Overview of the National Report on Human Exposure to Environmental Chemicals
The National Report on Human Exposure to Environmental Chemicals (Report) presents nationally representative, cumulative biomonitoring data gathered since 1999–2000.
In each survey period, the reported chemicals or their metabolites were measured in blood, serum, and urine samples from random subsamples of the National Health and Nutrition Examination Survey (NHANES). These subsamples typically consisted of about 2,500 participants – exact numbers are included in the tables. Survey data and samples are collected by the Centers for Disease Control and Prevention (CDC) National Center for Health Statistics. CDC’s Environmental Health Laboratory (Division of Laboratory Sciences (DLS), National Center for Environmental Health) used mass spectrometry methods to obtain the blood, serum, and urine exposure measurements presented in the Report.
The term environmental chemical refers to a chemical compound or chemical element present in air, water, food, soil, dust, or other environmental media (e.g., consumer products). Biomonitoring is the assessment of human exposure to chemicals by measuring the chemicals or their metabolites in human specimens such as blood or urine. A metabolite is a chemical alteration of the original compound produced by body tissues. Blood, serum, and urine levels reflect the amount of the chemical that gets into the body by all routes of exposure, including ingestion, inhalation, and dermal absorption. The measurement of an environmental chemical in a person’s blood or urine is a measure of exposure; it does not by itself mean that the chemical causes disease or an adverse effect. Research studies, separate from these data, are required to determine which blood or urine levels are safe and which are associated with disease or an adverse effect.
The Report provides geometric means and percentiles of environmental chemicals by age group, gender, and race/ethnicity for blood, serum, and urine levels measured in individual samples. For serum levels measured in pooled samples, weighted arithmetic means, and unadjusted standard errors are provided for categories defined by race/ethnicity, gender, age group, and survey years. More in-depth statistical analysis, including multivariate analysis incorporating health endpoints and other predictive variables, is beyond the scope of this document. We encourage scientists to examine the data further through analysis of the raw data available at https://www.cdc.gov/nchs/nhanes/.
The Updated Tables are organized into three sections:
- Analysis of Whole Blood, Serum, and Urine Samples, NHANES 1999-2018 provides data for chemicals measured in individual samples from the general U.S. population from NHANES 1999–2000, 2001–2002, 2003–2004, 2005–2006, 2007–2008, 2009–2010, 2011-2012, 2013–2014, 2015-2016, and 2017-2018.
- Analysis of Pooled Serum Samples for Select Chemicals, NHANES 2005-2016 provides data for chemicals measured in pooled samples from NHANES 2005–2006, 2007–2008, 2009–2010, 2011-2012, 2013–2014, and 2015-2016. Some of these chemicals were previously measured in individual samples from the general U.S. population; these data can be found in the section above.
- Analysis of Chemicals Found in Cigarette Smoke in a Special Sample of U.S. Adults, NHANES 2011-2016 provides data for a sample of adult cigarette smokers and nonsmokers from NHANES 2011-2012, 2013–2014, and 2015-2016. The Special Sample was created to determine the effectiveness of tobacco product standards under The Family Smoking Prevention and Tobacco Control Act of 2009. Of note, the age for eligibility in the Special Sample decreased from 20 years and older in NHANES 2011–2012 to 18 years and older in NHANES 2013–2014 and 2015–2016 (NHANES lowered the age for asking the smoking questions in 2013).
The table titles include the survey periods for which data are displayed in that table. Of note, not all chemicals have data for all survey cycles.
Hyperlinks to biomonitoring summaries that have information about a specific chemical or chemical group can be found in the footnotes for many data tables. Several tables also contain a link to a factsheet about the chemical or chemical group within the footnotes.
The National Report on Human Exposure to Environmental Chemicals website lists updates to the available data tables. It also includes the document, “Chemicals in CDC’s National Report on Human Exposure to Environmental Chemicals,” which is a complete list of the chemicals in the Report.
Public Health Uses of the Report
The overall purpose of the Report is to provide specific information to scientists, physicians, and health officials to help prevent exposure to environmental chemicals. Some public health uses of the exposure information in the Report include the following:
- To determine which chemicals are getting into U.S. residents and at what concentrations.
- To determine the prevalence of people with levels of chemicals above known toxicity levels (e.g., blood lead level greater than or equal to a specific concentration).
- To determine the prevalence of people with levels of chemicals that put them at increased risk for toxicity.
- To establish reference ranges that physicians and scientists can use to determine whether a person or group has an unusually high exposure. (This information is especially helpful to identify population groups that merit further assessment of exposure sources or health effects.)
- To assess the effectiveness of public health efforts to reduce exposure of U.S. residents to specific chemicals.
- To determine whether exposure levels are higher among potentially vulnerable groups, such as minorities and children.
- To track trends in levels of exposure of the population.
- To set priorities for research on human health effects.