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Common Drinking Water Contaminates - Part 1
By The Natural Resources Defense Council
Contanimation health effects, treatments, and recommendations for associated United States cities.
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Cryptosporidium
Total Coliform Bacteria
Turbidity (Cloudiness)
Arsenic
Chromium
Cyanide
Lead
Nitrate
Perchlorate
Thallium
Atrazine
Cis-1,2-Dichloroethylene
Dibromochloropropane (DBCP)
Dichloromethane (DCM)
Dichloropropane (2,2-DCP)
DEHP
Ethylene Dibromide (EDB)
NRDC’s review of city tap water quality revealed that there are several contaminantsthat 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 occurless frequently but still pose major health concerns. This chapter summarizes thehealth concerns for and sources of many of the most common tap water contaminants.
MICROBIOLOGICAL CONTAMINANTS
Cryptosporidium
National Standard
Treatment Technique (TT)
National Health Goal (MCLG)
0—no known fully safe level
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 fecesafter reproducing by the millions in the host’s intestines.1 Crypto forms a particularlyrobust, hard-shelled cyst that can withstand temperature extremes and even survivea dousing with pure chlorine bleach.
HIGH CONCERN
BOSTON
HOUSTON
PHILADELPHIA
SEATTLE
SOME CONCERN
ATLANTA
LOS ANGELES
SAN DIEGO
SAN FRANCISCO
WASHINGTON, D.C.
Health Effects
Crypto’s health effects include severe diarrhea for up to two weeks in otherwisehealthy people, nausea, abdominal cramps, and fever. Currently, no antibiotics orother medical treatments are available to kill Crypto.2 Crypto poses significant publichealth concerns, especially to individuals whose immune systems are weakened,including people living with HIV/AIDS, the elderly, young children, chemotherapypatients, 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 awater treatment plant in Milwaukee, Wisconsin. The plant did use poorly operatedfiltration 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, severalthousand of whom were hospitalized and approximately 100 of whom eventuallydied. The outbreak was the largest documented waterborne disease occurrence inU.S. history, but it is not the only such experience on record.4In the wake of the Milwaukee incident and several other Crypto outbreaks, theEPA negotiated a new set of rules with industry, NRDC, health groups, state andlocal governments, and others that will gradually reduce the risk of such outbreaks.The new rules require improved drinking water treatment and stricter controlson 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 volunteersfound that even a single Crypto cyst carries a risk of infection. The more cysts in aglass of drinking water, the higher the risk that people will become infected.6 Becausea single cyst may cause infection, the EPA has established a Maximum ContaminantLevel Goal (MCLG, or health goal) for Crypto of 0.7
Occurrence and TreatmentCrypto 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 certaintywhether the Crypto that is detected is viable—that is, that it can actually make peopleill.9 In addition, the current testing methods are especially poor at detecting the kindof 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 notpresent in treated drinking water simply because it has not been detected.10All large- and medium-size water utilities that use surface water must monitor forCrypto, report results in their right-to-know reports and use advanced treatment if theyfind significant levels. Chlorine disinfection of drinking water is ineffective in killingCrypto. Indeed, only very finely tuned filtration or state-of-the-art disinfection usingozone 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 thefirst 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 levelsof Crypto from protected watersheds pose far lower risks than high levels such as thosefound 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 WaterTreatment 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 plantsto 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 SystemsPeople who are immunocompromised or are concerned about the possibility thatCrypto may be in their water should consult with their health care provider aboutfinding a safe source of drinking water. The Centers for Disease Control andPrevention (CDC) recommends that people with severely compromised immunesystems may wish to avoid drinking tap water. The CDC has offered detailedrecommendations specifically to people with HIV/AIDS, but they are equallyapplicable to anyone who is seriously immunocompromised. Those recommendationsare quoted in full on page 13.
Total Coliform Bacteria
National Standard (MCL)5% maximum in any month13National Health Goal (MCLG)0—no known fully safe levelTotal coliform bacteria is a broad class of bacteria, many of which live in theintestines of humans and animals. It is a microbial contaminant whose presenceis a potential indicator that disease-causing organisms may be in tap water.
TOTAL COLIFORM
BACTERIA
HIGH CONCERN
BOSTON
DETROIT
WASHINGTON, D.C.
