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Common Drinking Water Contaminates

By Part 1 |

Contamination health effects, treatments, and recommendations for associated United States cities.

NRDC’s review of city tap water quality revealed that there are several contaminants that occur with surprising regularity in tap water throughout America’s cities, regardless of location—such as chlorination by-products, lead, and total coliform bacteria. Other contaminants, such as industrial chemicals, may occur less frequently but still pose major health concerns. This chapter summarizes the health concerns for and sources of many of the most common tap water contaminants.



Cryptosporidium (Crypto) is a microbial, waterborne protozoan. It has long been known to be a parasite in humans and animals, including cattle, and is shed in feces after reproducing by the millions in the host’s intestines.1 Crypto forms a particularly robust, hard-shelled cyst that can withstand temperature extremes and even survive a dousing with pure chlorine bleach.

Health Effects

Crypto’s health effects include severe diarrhea for up to two weeks in otherwise healthy people, nausea, abdominal cramps, and fever. Currently, no antibiotics or other medical treatments are available to kill Crypto.2 Crypto poses significant public health concerns, especially to individuals whose immune systems are weakened, including people living with HIV/AIDS, the elderly, young children, chemotherapy patients, and organ transplant patients.3 Indeed, individuals who are immunocompromised can and do die from Crypto infection.

In 1993, high levels of Crypto got through the filters and treatment process at a water treatment plant in Milwaukee, Wisconsin. The plant did use poorly operated filtration and chlorine disinfection and was apparently in full compliance with all EPA rules then in place. More than 400,000 people in Milwaukee became sick, several thousand of whom were hospitalized and approximately 100 of whom eventually died. The outbreak was the largest documented waterborne disease occurrence in U.S. history, but it is not the only such experience on record.4In the wake of the Milwaukee incident and several other Crypto outbreaks, the EPA negotiated a new set of rules with industry, NRDC, health groups, state and local governments, and others that will gradually reduce the risk of such outbreaks. The new rules require improved drinking water treatment and stricter control son turbidity (cloudy water) that can indicate poor filter performance. Many more waterborne Crypto outbreaks have occurred in the United States, England, and elsewhere in the world.5 Tests of healthy adult human volunteers found that even a single Crypto cyst carries a risk of infection. The more cysts in a glass of drinking water, the higher the risk that people will become infected.6 Because a single cyst may cause infection, the EPA has established a Maximum Contaminant Level Goal (MCLG, or health goal) for Crypto of 0.7

Occurrence and Treatment Crypto is found in most surface water supplies in the United States; surveys have found it in more than 80 percent of the U.S. surface waters tested.8 However, Crypto is difficult to detect in water, and testing methods available cannot identify with certainty whether the Crypto that is detected is viable—that is, that it can actually make people ill.9 In addition, the current testing methods are especially poor at detecting the kind of low-level Crypto concentrations that might be expected in finished, or treated, drinking water. Therefore, experts say it is incorrect to assume that Crypto is not present in treated drinking water simply because it has not been detected.10All large and medium size water utilities that use surface water must monitor for Crypto, report results in their right-to-know reports and use advanced treatment if they find significant levels. Chlorine disinfection of drinking water is ineffective in killing Crypto. Indeed, only very finely tuned filtration or state-of-the-art disinfection using ozone or intense ultraviolet light will kill Crypto once it is in water supplies.11 Of course, the best approach is to prevent Crypto from getting into drinking water sources in the first place, and that requires the adoption of strong source water protection programs. However, even cities with strong source water protection—including the use of completely undeveloped watersheds—find Crypto at low levels in their source water, possibly from wildlife or from humans using the watershed for recreation. Low levels of Crypto from protected watersheds pose far lower risks than high levels such as those found downstream from concentrated animal feeding operations or other major pollution sources. Nevertheless, they still pose a risk if not dealt with through treatment. However, if filtration is operating properly and is optimized, it will reduce Crypto levels.

