Chlorinated Byproducts of Neonicotinoids and Their Metabolites: An Unrecognized Human Exposure Potential?

American Chemical Society (ACS) | January 14th, 2019

We recently reported the initial discovery of neonicotinoid pesticides in drinking water and their potential for transformation through chlorination and alkaline hydrolys

We recently reported the initial discovery of neonicotinoid pesticides in drinking water and their potential for transformation through chlorination and alkaline hydrolysis during water treatment. The objectives of this research were: (1) to determine if neonicotinoid metabolites are relevant to drinking water exposure and (2) to identify the products formed from chlorination of neonicotinoids and their metabolites. Desnitroimidacloprid and imidacloprid-urea, two known metabolites of imidacloprid, are documented for the first time in drinking water. Desnitro-imidacloprid was present above the lower level of detection (0.03 ng/L) in 67% of samples (six of nine) from drinking water systems but detectable in all samples (up to 0.6 ng/L). Although concentrations of desnitro-imidacloprid were lower than concentrations of the parent neonicotinoids, desnitro-imidacloprid exhibits significantly greater mammalian toxicity than imidacloprid. Using LC-HR-ToF-MS/MS analysis of  results from laboratory experiments, we propose structures for novel transformation products resulting from the chlorination of clothianidin, imidacloprid, desnitro-imidacloprid, imidacloprid-urea, and hydrolysis products of thiamethoxam. Formation of chlorinated neonicotinoid byproducts occurs at time scales relevant to water treatment and/or distribution for the imidacloprid metabolites (t1/2 values from 2.4 min to 1.0 h) and thiamethoxam hydrolysis products (4.8 h). Neonicotinoid metabolites in finished drinking water and potential formation of novel disinfection byproducts during treatment and/or distribution are relevant to evaluating the exposure and potential impacts of neonicotinoids on human health.

Communities that rely on a contaminated groundwater source for drinking water

California State Water Resources Control Board (SWRCB) | January 1st, 2013

AB 2222 (Caballero, Chapter 670, Statutes of 2008) requires the State Water Resources Control Board to submit a report to the Legislature that identifies: 1) communities

AB 2222 (Caballero, Chapter 670, Statutes of 2008) requires the State Water Resources Control Board to submit a report to the Legislature that identifies: 1) communities in California that rely on contaminated groundwater as a primary source of drinking water; 2) the principal contaminants and other constituents of concern; and 3) potential solutions and funding sources to clean up or treat groundwater or provide alternative water supplies. A “community,” for the purposes of this report, is defined as a Community Public Water System (Health and Safety Code Section 116395). When this report refers to communities that rely on a contaminated groundwater source, it is referring to community public water systems that draw water from a contaminated groundwater source prior to any treatment. Over 95 percent of the 38 million Californians get their drinking water from a public water system. The findings in this report do not reflect private domestic wells or other unregulated water systems since the state does not require these groundwater users to sample their wells, and consequently a comprehensive database for these groundwater sources does not exist. This report identifies 680 community water systems that, prior to any treatment, relied on a contaminated groundwater source during the most recent California Department of Public Health (CDPH) compliance cycle (2002-2010). It is important to note that, according to CDPH, over 98% of Californians on public water supply are served safe drinking water. Although many water suppliers draw from contaminated groundwater sources, most suppliers are able to treat the water or blend it with cleaner supplies before serving it to the public. Consequently, when this report refers to communities that rely on contaminated groundwater, it is referring to community public water systems that draw water from one or more contaminated groundwater wells prior to any treatment or blending. Some community water systems, however, cannot afford treatment or lack alternative water sources, and have served water that exceeds a public drinking water standard. Of the 680 community water systems that rely on a contaminated groundwater source, 265 have served water that exceeded a public drinking water standard during the most recent CDPH compliance cycle (2002-2010).

Community Perspectives on SGMA Implementation

University of California, Davis (UC Davis) | June 13th, 2019

The Sustainable Groundwater Management Act (SGMA) of 2014 represents a historic opportunity to achieve long-term sustainable groundwater management and protect th