SOME CONCERN
ALBUQUERQUE
ATLANTA
CHICAGO
DENVER
FRESNO
HOUSTON
LOS ANGELES
MANCHESTER
NEW ORLEANS
NEWARK
PHOENIX
SAN DIEGO
SAN FRANCISCO
SEATTLE
LITTLE OR NO CONCERN
PHILADELPHIA
Health Effects
While most coliform bacteria are themselves harmless, their presence is a sign thatthe water may contain fecal pathogens, including noncoliform pathogens such asother forms of bacteria, viruses, or protozoa. Exposure to disease-carrying pathogenspotentially indicated by the presence of coliform bacteria may cause infection,resulting in diarrhea, cramps, nausea, jaundice, headaches, and fatigue.14 Somecoliform bacteria, such as Escherichia coli (E. coli), are dangerously infectious organismsthat can cause serious infections in exposed people. It was this type of coliformthat 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 outbreakin 1989 caused by contamination in the Cabool, Missouri, drinking water supply,four people died while 243 were sickened—but the incident generated virtually nopublicity.16 More recently, two people died, including a three-year-old girl, at least65 were hospitalized, and an estimated 1,061 were confirmed to have become ill as aresult of the same strain of E. coli, when drinking water was contaminated at a countyfair in upstate New York in 1999.17 Again, the incident generated some publicity, buthardly the nationwide attention caused by the hamburger incidents.
Occurrence, Treatment, and the Total Coliform RuleThe EPA says that “the presence of coliform bacteria in tap water suggests thatthe treatment system is not working properly or that there is a problem in thepipes."18 The EPA therefore has adopted the Total Coliform Rule (TCR), whichset the health goal for total coliform at 0. The EPA found that “since there have beenwaterborne disease outbreaks in which researchers have found very low levels ofcoliform, any level indicates some health risk."19 To avoid or eliminate microbial contamination, water systems may need to repair their disinfection or filtrationprocesses, flush or upgrade pipes from treatment plants to customers (their distributionsystem), and adopt source water protection programs to prevent contamination.The EPA’s TCR says that when water system tests reveal that more than 5 percentof monthly samples contain coliforms, system operators are required to reportthat violation to their state and the public.20 If a water system finds that any samplecontains total coliform, the TCR requires it to collect “repeat samples" within24 hours.21 When a sample tests positive for total coliforms, it must also be analyzedfor fecal coliforms and E. coli.22 If fecal coliform or E. coli are found, the incident isdeemed an “acute violation," triggering a requirement that the system rapidly notifythe 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 farmore often than small systems. Water suppliers serving fewer than 1,000 peoplemay test once a month or less frequently, but systems with 50,000 customers musttest 60 times per month, and those with 2.5 million customers must test at least420 times per month.24
Recommendations for People with Weakened Immune Systems
People with weak immune systems, including some infants, elderly people, organtransplant or cancer chemotherapy patients, and people living with HIV/AIDS, areat special risk from the pathogens whose presence may be indicated by total coliform.25 In some cases, immunocompromised people can die from consuming watercontaining dangerous bacteria.26Total coliform violations are a common trigger for boil-water orders issued in theUnited States. When total coliform levels are repeatedly high in a public watersystem, it is an indication that the system may pose serious risks, particularly topeople with immune system problems. The CDC has offered detailed recommendationsspecifically to people with HIV/AIDS, but they are equally applicable to anyonewho is seriously immunocompromised. The recommendations made by CDCregarding immunocompromised people taking action to avoid Crypto are equallyapplicable to water that has a high risk of E. coli or other pathogen contaminationthat may be indicated by boil-water alerts or total coliform violations. Those recommendationsare quoted in full on page 13.
Turbidity (Cloudiness)
National Standards (TT) (in Nephelometric Turbidity Units, or NTU)
Filtered water
0.5 NTU, 95% of the time (through 2001)
0.3 NTU, 95% of the time (as of 2002)
1 NTU, 100% of the time (as of 2002)
Unfiltered water
5 NTU maximum, 100% of the time
TURBIDITY
HIGH CONCERN
ATLANTA
BALTIMORE
NEW ORLEANS
SAN FRANCISCO
SOME CONCERN
PHILADELPHIA
SEATTLE
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 levelsof 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 Milwaukeetreatment plant that indicated the city had a serious problem with its drinking waterjust before the 1993 Crypto outbreak that sickened 400,000 and killed approximately100 people.28 It is important, therefore, to remember that disease-carrying organismsthat may be present during turbidity spikes can pose special, even mortal, threats topeople with weakened immune systems.
