Water Treatment Contaminants:
Water Treatment Contaminants:
Forgotten Toxics in American Water
View and Download the report here: 2013 Tap Water Report
Water treatment plants along the East Coast are struggling to recover from Superstorm Sandy, whose torrential rains washed tens of millions of gallons of raw or partially treated sewage into waterways.
The less dramatic but equally urgent story: inside those waterworks, and others across the nation, chlorine, added as a disinfectant to kill disease- causing microganisms in dirty source water, is reacting with rotting organic matter like sewage, manure from livestock, dead animals and fallen leaves to form toxic chemicals that are potentially harmful to people.
This unintended side effect of chlorinating water to meet federal drinking water regulations creates a family of chemicals known as trihalomethanes. The Environmental Protection Agency lumps them under the euphemism “disinfection byproducts” but we call them what they are: toxic trash.
The EPA regulates four members of the trihalomethane family, the best known of which is chloroform, once used as an anesthetic and, in pulp detective stories, to knock out victims. Today, the U.S. government classifies chloroform as a “probable” human carcinogen. California officials consider it a “known” carcinogen. Three other regulated trihalomethanes are bromodichloromethane, bromoform, and dibromochloromethane. Hundreds more types of toxic trash are unregulated.
Scientists suspect that trihalomethanes in drinking water may cause thousands of cases of bladder cancer every year. These chemicals have also been linked to colon and rectal cancer, birth defects, low birth weight and miscarriage (NHDES 2006).
When Does Water Treatment Contamination Reach the Danger Point?
An Environmental Working Group analysis of water quality tests conducted in 2011 and made public last year by 201 large American municipal water systems in 43 states has determined that each of these systems detected thihalomethane contamination. In short, more than 100 million Americans served by these large waterworks were exposed to toxic trash.
Only one of the systems studied by EWG – Davenport, Iowa – exceeded the EPA rule barring more than 80 parts per billion of trihalomethanes in drinking water (see Appendix). This legal limit was set in 1998, based on the potential for trihalomethanes to cause bladder cancer. The 80-parts-per-billion standard was part of a major Clinton administration initiative to improve federal drinking water protections under the federal Safe Drinking Water Act.
Yet the significant toxicity of trihalomethanes and other water contaminants generated by water treatment chemicals, documented by large numbers of scientists around the world, makes a compelling case for lowering the federal legal limit to well below 80 parts per billion. Since 1998, the evidence implicating trihalomethanes in serious disorders has mounted:
In 2011 a French research team, pooling data from studies in France, Finland and Spain, found that men exposed to more than 50 parts per billion of trihalomethanes had significantly increased bladder cancer risks (Costet 2011).
In 2007, a scientific team in Spain associated exposure to trihalomethanes greater than 35 parts per billion with increased bladder cancer risks (Villanueva 2007).
In 2007, researchers from four Taiwanese universities reported that people faced twice the odds of dying from bladder cancer if they drank water with trihalomethane contamination greater than 21 parts per billion. This study was cited in the 2011 National Report on Carcinogens, a Congressionally-mandated report produced by the National Toxicology Program, a federal interagency scientific body (Chang 2007, NTP 2011).
A 2010 study by the National Cancer Institute found that about a quarter of the human population may have a genetic susceptibility that raises its risk of bladder cancer from trihalomethanes (Cantor 2010).
Some 168 of the systems studied by EWG, or 84 percent, reported average annual trihalomethane contamination greater than 21 parts per billion – the level at which Taiwanese researchers detected a heightened risk of bladder cancer. Concentrations greater than 35 parts per billion were found in 107, or 53 percent of these systems. In 2005, the EPA considered lowering the legal limit for trihalomethanes to 40 parts per billion, calculating that this move would prevent nearly 1,300 bladder cancer cases each year and save the U.S. between $2.9 and $7.1 billion (EPA 2005). The agency did not attempt to establish this lower standard as a regulation with the force of law. Instead it made marginal improvements in the way it would measure trihalomethanes for compliance with existing regulations and gave water treatment facilities until 2016 to comply with these modest changes.
Contamination Spikes Present Special Risks During Pregnancy
EWG’s analysis suggests that many people are likely exposed to far higher concentrations of trihalomethanes than anyone knows. The EPA regulation for these toxic chemicals is based on the system-wide annual average. But in most water systems, trihalomethane contamination fluctuates from month to month, sometimes rising well beyond the 80 parts-per-billion federal cap. Contamination spikes are offset by low readings that keep the systems in legal compliance.
