ITHACA, NY -- April 25, 2003 -- Even at low blood concentrations, lead may harm children by lowering IQ and slowing mental development, according to a new report sponsored by the National Institute of Environmental Health Sciences (NIEHS). The five-year study found that children with blood lead levels below 10 micrograms per deciliter risked damage due to their lead exposure. Most previous reports concerned children with blood lead concentrations of at least 10 micrograms per deciliter, the threshold amount that the Centers for Disease Control considers a dangerous elevated lead level.
One hundred seventy-two children took part in the NIEHS study. Their blood lead concentrations were measured at 6, 12, 18, 24, 36, and 48 months of age. The children took IQ tests when they were three and five years old. In measuring the relationship between IQ and blood lead concentration, the researchers adjusted for factors such as birth weight, the mother's intelligence, income, and education.
They found that IQ declined by 7.4 points as estimated lifetime average blood lead concentrations increased from 1 to 10 micrograms per deciliter. They also found that an increase in blood lead from 10 to 30 micrograms per deciliter was associated with only a small additional decline in IQ. "In this sample of children we find that most of the damage to intellectual functioning occurs at blood lead concentrations that are below 10 micrograms per deciliter," commented Richard Canfield, a main author of the NIEHS study (Press Release, April 16, 2003, NIEHS).
"Our study suggests that there is no discernible threshold for the adverse effects of lead exposure and that many more children than previously estimated are affected by this toxin," said Bruce Lanphear, another NIEHS study author. Mr. Lanphear has also conducted a prior analysis of 4,854 children aged 6-16 years linking decreases in thinking ability and academic skills with blood lead concentrations lower than 5 micrograms per deciliter. (Public Health Rep 2000 Nov-Dec; 115(6): 521-9). The data was based on their scores on arithmetic, reading, and short-term memory tests.
Lead Exposure May Delay Puberty in Girls
The Environmental Protection Agency also recently reported on the effects of low levels of lead in the blood of young girls (N Engl J Med 2003 Apr 17;348(16):1527-36). They looked at the records of 2,186 girls aged 8-18 years and found that low levels of lead tended to delay the onset of puberty, especially among black and Latino groups. Specifically, black and Latino girls with 3 micrograms per deciliter of blood lead concentration began puberty at a later date than those with levels of 1 microgram of lead. The same effect was shown for white girls who were not Latino, but the results were not statistically significant. The authors said that "the data suggest that environmental exposure to lead may delay growth and pubertal development in girls, although confirmation is warranted in prospective studies."
Other Studies of the Effects of Lead Exposure
Lead works its damage by changing the way the blood-forming cells work, altering the way nerve cells signal each other, and disturbing the way the brain makes connections. Prior studies show that lead above the 10 microgram per deciliter level slows a child's development and even causes learning and behavior problems (Lead and Your Health, NIEHS ).
Lead accumulates in the human body, especially in children. Exposure to small amounts of lead over time can mean a long-term accumulation of lead in a child, raising his or her risk of health problems.
What A Parent Can Do About Lead
Many homes built before the 1970's still have surfaces painted with lead paint. Young children can eat and chew on lead-painted surfaces. Peeling lead paint is particularly dangerous, as it can expose children to lead chips as well as to lead dust. Lead may also be found in some soils situated near old highways that were once traveled by cars than ran on leaded fuel.
Parents should take the following steps to avoid lead exposure in their children, according to the Centers for Disease Control:
- Remove lead-based paint if it is peeling or damaged. Removal and clean-up should be done by trained, experienced individuals when the family is out of the home.
- Control dust and paint chip debris.
- Prevent children from eating dirt or other foreign substances.
- Provide good, healthy food for children. Good nutrition decreases the amount of swallowed lead that passes to the bloodstream and also may lower some of its toxic effects.
- Change work clothes and clean up before going home from a lead-related job.
- Avoid the use of lead around the home.
- Use cold tap water for drinking and for mixing infant formula. Most of the lead in household water usually comes from the plumbing rather than from the water supply, and hot water is more likely to contain higher levels of lead than cold water.
At Brayton Purcell, we are concerned about the effects of lead exposure on children and their families. We have extensive experience in handling cases involving toxic substances, including lead. If your child or another family member has suffered from lead poisoning or from exposure to other toxics, please feel free to contact us about your legal options.