In the wake of the above, EPA has adopted an "Interim Enhanced Surface Water Treatment Rule" for cities serving more than 10,000 people that filter surface water. The rules went into effect in January 2002, and they require water filtration plants to optimize the way they operate filters and to keep turbidity levels down, demonstrating filter efficiency (see turbidity section below).12

Recommendations for People with Weakened Immune Systems People who are immunocompromised or are concerned about the possibility that Crypto may be in their water should consult with their health care provider about finding a safe source of drinking water. The Centers for Disease Control and Prevention (CDC) recommends that people with severely compromised immune systems may wish to avoid drinking tap water. The CDC has offered detailed recommendations specifically to people with HIV/AIDS, but they are equally applicable to anyone who is seriously immunocompromised. Those recommendations are quoted in full on page 13.

Total Coliform Bacteria

Total coliform bacteria is a broad class of bacteria, many of which live in the intestines of humans and animals. It is a microbial contaminant whose presence is a potential indicator that disease-causing organisms may be in tap water.

Health Effects

While most coliform bacteria are themselves harmless, their presence is a sign that the water may contain fecal pathogens, including non-coliform pathogens such as other forms of bacteria, viruses, or protozoa. Exposure to disease-carrying pathogens potentially indicated by the presence of coliform bacteria may cause infection, resulting in diarrhea, cramps, nausea, jaundice, headaches, and fatigue.14 Some coliform bacteria, such as Escherichia coli (E. coli), are dangerously infectious organisms that can cause serious infections in exposed people. It was this type of coliform that caused the infamous Jack in the Box hamburger poisoning incidents in 1999, in which four children were killed and 700 sickened.15 In an E. coli disease outbreak in 1989 caused by contamination in the Cabool, Missouri, drinking water supply, four people died while 243 were sickened—but the incident generated virtually no publicity.16 More recently, two people died, including a three-year-old girl, at least 65 were hospitalized, and an estimated 1,061 were confirmed to have become ill as a result of the same strain of E. coli, when drinking water was contaminated at a county fair in upstate New York in 1999.17 Again, the incident generated some publicity, but hardly the nationwide attention caused by the hamburger incidents.

Occurrence, Treatment, and the Total Coliform Rule The EPA says that "the presence of coliform bacteria in tap water suggests that the treatment system is not working properly or that there is a problem in the pipes."18 The EPA therefore has adopted the Total Coliform Rule (TCR), which set the health goal for total coliform at 0. The EPA found that "since there have been waterborne disease outbreaks in which researchers have found very low levels of coliform, any level indicates some health risk."19 To avoid or eliminate microbial contamination, water systems may need to repair their disinfection or filtration processes, flush or upgrade pipes from treatment plants to customers (their distribution system), and adopt source water protection programs to prevent contamination. The EPA’s TCR says that when water system tests reveal that more than 5 percent of monthly samples contain coliforms, system operators are required to report that violation to their state and the public.20 If a water system finds that any sample contains total coliform, the TCR requires it to collect "repeat samples" within 24 hours.21 When a sample tests positive for total coliforms, it must also be analyzed for fecal coliforms and E. coli.22 If fecal coliform or E. coli are found, the incident is deemed an "acute violation," triggering a requirement that the system rapidly notify the state and the public, because such a violation "represents a direct health risk,"according to the EPA.23 Big city water systems are required to test for coliform far more often than small systems. Water suppliers serving fewer than 1,000 people may test once a month or less frequently, but systems with 50,000 customers must test 60 times per month, and those with 2.5 million customers must test at least 420 times per month.24

Recommendations for People with Weakened Immune Systems

People with weak immune systems, including some infants, elderly people, organ transplant or cancer chemotherapy patients, and people living with HIV/AIDS, are at special risk from the pathogens whose presence may be indicated by total coliform.25 In some cases, immunocompromised people can die from consuming water containing dangerous bacteria.26Total coliform violations are a common trigger for boil-water orders issued in the United States. When total coliform levels are repeatedly high in a public water system, it is an indication that the system may pose serious risks, particularly to people with immune system problems. The CDC has offered detailed recommendations specifically to people with HIV/AIDS, but they are equally applicable to anyone who is seriously immunocompromised. The recommendations made by CDC regarding immunocompromised people taking action to avoid Crypto are equally applicable to water that has a high risk of E. coli or other pathogen contamination that may be indicated by boil-water alerts or total coliform violations. Those recommendations are quoted in full on page 13.