The EPA standard for trihalomethanes is based on preventing bladder cancer, but the agency has noted that these chemicals may present reproductive and developmental risks as well (EPA 2012a). A spike that lasts three months exposes a pregnant woman and her fetus to excessive trihalomethane for an entire trimester, a critical window of development. Scientific research has shown that such intensive exposure can have serious consequences for the child. Three studies published last year:
Australian scientists found that when women in their third trimester of pregnancy consumed water with 25 parts per billion of chloroform, their newborns were small for their gestational age, meaning that they typically had birth weights in the lowest ten percent of newborns and were at higher risk for a various health problems (Summerhayes 2012).
Canadian researchers found that exposure to more than 100 parts per billion of trihalomethanes during the last trimester of pregnancy was associated with newborns small for their gestational age (Levallois 2012).
Taiwanese researchers linked stillbirth risks to trihalomethane levels as low as 20 parts per billion (Hwang 2012).
Numerous other studies have associated reproductive and developmental problems with trihalomethanes. Among them:
In 2008, scientists from the University of North Carolina found that women exposed to more than 80 parts per billion of trihalomethanes during their third trimester of pregnancy faced twice the risk of delivering a child small for gestational age (Hoffman 2008).
British scientists found a link between 60 parts per billion of trihalomethane exposure and stillbirths (Toledano 2005).
In 2003, a team from the Harvard School of Public Health linked exposures to more than 80 parts per billion of trihalomethanes during the second trimester of pregnancy to low birth weight and small-for-gestational-age newborns (Wright 2003).
In 2002 researchers at the Federal Agency for Toxic Substances and Disease Registry reviewed the findings of 14 major studies and concluded that there was “moderate evidence” for an association between trihalomethane exposure, small-for-gestational-age newborns, neural tube defects and miscarriage (Bove 2002). The neural tube is the structure in the fetus that develops into the brain and spinal cord.
Trihalomethanes Are Just the Tip of the Iceberg
Studies have shown that there are more than 600 unwanted chemicals created by the interaction of water treatment disinfectants and pollutants in source water (Barlow 2004, Richardson 1998, 1999a, 1999b, 2003). Most of these water treatment contaminants have not been studied in depth. Among them: haloacetonitriles, haloaldehydes, haloketones, halohydroxyfuranones, haloquinones, aldehydes, haloacetamides, halonitriles, halonitromethanes, nitrosamines, organic N-chloramines, iodoacids, ketones and carboxylic acids (Bond 2011, Bull 2011, EWG 2001, Plewa 2004, Yang 2012). Some of these compounds are suspected carcinogens (Bull 2011). Notably, scientists believe that hundreds more water treatment contaminants are present in drinking water but have not yet been identified (Barlow 2004).
Besides the four regulated trihalomethanes, the EPA regulates five other contaminants in a family of chemicals known as haloacetic acids -- monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid (EPA 2012b). The current EPA legal limit for these five chemicals is 60 parts per billion.
While there have been relatively few epidemiological studies on the potential health effects of haloacetic acids, there is evidence suggesting that exposure to these chemicals during the second and third trimesters of pregnancy may be linked to intrauterine growth retardation and low birth weight (Levallois 2012, Hinckley 2005; Porter 2005).
Haloacetic acids have been classified by the EPA as possibly carcinogenic to humans because of evidence of carcinogenicity in animals. According to the EPA, long-term consumption of water that contains haloacetic acid concentrations in excess the legal limit of 60 parts per billion is associated with an increased risk of cancer (EPA 2002). A technical bulletin released by the Oregon Department of Human Services in 2004 warned that long-term exposure to haloacetic acids at or above 60 parts per billion may cause injury to the brain, nerves, liver, kidneys, eyes and reproductive systems.
Some studies point to concerns with specific haloacetic acids. Dibromoacetic acid has been shown to disturb the balance of the intestinal tract and to cause disease, especially in people with weakened immune systems (Rusin 1997). This particular haloacetic acid compound is toxic to the sperm of adult rats at concentrations as low as 10 parts per billion. At high doses, it has caused a range of neurological problems in test animals, including awkward gait, tremors and immovable hind limbs (Linder 1995). Two members of the haloacetic acid family -- dichloroacetic acid and trichloroacetic acid -- have been shown to cause severe skin and eye irritations in humans (NTP 2005).
