A new report in ACS’ journal Environmental Science & Technology found that U.S. public-supply tap water generally meets all enforceable standards.
Samples from private wells, public water supplies and a water cooler were checked for 482 organic and 19 inorganic compounds.
However, lead was detected in 23 samples.
Although none of these samples exceeded current lead regulations, the EPA drinking water goal of zero indicates that no lead exposure is considered safe.
The researchers note that little is known about the cumulative health effects of exposure to these mixtures of low-level contaminants among vulnerable populations, such as children and pregnant or breast-feeding women.
Tap water monitoring will provide the exposure data needed for public health researchers to address this gap.
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Natural sources of the toxic form of chromium appear in wells that provide drinking water to a large population in California, offering a new perspective on California’s groundwater management challenges.
(Image credit: Richard Thornton / Shutterstock) In a study that appeared online June 27 in Environmental Science & Technology, Stanford scientists used a statewide groundwater database and a new means of tracing sources to identify wells containing hexavalent chromium from industry versus those that became contaminated from naturally occurring sources – some of which may also have resulted from human activity.
“As we continue to push the need to use and manage groundwater, understanding how these naturally occurring contaminants can jeopardize water becomes really, really important.” Benign vs. toxic chromium The benign, natural form of the chemical, known as trivalent chromium, is needed to help people break down glucose.
(Image credit: Debra Hausladen and Scott Fendorf) The toxic form, hexavalent chromium, is very soluble and moves easily within the environment.
Industrial uses of hexavalent chromium include electroplating, steel manufacturing, leather tanning and wood treatment.
Drinking water that contains hexavalent chromium, also known as chromium-6 or Cr(VI), is considered a human health threat, increasing the risk for stomach and intestinal cancer.
Based on where they find the toxic form in the Central Valley and other regions, the study co-authors suspect human activities, such as groundwater pumping, could contribute to that transformation.
Of those, 15 percent contained higher levels of hexavalent chromium than the 2014 drinking water standard of 10 parts per billion.
The scientists determined which of the 234 other chemicals in the database were commonly found with hexavalent chromium and used that information to figure out where natural occurring chromium is threatening groundwater quality and which processes may be responsible.
“It’s really important to have this holistic view as we develop groundwater management strategies.” The researchers hope to create more detailed distribution maps of where naturally occurring contaminants can threaten groundwater and the pathways that would cause them to move into California’s water system.

MEDFORD/SOMERVILLE (August 15, 2017) – Harmful algal blooms known to pose risks to human and environmental health in large freshwater reservoirs and lakes are projected to increase because of climate change, according to a team of researchers led by a Tufts University scientist.
The team developed a modeling framework that predicts that the largest increase in cyanobacterial harmful algal blooms (CyanoHABs) would occur in the Northeast region of the United States, but the biggest economic harm would be felt by recreation areas in the Southeast.
The research, which is published in print today in the journal Environmental Science & Technology, is part of larger, ongoing efforts among scientists to quantify and monetize the degree to which climate change will impact and damage various U.S. sectors.
"Our study shows that higher water temperature, changes in rainfall, and increased nutrient inputs will combine to cause more frequent occurrence of harmful algal blooms in the future," he added.
Throughout their 3.5 billion-year-old evolutionary history, these organisms have proven resilient and adaptable to a wide range of climates.
It is among the few studies to combine climate projections with a hydrologic/water quality network model of U.S. lakes and reservoirs.
Finally, these water flows and reservoir states are entered into a water quality model to simulate a number of water quality characteristics, including cyanobacteria concentrations, in each of the nation’s waterbodies.
The end result is a framework that can predict the combined impact of climate, population growth, and other factors on future water quality for different U.S. regions.
The research was supported by the U.S. EPA and the U.S. National Science Foundation, and access to the reservoir datasets from the U.S. Army Corps of Engineers.
Environmental Science & Technology.

Stormwater retention ponds may not protect surface waters from road salt contamination.
Stormwater management practices are designed to intercept water runoff from roads and parking lots before pollutants reach surface waters.
Detaining runoff in retention ponds can reduce flooding, increase the amount of water that is absorbed into the ground, and allow pollutants to bind to sediments in the ponds or be absorbed by algae and plants instead of traveling to streams and wetlands where they may harm wildlife and human health.
The research team recently completed a study, published in Environmental Science and Technology, to determine how well current stormwater management practices mitigate the effects of road salts and how those salts might be impacting both the surface waters in streams and ponds, and the groundwater that many citizens using well systems rely on daily.
If the stormwater ponds were working effectively, Snodgrass explained, he and his team could test the groundwater between the ponds and streams and expect to find very little sodium chloride because it would have been retained in the ponds.
The researchers discovered that routing runoff contaminated with road salts to stormwater ponds actually resulted in plumes of highly contaminated groundwater moving from the ponds to streams.
If salt levels continue to increase in freshwater areas, many fish and amphibians will stop breeding and eventually die because their bodies cannot adjust to the change.
"Some counties are already reimbursing people for the costs associated with replacing contaminated water wells," he added.
Snodgrass and his team plan to continue researching how road salts and other chemicals affect wildlife and the environment, while other researchers are exploring the effectiveness of alternatives to road salts and their potential effects on the environment and human health.
"It’s a balance sheet we’re looking at between economics and the environment and human health," Snodgrass said.