Turbidity (Cloudiness)

Turbidity is a measure of the cloudiness of water, often the result of suspended
mud or organic matter, and may sometimes indicate that the water is contaminated with Cryptosporidium or other pathogens. In addition, turbidity can interfere with disinfection of the water because it can impede the effectiveness of chlorine or other
chemical disinfectants.

Health Effects

According to the EPA, "higher turbidity levels are often associated with higher levels of disease-causing microorganisms such as viruses, parasites, and some bacteria. These organisms can cause symptoms such as nausea, cramps, diarrhea, and associated headaches."27 Indeed, it was a spike in the level of turbidity at a Milwaukee treatment plant that indicated the city had a serious problem with its drinking water just before the 1993 Crypto outbreak that sickened 400,000 and killed approximately 100 people.28 It is important, therefore, to remember that disease-carrying organisms that may be present during turbidity spikes can pose special, even mortal, threats to people with weakened immune systems.

Treatment and Regulation From 1989 until 2002, the EPA had a lax standard for turbidity in filtered drinking water, allowing up to 5 NTU as a maximum and requiring only that water systems maintain 0.5 NTU 95 percent of the time. (Most cities take samples every hour or every few hours.29) The laxity of this old standard was made all too clear by the Milwaukee outbreak. According to some investigators, although Milwaukee had a spike in turbidity, it reportedly did not violate the EPA standard during the outbreak.30 In 1998, after an extensive set of regulatory negotiations among the EPA, the water industry, NRDC, health groups, and others, the EPA issued the Interim Enhanced Surface Water Treatment Rule, establishing a new turbidity standard for large filtered water systems serving more than 10,000 people. Under the new rules, which went into effect in 2002, large filtered systems can never exceed 1 NTU(down from the previous maximum of 5) and must achieve a limit of 0.3 NTU or less in at least 95 percent of its samples. In 2000, regulatory negotiators agreed to a rule to reduce Crypto and turbidity problems in smaller filtered systems; NRDC holds that this rule was legally required to have been issued, but the Bush administration has failed even to publish the proposal in The Federal Register.31 Because the rules for unfiltered surface water systems have not been updated, unfiltered systems need only meet the old and outdated 5 NTU maximum limit, the Milwaukee experience notwithstanding.

Recommendations for People with Weakened Immune Systems Like coliform violations, turbidity violations often trigger boil-water orders. When turbidity levels are repeatedly high in a public water system, it is an indication that the system’s filters are not being well operated or maintained or, if the system is unfiltered, that its source water is not as well protected as it should be. Which ever is the case, the circumstance may pose serious risks, particularly to people with immune system problems. The recommendations made by CDC regarding immunocompromised people taking action to avoid Crypto are equally applicable to water that has a high risk of significant turbidity spikes and violations.

Inorganic Contaminates


Arsenic in drinking water supplies comes from mining, industrial processes, past use of arsenic-containing pesticides, and natural leaching or erosion from rock.

Recent studies indicate that heavy pumping of groundwater can actually increase arsenic levels in some cases, perhaps because the pumping allows oxygen to reach the arsenic source, permitting oxidization and mobilization of the poison.

Health Effects Arsenic is toxic to humans and causes cancer, and for this reason, no amount of arsenic is considered fully safe. Many scientific studies, including no fewer than seven reviews of the problem by the National Academy of Sciences (NAS),have determined that arsenic in drinking water is known to cause cancer of the bladder, skin, and lungs; likely causes other cancers; and is responsible for a variety of other serious health ailments. The NAS reviews culminated in the important recent reports Arsenic in Drinking Water (issued in 1999) and Arsenic in Drinking Water: 2001 Update, which counter the long-standing water utility and industry arguments that arsenic in tap water poses no significant threat.32,33 The NAS found in its 2001 report that a person who drinks two liters of water a day containing 10 ppb arsenic—the new EPA standard—has a lifetime total fatal cancer risk greater than 1 in 333 (that is, about 1 in 333 people who drink water containing this level of arsenic will die of arsenic-caused cancer).34 The EPA traditionally has allowed no greater than a 1 in 10,000 lifetime fatal cancer risk for any drinking water contaminants. In other words, the risk level allowed by the new arsenic standard is more than 30 times higher than what the EPA traditionally allows in tap water. NAS’s risk estimates were more than 10 times higher than the estimates the EPA used to justify its new January 2001 standard (see below). This 2001 NAS report’s staggering findings likely would have been major news across the nation, but they were released on September 11, 2001.35