Treatment and RegulationFrom 1989 until 2002, the EPA had a lax standard for turbidity in filtered drinkingwater, allowing up to 5 NTU as a maximum and requiring only that water systemsmaintain 0.5 NTU 95 percent of the time. (Most cities take samples every hour orevery few hours.29) The laxity of this old standard was made all too clear by theMilwaukee outbreak. According to some investigators, although Milwaukee hada 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 InterimEnhanced Surface Water Treatment Rule, establishing a new turbidity standard forlarge 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 orless in at least 95 percent of its samples. In 2000, regulatory negotiators agreed toa rule to reduce Crypto and turbidity problems in smaller filtered systems; NRDCholds 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 SystemsLike coliform violations, turbidity violations often trigger boil-water orders. Whenturbidity levels are repeatedly high in a public water system, it is an indication thatthe system’s filters are not being well operated or maintained or, if the system isunfiltered, that its source water is not as well protected as it should be. Whicheveris the case, the circumstance may pose serious risks, particularly to people withimmune 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. Those recommendations are quoted in full on page 13.
Inorganic Contaminates
Arsenic National Standard (MCL)50 ppb (average) through 200510 ppb (average) effective in 2006National Health Goal (MCLG)0—no known fully safe level
ARSENICHIGH CONCERNALBUQUERQUE
HOUSTON
PHOENIX
SOME CONCERN
FRESNO
LOS ANGELES
LITTLE OR NO CONCERN
DETROIT
NEW ORLEANS
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 increasearsenic levels in some cases, perhaps because the pumping allows oxygen to reachthe arsenic source, permitting oxidization and mobilization of the poison.
Health EffectsArsenic is toxic to humans and causes cancer, and for this reason, no amountof arsenic is considered fully safe. Many scientific studies, including no fewerthan 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 thebladder, skin, and lungs; likely causes other cancers; and is responsible for a varietyof other serious health ailments. The NAS reviews culminated in the importantrecent reports Arsenic in Drinking Water (issued in 1999) and Arsenic in DrinkingWater: 2001 Update, which counter the long-standing water utility and industryarguments that arsenic in tap water poses no significant threat.32,33 The NAS foundin its 2001 report that a person who drinks two liters of water a day containing10 ppb arsenic—the new EPA standard—has a lifetime total fatal cancer risk greaterthan 1 in 333 (that is, about 1 in 333 people who drink water containing this levelof arsenic will die of arsenic-caused cancer).34 The EPA traditionally has allowedno 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 morethan 30 times higher than what the EPA traditionally allows in tap water. NAS’s riskestimates were more than 10 times higher than the estimates the EPA used to justifyits new January 2001 standard (see below). This 2001 NAS report’s staggering findingslikely would have been major news across the nation, but they were releasedon September 11, 2001.35
Treatment and Regulation
Arsenic can readily be removed from drinking water with off-the-shelf treatmenttechnology, including activated alumina and membrane treatment.36 Accordingto the EPA, the cost of using current, easily available treatment for arsenic is lessthan $2 per household per month for city water customers.37 A working group of the National Drinking Water Advisory Council, appointed by the Bush administrationin 2001 to review these EPA estimates (in light of industry allegationsthat the EPA had grossly underestimated arsenic treatment costs), found the EPA’sestimates “credible" and noted that newer technologies, such as granular ferrichydroxide and other cutting-edge treatments may bring even these already quiteaffordable costs of treatment down.38 More than 60 years ago, in 1942, the PublicHealth Service issued a 50 ppb arsenic guideline. The EPA adopted that guidelinein 1975, and this extremely lax tap water standard remains applicable today.39 Afterthe EPA missed at least three statutory deadlines to update the standard, and afterNRDC sued the EPA to get the agency to move forward with issuing a new arsenicrule, the Clinton administration finally adopted the new arsenic standard (a MaximumContaminant Level) of 10 ppb in January 2001.40 That standard becomeseffective in 2006.
However, upon taking office, the Bush administration suspended the EPA’s newarsenic standard, responding to pleas from the mining industry and utilities andarguing that the EPA had overestimated arsenic’s risks and underestimated therule’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 riskstenfold.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 administrationstandard instead.
