Drinking Water Contamination Essay, Research Paper
Due to the Safe Drinking Water Act (SDWA), America’s drinking water is safer than it has been in decades, and of better quality than that of many other countries. Accordingly, many Americans believe that while people elsewhere may have reason to be concerned about getting sick from contaminated tap water, we are safe. Yet, incidents in the United States such as the outbreak of the microorganism cryptosporidium in Milwaukee’s water supply in 1993 that killed more than one hundred people and sickened over 400,000, and lead and pesticide contamination while not affecting most, threaten the tap water of millions of Americans.
In truth, according to Environmental Protection Agency (EPA) data, in 1994 and 1995, 45 million Americans drank water from water systems that fell short of SDWA standards. Adding gravity to the situation, the Centers for Disease Control (CDC) and the EPA advised that people with weakened immune systems should consult with their doctors and consider boiling their drinking water to kill any cryptosporidium.
This is just the tip of the iceberg. Some scientists believe that for every outbreak reported in the United States, another ten may be occurring. One such study found that as many as one in three gastrointestinal illnesses often chalked up to “stomach flu” are caused by drinking water contaminated with microorganisms.
Such microbial-related outbreaks say nothing about the many other hazards borne by our nation’s water supply. Researchers have shown that millions of Americans regularly drink tap water that is contaminated with toxic and cancer-causing chemicals such as lead, trihalomethanes (THMs), arsenic, radioactive materials, and pesticides. A 1994 study estimated that some 14.1 million Americans drank water contaminated with the pesticides atrazine, cyanazine, simazine, alachlor, and metolachlor. The manufacturers of these agricultural herbicides have shown that these chemicals may cause cancer, birth defects, and genetic mutations.
To make matters worse, some water utilities have been less than forthcoming with information about their drinking water supplies and the efficacy of their purifying methods. While the primary concern of most water utilities is delivering safe drinking water and a large number readily share their water quality data with the public many insist on erecting barriers between the public they serve and information about the water they supply.
As a result of the failure of the government and many water systems in the country to protect the drinking water supply, many Americans no longer trust the purity of their tap water, and so pay enormous amounts of money nearly $2 billion annually for bottled water and home tap water treatment units. Unfortunately, there are few standards guaranteeing the quality of these options. According to one study, as much as one-quarter to one-third of all bottled water sold in the United States originates from water supplied by public water utilities.
Unhealthy drinking water affects children in different ways than it does adults. There is cause for special concern for the health of children who drink tap water. Legal standards for most waterborne contaminants generally have been set based on the health effects of pollutants on average adults; consequently, the health of millions of people including infants, children, pregnant women and their fetuses, the elderly, and the chronically ill -may not be protected. To compound matters, infants and children drink more than two and a half times as much water as adults as a proportion of their body weight. An infant living solely on formula consumes about one-seventh of its own weight of water each day, which would correspond to approximately three gallons of water for a 155-pound adult man.
The hazards posed by waterborne lead are especially pernicious. In 1991, the EPA estimated that lead in drinking water harms the health of millions of children, causing more than 560,000 children to exceed the level of concern for blood-lead levels defined by the CDC. (A recent EPA rule regulating lead in drinking water may have reduced this number of children.) Particularly susceptible to waterborne lead poisoning are infants, who are often exposed when their formula is reconstituted with tap water.
This chapter discusses the widespread contamination of the United States’ drinking water supplies by microorganisms, pesticides, lead, disinfectant by-products, arsenic, and radioactivity. Citizens need to seek remedies to ensure the health of their families in the face of increasing threats to the nation’s water supply. Toward that end this chapter describes scientific research bearing on the health impacts of water contamination on children, suggests measures that concerned parents and others can take and identifies model programs of local solutions that have worked throughout the nation.
HAZARDS OF DRINKING WATER CONTAMINATION
William K. Reilly, Administrator of the EPA under the Bush Administration, classified drinking water contamination among the top four public health risks posed by environmental problems. Some experts estimate that 560,000 people become moderately to severely ill each year from consuming contaminated water. About 10,700 bladder and rectal cancers each year may be associated with THMs and their chemical cousins. That translates into about thirty cancers per day.
The large number of disease outbreaks throughout the country should come as no surprise, considering how many Americans drink tap water that fails to meet minimum EPA health and treatment standards for infectious microorganisms standards which themselves overlook some of the most hazardous pathogens presently infecting our nation’s water supply. Waterborne pathogen sources that can cause disease outbreaks include leaking septic tanks; uncontrolled urban runoff contaminated with animal waste; manure in farm, feedlot, and slaughterhouse runoff or direct discharges; and raw or inadequately treated sewage overflows from aging, poorly managed, or inadequately designed sewage conveyance and treatment systems. Drinking water disease outbreaks occur when drinking water wells, surface sources, or post-treatment water in pipes or storage areas of water systems become contaminated with disease-causing microbes that originate from these sources. Since many drinking water watersheds and recharge areas are now under heavy development pressure, this problem is likely to worsen in the absence of political or legal action.