A Chlorine Substitute That Doesn’t Solve the Problem – and May Make it Worse
In recent years, many water utilities have tried to reduce contamination caused by water treatment by switching from free chlorine to chloramines, compounds made from chlorine and ammonia gases.
Chloramines are more stable than chlorine and do not produce as many trihalomethanes and haloacetic acids. The EPA has reported that when Washington Aqueduct, a U.S. Corps of Engineers facility that treats drinking water for Washington D.C., switched to chloramines, the estimated average of the regulated water treatment contaminants in these two families dropped by 47 percent (EPA 2006).
Yet switching to chloramines has not solved the problem but rather moved the problem – and may have complicated it.
Chloramines are toxic to kidney dialysis patients and extremely toxic to fish (EPA 2012b).
A nationwide study on water treatment contaminants conducted by the EPA reported that chloraminated drinking water had the highest levels of an unregulated chemical family known as iodoacids (EPA 2002). Some researchers consider iodoacids to be potentially the most toxic group of water treatment contaminants found to date, but there is still relatively little research on them (Barlow 2004, Plewa 2004).
Other dangerous compounds formed by chloramine are nitrosamines. In 2010, then-EPA Administrator Lisa Jackson launched a new “drinking water strategy.” During these deliberations, the agency is addressing, among other things, nitrosamine contamination. Nitrosamines, which are currently unregulated, form when water is disinfected with chloramine. The U.S. government says some chemicals in the nitrosamine family are “reasonably anticipated” to be human carcinogens.
In a 2011 report called “The Chlorine Dilemma,” David Sedlak, a professor of civil and environmental engineering at the University of California, Berkeley, detailed the “dark side” of water treatment and the new and unanticipated hazards of water treatment plants’ shift from chlorine to chloramine. “Nitrosamines are the compounds that people warned you about when they told you you shouldn’t be eating those nitrite-cured hot dogs,” Sedlak told National Public Radio in 2011. “They’re about a thousand times more carcinogenic than the disinfection byproducts that we’d been worried about with regular old chlorine.”
The bottom line is that switching to chloramination may have achieved the desired effect of reducing trihalomethane and haloacetic acid levels, but it may have inadvertently exposed the population to additional unregulated byproducts that are more harmful in the long run.
Chloramines present other potential problems. Utilities observed that chloramines were not as effective at disinfection as free chlorine, so, according to the EPA, many treatment plants began to alternate between chloramines and chlorine to “dislodge biofilms and sediment in water mains” (EPA 2007). When chlorine was reintroduced to a system for a month-long “chlorine flush” (EWG 2007), the result was “chlorine burn,” which removed sludge and sediment from pipes but also temporarily raised the level of chlorine-generated contaminants. Customers of utilities that used both types of chemicals were exposed to varying amounts of multiple water treatment contaminants.
There were more severe and long-lasting complications. In 2000, the Washington Aqueduct switched to chloramine without realizing that chlorine prevented corrosion of old lead pipes but chloramine did not (Brown 2010). The switch caused D.C.’s old lead pipes to discharge quantities of lead into the city’s drinking water, triggering a public health crisis when the problem was detected in 2004. The belated discovery of high lead levels triggered warnings, broad distribution of water filters, firings, Congressional hearings and extensive replacement of lead water lines.
In a study published in January 2009 in the Journal of Environmental Science and Technology, scientists Marc Edwards and Simoni Triantafyllidou of Virginia Tech and Dana Best of the Children’s National Medical Center in Washington wrote that during the D.C. lead crisis, the number of babies and toddlers with elevated lead levels in their blood increased by more than four times, compared to the pre-2001 period (Edwards 2009). The authors warned that many of the youngest could suffer irreversible IQ loss or other developmental difficulties.
Cleaning Up Source Water
Cleaner source water is critical to breaking this cycle. By failing to protect source water, Congress, EPA and polluters leave Americans with no choice but to treat it with chemical disinfectants and then consume the residual chemicals generated by the treatment process.
For most utilities with chronically high readings of treatment pollutants, cleaning up source water will require aggressive action to reduce agricultural pollution, runoff from suburban sprawl and upstream sewage discharges.