NRDC and many public health and medical group activists recommend astandard of 3 ppb because it is the lowest level deemed achievable by the EPA inusing existing treatment technology. The NAS found that arsenic in tap water, evenat 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
National Standard (MCL)
100 ppb (average)
National Health Goal (MCLG)
100 ppb
CHROMIUM
SOME CONCERN
LOS ANGELES
PHOENIX
SAN DIEGO
Chromium is a naturally occurring metal used in industrial processes, includingmetal plating for chrome bumpers and making stainless steel, paint, rubber, andwood preservatives.43
Health Effects
Health effects from human exposure to chromium range from skin irritation todamage to kidney, liver, and nerve tissues. A heated debate has taken shape recentlyover 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 intap water.44
Treatment and Regulation
The EPA has found that chromium can be removed from drinking water throughcoagulation/filtration, ion exchange, reverse osmosis, and lime softening.45
Cyanide
National Standard (MCL)
200 ppb (average)
National Health Goal (MCLG)
200 ppb
CYANIDE
SOME CONCERN
WASHINGTON, D.C.
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 cancreate cyanide, according to the EPA.48
Health EffectsThe EPA says short-term exposure to cyanide at levels above the standard can causerapid breathing, tremors, and other neurological effects, and long-term exposure cancause weight loss, thyroid effects, and nerve damage.49
Treatment and Regulation
Cyanide can be removed from drinking water with reverse osmosis membranes andion exchange. In some cases, chlorine will assist in its removal.
Lead
National Standard (TT)
15 ppb (action level, at 90th percentile)50
National Health Goal (MCLG)
0 ppb—no known fully safe level
LEAD
EXCEEDS ACTION LEVEL
BOSTON
NEWARK
SEATTLE
HIGH CONCERN
BALTIMORE
LOS ANGELES
MANCHESTER
PHILADELPHIA
WASHINGTON, D.C.
SOME CONCERN
ATLANTA
CHICAGO
DENVER
DETROIT
FRESNO
HOUSTON
PHOENIX
SAN DIEGO
SAN FRANCISCO
LITTLE OR NO CONCERN
NEW ORLEANS
Health Effects
Lead is a major environmental threat and is often referred to as the number oneenvironmental health threat to children in the United States. No amount of it isconsidered safe.51 Infants, young children, and pregnant women’s fetuses are particularly susceptible to the adverse health effects of lead. Lead poisoning can causepermanent brain damage in serious cases, and in less severe cases can cause childrento suffer from decreased intelligence and problems with growth, development, andbehavior. Lead can also increase blood pressure, harm kidney function, adverselyaffect the nervous system, and damage red blood cells.52One way lead enters drinking water supplies is from the corrosion of water utilitypipes in the distribution system—the system of pipes through which water reachesconsumers’ 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 RegulationThe easiest way for cities to reduce lead levels in tap water is to treat their water usingcorrosion 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 thelikelihood 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 householdpipes, thus reducing corrosion. The EPA’s lead and copper rule requires city watersystems 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 EPAhas also adopted an action level standard for lead that is different from thestandard 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 plumbingcomponents, or in the case of homes built after 1982, because they have lead-solderedcopper pipes likely to be heavy lead leachers.54 The actual number of required samplesis 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. Awater 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 highlead 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, issupposed to help on this front, but testing by NRDC and others has found leadleaching at high levels from faucets and water meters since Congress amendedthe SDWA. NRDC sued the faucet and water-meter manufacturers under a stricterCalifornia law (Proposition 65) and agreed to a settlement to phase out lead fromfaucets and water meters.