The Sustainable Groundwater Management Act (SGMA) of 2014 represents a historic opportunity to achieve long-term sustainable groundwater management and protect the drinking water supplies of hundreds of small and rural low-income communities that rely on this shared resource, especially in the San Joaquin Valley. Prior research, however, indicates that few of these communities are represented in the Groundwater Sustainability Agencies (GSAs) formed to implement the new law. This raises questions about other forms of community involvement, and concerns about the extent to which small and rural drinking-water interests are being incorporated into the process. This report details the results of twenty-three interviews with thirty-one representatives of small, low-income communities who rely on groundwater for their drinking-water supplies. The findings suggest community stakeholders are highly interested in SGMA and desire to be involved in its implementation, which many deemed indispensable for the future of their communities. Many are actively participating or following the process, including by serving on boards and committees, attending meetings and workshops, and monitoring meeting minutes and agendas. The experience of small and rural communities with SGMA is predictably diverse. Some interviewees have had very positive experiences thus far and are hopeful about the ways SGMA could benefit their communities and regions in the future. Others have felt overlooked or intentionally excluded. Yet many similarities also arose across the interviews including six common challenges and concerns about SGMA implementation: 1. Resource constraints to participation: Lack of staff, small budgets, in-house experts and an inability to pay for outside services/support limited communities’ formal participation in GSA governance and attendance and involvement in SGMA meetings. 2. Accessibility: Additional factors limiting the accessibility of the SGMA process included day-time meetings, language barriers, the proliferation of board and committee meetings, and irregular and unclear meeting schedules and notices. 3. Transparency: A lack of transparency in GSA decision-making as well as limited access to the data and information being used to develop Groundwater Sustainability Plans (GSPs) were common concerns for interviewees. 4. Lack of formal representation: The relegation of communities to advisory, rather than decision-making, roles in the SGMA process was also a common concern. 5. Limited opportunities to provide meaningful input and feedback: Whether participating as a decision-maker, committee member or as a member of the public attending meetings, many were frustrated at the lack of opportunities to provide meaningful input into decisions or on draft documents due to short turnaround times, not being provided necessary background or materials, and limited opportunities for public comment and open discussion. 6. Lack of addressing drinking water interests and priorities: Overwhelmingly, interviewees reported that drinking water interests, especially water quality and domestic wells, were not part of their local SGMA conversations, leading many to be skeptical that SGMA would have drinking-water benefits. Best practices detailed by interviewees with particularly positive experiences and suggestions and recommendations from all of the interviewees, however, demonstrate ample opportunities to address these issues and increase the integration of drinking-water stakeholders and interests into sustainable groundwater management. Targeted efforts to reduce barriers to participation, improve communication and transparency, and promote diverse representation could go a long way to ensuring the “consideration” and “active involvement” of this important, historically marginalized, stakeholder group. For example, communities can educate their GSA about drinking-water priorities and the variety of regulations and requirements public water systems must comply with and coordinate with other small and rural communities to elevate and advocate for drinking water needs. GSAs should incorporate available public data into Groundwater Sustainability Plans (GSPs) while developing plans to fill data gaps, provide ample time for feedback on staggered and sequential GSP sections and streamline and increase interaction with stakeholders in meetings. State agencies should consider requiring or incentivizing collaborative community projects be included in GSPs, and community representation in GSP development and implementation as well as provide funding to support meaningful community involvement in all phases of SGMA implementation.

Comparing Domestic and Public-Supply Groundwater Quality in the Northern San Joaquin Valley, 2019: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | June 5th, 2023

Analysis of construction data for wells included in the comparative assessment indicated that, although depth to top of perforations are comparable for domestic and publi

Analysis of construction data for wells included in the comparative assessment indicated that, although depth to top of perforations are comparable for domestic and public-supply wells in the Northern San Joaquin Valley (median depth about 60 meters [m]), public-supply wells have longer perforation intervals and extend to deeper parts of the aquifer system (exceeding 120 m) than domestic wells that typically draw exclusively from the shallower aquifer system in the upper 80 m of unconsolidated sediments. Analysis of the vertical and lateral distribution of constituents of interest (nitrate, fumigants, and arsenic) across domestic- and public-supply aquifers indicated that nitrate is prevalent in shallow aquifers throughout the Northern San Joaquin Valley but is potentially diluted by mixing with deeper, older groundwater at long-screened public-supply wells. Fumigants were prevalent in areas of urban and agricultural land use in the western part of the Northern San Joaquin Valley, particularly in areas near Lodi, California, but 1,2,3-TCP was more widespread than DBCP and was detected in shallow and deeper parts of the aquifer system, potentially because of its recalcitrance in groundwater and ability to be detected at low concentrations. Arsenic was most prevalent in the western part of the Northern San Joaquin Valley with proximity to deltaic sediments and was detected at high RCs in wells tapping shallow and deep parts of the aquifer system.

