Water Wells in US and Canada Tainted by Arsenic
Synopsis: Naturally occurring arsenic in private wells threatens people in many U.S. states and parts of Canada. The studies come amid new evidence that even low doses of arsenic may reduce IQ in children, in addition to well-documented risks of heart disease, cancer, and reduced lung function. The risk for pregnant women and children is much higher. We hope that recognition may be a turning point in getting more action.
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic is a natural component of the earth's crust and is widely distributed throughout the environment in the air, water, and land. It is highly toxic in its inorganic form. Inorganic arsenic is a confirmed carcinogen and is the most significant chemical contaminant in drinking water globally. People are exposed to elevated levels of inorganic arsenic by drinking contaminated water, using contaminated water in food preparation and irrigation of crops, industrial processes, eating contaminated food, and smoking tobacco.
The studies, focused mainly on New England but applicable elsewhere, say private wells present continuing risks due to almost nonexistent regulation in most states, homeowner inaction, and inadequate mitigation measures.
The reports also shed new light on the geologic mechanisms behind the contamination. The studies come amid new evidence that even low doses of arsenic may reduce IQ in children, in addition to well-documented risks of heart disease, cancer, and reduced lung function. The reports comprise a special section in the journal Science of the Total Environment.
"Arsenic is the biggest public-health problem for water in the United States - it's the most toxic thing we drink," said geochemist Yan Zheng, an adjunct research scientist at Columbia University's Lamont-Doherty Earth Observatory who coedited the special section and coauthored some of the articles. "For some reason, we pay far less attention to it than we do to lesser problems."
Much long-term work on arsenic in the United States and southeast Asia has been done via an extensive program at Lamont-Doherty and Columbia's Mailman School of Public Health.
Many Rocks and Sediments Have Inert, Harmless Traces of Arsenic Locked into Them
But in recent years, geologists have observed that some geologic formations can become enriched in arsenic. Certain chemical conditions may cause rocks to react with groundwater and liberate the element into aquifers. Since the 1990s, the problem has been identified in some 70 countries; it is worst in Southeast Asia, where as many as 100 million people are exposed.
Largely unregulated private wells serve some 43 million Americans; previous work by the U.S. Geological Survey indicates that 6.8 percent tested nationwide violate federal standards governing arsenic in public water supplies. This could be interpreted to mean that some 3 million people are affected. Still, USGS hydrologist Joseph Ayotte, the special section's other coeditor, says the distribution of high arsenic levels is spotty, so it is hard to extract a reliable number. Maps show hot spots in many states, with patches breaking out not only through New England but the Great Lakes, and from the Pacific Northwest and California, across the western states into Texas. Twenty percent of wells in eastern New England are above limits, affecting some 80,000 people in Maine alone, where the contamination rate in the central part of the state is 45 percent. In 2001, the U.S Environmental Protection Agency lowered the permissible standard from 50 parts per billion down to 10.
Public water supplies serving more than 25 people are supposed to meet that standard, and most do - some, by filtering water if necessary. But according to a 2014 study done in part by the Columbia Water Center, 500 mostly small rural public utilities are still in violation, mainly due to cost.
Private Wells Are Almost Certainly a Much Greater Problem in Terms of Number of People Exposed
The researchers did much of their work in Maine, where half the population relies on private wells. Unlike public utilities, these remain completely unregulated and often untested for arsenic. In one study, the researchers found that 41 percent of good owners in a 17-town study area of central Maine had never had their wells tested--and of those who did, many did not remember the results. Based on this and other data, the authors estimated that nearly a third of the people in the study area could be exposed to levels above the federal standard.
As part of the work, a study led by Lamont-Doherty researcher Sara Flanagan surveyed a subgroup of homeowners who remembered being notified three to seven years earlier that their wells were tainted. Among them, 43 percent had since installed filtration systems, and 30 percent had taken other measures, such as drinking bottled water. But the other 27 percent had done nothing. The study says that many people tended to be too optimistic, underestimating their own risk compared with their neighbors. Another study of an arsenic-affected area in Nova Scotia, led by Dalhousie University, also found that people were unjustifiably confident that their well was safe.
"People say, 'I'm not going to worry about it - maybe I'll get cancer, maybe I won't," said pharmacologist Joseph Graziano, a leading arsenic expert, and Earth Institute professor at Mailman who oversees Columbia's work on the issue. "For local and state government, it's a hardy perennial - once in a while, it gets some press, there's a little shuffle of activity, then it dies again until the next study comes out."
In the Maine study area, the research showed that even when households did install filtration systems, 15 percent failed to produce water meeting the EPA standard. A separate study in the package by researchers from Rutgers University in an arsenic-plagued part of New Jersey reported that filters treating water only at the kitchen sink are less effective at reducing exposure than systems that treat a home's entire water intake. But reduced exposure comes at a cost: whole-house systems cost an average of $2,740 to install, while faucet filters average $365.
The 10-parts-per-billion Federal Standard Could be Deficient
Risks of heart disease and lung, skin, and bladder cancers are well documented above such levels. Still, a study last year of three Maine school districts by a related team of Columbia researchers found that even subtler traces--5 parts per billion--took 5 or 6 points off the IQs of children studied. Maine state officials say 20 percent of the state's wells may violate this lower level.
"The risk for pregnant women and children is much higher. We're hoping that recognition may be a turning point in getting more action," said Graziano.
New Jersey, one of the few states to have any regulations regarding arsenic, has already lowered its limit to 5 parts per billion.