Treatment and Regulation

Arsenic can readily be removed from drinking water with off-the-shelf treatment technology, including activated alumina and membrane treatment.36 According to the EPA, the cost of using current, easily available treatment for arsenic is less than $2 per household per month for city water customers.37 A working group of the National Drinking Water Advisory Council, appointed by the Bush administration in 2001 to review these EPA estimates (in light of industry allegations that the EPA had grossly underestimated arsenic treatment costs), found the EPA’s estimates "credible" and noted that newer technologies, such as granular ferric-hydroxide and other cutting-edge treatments may bring even these already quite affordable costs of treatment down.38 More than 60 years ago, in 1942, the Public Health Service issued a 50 ppb arsenic guideline. The EPA adopted that guideline in 1975, and this extremely lax tap water standard remains applicable today.39 After the EPA missed at least three statutory deadlines to update the standard, and after NRDC sued the EPA to get the agency to move forward with issuing a new arsenic rule, the Clinton administration finally adopted the new arsenic standard (a Maximum Contaminant Level) of 10 ppb in January 2001.40 That standard becomes effective in 2006.

However, upon taking office, the Bush administration suspended the EPA’s new arsenic standard, responding to pleas from the mining industry and utilities and arguing that the EPA had overestimated arsenic’s risks and underestimated the rule’s costs. A public outcry ensued, and the NAS issued a study, at the Bush administration’s behest, finding that the EPA had actually underestimated cancer risks tenfold.41 The NAS’s finding ought to have led to a standard lower than 10 ppb, but the Bush administration moved hurriedly to ratify the Clinton administration standard instead.

NRDC and many public health and medical group activists recommend a standard of 3 ppb because it is the lowest level deemed achievable by the EPA in using existing treatment technology. The NAS found that arsenic in tap water, even at 3 ppb, poses a cancer risk of about 1 in 1,00042—which is 10 times higher than what the EPA traditionally allows for any single tap water contaminant; this is a significant concern for human health.


Chromium is a naturally occurring metal used in industrial processes, including metal plating for chrome bumpers and making stainless steel, paint, rubber, and wood preservatives.43

Health Effects
Health effects from human exposure to chromium range from skin irritation to damage to kidney, liver, and nerve tissues. A heated debate has taken shape recently over whether states and the EPA should adopt a separate standard for Chromium VI(hexavalent chromium), a form of chromium known to cause cancer when inhaled. The EPA has refused so far to consider it a carcinogen when it is consumed in tap water.44

Treatment and Regulation
The EPA has found that chromium can be removed from drinking water through coagulation/filtration, ion exchange, reverse osmosis, and lime softening.45


A well-known poison, cyanide is a nitrogen-carbon compound.46 Cyanide is used
in various forms in mining, steel and metal manufacturing, and to make resin, nylon, and other synthetic fibers.47 Also, chlorination treatment of some wastewater can create cyanide, according to the EPA.48

Health Effects The EPA says short-term exposure to cyanide at levels above the standard can cause rapid breathing, tremors, and other neurological effects, and long-term exposure can cause weight loss, thyroid effects, and nerve damage.49

Treatment and Regulation
Cyanide can be removed from drinking water with reverse osmosis membranes and ion exchange. In some cases, chlorine will assist in its removal.


Health Effects

Lead is a major environmental threat and is often referred to as the number one environmental health threat to children in the United States. No amount of it is considered safe.51 Infants, young children, and pregnant women’s fetuses are particularly susceptible to the adverse health effects of lead. Lead poisoning can cause permanent brain damage in serious cases, and in less severe cases can cause children to suffer from decreased intelligence and problems with growth, development, and behavior. Lead can also increase blood pressure, harm kidney function, adversely affect the nervous system, and damage red blood cells.52One way lead enters drinking water supplies is from the corrosion of water utility pipes in the distribution system—the system of pipes through which water reaches consumers’ homes from the water utility, including water mains and their connectors, service lines (between the main and the home), goosenecks (which connect service lines to the main), and water meters. Lead can also leach from pipes or faucets in homes, schools, and businesses.

