Guideline levels for PFOA and PFOS in drinking water: the role of scientific uncertainty, risk assessment decisions, and social factors

Journal of Exposure Science & Environmental Epidemiology (Springer) | January 8th, 2019

Communities across the U.S. are discovering drinking water contaminated by perfluoroalkyl and polyfluoroalkyl substances (PFAS) and determining appropriate actions. Ther

Communities across the U.S. are discovering drinking water contaminated by perfluoroalkyl and polyfluoroalkyl substances (PFAS) and determining appropriate actions. There are currently no federal PFAS drinking water standards despite widespread drinking water contamination, ubiquitous population-level exposure, and toxicological and epidemiological evidence of adverse health effects. Absent federal PFAS standards, multiple U.S. states have developed their own healthbased water guideline levels to guide decisions about contaminated site cleanup and drinking water surveillance and treatment. We examined perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) water guideline levels developed by the U.S. Environmental Protection Agency (EPA) and state agencies to protect people drinking the water, and summarized how and why these levels differ. We referenced documents and tables released in June 2018 by the Interstate Technology and Regulatory Council (ITRC) to identify states that have drinking water and groundwater guideline levels for PFOA and/or PFOS that differ from EPA’s health advisories (HAs). We also gathered assessment documents from state websites and contacted state environmental and health agencies to identify and confirm current guidelines. Seven states have developed their own water guideline levels for PFOA and/or PFOS ranging from 13 to 1000 ng/L, compared to EPA’s HA of 70 ng/L for both compounds individually or combined. We find that the development of PFAS guideline levels via exposure and hazard assessment decisions is influenced by multiple scientific, technical, and social factors, including managing scientific uncertainty, technical decisions and capacity, and social, political, and economic influences from involved stakeholders. Assessments by multiple states and academic scientists suggest that EPA’s HA is not sufficiently protective. The ability of states to develop their own guideline levels and standards provides diverse risk assessment approaches as models for other state and federal regulators, while a sufficiently protective, scientifically sound, and enforceable federal standard would provide more consistent protection.

Hexavalent Chromium Maximum Contaminant Level (MCL) Standardized Regulatory Impact Assessment (SRIA)

California State Water Resources Control Board (SWRCB) | May 4th, 2023

The Division of Drinking Water (DDW) of the State Water Resources Control Board (State Water Board) is responsible for adopting drinking water standards. Primary drinking

The Division of Drinking Water (DDW) of the State Water Resources Control Board (State Water Board) is responsible for adopting drinking water standards. Primary drinking water standards, as defined in section 116275 of the California Safe Drinking Water Act (Health & Safety Code (HSC), div. 104, pt. 12, ch. 4, section 116270 et seq.), must be set in accordance with the requirements of HSC 116365. The purpose of the proposed regulation addressed in this Standardized Regulatory Impact Assessment (SRIA) is to adopt a primary drinking water standard for hexavalent chromium in drinking water consisting of a maximum contaminant level (MCL) and pertinent monitoring and reporting requirements. Consistent with title 1 of the California Code of Regulations (CCR), section 2003(a), the economic impact method used for the assessment was the Regional Input-Output Modeling System (RIMS II) developed by the U.S. Bureau of Economic Analysis (BEA).

High organofluorine concentrations in municipal wastewater affect downstream drinking water supplies for millions of Americans

National Academy of Sciences (NAS) | January 6th, 2025

How much potable water is saved by wastewater recycling? Quasi-experimental evidence from California

Resources, Conservation & Recycling (Elsevier) | October 6th, 2021

Recently, California has made large investments in wastewater recycling to replace applications that use potable water. It may be expected that the use of recycled water

Recently, California has made large investments in wastewater recycling to replace applications that use potable water. It may be expected that the use of recycled water reduces potable water use, but such an equivalency is not assured. The addition of recycled water infrastructure in a large Californian water district creates a natural experiment where this work tests how recycled water usage affects primary potable water. This is done using econometric methods for causal inference in an observational setting that mirror a randomized control trial (RCT). From 2001 to 2014, a number of public parks were given recycled water infrastructure, while others in those regions remained exclusively on potable supply. A two-way fixed effects regression is used to produce a difference-in-differences estimate of the average treatment effect of recycled water on total and potable water usage. The results indicate that potable water usage is reduced significantly when a park is connected to the recycled water supply. The estimated rate of displacement in the study period is 81.7%, meaning each unit of recycled water use avoided 0.817 units of potable water usage, which implies the connection of parks to recycled water supply increases total water use. The analysis provides, to the best of our knowledge, the first empirical estimate of the water savings claimed by urban water recycling programs, and the first empirical estimate of displacement using quasi-experimental methods. The methodology can be utilized to evaluate the effectiveness of recycling programs around the world.