A Half Dozen of New Studies Examine Geologic Factors That Introduce Arsenic into Wells
But in Maine, Vermont, New Hampshire, and neighboring states, many penetrate low-grade metamorphic rocks such as slate and phyllite. The studies find that these form when sedimentary rocks such as shale are squeezed and heated just a bit more, which tends to form minerals rich in arsenic. Groundwater high in organic matter and low in oxygen may react with such rocks to dissolve the poison; certain poorly known microbial communities may also play a role. According to one study of Maine wells, led by Lamont-Doherty scientist Qiang Yang, undissolved particles of arsenic-rich iron minerals may be swept through fissures and sucked up--possibly one of the major pathways of arsenic transport in this kind of aquifers, said Yang. In other parts of the country, tainted wells draw water not from fractured bedrock but from deep jumbles of rocky debris and sediment left behind by retreating glaciers; the hydrology may work differently in these regions. Another study in the package by researchers at Lehigh University found that highly alkaline water in parts of New Jersey and Pennsylvania was more apt to take up arsenic.
Zheng (a professor at the City University of New York) said such findings would help geologists draw better maps of hazardous areas. But, she said, underground terrain can vary, so many individual tests are the only way to know about a particular well.
In conjunction with the Maine Geological Survey and Maine Center for Disease Control and Prevention, the Columbia team is now embarking on a project to test ways to motivate well owners in one county to test their water. Maine legislators are also considering a law requiring that a well be tested whenever a house is sold.
Much of the work in the special issue was funded by the U.S. National Institute of Environmental Health Sciences Superfund Research Program. Other study authors came from Middlebury College, the Vermont Geological Survey, Castleton State College, the University of San Diego, the University of Ottawa, and the Nova Scotia Department of Natural Resources.
Papers from the special section, "Arsenic in well waters of the northeastern United States and Atlantic Canada," are posted online or available from the editors or the Earth Institute office.
Arsenic Contaminates Private Drinking Water Wells Across the Western Great Basin
Predictions of arsenic in domestic well water sourced from alluvial aquifers of the western Great Basin, USA - Desert Research Institute.
A new study maps risk of elevated arsenic levels in groundwater wells across northern Nevada, northeastern California, and western Utah.
In the arid and drought-stricken western Great Basin, sparse surface water means rural communities often rely on private groundwater wells. Unlike municipal water systems, well water quality in private wells is unregulated. A new study shows that more than 49 thousand well users across the region may be at risk of exposure to unhealthy levels of arsenic in drinking water.
Led by researchers at DRI and the University of Hawai'i Cancer Center and published February 16th, 2023, in Environmental Science and Technology, the study used data from groundwater wells across the western Great Basin to build a model to predict the probability of elevated arsenic in groundwater, and the location and number of private well users at risk. According to the study, the Carson Desert basin (including the town of Fallon, Nevada), Carson Valley (Minden and Gardnerville, Nevada), and the Truckee Meadows (Reno) have the highest population of well users at risk. The new study builds on previous research showing that 22% of 174 domestic wells sampled in Northern Nevada had arsenic levels exceeding the EPA guideline.
"What we are finding is that in our region, we have a high probability for elevated arsenic compared to most other regions in the country," said Daniel Saftner, M.S., a hydrogeologist at DRI and lead author of the study. "And we are seeing that geothermal and tectonic processes characteristic of the Great Basin contribute to the high concentrations of naturally occurring arsenic in the region's groundwater."
The region's mountains are also primary sources of arsenic.
"As the arsenic-rich volcanic and meta-sedimentary rocks that form the mountains erode, sediment is transported to the valleys below," says Steve Bacon, Ph.D., DRI geologist, and study co-author.
Water percolates through the valley floor and then carries arsenic into the groundwater. Deeper, older groundwater and geothermal waters tend to have a higher arsenic concentration and can migrate upward along faults and mix with shallow groundwater.
"We wanted to understand better the unique geologic factors that contribute to high arsenic in this study," Saftner says. "It's important for us to think about the role of the environment as it pertains to human health - where we live can influence our long-term health."
To train and test the predictive model, the research team used data collected through the Healthy Nevada Project, including water samples from 163 domestic wells near Reno, Carson City, and Fallon. These data were supplemented with 749 USGS National Water Information System groundwater samples. The model uses tectonic, geothermal, geologic, and hydrologic variables to predict the probability of elevated arsenic levels across the region.
Although the U.S. EPA has set an arsenic concentration guideline of 10 µg/L for public drinking water, previous research has shown various health effects from long-term exposure to levels above five µg/L. Using this concentration as the benchmark, the model and map show that much of the region's groundwater - particularly in western and central Nevada - is predicted to have more than a 50% probability of elevated arsenic levels.
"Community members can use our arsenic hazard map to see what the risk is at their location, which might motivate them to test their well water," says Monica Arienzo, Ph.D., associate research professor at DRI and study co-author. "Then, if they have high levels of arsenic or other contaminants, they can take steps to reduce their exposure, such as installing a water treatment system."
The findings from this study are potentially useful for various applications.
"The results can be useful for water utilities or water managers who tap similar shallow aquifers for their water supply," says Saftner, "as well as irrigation wells that source water from these aquifers."
The research team plans to use their model to examine the health impacts of prolonged arsenic exposure.
"Through the Healthy Nevada Project, genetic data and health records are paired with environmental data to help determine whether there are associations between the levels of arsenic in a community's groundwater and specific health outcomes," stated Joe Grzymski, Ph.D., research professor at DRI and principal investigator of the project.
This peer reviewed article relating to our Food Security Information section was selected for publishing by the editors of Disabled World due to its likely interest to our disability community readers. Though the content may have been edited for style, clarity, or length, the article "Water Wells in US and Canada Tainted by Arsenic" was originally written by The Earth Institute at Columbia University, and published by Disabled-World.com on 2015/01/31 (Updated: 2023/02/22). Should you require further information or clarification, The Earth Institute at Columbia University can be contacted at earth.columbia.edu. Disabled World makes no warranties or representations in connection therewith.
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