest level yet at which effects from lead exposure have been seen.
One of the most effective ways to deal with the problem continues to be education. UC Cooperative Extension efforts to educate Californians about the dangers of lead poisoning and methods for its prevention include workshops for community health care workers, as well as the development of a lead test designed to determine if household ceramics and pottery are leaching lead (see opposite page).
Cookie Monster decorates a “hot” lead-leaching piece of ceramicware. However, similar plates made of plastic do not leach lead. (Photo by Ron Goble)
Nutrition Science Specialist Sheri Zidenberg-Cherr, colleagues from the Department of Nutrition at UC Davis and county advisors in Tulare, Fresno and San Bernardino, are conducting research designed to determine what impact diet has on a child's susceptibility to lead poisoning. If a relationship between certain nutrients and lead absorption can be found, then detailed nutrition education programs might be targeted to high-risk populations, she explained.
Chronic exposure to lead can lead to serious health and behavioral problems such as anemia, kidney disease, lower IQ and other permanent cognitive deficiencies, Zidenberg-Cherr noted.
Children are considered especially at risk of lead poisoning because their central nervous systems are still developing. They are also the ones most likely to pick up lead in the environment through crawling or putting things in their mouth.
Although blood lead levels for children have dropped in the last decade, due in part to such efforts as banning lead-based house paint and introducing lead-free gasoline, experts remain concerned about the effects of low-level exposure from such sources as water, soil, and the colorful pottery Americans may pick up when traveling.
The most common source of lead poisoning is lead-based paint which was commonly used in homes until it was banned for such use in 1977. Children who live in older homes are at risk of lead poisoning, especially if the paint is chipped or peeling, or the house is undergoing renovation. Lead also can be ingested or inhaled from dust kicked up during remodeling.
Lead exposure also can occur in some jobs, such as radiator repair or battery making, and in some hobbies, such as working with stained glass which uses lead in the soldering process.
Children of migrant workers are considered at high risk of lead exposure due to environmental contamination in their homes and work environments. Poverty is a risk factor for lead toxicity, in part because more low-income children live in older, dilapidated homes. People who are poor may not have adequate diets, which can increase a child's susceptibility to lead poisoning, according to Zidenberg-Cherr.
Animal studies have shown that diets low in calcium or iron, or high in fat, can enhance lead absorption.
Zidenberg-Cherr's study involves more than 200 children between the ages of one through five.
The study population comes from San Bernardino, Fresno, and Tulare counties, all counties within the top 10 for reported elevated blood lead levels in children. In addition, Sonoma County was also sampled since it is in the top third of California counties with houses built prior to 1950.
Using a Food Frequency Questionnaire and three 24-hour dietary recalls, along with blood tests, Zidenberg-Cherr hopes to determine whether diets low in such nutrients as calcium, iron and zinc increase a child's susceptibility to lead toxicity.
The pilot project is also designed to test how well their methods work in getting dietary information about children. Among other things, parents are asked to recount what their children typically eat and the size of their portions. “With kids that's really hard,” she said.
Zidenberg-Cherr said this study is designed to determine whether a relationship exists between certain nutrients and blood lead levels. She hopes to conduct a second study, using the results from the current study to determine whether supplemental diets might be used as a means to reduce lead toxicity in children.
The California Department of Health has estimated that some 80,000 children have blood lead levels above 15 ug/dl. Children with extremely high blood lead levels are treated with drugs called “chelators” which have the ability to bind to lead and remove it from the body. Cost of such treatment is dependent on severity, and ranges from about $200 to $5,000, Zidenberg-Cherr said.
Some have argued for universal screening, which would cost about $25 per child, she said. Reaction among health care professionals is mixed in part because of the cost, and because no therapy is available for children with slightly elevated blood lead levels, beyond simply removing the sources of lead and educating parents. —Editor