Nitrate
National Standard (MCL)
10 ppm (two-sample average within 24 hours)
National Health Goal (MCLG)
10 ppm
NITRATE
HIGH CONCERN
FRESNO
PHOENIX
SOME CONCERN
PHILADELPHIA
LITTLE OR NO CONCERN
LOS ANGELES
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 heavilyfertilized with inorganic nitrogen fertilizer or overfertilized with manure.56 Highlevels 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 oftime can develop blue baby syndrome, in which nitrate poisoning preventstheir blood from holding oxygen.58 Shortness of breath, nausea, vomiting, diarrhea,lethargy, loss of consciousness, and even death can result from infants’ exposureto high levels of nitrates in water.59 Pregnant women are also particularly vulnerableto high nitrate levels in drinking water, again because it can affect the abilityof their blood to carry oxygen.60 The medical literature continues to report deathsand serious illnesses of infants fed formula made with nitrate-contaminatedwater.61 In addition, recent literature suggests that pregnant women who drinknitrate-contaminated water can have miscarriages possibly caused by the contaminant.62 Moreover, a comprehensive study conducted by the California BirthDefects Monitoring Program discovered an association between nitrate exposureand increased risk of neural tube defects.63 The study found that pregnant womenwhose drinking water contained nitrates above the regulatory standard faceda fourfold increase in the risk of anencephaly—absence of the brain—in theirdeveloping fetus. In addition to these short-term effects, several chronic effects of elevated nitrate levels have also been observed. According to the EPA, drinking watercontaining nitrates at levels above the Maximum Contaminant Level (MCL) fora prolonged period has “the potential to cause . . . diuresis, increased starchydeposits, and hemorrhaging of the spleen."64 In addition, indications are thatbreakdown products of nitrates called N-nitrosamines and compounds thatform when nitrates react with pesticides with which they commonly co-occur(the nation’s most used pesticide, the corn herbicide atrazine, among them) maycause 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 hoursof a sample showing a level over 10 parts per million, is allowed. The EPA’s nitratestandard remains controversial. Many European and other nations have adopted astandard allowing less than half the nitrates the EPA permits.66 While a NationalAcademy of Sciences review conducted in 1995 concluded that the EPA’s 10-partsper-million health goal and standard were protective of health,67 that conclusion maynot be justified in light of emerging evidence of nitrates’ possible reproductive andother toxicity and nitrosamines’ potential cancer risks.68 Clearly, the current EPAnitrate MCL and MCLG leave virtually no margin of safety, since blue babysyndrome has been observed in infants who drink water containing nitrates at12 parts per million or possibly lower concentrations.69
Perchlorate
National Standard (MCL)
None established
National Draft Safe Level (“Drinking Water Equivalent Level" or DWEL)70
1 ppb
PERCHLORATE
HIGH CONCERN
LOS ANGELES
PHOENIX
SAN DIEGO
Perchlorate is an inorganic contaminant that usually comes from rocket fuelspills or leaks at military facilities. Perchlorate contaminates the tap water ofmuch of southern California via the Metropolitan Water District’s Colorado RiverAqueduct. It also is in the water of Phoenix, Las Vegas, and many other cities andtowns reliant upon the Colorado River for their water. The source of the Colorado’scontamination is reportedly a Kerr-McGee site in Henderson, Nevada, whereperchlorate was manufactured and whose waste leaks into the Colorado River.71Perchlorate also contaminated water sources for many other towns and citiesacross the nation, where it has been manufactured or used at military bases orin commercial applications. In addition to its heavy use in rocket fuel, perchlorateis 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 regulatemetabolism. In children, the thyroid plays a major role in proper developmentin addition to metabolism. Impairment of thyroid function in expectantmothers may impact the fetus and newborn and result in effects includingchanges in behavior, delayed development, and decreased learning capability.Changes in thyroid hormone levels may also result in thyroid glandtumors. [The EPA finds that] perchlorate’s disruption of iodide uptake isthe key event leading to changes in development or tumor formation.74
StandardThere is no national standard for perchlorate. In early 2002, the EPA proposed a referencedose, (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 tapwater—should be 1 ppb. The EPAappears reluctant to establish a permanent standardof any sort, however. It now maintains that it does not yet know enough to warrantestablishing a standard and will continue studying the problem.75, 76 In the meantime, asmany as 20 million Americans (or more) have perchlorate in their tap water, a circumstancethat the EPA’s own draft risk assessment acknowledges is an unacceptable risk.
Thallium
National Standard (MCL)
2 ppb (average)
National Health Goal (MCLG)
0.5 ppb
THALLIUM
SOME CONCERN
ALBUQUERQUE
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 thatthallium pollution sources include gaseous emissions from cement factories, coalburning power plants, and metal sewers.79 The chief source of thallium in water is oreprocessing—the metal leaches out during processing.80
Health Effects
High exposure to thallium for a short period can cause gastrointestinal irritation andnerve 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
TreatmentThallium can be removed from tap water with activated alumina, ion exchange, orreverse osmosis.
