CDC’s National Report on Human Exposure to Environmental Chemicals

Ann Verwiel, LeeAnn Racz, Liz Mittal and William Rish, ToxStrategies

Recently, the U.S. Centers for Disease Control and Prevention (CDC) made available an online, interactive version of biomarker data in its National Report on Human Exposure to Environmental Chemicals (CDC Report). The CDC Report presents biomonitoring data for a variety of chemicals—data that are representative of national exposures. These data have been collected as part of the National Health and Nutrition Examination Survey (NHANES) but, until now, have not been readily and publicly accessible. The CDC Report provides descriptive statistics (geometric means and percentiles with confidence intervals) from the NHANES data set for the total population and by age group, gender, race and ethnicity. Whereas more in-depth statistical and multivariate analyses can be performed with the original NHANES data, the online CDC Report webpage (Biomonitoring Data Tables for Environmental Chemicals | CDC) provides summary tables that can be used to quickly review and compare to other data. This new capability offers easy access to scientists, physicians and public health officials and provides context for local environmental chemical exposures.

The CDC Report presents summary statistics for biomonitoring surveys conducted at the national level since 1999 for:

• Whole blood, serum and urine samples (NHANES 1999–2018)
• Pooled serum samples (NHANES 2005–2016)
• Chemicals found in cigarette smoke in a special sample of U.S. adults (NHANES 2011–2016)

The NHANES data set addresses a wide variety of chemicals and metabolites that are indicative of potential environmental exposures, including metals, volatile organic compounds, polycyclic aromatic hydrocarbons, flame retardants, tobacco-related chemicals, per- and polyfluoroalkyl substances, pesticides, herbicides, perchlorate and phthalates. The 2022 CDC report has dramatically expanded the list of chemicals and chemical groups over that of previous reports.

Example table for blood lead levels (2011–2018) in micrograms per deciliter (mg/dL) – Click image to enlarge.

The data set is summarized in simple tables for the data set as a whole and for sub-populations, such as age groups, sex, race or ethnicity. The summary tables can be simply downloaded as PDFs for a specific chemical or all chemicals within a chemical group (e.g., metalloids).

The CDC Report’s introductory materials suggest the following uses for these data:

• Identify concentrations of chemicals in U.S. residents
• Assess 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)
• Develop reference ranges for physicians and scientists to evaluate whether an individual or group has an unusually high exposure
• Observe trends in concentrations following public health efforts to reduce exposure of U.S. residents to specific chemicals
• Identify whether exposure levels are higher among potentially vulnerable groups, such as minorities and children
• Develop priorities for research on human health effects from chemical exposures

The descriptive statistics provided are sufficient to compare to exposures in a specific population, such as communities with environmental justice concerns. Communities with disadvantaged populations frequently live near industrial facilities, transportation hubs and other operations that may result in disparate exposure. The national data in the CDC Report can be used as a benchmark for local community data or to assess national exposures among minorities and children, who may be more vulnerable to chemical stressors or cumulative impacts from multiple stressors.

Polycyclic dibenzo-p-dioxins/furans (PCDD/Fs) measured in the serum of Midland and Saginaw county residents that live in the vicinity of a chemical manufacturing facility as well as a local reference population (i.e., Jackson and Calhoun counties) were compared by David Garabrant and colleagues to PCDD/F serum values measured across the national population as available in the CDC Report. The authors found that PCDD/F serum levels in the local referent population were similar to the U.S. general population, and serum levels in the Midland Saginaw county residents were not significantly different from the reference population, suggesting that site-specific conditions (i.e., dioxins in soil and household dust) in that community did not contribute significantly to exposure and that generally, other factors contribute more substantially to variations in PCDD/F serum levels.

The CDC Report’s data tables can also be used to assess whether the NHANES data sets have information worth exploring further in a more detailed evaluation. For example, work by JM Reyes and PS Price used NHANES biomonitoring data to evaluate co-exposures to phthalates and determine values for the maximum cumulative ratio, hazard index and hazard quotient. Barbara Hudson-Hanley and colleagues also used NHANES biomonitoring data to find that exposures to certain polycyclic aromatic hydrocarbons (PAHs) have changed among non-smokers in the U.S. between 2001 and 2014. These robust studies require substantial data management and statistical computations to derive meaningful scientific conclusions. Using the readily available data tables allows scientists to assess whether that level of effort may provide meaningful results.

The 2022 online CDC Report provides information on a broad group of biomarkers in an accessible format that will help us better understand general and site-specific exposures using actual measures of exposure. Having the information a few clicks away will open the doors to more research and a better understanding of the spatial variation in environmental exposures in the United States.

Author’s contact: Ann Verwiel [email protected]