Treatment and Regulation The easiest way for cities to reduce lead levels in tap water is to treat their water using corrosion control. This approach involves adjusting the water’s pH upward—that is, making it less acidic—by adding a chemical such as lime and thereby decreasing the likelihood of lead leaching from pipes. Many water utilities also add an orthophosphate, such as zinc orthophosphate, that forms a thin coating on the inside of utility and household pipes, thus reducing corrosion. The EPA’s lead and copper rule requires city water systems to reduce lead levels at the tap by optimizing corrosion control for their water, which reduces its ability to corrode pipes and therefore to leach lead into tap water. The EPA has also adopted an action level standard for lead that is different from the standard for most other contaminants.53 Water utilities are required to take many samples of lead in tap water, including some samples at identified high-risk homes—those that are likely to have high lead because they are old and have lead plumbing components, or in the case of homes built after 1982, because they have lead-soldered copper pipes likely to be heavy lead leachers.54 The actual number of required samples is determined by system size; a large city generally must take at least 100 samples. If the amount of lead detected in the samples exceeds 15 ppb at the 90th percentile—which is to say that 10 percent or more of taps tested have 15 ppb or more of lead—then the amount is said to exceed the action level. A water system that exceeds the action level is not necessarily in violation, but additional measures are required, such as chemical treatment to reduce the water’s ability to corrode pipes and thus its ability to leach lead from pipes. If such chemical treatment does not work, the water system must then replace lead portions of its distribution system, including lead service lines and goosenecks owned by the water system, if they are still contributing to the lead problem. In addition, Congress amended the Safe Drinking Water Act (SDWA) to ban high lead solder (more than 0.2 percent lead) and high-lead plumbing (over 8 percent lead), but this plumbing can still contribute significantly to lead contamination of tap water.55 An NSF standard for lead in plumbing, adopted by most states, is supposed to help on this front, but testing by NRDC and others has found lead leaching at high levels from faucets and water meters since Congress amended the SDWA. NRDC sued the faucet and water-meter manufacturers under a stricter California law (Proposition 65) and agreed to a settlement to phase out lead from faucets and water meters.


Nitrates are the product of fertilizers and human or animal waste. Elevated
levels of nitrates in water generally result from agricultural runoff from dairy and cattle farms or concentrated animal feeding operations, and from fields heavily fertilized with inorganic nitrogen fertilizer or over fertilized with manure.56 High levels of nitrate contamination also can come from septic tanks and sewage.57

Health Effects

Infants who drink water containing excessive nitrates for even a short period of time can develop blue baby syndrome, in which nitrate poisoning prevents their blood from holding oxygen.58 Shortness of breath, nausea, vomiting, diarrhea, lethargy, loss of consciousness, and even death can result from infants’ exposure to high levels of nitrates in water.59 Pregnant women are also particularly vulnerable to high nitrate levels in drinking water, again because it can affect the ability of their blood to carry oxygen.60 The medical literature continues to report deaths and serious illnesses of infants fed formula made with nitrate-contaminated water.61 In addition, recent literature suggests that pregnant women who drink nitrate-contaminated water can have miscarriages possibly caused by the contaminant.62 Moreover, a comprehensive study conducted by the California Birth Defects Monitoring Program discovered an association between nitrate exposure and increased risk of neural tube defects.63 The study found that pregnant women whose drinking water contained nitrates above the regulatory standard faced a fourfold increase in the risk of anencephaly—absence of the brain—in their developing fetus. In addition to these short-term effects, several chronic effects of elevated nitrate levels have also been observed. According to the EPA, drinking water containing nitrates at levels above the Maximum Contaminant Level (MCL) fora prolonged period has "the potential to cause . . . diuresis, increased starchy deposits, and hemorrhaging of the spleen."64 In addition, indications are that breakdown products of nitrates called N-nitrosamines and compounds that form when nitrates react with pesticides with which they commonly co-occur(the nation’s most used pesticide, the corn herbicide atrazine, among them) may cause cancer.65

