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California Regional Exposure (CARE) Study

Study of metals, perfluoroalkyl and polyfluoroalkyl substances (PFASs), and other environmental chemicals in adults across the state, conducted one region at a time

CARE Study logo, showing California in outline, with words: California Regional Exposure Study

The goal of the California Regional Exposure (CARE) Study is to measure and compare environmental chemicals in people across the state. This information will support efforts to reduce chemical exposures in Californians and improve public health.

The study measured levels of selected metals in urine and/or blood, perfluoroalkyl and polyfluoroalkyl substances (PFASs) in serum, and other environmental chemicals. We divided the state into eight regions and recruited participants from three of those regions from 2018 to 2020, one region per year. 

In each region, our goal was to:

  • Enroll between 300-500 adults, representing different racial and ethnic backgrounds, income levels, and communities within the study area
  • Collect information from participants to identify potential exposure sources
  • Collect blood and urine samples
  • Measure levels of selected metals, perfluoroalkyl and polyfluoroalkyl substances, and other environmental chemicals
  • Return individual results to participants
  • Hold community meetings to describe overall study findings
  • Release summary results to the public through our website

The CARE Study was launched in 2018 in our first region, Los Angeles County (CARE-LA). In 2019, we visited Region 2, which included Riverside, San Bernardino, Imperial, Mono, and Inyo counties (CARE-2). Enrollment and sample collection for CARE-3 began in San Diego and Orange counties in early 2020, but these activities were suspended due to the COVID-19 emergency. 

CARE-LA and CARE-2 were supported in part by the Centers for Disease Control and Prevention cooperative agreement #U88EH001148.

Project Type:

Full project collaboration

Project Status:

Ongoing

Participants:

Between 300-500 adults (age 18 and up) per region, for a total of up to 8000 statewide

Sample Collection Date:

to

Sample Collection Area:

California, divided into eight regions

Project Map:

Map of California, showing different regions of the state

CARE Study report

A detailed report, The California Regional Exposure (CARE) Study 2018 - 2020, was published in 2024. A brief overview of this report can also be viewed here: CARE Study At a Glance. Some key findings include:

  • 100% of the population had lead detected in their body.
  • Over 99% of the population had PFASs in their body. On average, seven different PFASs were found in each person.
  • Arsenic, mercury, and PFASs were highest in the Asian populations.

Sources of PFAS exposures

The California Regional Exposure (CARE) Study measured per- and polyfluoroalkyl substances (PFASs) in California adults from 2018-2020. PFASs are widely used in products like clothing, cosmetics, furniture, and food packaging and are persistent in the environment. Drinking water contaminated with PFASs and dietary intake are often considered two of the main routes of human exposure. Groundwater used for drinking water can become contaminated by runoff from airports and military facilities that use firefighting foam, as well as industrial sites, landfills, and wastewater treatment plants. Some PFASs have been linked to human health effects, including affecting the immune system and increasing cancer risk.

PFAS exposures linked to drinking water

To understand how study participants might have been exposed to PFASs from drinking water, we linked biomonitoring data with public drinking water sampling data collected by the California State Water Resources Control Board (SWRCB) from 2019-2022. We matched 563 of 879 CARE participants’ home addresses to 70 public water systems monitored by the SWRCB for PFASs. Building off the findings by Pennoyer et al (2025), this analysis uses more recent and detailed drinking water data to examine the association between PFASs in drinking water and participants’ serum PFAS levels. This analysis found that among the 563 participants, people with PFHxS detections in their untreated source well water and/or post-treatment drinking water had 32% higher serum PFHxS levels compared with those without detectable levels of PFHxS. Among a subgroup of participants (n=235), people with PFAS detections in their post-treatment drinking water had up to 80% higher serum PFAS levels. These findings highlight the importance of reducing PFASs in drinking water and support the need for continued work to understand PFAS exposures in California.

>Fillman T, Coffin S, Ta B, Beglarian E, Linck W, Baek H-G, Gao S, Smith S, Park J-S, Wu N, Attfield K (2025). Associations Between PFASs in Drinking Water and Serum Among Southern California Adults. J Expo Sci Environ Epidemiol. doi: 10.1038/s41370-025-00817-8

PFAS exposures linked to drinking water, seafood, and eggs

We also asked participants about their dietary consumption patterns and linked to 2013-2015 data on PFAS sampling in drinking water from the US Environmental Protection Agency (US EPA). This analysis found that drinking water was a significant source of exposure to PFOA and PFHxS, two commonly studied PFASs. Participants with measurable levels of these chemicals in their water had higher corresponding blood levels. These findings highlight the importance of reducing PFASs in drinking water, aligning with the US EPA’s efforts to limit the maximum levels of six PFASs in public water supplies and reduce exposures for approximately 100 million people nationwide. This study also found that seafood and egg consumption was associated with higher blood levels of certain PFASs in participants’ bodies.

>Pennoyer EH, Fillman T, Heiger-Bernays W, Attfield KR, Baek H-G, Gao S, Smith S, Park J-S, Wu N, Webster TF (2025). Exposure to Legacy Per- and Polyfluoroalkyl Substances from Diet and Drinking Water in California Adults, 2018–2020. Environ. Sci. Technol. doi: 10.1021/acs.est.4c11872