CDC details U.S. toxic exposures

WASHINGTON, Jul 22, 2005 (United Press International via COMTEX) -- Exposure of U.S. children to toxic lead and secondhand cigarette smoke is declining, but many adults show evidence of at least some potentially dangerous industrial chemicals or pesticides in their bodies, a large federal study has concluded.

Average blood-lead levels in children ages 1 to 5 dropped from 2.23 micrograms to 1.70 micrograms per deciliter between 2000 and 2002, according to the study, conducted by the Centers for Disease Control and Prevention in Atlanta. Still, nearly 2 percent of U.S. children showed more that 10 micrograms/dL of lead in their blood -- a level that public-health experts consider potentially hazardous.

Lead poisoning impedes brain development in young children, causing IQ deficits and other cognitive problems.

Overall, CDC officials said they were encouraged by the apparent drop in lead levels. They attributed the trend to the complete removal of lead from gasoline in the United States about 10 years ago and to nationwide programs designed to remove lead paint from aging houses and buildings.

"We still don't know what is a safe level," CDC Director Julie M. Gerberding said at a news briefing Thursday.

The agency's researchers studied the concentration of 148 industrial chemicals and toxins in the U.S. population. They then computed average chemical exposures based on blood samples taken from several thousand volunteers across the country. The study did not take into account differences in geographical location that could greatly affect exposure levels.

Based on the samples, researchers found falling levels of cotinine, a chemical produced in the body in reaction to nicotine. The chemical's presence in non-smokers indicates exposure to secondhand smoke.

Gerberding said the CDC found an "astonishing reduction" in the chemical, suggesting laws limiting smoking in buildings are having a positive effect.

The benefits largely were limited to whites, however, while exposures in blacks were unchanged. Researchers suspect that African-Americans either are being exposed to more secondhand smoke or perhaps they metabolize nicotine differently than do whites, Gerberding said.

The study also found low but relatively widespread exposure to phthalates, a class of chemicals found in cosmetics, plastics and food packaging. The chemicals are known to affect hormone functioning and can cause liver and testicular damage in lab animals.

Half of adolescents ages 12 to 19 showed monomethyl phthalate levels of 2.1 micrograms/dL in their urine, though researchers said they still do not know the potential hazards of that level of exposure.

"We have reason now to look further" at the possible consequences, Gerberding said.

The study showed an apparent overall drop in mercury exposure, though the toxin remains widely prevalent in the U.S. population. No women of childbearing age approached levels known to affect newborns' brains and cognitive development.

Gerberding suggested the figures would cause CDC to conduct more research into what the health effects of lower levels of mercury exposure may be on fetuses and newborns.

The study also recorded falling levels of many pesticides, though levels of at least one industrial pesticide, DDE, were up since 2000 in all groups studied.

Meanwhile, an analysis of the study released by Pesticide Action Network North America showed 90 percent of participants tested positive for between five and 16 different pesticides. On average, Americans harbor 10 to 11 different pesticides, according to the analysis.

"It just shows that we are carrying around a lot of pesticides, and this is just the tip of the iceberg," Margaret Reeves, the group's senior scientist, told United Press International.

Chemical manufacturers released a statement Thursday calling the CDC report "a useful public health tool." A group representing the industry stressed that low levels of toxic exposure do not necessarily translate to increased health risk.

"The benefits of chemistry have helped all of us live longer and healthier lives," said the statement, from the American Chemistry Council. "These advances should not be underestimated or undermined by alarming people about everyday products that protect our health, keep us from harm and contribute to our well being."

--

Todd Zwillich covers health and healthcare policy for UPI Science News. E-mail: sciencemail@upi.com