The first national US report on human exposure to environmental chemicals, produced by the Centers for Disease Control and Prevention (CDC), in Atlanta, Georgia, has shown surprisingly high levels of pthalates (plasticising compounds found in cosmetics and household products) in the blood and urine of subjects. It seems that these chemicals may be absorbed through the skin.
Pthalates are known to cause hormonal disruptions and fetal malformations in animals, but no studies have been performed to determine whether a causal link also exists in humans.
The study set out to determine baseline levels of environmental chemical exposure, to measure the prevalence of high levels across the population, and to assess the effectiveness of public health efforts to reduce exposure.
The study, based on 1999 data, is the first nationwide effort to measure the levels of various environmental toxins in the blood and urine of human subjects. It covered 27 environmental chemicals, including 24 that had never been tested for before. Previously, the CDC has assessed exposures to lead, cadmium and cotinine, a nicotine metabolite.
The newly monitored chemicals include heavy metals such as mercury, beryllium, caesium, uranium, and barium; organophosphates, found in pesticides; and pthalates, found in products such as shampoos, nail polish, and soaps.
Although some of the toxins have been tested for in soil, air, and water samples, levels in humans had not been directly measured before, so safe and toxic levels of these chemicals have not yet been established.
The data were obtained from testing the blood and urine of 3800 participants enrolled in the national health and nutrition examination survey, an ongoing public health study of the US population. Study subjects were selected from 12 different regions of the United States to give a representative cross section of typical Americans.
The US Consumer Product Safety Council previously raised concern about pthalates and recommended that toy manufacturers stop using them as softening agents in toys and teething rings.
On the positive side, the CDC report found a 75% reduction in the level of cotinine, a nicotine metabolite, found as the result of exposure to secondhand smoke. This substantial reduction suggested that public health efforts against the use of tobacco—such as banning smoking in bars, restaurants, and aeroplanes—are having an effect.
Levels of exposure to lead also dropped, reflecting the lower levels of lead found in newer buildings and houses and the eradication of lead based paints. Mercury levels, though relatively low in children, were higher than expected in women of childbearing age.
Commenting on the report, Dr Richard Jackson, director of the CDC's National Center for Environmental Health, said: "The report is a major step toward assessing in the US population which environmental chemicals are present in blood and urine samples, who is exposed, trends in exposure over time, and whether interventions to reduce exposure are working."
The National Report on Human Exposure to Environmental Chemicals is available at http://www.cdc.gov/nceh/dls/reportwww.cdc.gov/nceh/dls/report