Superstorm Sandy exerted unprecedented pressure on sources of drinking water along the East Coast. In the storm’s wake, tens of millions of gallons of sewage washed into waterways and the Chesapeake Bay. The Federal Emergency Management Agency advised people in areas slammed by the storm to boil tap water. New York Gov. Andrew Cuomo estimated that the costs of repairing damaged sewage pumping stations and treatment plants in his state alone could surpass $1.1 billion. The fragile Chesapeake, already the site of a long-running environmental cleanup, was deluged with sewage from water treatment systems swamped by pounding rains. In Virginia, most of the lower Chesapeake Bay suffered widespread sewage contamination and was closed to shell-fishing for a period.
These are serious issues that must be addressed. The smart choice will be to make infrastructure improvements that help protect source water. It doesn’t take a perfect storm for sewage to pollute the Potomac River. The Washington D.C. area’s aging sewage pipes do that regularly. To remedy the problem, Washington authorities have embarked on a complex, long-term sewage control plan called the Clean Rivers project, estimated to cost $2.6 billion and wind up in 2025.
Other urban areas are long overdue for upgrades to their sewage and storm water management systems. In 2009, the American Society of Civil Engineers gave the nation a D-minus for inattention to its wastewater systems. “Clean and safe water is no less a national priority than are national defense, an adequate system of interstate highways, and a safe and efficient aviation system,” the organization said. “Many other highly important infrastructure programs enjoy sustainable, long-term sources of federal backing, often through the use of dedicated trust funds; under current policy, water and wastewater infrastructure do not.”
Treating fouled water with chemicals can be more expensive than reducing pollution before it gets to the treatment plant. Research has shown that the long-term economic benefits of keeping source water clean often far outweigh the costs. The EPA has found that every dollar spent to protect source water reduced water treatment costs by an average of $27 (CBF 2012). Philadelphia officials have estimated that every dollar they invest in green infrastructure to reduce storm water flows will create more than double the economic benefits (PWD 2009).
In much of the country, farming is a major source of organic pollution in drinking water and a contributor to water treatment contamination. Farming communities need common sense standards to reduce soil erosion and polluted runoff from agricultural operations. Farm operators and landowners should be expected to implement a basic standard of care involving simple and often conventional practices that improve soil and water quality. These should be a condition of eligibility for receiving the generous federal benefits accorded agricultural operations. States should take action to enact narrowly-targeted standards that restrict farming practices that inflict a disproportionally large amount of natural resource damage.
About 1 billion tons of topsoil erode from American cropland each year, much of it deposited in streams and rivers. Soil mixed with manure washed from pasture and rangelands contains even more fecal matter and other organic substances (USDA 2001, EWG 2012a).
Studies by the U.S. Geological Survey have found that fertilizer used in agriculture accounted for 17 percent of total phosphorus in major U.S. river basins (CSP 2007). Most phosphorus from fertilizer is absorbed into soil in fields and is carried to streams and rivers during soil erosion. USGS studies show that three-quarters of all American streams and rivers are polluted with enough phosphorus to support uncontrolled algae growth (USGS 1999, Cooke 1989). In bodies of water, algae blooms die, decompose and, like other organic matter, give off fulvic and humic acids that react with chlorine during treatment to form trihalomethanes.
With the exception of large animal feeding operations, farm businesses are exempt from the pollution control requirements of the federal Clean Water Act. Few states have authority to compel farms to adopt practices that would reduce agricultural pollution reaching rivers, lakes and bays.
For example, according to the Iowa Department of Natural Resources, 92 percent of the nitrogen and 80 percent of the phosphorus – the two pollutants most responsible for the poor condition of the waterways that it monitors – come mainly from agricultural runoff. Only 8 percent of the nitrogen and 20 percent of the phosphorus come from “municipal and industrial discharges.” Yet Iowa’s water quality regulation almost exclusively targets municipal and industrial discharges. Agricultural runoff remains largely unregulated (EWG 2012b).
The federal farm bill, reauthorized every five years, sets national policy for source water protection. The current debate over renewing the farm bill can be viewed as a referendum on the nation’s commitment to protect drinking water supplies at the source. This legislation affects the nation’s waters in two opposing ways. On one hand it authorizes subsidies that encourage all-out production of feed grains and oilseeds, spurring increased pollution and habitat destruction. On the other, it offers incentives to farmers who protect the environment.
