Blood Cadmium Level

Cadmium is a metal that is usually found in nature combined with oxygen, chlorine, or sulfur. Cadmium enters the environment from the weathering of rocks and minerals that contain cadmium. Exposure to cadmium can occur in occupations such as mining or electroplating, where cadmium is produced or used. The general population may be exposed from smoking, breathing cigarette smoke, or eating contaminated foods (ATSDR, 2012; CDC, 2017).

Cadmium and its compounds are toxic to humans and animals and are classified as "Group 1" human carcinogens by the International Agency for Research on Cancer (IARC) (WHO, 2022). Once absorbed into the human body, cadmium can accumulate in the kidneys and remain in the body for decades. Chronic exposure to cadmium can result in serious kidney damage. Osteomalacia, a bone disorder similar to rickets, is also associated with long-term exposure to cadmium. Acute airborne exposure, as occurs from welding on cadmium-alloy metals, can result in swelling (edema) and scarring (fibrosis) of the lungs (CDC, 2017).

This indicator reflects blood cadmium concentrations in micrograms per liter (µg/L) for the U.S. population, age 1 year and older, as measured in the 1999-2018 continuous National Health and Nutrition Examination Survey (NHANES). NHANES is a series of surveys conducted by the Centers for Disease Control and Prevention's (CDC's) National Center for Health Statistics that is designed to collect data on the health and nutritional status of the civilian, non-institutionalized U.S. population using a complex, stratified, multistage, probability-cluster design. CDC's National Center for Environmental Health conducts the laboratory analyses for the biomonitoring samples. Beginning in 1999, NHANES became a continuous and annual national survey. The data presented here cover 10 different survey periods: 1999-2000, 2001-2002, 2003-2004, 2005-2006, 2007-2008, 2009-2010, 2011-2012, 2013-2014, 2015-2016, and 2017-2018.

Between 1999 and 2018, the calculated geometric mean blood cadmium levels among total NHANES participants age 1 year and older ranged from 0.235 µg/L (2013-2014) to 0.412 µg/L (1999-2000) (Exhibit 1). Overall, there is not much variation in the geometric means across the different time periods by sex or across different race/ethnicity groups. The blood cadmium geometric mean measurements were slightly lower among males than among females across time periods (Exhibit 1). For the race and ethnicity groups, blood cadmium geometric means were highest among Asians for all survey periods since reporting began for this group (2011-2012). The lowest blood cadmium level at each reported percentile across all but two of the survey periods (1999-2000 and 2015-2016) was observed in Mexican Americans (Exhibit 2).

The geometric mean blood cadmium level was not calculated for several subgroups because of the high number of samples that were below the analytical method's limit of detection. This is most obvious for the age group analysis (Exhibit 3), where a sufficient proportion of samples above the limit of detection was not available to calculate valid geometric means for any survey period for the 1-5 and 6-11 years age groups. For the 12-19 years age group, geometric means could only be calculated for four survey periods (1999-2000, 2013-2014, 2015-2016, and 2017-2018). The highest blood cadmium levels are seen in the 20 years and older age group, with geometric means ranging from 0.295 µg/L (2015-2016 and 2017-2018) to 0.468 µg/L (1999-2000). The 95^th percentiles of blood cadmium levels for the 20 years and older age group ranged from 1.35 µg/L (2015-2016) to 1.80 µg/L (2003-2004) (Exhibit 3).  

• The relatively small number of samples collected in a 2-year cycle (e.g., 1999-2000 or 2001-2002) may, in some cases, result in measures of central tendency that are unstable from one survey period to the next.

• Health-based benchmarks for blood levels of cadmium have not been established.

Data used for this indicator were obtained directly from CDC’s National Report on Human Exposure to Environmental Chemicals: Analysis of whole blood, serum, and urine samples, NHANES 1999-2018, which was updated in March 2022 and presents the results of the ongoing NHANES (CDC, 2022).

ATSDR (Agency for Toxic Substances and Disease Registry). 2012. Cadmium fact sheet. Division of Toxicology and Environmental Medicine ToxFAQs. https://www.atsdr.cdc.gov/toxfaqs/tfacts5.pdf (PDF) (2 pp, 93K).

CDC (Centers for Disease Control and Prevention). 2022. National report on human exposure to environmental chemicals: Analysis of whole blood, serum, and urine samples, NHANES 1999-2018. Updated March 2022. Accessed April 20, 2022. https://www.cdc.gov/exposurereport/data_tables.html.

CDC. 2017. National Biomonitoring Program, biomonitoring summary for cadmium. Last reviewed April 7, 2017. Accessed July 7, 2022. https://www.cdc.gov/biomonitoring/Cadmium_BiomonitoringSummary.html.

WHO (World Health Organization). 2022. International Agency for Research on Cancer monographs on the identification of carcinogenic hazards to humans: List of classifications. Last updated July 1, 2022. Accessed July 7, 2022. https://monographs.iarc.who.int/list-of-classifications/.