Arsenic in California Drinking Water

Environmental Integrity Project | September 15th, 2016

More than three years after the U.S. Environmental Protection Agency found California in noncompliance with the federal Safe Drinking Water Act, 95 community water system

More than three years after the U.S. Environmental Protection Agency found California in noncompliance with the federal Safe Drinking Water Act, 95 community water systems in the state, serving more than 55,000 people, are still providing water with illegal levels of arsenic, according to an examination of state data for the last two years. Arsenic occurs naturally in the soil and groundwater in parts of California and is a known carcinogen that may also damage the developing brains of children and cause other health problems. Many of the people drinking excessive levels of arsenic are poor and/or Latino or African- American, with a cluster in the San Joaquin Valley. Nearly all have been exposed to excessive arsenic levels for at least five years and probably longer.

As lockdowns lift, new hazards lurk in the water

Nature Portfolio (Springer Nature) | April 28th, 2020

As some regions prepare to lift the lockdowns in response to COVID-19, scientists who study water are worried about the potential for a secondary health crisis waiting

As some regions prepare to lift the lockdowns in response to COVID-19, scientists who study water are worried about the potential for a secondary health crisis waiting in the dormant plumbing of offices, gyms, restaurants and schools.

Assessing Water Affordability

Pacific Institute | August 14th, 2013

A new pilot study in California shows many households, even within affluent communities, routinely spend over the affordability threshold of 2 percent of their household

A new pilot study in California shows many households, even within affluent communities, routinely spend over the affordability threshold of 2 percent of their household income on their water bill. The number of water systems with “unaffordable” rates varies by region and measure used – which has important implications for policy makers. Assessing Water Affordability: A Pilot Study in Two Regions of California, from the Pacific Institute in partnership with Community Water Center and Fresno State University, looks at both an urban and rural case: the Sacramento metropolitan area and the Tulare Lake Basin. In Sacramento, using the most common form of determining affordability – the annual water bill as a percent of median household income at the water system scale – few water systems appeared to suffer from unaffordable rates. In contrast, in the Tulare Lake Basin, 18 percent of systems had unaffordable rates. Using a more fine-grained measure based on household income levels reveals even higher levels of unaffordability in both regions. In the Sacramento metropolitan region, measuring on a water-system-wide scale vs. a household scale means the difference between recognizing zero water systems with unaffordable rates vs. 100,000 households with unaffordable water rates. In the rural Tulare Lake Basin, measuring on these different scales means finding only nine out of 51 water systems with unaffordable rates vs. nearly 4000 households with unaffordable water rates – some 40% of the households in the study group. “Water rate affordability is a central element to water access, and cost makes water excludable and inaccessible to those who cannot afford it,” said Dr. Juliet Christian-Smith of the Pacific Institute. “Water affordability is also a major concern to public welfare, safety, and security. When households are unable to make their water payments, consequences can include public health crises, social unrest, and lost revenue for water providers that can threaten their fiscal stability.” The study’s results show that a significant number of areas within water systems have unaffordable rates, even if the system as a whole does not, and so it may be more important to consider household income rather than median income when assessing and addressing water affordability.

Associations between per-and polyfluoroalkyl substances (PFAS) and county-level cancer incidence between 2016 and 2021 and incident cancer burden attributable to PFAS in drinking water in the United States

Nature Portfolio (Springer Nature) | January 9th, 2025

Associations between PFAS in public water system drinking water and serum among Southern California adults

Nature Portfolio (Springer Nature) | October 30th, 2025

The CARE (California Regional Exposure) biomonitoring study measured PFAS in serum of Southern and Eastern California adults between 2018 and 2020. Participant addresses

The CARE (California Regional Exposure) biomonitoring study measured PFAS in serum of Southern and Eastern California adults between 2018 and 2020. Participant addresses were geocoded and geographically assigned to public water systems (PWS). Between 2019 and 2022, the California State Water Resources Control Board issued investigative PFAS monitoring orders to potentially impacted PWS, focusing primarily on source wells. PFAS detections above the required reporting limit (4 ng/L for PFAS included in the final analysis) were used to assess associations with serum PFAS levels.

At Risk: Public Supply Well Vulnerability Under California’s Sustainable Groundwater Management Act

Pacific Institute | June 1st, 2021

Basic & Urgent: Realizing the Human Right to Water & Sanitation for Californians Experiencing Homelessness

University of California, Berkeley (UC Berkeley) | August 15th, 2018

The report’s three main sections follow this executive summary. The Problem Overview examines: what is driving what one source called an “explosion” in the numbe

The report’s three main sections follow this executive summary. The Problem Overview examines: what is driving what one source called an “explosion” in the number of Californians who are unsheltered; the stark reality of a severe shortfall between the number of affordable housing units needed and the number that will be available for the foreseeable future; the many problems associated with failing to ensure access to water and sanitation for homeless Californians, and how access to these basic needs compares with international minimum standards; and key barriers to progress. The Case Studies on Berkeley, Oakland, and Sacramento offer: an inventory of publicly available potable water, toilets, and showers in the three cities; discussion of how unsheltered residents struggle to meet their basic water-related needs; and an examination of municipal, non-profit, and resident-driven efforts to connect people experiencing homelessness to water and sanitation. Finally, based on the research conducted for this report, the Recommendations section offers six policies, programs, and actions that advocates can bring to State or municipal leaders responsible for upholding the human rights to water and sanitation for all Californians, particularly the State’s most vulnerable unsheltered residents.