In exchange for federal subsidies, farmers since 1985 have agreed to adopt soil conservation measures to minimize erosion and protect wetlands. As a result of this “conservation compact” between farmers and taxpayers, soil erosion on highly erodible land was reduced by 40 percent in recent decades. The nation met the long-sought goal of no net loss of wetlands.
Now, however, some lobbyists and legislators want to end this compact, opposing proposals to restore the link between “conservation compliance” and crop insurance subsidies, which are the government’s chief form of income support for farm businesses. To finance those subsidies, many of the same lobbyists and legislators have proposed cutting programs managed by the U.S. Department of Agriculture to help farmers pay for conservation measures. These cuts would reverse a gradual trend in recent decades that has seen annual spending on conservation increase from $2 billion to more than $4 billion, with greater incentives for farmers who take steps to reduce water pollution (EWG 2012a).
If conservation funding is slashed, the U.S. will give up important gains that have constrained agricultural pollution. The problem of water treatment contaminants is likely to become more pronounced.
The Trouble with EPA
The EPA’s rules for water treatment contaminants date back to 1974, when scientists discovered that chlorine was reacting with dissolved pollution in the water supply to create more contaminants. Five years later, the EPA set the nation’s first standards for trihalomethanes at 100 parts per billion, calculated as the running annual average of total concentration of the chemicals.
In 1998, the Clinton EPA lowered the trihalomethane cap to a running annual average of 80 parts per billion and set a new legal limit for haloacetic acids at a running annual average of 60 parts per billion.
But the agency’s regulatory scheme succeeded in conveying a false sense of security to the public.
As noted earlier, the EPA regulates just nine pollutants generated by chlorine or chloramine-- four trihalomethanes and five haloacetic acids (EPA 2012a). These nine regulated chemicals represent less than 2 percent of the more than 600 unwanted chemicals created by the interaction of water treatment disinfectants and pollutants in source water (Barlow 2004).
The legal limits for the nine regulated chemicals are not what either the agency or many independent scientists believe is truly safe. Rather, the regulations represent political compromises that take into account the costs and feasibility of treatment.
In 2010, California’s Office of Environmental Health Hazard Assessment proposed a “public health goal” for trihalomethanes of 0.8 parts per billion. A “goal” is not a binding legal limit, but setting a goal is the first step in the process that establishes such a limit. California regulators estimated that if the goal of 0.8 parts per billion were attained, bladder cancer risks would be reduced to no more than 1 in a million (OEHHA 2010). The state is still in the process of publishing its final goal. Still, the 2010 proposal represents what California’s public health and environmental experts believe should be done to protect the public from carcinogenic trihalomethanes. It is significant that this proposed goal is one-hundredth of the EPA cap.
Yet another problem is of the EPA’s own making. The agency established an unusual monitoring method that all but guaranteed that many Americans would be overexposed periodically to spikes in water treatment contamination. For most toxic chemicals in drinking water, the agency set a simple limit on the maximum level of the contaminant that could be measured at any time. But for water treatment contaminants, the agency permitted utilities to average the pollution throughout their systems and over the previous four quarters. This method made it legal for utilities to distribute excessively contaminated water from chronically problematic sections and use readings from other sections that were below average to remain in compliance with federal law and regulations.
This flaw is not theoretical. EWG’s analysis of 201 utilities’ water quality reports for 2012, known as “consumer confidence reports,” uncovered several utilities in which annual trihalomethane and/or haloaceticacid levels for some sampling locations spiked to between 2 and 8 times higher than other sampling locations within the same systems. The entire systems escaped penalties because their water averaged out with a passing grade from EPA. But at certain times and in certain places, the water was excessively tainted, sometimes severely so. Pregnant women and their unborn children could be affected by these spikes.
In 2005, responding to critics of this complicated and flawed method, the EPA proposed new rules to go into effect between 2012 and 2016, depending on the size of the water system. These would require water utilities to find spots within their systems that had markedly high concentrations of water treatment contaminants and designate these locations as monitoring sites for compliance with federal drinking water standards. The EPA asserted that these new rules would prevent an estimated 280 cases of bladder cancer each year.
But EPA’s plan represented only a partial solution. It retained the system-wide averaging method and would not solve the problem of recurrent contaminant spikes at particular locations.