Human Costs of Nitrate-contaminated Drinking Water in the San Joaquin Valley

Pacific Institute | March 1st, 2011

While most Californians take for granted that safe water is readily available at the turn of a tap, a growing number of communities, primarily in the San Joaquin Valley a

While most Californians take for granted that safe water is readily available at the turn of a tap, a growing number of communities, primarily in the San Joaquin Valley and other agricultural areas of the state, face very real impacts from nitrate contamination of the drinking water sources serving their homes and schools. New research led by the Pacific Institute, The Human Costs of Nitrate-Contaminated Drinking Water in the San Joaquin Valley, finds that nitrate contamination of groundwater has wide-reaching effects on California’s health, economic vitality, and environmental well being, disproportionately affecting low-income households and Spanish-speaking residents. The analysis brings a stark reality check to the fore as the Central Valley Water Board considers a new regulatory program for irrigated lands, the primary source of nitrate contamination in the San Joaquin Valley. There have never been any regulatory requirements on irrigated agriculture to protect groundwater from fertilizers, which are the primary source of nitrate in the valley. Nitrate levels have increased dramatically in drinking water supplies over the last few decades. The new study, The Human Costs of Nitrate-Contaminated Drinking Water in the San Joaquin Valley, a collaboration of the Pacific Institute, Community Water Center, Clean Water Fund, and California Rural Legal Assistance Foundation, focuses on the household costs of avoiding nitrate-contaminated drinking water connected to community water systems and the costs to these systems of removing or avoiding nitrates, and it points to key policies and further research needed to better understand and resolve this entrenched challenge. The eight-county San Joaquin Valley has some of the most contaminated aquifers in the nation: 92 drinking water systems in the San Joaquin Valley had a well with nitrate levels above the legal limit from 2005-2008, potentially affecting the water quality of approximately 1.3 million residents. In addition to public water systems, the State Water Board sampled 181 domestic wells in Tulare County in 2006 and found that 40% of those tested had nitrate levels above the legal limit.

Identification of Bacteria in Groundwater Used for Domestic Supply in the Southeast San Joaquin Valley, California, 2014

U.S. Geological Survey (USGS) | June 22nd, 2021

Groundwater is an important source of drinking water in California. Water-borne diseases caused by microbial contamination are a growing concern. The MI test, a membrane

Groundwater is an important source of drinking water in California. Water-borne diseases caused by microbial contamination are a growing concern. The MI test, a membrane filtration method for the chromogenic-/-fluorogenic detection of total coliforms and Escherichia coli, was used for samples collected January to April 2014 from 42 domestic wells in the southeastern San Joaquin Valley. The wells were sampled as part of the Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP), a cooperative study between the U.S. Geological Survey and the California State Water Resources Control Board. Polymerase chain reaction analysis and sequencing of deoxyribonucleic acid (DNA) were used for 34 target and nontarget colonies that grew on the MI media from samples collected from 13 of the domestic wells to identify what genera of bacteria could exist in groundwater used by domestic wells. Gene sequences obtained using the Sanger method were entered into the basic local alignment search tool (BLAST) database, and 17 genera of bacteria were identified. Of these, 13 genera contain species that are human pathogens or opportunistic human pathogens. All the genera that include human pathogens are naturally present in soil, plants, or water; one of the pathogens also can be found in fecal matter. Six of the human pathogens were from non-target colony growth on the MI media. Target and non-target microbial growth on MI media are indicators of the possible presence of pathogenic bacteria even if the bacteria naturally are from soil rather than from a fecal source.

Identification of Bacteria in Groundwater Used for Domestic Supply in the Southeast San Joaquin Valley, California, 2014

U.S. Geological Survey (USGS) | June 22nd, 2021

Groundwater is an important source of drinking water in California. Water-borne diseases caused by microbial contamination are a growing concern. The MI test, a membrane

Groundwater is an important source of drinking water in California. Water-borne diseases caused by microbial contamination are a growing concern. The MI test, a membrane filtration method for the chromogenic / fluorogenic detection of total coliforms and Escherichia coli, was used for samples collected January to April 2014 from 42 domestic wells in the southeastern San Joaquin Valley. The wells were sampled as part of the Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP), a cooperative study between the U.S. Geological Survey and the California State Water Resources Control Board. Polymerase chain reaction analysis and sequencing of deoxyribonucleic acid (DNA) were used for 34 target and nontarget colonies that grew on the MI media from samples collected from 13 of the domestic wells to identify what genera of bacteria could exist in groundwater used by domestic wells. Gene sequences obtained using the Sanger method were entered into the basic local alignment search tool (BLAST) database, and 17 genera of bacteria were identified. Of these, 13 genera contain species that are human pathogens or opportunistic human pathogens. All the genera that include human pathogens are naturally present in soil, plants, or water; one of the pathogens also can be found in fecal matter. Six of the human pathogens were from non-target colony growth on the MI media. Target and non-target microbial growth on MI media are indicators of the possible presence of pathogenic bacteria even if the bacteria naturally are from soil rather than from a fecal source.