Basin-scale responses of groundwater-resource quality to drought and recovery, San Joaquin Valley, California

Hydrological Processes (Wiley) | April 15th, 2024

Groundwater-resource quality is assumed to be less responsive to drought compared to that of surface water due to relatively long transit times of recharge to drinking-su

Groundwater-resource quality is assumed to be less responsive to drought compared to that of surface water due to relatively long transit times of recharge to drinking-supply wells. Here, we evidence dynamic perturbations in aquifer pressure dynamics during drought and subsequent recovery periods cause dramatic shifts in groundwater quality on a basin scale. We used a novel application of time-series clustering on annual nitrate anomalies at >450 public-supply wells (PSWs) across California's San Joaquin Valley during 2000–22 to group subpopulations of wells with similar water-quality responses to drought. Additionally, we statistically evaluated the direction and magnitude of multi-constituent water-quality changes across the San Joaquin Valley using a broader dataset of >3000 PSWs with data during two select hydrologic stress periods representing an extreme drought (2012–16) and subsequent recovery (2016–19). Results of time-series clustering and stress-period change analyses corroborate a predominant regional response to pumping stress characterized by increased concentrations of anthropogenic constituents (nitrate, total dissolved solids) and decreased concentrations of geogenic constituents (arsenic, fluoride), which largely reversed during recovery. Cluster analysis also identified a secondary, less commonly occurring group of PSWs where nitrate decreased during drought, but explanatory factor analysis was not able to discern hydrogeologic drivers for these two divergent response patterns. Long-term tracer data support the hypothesis that the predominant regional signal of nitrate increase during drought is caused by enhanced capture of modern-aged groundwater by PSWs during periods of pumping stress, which can drive rapid changes in water quality on seasonal and multiannual timescales. Pumping-induced migration of modern, oxic groundwater to depth during drought may affect geochemical conditions in deeper portions of regional aquifers controlling the mobility of geogenic contaminants over the long term.

Bottled water contaminant exposures and potential human effects

Environment International (Elsevier) | December 19th, 2022

Background: Bottled water (BW) consumption in the United States and globally has increased amidst heightened concern about environmental contaminant exposures and health

Background: Bottled water (BW) consumption in the United States and globally has increased amidst heightened concern about environmental contaminant exposures and health risks in drinking water supplies, despite a paucity of directly comparable, environmentally-relevant contaminant exposure data for BW. This study provides insight into exposures and cumulative risks to human health from inorganic/organic/microbial contaminants in BW. Methods: BW from 30 total domestic US (23) and imported (7) sources, including purified tapwater (7) and spring water (23), were analyzed for 3 field parameters, 53 inorganics, 465 organics, 14 microbial metrics, and in vitro estrogen receptor (ER) bioactivity. Health-benchmark-weighted cumulative hazard indices and ratios of organic- contaminant in vitro exposure-activity cutoffs were assessed for detected regulated and unregulated inorganic and organic contaminants. Results: 48 inorganics and 45 organics were detected in sampled BW. No enforceable chemical quality standards were exceeded, but several inorganic and organic contaminants with maximum contaminant level goal(s) (MCLG) of zero (no known safe level of exposure to vulnerable sub-populations) were detected. Among these, arsenic, lead, and uranium were detected in 67 %, 17 %, and 57 % of BW, respectively, almost exclusively in spring-sourced samples not treated by advanced filtration. Organic MCLG exceedances included frequent detections of disinfection byproducts (DBP) in tapwater-sourced BW and sporadic detections of DBP and volatile organic chemicals in BW sourced from tapwater and springs. Precautionary health-based screening levels were exceeded frequently and attributed primarily to DBP in tapwater-sourced BW and co-occurring inorganic and organic contaminants in spring-sourced BW. Conclusion: The results indicate that simultaneous exposures to multiple drinking-water contaminants of potential human-health concern are common in BW. Improved understandings of human exposures based on more environmentally realistic and directly comparable point-of-use exposure characterizations, like this BW study, are essential to public health because drinking water is a biological necessity and, consequently, a high vulnerability vector for human contaminant exposures.

California Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project: Domestic-Supply Assessment

U.S. Geological Survey (USGS) | March 14th, 2024