To examine this issue further. EWG created a case study, analyzing detailed water treatment contaminant data for all 936 water utilities in Florida.
We found that fully nine percent of all the tests exceeded the EPA maximum for trihalomethanes. The most contaminated water measured an astonishing 595 parts per billion. In four percent of the tests, haloacetic acids exceeded the EPA maximum, with some levels as high as 260 parts per billion. Spikes typically appeared in early spring and late summer.
If source water were less polluted as it flowed into a water utility’s intake pipes, less disinfection with chlorine and chloramines would be needed, and these treatment chemicals would produce less contamination. But government policies do little to advance this goal.
Instead, taxpayers pour billions of dollars into federal programs like farm subsidy payments that exacerbate pollution and then pile on additional billions of dollars for water treatment facilities. Not enough federal money and effort are being devoted to finding more effective and efficient measures to protect rivers and streams from pollution in the first place.
Until such measures are in place and contaminant levels are dramatically reduced, EWG makes these recommendations for national policy:
- The EPA should reevaluate its legal limits for water treatment contaminants in light of the latest scientific research indicating that lower limits are well justified to protect human health.
- Congress should reform farm policies to provide more funds to programs designed to keep agricultural pollutants such as manure, fertilizer, pesticides and soil out of tap water.
- Congress should renew the “conservation compliance” provisions of the 1985 farm bill by tying wetland and soil protection requirements to crop insurance programs, by requiring farm businesses that receive subsidies to update their conservation plans and by strengthening the government’s enforcement tools.
- Congress should strengthen and adequately fund conservation programs that reward farmers who take steps to protect sources of drinking water. Congress should expand “collaborative conservation” tools that award funds to groups of farmers who work together to protect drinking water sources.
- The USDA and other federal agencies involved in federal agriculture policy should place greater emphasis on restoring buffers and wetlands that filter runoff contaminated with farm pollutants.
- The federal government should fund more research on the identity of and toxicological profiles for the hundreds of water treatment contaminants in drinking water.
- The EPA must reevaluate the way it measures water treatment contaminants so that consumers cannot be legally exposed to spikes of toxic chemicals.
- Congress must allocate significant money to help repair and upgrade the nation’s water infrastructure.
- Source water protection programs should be significantly expanded, including efforts to prevent or reduce pollution of source waters and to conserve land in buffer zones around public water supplies. Financial support for these projects is crucial.
Recommendations for Consumers
Anyone drinking tap water should use some form of carbon filtration designed to reduce exposures to trihalomethanes, haloacetic acids and other water treatment contaminants.
Carbon filtration systems come in various forms, including pitchers, faucet-mounted attachments and larger systems installed on or under countertops. Prices vary. They may be deceiving, because different systems require filter replacement periodically.
EWG research shows that pitcher and faucet- mounted systems are typically the most economical, costing about $100 a year. Countertop and under- counter systems are more expensive to install, with yearly maintenance costs roughly equal to pitcher and faucet-mounted systems.
The prices for all of these systems pale in comparison to the expense of purchasing bottled water for a family of four, which EWG estimates to range between $950 and $1,800 a year.
Before purchasing any filtration system, it is important to research them. Not all activated carbon systems remove water treatment contaminants. Click here to see a list of some filters that reduce the concentrations of at least one of these chemical families. (https://www.ewg.org/report/ewgs-water-filter-buying-guide)
Consumers who are serious about avoiding water treatment contaminants should consider installing a whole-house filtration system. Numerous studies have shown that showering and bathing are important routes of exposure for trihalomethanes and may actually contribute more to total exposure than drinking water (OEHHA 2004, Xu and Weisel 2003).
It is critical, however, that consumers research their choices carefully. many whole-house systems do not remove water treatment contaminants. In fact, when EWG was assembling the latest edition of its filter guide, we could not find a single whole-house system that was certified by the state of California or NSF International, an independent, non-profit certification body, to reduce trihalomethanes. Those that do may cost several hundred or even thousands of dollars and incur yearly maintenance costs of hundreds of dollars more.
Whichever system you choose, remember to change the filter according to the manufacturer’s guidelines, or it will become clogged and cease to function effectively. (https://www.ewg.org/report/water-filter-maintenance)
Sources are listed in detail within the full PDF version of this report. View and Download the report here: 2013 Tap Water Report