Cadmium, Mercury, Pesticides: Environmental Chemicals of Concern
ATLANTA, Georgia, July 22, 2005 (ENS) - A decline in exposure to secondhand smoke and continued decreases in children’s blood lead levels represent the good news from a new report on human exposure to environmental chemicals by the Centers for Disease Control (CDC). But chemicals such as cadmium, mercury and insecticides were found in the bodies of test subjects at levels that could be causing health problems, agency officials said.
National reports on human exposure to environmental chemicals have been issued by the CDC every two years since 1999. For this year’s report, issued Thursday, CDC’s Environmental Health Laboratory measured 148 chemicals or their breakdown products in blood or urine.
Of the chemicals tested, 38 have never been measured before in the U.S. population.
Commenting on the report Thursday, House Democratic Leader Nancy Pelosi said the funding for CDC's Environmental Health Lab to conduct these studies was well spent. "The report will assist researchers in determining whether these exposures are contributing to birth defects, cancer, asthma, Alzheimer's and Parkinson's diseases, and other health problems," she said.
“Exposure to secondhand smoke continues to plummet and blood lead levels in children are way down," Dr. Gerberding said. "However, many challenges remain."
Cadmium, a metal primarily associated with exposure to cigarettes through tobacco use, is one of those challenges. About five percent of the population of adults 20 years and older, had cadmium levels in their urine that were close to the point at which there was concern for health effects, Gerberding said.
Finding cadmium of this level indicates a need for further research, she said.
The samples for this report were collected from 2,400 people who participated in CDC's National Health and Nutrition Examination Survey (NHANES) from 1999 to 2002. NHANES is an ongoing national health survey of the general U.S. population. The report provides exposure data on the U.S. population by age, sex, and race or ethnicity.
Health experts determined that exposure to secondhand smoke is decreasing when they looked at levels of a chemical called cotinine, a marker of exposure to secondhand smoke in nonsmokers.
Compared with median cotinine levels for 1988-1991, median levels measured from 1999-2002 have decreased 68 percent in children, 69 percent in adolescents, and about 75 percent in adults.
Still, some people are at greater risk. The new report shows that non-Hispanic blacks have levels twice as high as those of non-Hispanic whites or Mexican Americans, and children’s levels are twice as high as adults’ levels.
New data on blood lead levels in children aged one to five years show that for 1999 to 2002, 1.6 percent of those children had elevated blood lead levels. The levels of lead in their blood were 10 micrograms per deciliter or greater – the CDC blood lead level of concern.
While this percentage has decreased from 4.4 percent in the early 1990s, Dr. Jim Pirkle, deputy director for science at CDC’s Environmental Health Laboratory, said 1.6 percent still means too many children are being damaged by lead in their blood.
“Lowering blood lead levels in children is one of the major environmental health accomplishments of the past 30 years," Dr. Pirkle said. However, CDC is still concerned about exposure to lead from lead-based paint and lead-contaminated house dust, soil and consumer products."
“There is no safe blood lead level in children," he said. "Children are best protected by controlling or eliminating lead sources before they are exposed.”
Dr. Gerberding says the decrease in blood lead levels is due partly to the replacement of leaded gasoline with unleaded. "I think really speaks to the removal of lead from gasoline, which was one of the major correlates of this reduction but also the lead abatement programs and other steps, being able to screen, treat and protect children from lead exposure," she said.
The report provides information about exposure to methyl mercury, found in fish and shellfish. Methyl mercury is formed when metallic mercury enters the air or water from mining ore deposits, burning coal and waste, and from manufacturing plants. Methylmercury may be formed in water and soil by small organisms called bacteria. Methylmercury builds up in the tissues of fish.
Mercury levels above 58 micrograms, millionths of a gram, are associated with neurodevelopmental effects in the fetus, the CDC report states
"No women in the survey had mercury levels that approached this concentration," Dr. Gerberding said, "but we do see that a small percentage of women, about 5.7 percent of women had levels within a factor of ten of what has been defined as the health threshold effect."
Mercury's harmful effects that may be passed from the mother to the fetus include brain damage, mental retardation, incoordination, blindness, seizures, and inability to speak, according to the federal Agency for Toxic Substances, which operates under CDC jurisdiction. Children poisoned by mercury may develop problems of their nervous and digestive systems, and kidney damage.