Identifying the location and population served by domestic wells in California

Journal of Hydrology: Regional Studies (Elsevier) | November 17th, 2014

Study region: California, USA. Study focus: Identification of groundwater use is an important stepin the regional-scale assessment of groundwater quality. In Califo

Study region: California, USA. Study focus: Identification of groundwater use is an important stepin the regional-scale assessment of groundwater quality. In California, 1990 US Census data indicate that domestic wells provide drinking-water to about 1.2 million people. However, the location of these domestic well users of groundwater is poorly identified because the census tracts can be quite large (up to 20,000 km2). The purposes of this paper are to present methods used for (1) estimating the location of domestic wells, (2) estimating the location of households using domes-tic well water; and (3) identifying where in California groundwater isan important source of domestic drinking supply.New hydrological insights for the region: Aggregating the results indicates that three hydrogeologic provinces contain nearly 80% of all domestic wells and also have the highest density of domestic well-users: Central Valley (31.6%), Sierra Nevada (31.5%), and NorthernCoast Ranges (16.6%). Results were also aggregated into groundwater basins and highland areas, collectively called Groundwater Units(GUs). Twenty-eight of the 938 GUs contain more than 50% of the total population served by domestic wells, 70 GUs contain more than 75%, and 150 GUs contain 90%. The 28 GUs are mostly located in the eastern and southern San Joaquin Valley (11), the Sacramento Valley (7), and the western foothills of the Sierra Nevada province (5). Using the information presented in this research along with other information about domestic-well use, the US Geological Survey has begun sampling high-use GUs for the Shallow Aquifer Assessment component of the Groundwater Ambient Assessment (GAMA) program.

Implicit and Explicit Biases for Recycled Water and Tap Water

American Geophysical Union (AGU) | May 31st, 2022

Increasing use of recycled water to irrigate agricultural products and decreasing consumption of bottled water are important components of sustainable water management pr

Increasing use of recycled water to irrigate agricultural products and decreasing consumption of bottled water are important components of sustainable water management practices and consumer-driven efforts to improve water security and quality. However, consumers frequently discount agricultural products irrigated with recycled water relative to products irrigated with conventional water and place a premium on bottled water relative to tap water. This study measures consumer attitudes regarding recycled water and bottled water to understand more fully the reasons behind these preferences. We conduct two studies involving 2,616 adult consumers in the United States designed to measure consumer attitudes and preferences: the use of recycled water versus conventional water to irrigate food products and tap water versus bottled water for drinking. In each study, implicit attitudes are measured using an Implicit Association Test as well as explicit attitudes. We find that respondents have negative implicit attitudes regarding recycled water compared to conventional water and tap water compared to bottled water, and a negative explicit attitude toward recycled water. Tap water and food grown with recycled water were believed to be less healthy to consume and less tasty, although these are believed to be more sustainable options. Beliefs about water attributes (i.e., healthfulness, taste, and sustainability) are associated with attitudes, and both beliefs about attributes and attitudes are associated with preferences for products. Further, we find that respondents' stated preferences are consistent with their implicit and explicit attitudes.

Increasingly frequent extreme weather events urge the development of point-of-use water treatment systems

Nature Portfolio (Springer Nature) | August 13th, 2022

The frequency of extreme weather events, including floods, storms, droughts, extreme temperatures, and wildfires, has intensified globally over recent decades due to clim

The frequency of extreme weather events, including floods, storms, droughts, extreme temperatures, and wildfires, has intensified globally over recent decades due to climate change, affecting human society profoundly. Among all the impacts of these extreme weather events, the consequences to our reliable water supply have gained increasing attention as they exacerbate the inequities in health and education, especially in marginalized populations. In this perspective, we emphasize that extreme weather events are able to undermine a stable supply of drinking water through a number of approaches, and conventional centralized water treatment is insufficient at addressing these challenges. We urge that greater recognition, increased public awareness, and more efforts on technological innovation on decentralized, especially point-of-use (POU), water treatment should be prioritized to better help tackle the challenges faced by increasingly frequent extreme weather events.