ORGANIC CONTAMINANTS
Atrazine
National Standard (MCL)
3 ppb (average)
National Health Goal (MCLG)
3 ppb
ATRAZINE
SOME CONCERN
NEW ORLEANS
PHILADELPHIA
Atrazine is among the most widely used pesticides in this country, applied to cornand other crops to protect from broad-leaved and grassy weeds.83 Atrazine enterssource waters through agricultural runoff, and also volatilizes, or evaporates, and isthen redeposited with rain.84 It is among the most commonly detected pesticide indrinking water, particularly during spring runoff season throughout most of theMississippi 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 humanexposure to atrazine may cause prostate cancer; congestion of the heart, lungs,and kidneys; low blood pressure; muscle spasms; weight loss; and damage to theadrenal glands.87 Over the long term, the EPA reports, atrazine may cause weightloss, cardiovascular damage, retinal and some muscle degeneration, and possiblycancer.88 In addition, as noted above, atrazine is a known endocrine disrupter,meaning that it interferes with the body’s hormonal development and may causecancer 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 EPAdetermined 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 comtamination, well above EPA tap water standards.
Cis-1,2-Dichloroethylene
National Standard (MCL)
70 ppb (average)
National Health Goal (MCLG)
70 ppb
CIS-1,2- DICHLOROETHYLENE
LITTLE OR NO CONCERN
FRESNO
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)
National Standard (MCL)
200 ppt (average)
National Health Goal (MCLG)
0—no known fully safe level
DBCP
SOME CONCERN
FRESNO
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 thetestes 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 pertrillion. DBCP has been shown to cause cancer, kidney and liver damage, and atrophyof the testes leading to sterility.
Dichloromethane (DCM)
National Standard (MCL)
5 ppb (average)
National Health Goal (MCLG)
0—no known fully safe level
DCM
SOME CONCERN
PHILADELPHIA
Dichloromethane (DCM) is an industrial chemical used as a paint remover,
solvent, and cleaning agent; as a fumigant for strawberries and grains; and to extractsubstances from food.94 It is sometimes discharged by the pharmaceutical and chemicalindustries.95
Health Effects
The EPA has found that exposure to dichloromethane over a relatively short term atlevels exceeding the EPA’s standard potentially causes damage to the nervous systemand to blood.96 Over the long term, the EPA says, dichloromethane has the potentialto cause liver damage and cancer.97
Treatment
DCM can be removed from drinking water by granular activated carbon in combinationwith packed tower aeration or by reverse osmosis.
2,2-Dichloropropane (2,2-DCP)
National Standard (MCL)
None
National Health Goal (MCLG)
None
2,2-DCP
LITTLE OR NO CONCERN
FRESNO
2,2-Dichloropropane (2,2-DCP) is a volatile organic chemical that evaporatesat room temperature and is found in a few drinking water supplies, most of whichare reliant on groundwater sources. It was once used as a soil fumigant by thefarming 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 levelexposure to the chemical.
Treatment and Standard
2,2-DCP can be removed from water with activated carbon in combination withpacked tower aeration.
Di-(2-Ethylhexyl)phthalate (DEHP or Phthalate)
National Standard (MCL)
6 ppb (average)
National Health Goal (MCLG)
0—no known fully safe level
DEHP
SOME CONCERN
PHILADELPHIA
PHOENIX
WASHINGTON, D.C.
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 tothe 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 reverseosmosis.
Ethylene Dibromide (EDB)
National Standard (MCL)
50 ppt (average)
National Health Goal (MCLG)
0—no known fully safe level
EDB
SOME CONCERN
FRESNO
SAN DIEGO
Ethylene Dibromide (EDB) is used as an additive in gasoline, as a pesticide, inwaterproofing 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 whenpeople are exposed to it at levels above the MCL for relatively short periods oftime: damage to the liver, stomach, and adrenal glands, along with significantreproductive system toxicity, particularly the testes."101 The EPA also says that“EDB has the potential to cause the following effects from a lifetime exposure atlevels above the MCL: damage to the respiratory system, nervous system, liver,heart, and kidneys; cancer."102
Treatment
EDB can be removed from water with granular activated carbon or reverse osmosis.
Proceed to Part 2