For the first time, the CDC studied the effect of organochlorine based pesticides and other pesticides known as pyrethroids.
Organochlorine pesticides like Aldrin and Endrin and Dieldrin, used in the United States for decades, were mostly eliminated from use in the late 1980s. Dr. Gerberding said the exposure report shows that since these chemicals have no longer been used as pesticides, they have been "virtually eliminated" from the human population.
"So over time there's been a decay, the pesticides have been eliminated from our environment and people are no longer experiencing any potential risk from exposure to them," she said.
The pyrethroids are insecticides that are found in almost any product that we would use today when we go to the store to buy an insect agent, Gerberding explained. "We have been able to measure five of these for the first time ever in the United States population."
"What we know is that because they're used so ubiquitously, there is widespread exposure to them and our exposure report bears this out," the CDC director said. "So we have a reason now to look further to see if there are any health effects from these exposures."
"We have no evidence of that at this point in time, but, again, now that we've documented that not only are they being used in the environment, but they can be measured in the blood of people in that environment, it's our responsibility to take this to the next step and to work with our scientific partners to assess what if any health effects are a consequence of this, Dr. Gerberding said.
CropLife agreed with the CDC conclusion that, “Just because people have an environmental chemical in their blood or urine does not mean that the chemical causes disease…Small amounts may be of no health consequence, whereas larger amounts may cause adverse health effects.”
Pesticides are the most intensely researched, tested and regulated chemicals in the United States, the industry group said, and in addition, we need them. "The benefits of having safe, affordable and nutritious fruits and vegetables are well documented and the proper use of pesticides ensures these benefits to all Americans," CropLife said.
"Pesticides and pest management products also help safeguard public health by controlling or eliminating pests that cause disease and property damage," said CropLife. "They reduce waterborne and insect-transmitted diseases such as Lyme disease and West Nile virus and protect homes and gardens from damage from termites and other pests."
For the first time, the CDC tested for a family of compounds called phthalates, used to soften vinyl plastics and in cosmetics such as nail polish.
Phthlates were identified as problem chemicals in the mid-nineties by Greenpeace, which campaigned against them for years to the ridicule of the plastics industry. But now some convincing scientific studies are in and earlier this month six phthlates were banned across the European Union.
"These compounds are associated with plastics and vinyl, they come in a variety of chemical variations," said Dr. Gerberding, "and in this report our scientists were able to refine the ability to separate out the various phthalates and to look at them with much more precision individually than ever before."
"I think this is going to really help us refine our ability to study the relationship, if any, between phthalate exposure and potential immunologic and other toxicities," she said.
As the report was released, the Washington, DC research and advocacy organization Environmental Working Group (EWG) asked the agency to begin testing the umbilical cord blood of newborn babies.
EWG also sent letters to 20 top chemical manufacturers asking them to release any internal tests to determine whether their products pollute babies.
The letters follow an investigative report that EWG released last week commissioning laboratory tests of 10 umbilical cord blood samples for the most extensive array of industrial chemicals, pesticides and other pollutants ever studied in newborns.
EWG found that the babies averaged 200 contaminants in their blood, including mercury, fire retardants, pesticides and the Teflon production chemical PFOA. In total, the babies' blood contained 287 chemicals, including 209 never before detected in cord blood. The study is available at www.ewg.org/reports/bodyburden2.
"Chemical exposures during childhood can be far more harmful than those later in life. Our cord blood findings above all raise the need for testing that ensures the safety of the widespread exposures we've documented that begin even before birth," Jane Houlihan, EWG's vice president for research, said.
"CDC is uniquely positioned and funded to respond to this need through its national body burden testing program, but CDC cannot test for all 80,000 industrial chemicals registered for use today," Houlihan said. "The companies that produce these chemicals have a responsibility to know if their products end up in babies, and to share what they learn with the public."
The American Chemistry Council, which represents the industry supports the biomonitoring studies, and agrees with the CDC's cautionary statement that the mere detection of a chemical does not necessarily indicate a risk to health.
"The information in the report should not be cause for undue concern," said the Council, "but a springboard for better understanding of exposure and - with more information - how the human body interacts with the environment."
The Third National Report on Human Exposure to Environmental Chemicals and an executive summary are available online at: http://www.cdc.gov/exposurereport.