The National Report on Human Exposure to Environmental Chemicals
The National Report on Human Exposure to Environmental Chemicals is a series of ongoing assessments of the U.S. population's exposure to environmental chemicals by measuring chemicals in a person's blood or urine—a process called biomonitoring. The Environmental Health Laboratory within the National Center for Environmental Health (NCEH) at the Centers for Disease Control and Prevention (CDC) has produced four of these reports since 2001.
The Fourth National Report on Human Exposure to Environmental Chemicals (Fourth Report) [PDF Format - 17 MB] presents exposure data for the U.S. population over the two-year survey period of 2003–2004. The Fourth Report also includes data from 1999–2000 and 2001–2002, as reported in the Second and Third National Reports on Human Exposure to Environmental Chemicals. In the Fourth Report, CDC presents data on 212 chemicals, including results for 75 chemicals measured for the first time in the U.S. population.
Levels of Chemicals in the U.S. Population
For the Fourth Report, CDC scientists used information collected from the National Health and Nutrition Examination Survey (NHANES), a representative sampling of the civilian, non-institutionalized U.S. population. CDC asks people who take part in NHANES about their diet, exercise, and other health habits. Participants also are asked about their medical histories, and they take medical tests and give blood and urine samples. CDC scientists at the Environmental Health Laboratory measured levels of different chemicals in these blood and urine samples, such as lead and pesticides like DDT.
Uses of the Fourth Report
The biomonitoring results help CDC scientists find out what chemicals enter a person's body and at what concentration. The results also help scientists learn about the general population's exposure to certain chemicals. Sharing information about the results is useful to health professionals and researchers, and benefits the public. For example, public health officials can use the Fourth Report to compare an individual's test results with biomonitoring results of the general population. Researchers can use the information to study the effects of exposure levels and health outcomes. The survey results also tell us whether public health efforts have succeeded in reducing the population's exposure to certain chemicals, such as lead or the chemicals in secondhand cigarette smoke.
Finding measurable amounts of these chemicals in people's bodies does not mean that people will become sick or will have any health effects. For many of the chemicals measured for the Fourth Report, more research is needed to determine whether measured levels cause health problems.
Key Findings from the Fourth Report
Widespread exposure to some commonly used industrial chemicals
- Polybrominated diphenyl ethers (PBDEs) are chemicals used to make it difficult for materials to catch fire. They accumulate in the environment and in human fatty tissue. Levels of one type of polybrominated diphenyl ether, BDE-47, was found in nearly all of the NHANES participants.
- Bisphenol A (BPA) is used to manufacture polycarbonate-type plastics, found in some types of beverage containers, plastic dinnerware, automobile parts, and toys. Other BPA products are used in such items as the protective linings of food cans and in dental sealants. General population exposure to BPA may occur through eating foods in contact with BPA-containing materials or having hand-to-mouth contact with BPA-containing materials. CDC scientists found BPA in the urine of nearly all the people tested, a finding that indicates widespread exposure in the U.S. population.
- Perfluorinated chemicals (PFCs) are a large group of chemicals used to make products that resist heat, oil, stains, grease, and water. Many chemicals in this group do not break down in the environment, and they build up in wildlife. CDC scientists found measurable levels of these chemicals in most study participants.
Ongoing progress in reducing blood lead levels in children
- Lead is a soft, dense, blue-gray metal. Lead occurs naturally in the earth's crust and combines with other elements, such as oxygen and sulfur. It is used to make batteries and other metal mixtures. For adults, the diet is the source of most general environmental exposure to lead. Children are commonly exposed to lead from hand-to-mouth activities involving contaminated dust and soils in older homes that contain lead-based paint or from eating paint chips that contain lead. Data in the Fourth Report show that public health efforts to reduce the number of children with elevated blood lead levels in the general population continue to be successful. Nonetheless, special populations of children at high risk for lead exposure (for example, children living in homes containing lead-based paint or lead-contaminated dust) have higher rates of elevated blood lead levels, and lead remains a major public health concern.
First available exposure data on mercury in the U.S. population
- Mercury is a metal that is found in air, water, and soil. Most people are exposed to one type of mercury, organic mercury, after eating seafood containing this metal. This is the first time that exposure to mercury has been measured for the U.S. population aged 1 year and older. CDC scientists found mercury in most of the study participants. Both blood and urine mercury levels tend to increase with age.
First-time assessment of acrylamide exposure in the U.S. population
- Acrylamide is a chemical formed when carbohydrate (starchy) foods are cooked. It is also present in tobacco smoke. Most people are exposed to acrylamide through the diet and from smoking. The data in the Fourth Report show that acrylamide exposure is extremely common in the U.S. population.
For More Information
If you have questions about the report, you can send an e-mail to CDCINFO@cdc.gov; call toll free at 1-800-CDC-INFO (1-800-232-4636); or write to the following address:
Centers for Disease Control and Prevention
1600 Clifton Rd
Atlanta, GA 30333
- Fourth National Report on Human Exposure to Environmental Chemicals, Centers for Disease Control and Prevention