Comparison of potential drinking water source contamination across one hundred U.S. cities

Nature Portfolio (Springer Nature) | December 13th, 2021

Drinking water supplies of cities are exposed to potential contamination arising from land use and other anthropogenic activities in local and distal source watersheds. B

Drinking water supplies of cities are exposed to potential contamination arising from land use and other anthropogenic activities in local and distal source watersheds. Because water quality sampling surveys are often piecemeal, regionally inconsistent, and incomplete with respect to unregulated contaminants, the United States lacks a detailed comparison of potential source water contamination across all of its large cities. Here we combine national scale geospatial datasets with hydrologic simulations to compute two metrics representing potential contamination of water supplies from point and nonpoint sources for over a hundred U.S. cities. We reveal enormous diversity in anthropogenic activities across watersheds with corresponding disparities in the potential contamination of drinking water supplies to cities. Approximately 5% of large cities rely on water that is composed primarily of runoff from non-pristine lands (e.g., agriculture, residential, industrial), while four-fifths of all large cities that withdraw surface water are exposed to treated wastewater in their supplies.

Critical Aquifer Overdraft Accelerates Degradation of Groundwater Quality in California's Central Valley During Drought

American Geophysical Union (AGU) | September 1st, 2021

It has been established that wells are at risk to run dry when groundwater levels decline during drought, but associated impacts to water quality are poorly understood. 

It has been established that wells are at risk to run dry when groundwater levels decline during drought, but associated impacts to water quality are poorly understood. This study examined 30 yr of data from California's Central Valley to find dramatic groundwater-level declines during drought were associated with worsening groundwater quality. This likely happens because increased pumping during drought can draw shallow, contaminated groundwater to depths commonly tapped by public drinking water wells. This is the first study of its kind to show direct linkages between drought and groundwater quality at such a broad spatial scale

Customer Debt and Lost Revenue: The Financial Impacts of COVID-19 on Small Community Water Systems

Pacific Institute | May 4th, 2021

This report provides information on revenue losses experienced by small community water systems (SCWS) in the United States and debt accumulated by their customers during

This report provides information on revenue losses experienced by small community water systems (SCWS) in the United States and debt accumulated by their customers during the COVID-19 pandemic. More than 45,000 SCWS, defined as systems serving fewer than 10,000 people, exist across the United States. The pandemic has exacerbated pre-existing challenges for these water systems and for poorer communities faced with rapidly rising water bills, including financial and cyber insecurity, and the rising costs of treating new contaminants in their water and wastewater. The report includes case studies illustrating the breadth and depth of challenges SCWS face due to the COVID-19 pandemic. 

CV SALTS Prioritization & Optimization Study Year 1 Progress Report

Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) | March 24th, 2023

CV-SALTS Central Valley Region Salt & Nitrate Control Program Surveillance and Monitoring Program

Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) | February 3rd, 2023

The prioritized Nitrate Control Program and phased Salt Control Program are designed to address both legacy and ongoing salt and nitrate accumulation issues in groundwate

The prioritized Nitrate Control Program and phased Salt Control Program are designed to address both legacy and ongoing salt and nitrate accumulation issues in groundwater and salinity concerns in surface waters. However, the primary focus of early actions being implemented under the Nitrate Control Program (i.e., the first ten years) is on groundwater quality and in particular nitrate impacts to drinking water supplies. The overarching management goals and priorities of the SNCP are to: Ensure safe drinking water supply; Reduce salt and nitrate loading so that ongoing discharges neither threaten to degrade high quality waters absent appropriate findings by the Central Valley Board, nor cause or contribute to exceedances of water quality objectives; and Implement long-term, managed restoration of impaired waterbodies.

CV-SALTS Groundwater Sustainability Plan Data Collection - Pilot Study Results

Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) | February 1st, 2024

The purpose of Prioritization & Optimization (P&O) Study Task 5.3 (Information Extraction from Groundwater Sustainability Plans [GSP]) is to extract and organize relevan

The purpose of Prioritization & Optimization (P&O) Study Task 5.3 (Information Extraction from Groundwater Sustainability Plans [GSP]) is to extract and organize relevant GSP data and information that can be used to (1) validate or refine information contained in the P&O Study’s CV-SWAT watershed model (developed to support ongoing baseline characterization work); (2) support the eventual development of salinity management alternatives within specified planning areas; and (3) help ensure that long-term Central Valley salt planning considers ongoing Groundwater Sustainability Agency (GSA) planning efforts, which is of particular interest to the State Water Resources Control Board.