Treatment and Standard

The EPA set the MCLG and MCL for nitrate at 10 ppm. Because it is an acute toxin, no long-term averaging is allowed; one confirmation sample, taken within 24 hours of a sample showing a level over 10 parts per million, is allowed. The EPA’s nitrate standard remains controversial. Many European and other nations have adopted a standard allowing less than half the nitrates the EPA permits.66 While a National Academy of Sciences review conducted in 1995 concluded that the EPA’s 10-parts per-million health goal and standard were protective of health,67 that conclusion may not be justified in light of emerging evidence of nitrates’ possible reproductive and other toxicity and nitrosamines’ potential cancer risks.68 Clearly, the current EPA nitrate MCL and MCLG leave virtually no margin of safety, since blue baby syndrome has been observed in infants who drink water containing nitrates at 12 parts per million or possibly lower concentrations.69


Perchlorate is an inorganic contaminant that usually comes from rocket fuel spills or leaks at military facilities. Perchlorate contaminates the tap water of much of southern California via the Metropolitan Water District’s Colorado River Aqueduct. It also is in the water of Phoenix, Las Vegas, and many other cities and towns reliant upon the Colorado River for their water. The source of the Colorado’s contamination is reportedly a Kerr-McGee site in Henderson, Nevada, where perchlorate was manufactured and whose waste leaks into the Colorado River.71Perchlorate also contaminated water sources for many other towns and cities across the nation, where it has been manufactured or used at military bases orin commercial applications. In addition to its heavy use in rocket fuel, perchlorate is also used, in far lower quantities, in a variety of products and applications, including electronic tubes, automobile air bags, leather tanning, and fireworks.72

Health Effects

Perchlorate harms the thyroid and may cause cancer.73 According to the EPA, perchlorate:disrupts how the thyroid functions. In adults, the thyroid helps to regulate metabolism. In children, the thyroid plays a major role in proper development in addition to metabolism. Impairment of thyroid function in expectant mothers may impact the fetus and newborn and result in effects including changes in behavior, delayed development, and decreased learning capability. Changes in thyroid hormone levels may also result in thyroid gland tumors. [The EPA finds that] perchlorate’s disruption of iodide uptake is the key event leading to changes in development or tumor formation.74

Standard There is no national standard for perchlorate. In early 2002, the EPA proposed a reference dose, (a level the EPA says is safe) and with that as a basis, estimated that the"drinking water equivalent level" (DWEL)— essentially the highest safe dose in tap water—should be 1 ppb. The EPA appears reluctant to establish a permanent standard of any sort, however. It now maintains that it does not yet know enough to warrant establishing a standard and will continue studying the problem.75, 76 In the meantime, as many as 20 million Americans (or more) have perchlorate in their tap water, a circumstance that the EPA’s own draft risk assessment acknowledges is an unacceptable risk.


Thallium is a trace metal often associated with copper, gold, zinc, and cadmium
and is found in rock and in ores containing these other commercially used metals.77
Thallium is used principally in electronic research equipment.78 The EPA reports that thallium pollution sources include gaseous emissions from cement factories, coal burning power plants, and metal sewers.79 The chief source of thallium in water is ore processing—the metal leaches out during processing.80

Health Effects
High exposure to thallium for a short period can cause gastrointestinal irritation and nerve damage.81 Of even greater concern are the long-term effects of exposure overtime, even at lower levels (but still above the EPA standard): changes in blood chemistry;damage to the liver, kidney, intestines, and testicles; and hair loss.82

Treatment Thallium can be removed from tap water with activated alumina, ion exchange, or reverse osmosis.



Atrazine is among the most widely used pesticides in this country, applied to corn and other crops to protect from broad-leaved and grassy weeds.83 Atrazine enters source waters through agricultural runoff, and also volatilizes, or evaporates, and is then redeposited with rain.84 It is among the most commonly detected pesticide in drinking water, particularly during spring runoff season throughout most of the Mississippi River basin and virtually anywhere else that corn is grown.85

Health Effects

Atrazine is an animal carcinogen.86 According to the EPA, short-term human exposure to atrazine may cause prostate cancer; congestion of the heart, lungs, and kidneys; low blood pressure; muscle spasms; weight loss; and damage to the adrenal glands.87 Over the long term, the EPA reports, atrazine may cause weight-loss, cardiovascular damage, retinal and some muscle degeneration, and possibly cancer.88 In addition, as noted above, atrazine is a known endocrine disrupter, meaning that it interferes with the body’s hormonal development and may cause cancer of the mammary gland.89

Treatment and Standard
Atrazine can be removed from tap water through the use of granular activated
carbon, powdered activated carbon, or reverse osmosis. The EPA recently reversed its previous judgment of atrazine’s hazards and downgraded it from a "probable" to a "possible" carcinogen in humans, but new evidence collected about its link to prostate cancer in workers and its ability to harm the reproductive system as an endocrine disrupter have called the EPA’s actions into question.90 The EPA determined in 2002 that the chemical cousins triazine pesticides— atrazine, simazine, and propazine, and several of their degradates— all share a "common mechanism of toxicity," which is to say that they all poison the body in the same way.91 However, the EPA has yet to take action to reduce allowable tap water or other exposure levels to these chemicals in combination. Moreover, in an early 2003 EPA announcement, the agency said that it would continue to allow atrazine to be used even if it causes serious drinking water contamination, well above EPA tap water standards.


Cis-1,2-Dichloroethylene is a volatile organic chemical that reaches drinking water
supplies as discharge from industrial chemical factories.

Health Effects

Cis-1,2-Dichloroethylene is linked with liver and nervous system problems.92

Treatment and Standard

The federal Maximum Contaminant Level (MCL) and health goal for the chemical are
both 70 ppb, with averaging allowed.

Dibromochloropropane (DBCP)

DBCP is a banned pesticide still detected in some cities’ tap water.

Health Effects

DBCP has been shown to cause cancer, kidney and liver damage, and atrophy of the testes leading to sterility.93

Treatment and Standard

DBCP can be removed from water with granular activated carbon, reverse osmosis, and certain other treatments. The enforceable standard is an average of 200 parts per trillion. DBCP has been shown to cause cancer, kidney and liver damage, and atrophy of the testes leading to sterility.

Dichloromethane (DCM)

Dichloromethane (DCM) is an industrial chemical used as a paint remover,
solvent, and cleaning agent; as a fumigant for strawberries and grains; and to extract substances from food.94 It is sometimes discharged by the pharmaceutical and chemical industries.95

Health Effects
The EPA has found that exposure to dichloromethane over a relatively short term at levels exceeding the EPA’s standard potentially causes damage to the nervous system and to blood.96 Over the long term, the EPA says, dichloromethane has the potential to cause liver damage and cancer.97

DCM can be removed from drinking water by granular activated carbon in combination with packed tower aeration or by reverse osmosis.

2,2-Dichloropropane (2,2-DCP)
National Standard (MCL)
National Health Goal (MCLG)

2,2-Dichloropropane (2,2-DCP) is a volatile organic chemical that evaporates at room temperature and is found in a few drinking water supplies, most of which are reliant on groundwater sources. It was once used as a soil fumigant by the farming industry.

Health Effects
Although its isomer 1,2-dichloropropane is linked to liver problems and cancer, NRDC has been unable to find specific studies on the health effects of low level exposure to the chemical.

Treatment and Standard

2,2-DCP can be removed from water with activated carbon in combination with packed tower aeration.

Di-(2-Ethylhexyl)phthalate (DEHP or Phthalate)

Di-(2-Ethylhexyl)Phthalate (DEHP) is a plasticizing agent used widely in the
chemical and rubber industries. It is also contained in many plastics.98

Health Effects

The EPA has listed it as a probable human carcinogen, but it also causes damage to the liver and testes. As a result, the agency set a health goal of 0 for DEHP.99

Treatment and Standard

DEHP can be removed from drinking water with granular activated carbon or reverse osmosis.

Ethylene Dibromide (EDB)

National Standard (MCL)
50 ppt (average)
National Health Goal (MCLG)
0—no known fully safe level

Ethylene Dibromide (EDB) is used as an additive in gasoline, as a pesticide, in waterproofing preparations, and as a solvent in resins, gums, and waxes.100

Health Effects
The EPA has found EDB to "potentially cause the following health effects when people are exposed to it at levels above the MCL for relatively short periods of time: damage to the liver, stomach, and adrenal glands, along with significant reproductive system toxicity, particularly the testes."101 The EPA also says that"EDB has the potential to cause the following effects from a lifetime exposure at levels above the MCL: damage to the respiratory system, nervous system, liver, heart, and kidneys; cancer."102


EDB can be removed from water with granular activated carbon or reverse osmosis.



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Updated: Dec 21 2013