Existing data on contamination are troubling. A 1991 survey of sixty-six surface water plants in fourteen states and one Canadian province revealed that 87 percent of raw water samples contained cryptosporidium, and 81 percent contained a similar parasite called giardia; overall, the study showed, some 97 percent of the samples contained one of these two disease carriers. Some of these organisms may have been “nonviable,” and therefore unable to infect people. In many cases, these organisms cannot be sufficiently controlled with chlorine disinfection.
EPA data show that more than 29 million people drank water served by systems with coliform bacteria higher than the EPA’s health standards allow, and that 19.6 million Americans drank water from systems that failed to meet the EPA’s basic treatment standards, which indicate inadequate quality, filtration, or disinfection.  Another 10.2 million people in the United States were being served water found to contain turbidity the cloudiness that often signals microbiological contamination and that can make it impossible to effectively disinfect the water even with heavy doses of chlorine. In Milwaukee, for instance, the only initial sign of a problem was the water’s turbidity. Testing for cryptosporidium, the deadly parasite that caused the diarrhea and vomiting, did not occur until after people became sick.
In fact, until 1997, EPA regulations failed to require any monitoring of water supplies for cryptosporidium. Amendments to SDWA in 1996 require the EPA to regulate cryptosporidium levels, starting with large supply systems. As a result, commencing in the summer of 1997, large systems serving over 100,000 started monitoring for cryptosporidium, and under a rule scheduled to be issued in 1998, most large systems will have to take preliminary steps to filter out cryptosporidium. By the year 2000, the EPA must issue a final rule applicable to all drinking water systems using surface water.
Many water systems in the United States may be more vulnerable than Milwaukee’s to contamination by disease-carrying organisms. The Milwaukee water supply is filtered, though apparently the filter suffered from some type of failure. Unfiltered systems or systems with poorly operated and maintained filters may be at even greater risk.
In a limited sampling of fewer than one hundred utilities, NRDC found that more than 45.6 million Americans drank water supplied by systems where the unregulated and potentially deadly contaminant cryptosporidium was found in their raw or treated water. Hundreds of chemicals and microbes have been detected in drinking water supplies throughout the country, yet tests are required for just over a hundred of these.
There has been no coordinated effort between government agencies and researchers to document levels of contamination or illness caused by many waterborne microbes, including cryptosporidium. The lack of an active waterborne disease surveillance program in the United States means that reports of outbreaks are haphazard. A CDC report found that the waterborne-related illnesses reported each year “probably represent only a small proportion of all illnesses associated with waterborne-disease agents.” This report goes on to state that “illnesses occurring after years of exposure to low-level toxins are not detectable,” nor are outbreaks of sporadic illnesses resulting from opportunistic pathogens “that may be widespread in chlorinated drinking water systems but that may cause illness with insidious onset and long incubation periods in persons who are immunocompromised.”
The CDC tracked 116 waterborne disease outbreaks that killed more than a hundred and sickened more than 450,000 others between 1971 and 1994. Although the majority of those illnesses occurred during one incident in Milwaukee, other significant outbreaks occurred, including one affecting 13,000 people in Georgia. Aside from the Milwaukee incident, where 400,000 people became ill due to cryptosporidium, none of these outbreaks of waterborne disease have received significant national attention.
Epidemic outbreaks of waterborne disease those in which many people fall ill at once are difficult to ignore, say some researchers, whereas endemic levels of waterborne disease incidents in which a modest percentage of the population fall ill, or in which the illnesses are chronic and long-term may be occurring continually with nobody’s knowledge. One CDC expert concluded that thousands of people would have to become afflicted with a waterborne illness in New York City before public officials would be able to recognize it as an outbreak, and even then there would be no guarantee that the disease source would be properly identified.
One study sheds light on the grave situation in which our ignorance places us. Researchers installed sophisticated under-the-sink filters in a number of homes served by a water system meeting all current standards for water treatment, including filtration and disinfection. Then they tracked the number of illnesses in these homes, as well as the illnesses in homes served by the same water system but which lacked the sophisticated filters. What the researchers found was as surprising as it was troubling: significantly higher rates of people who did not have the filters became sick compared with those whose water was filtered. The researchers estimated that “35 percent of the reported [gastrointestinal] illnesses among tap water drinkers were water-related and preventable.”
Contamination of water resources is one of the most damaging and widespread environmental effects of agricultural production. Drinking water is vulnerable to pollution by agricultural chemicals, including pesticides, herbicides, fungicides, and fertilizers, as well as their metabolites.
According to a National Academy of Sciences report, the residues of 39 pesticides and their degradation products have been detected in the groundwater of thirty-four states and Canadian provinces. The pesticides most frequently reported included aldicarb and its by-products, which were detected in twenty-four states from California to Maine; EDB was found in twelve states; 1,2-dichloropropane (1,2-D) in seven states; and dibromochloropropane (DBCP) in five states. Also prominent were alachlor, atrazine and its products, cyanazine, dicamba, dinoseb, metolachlor, metribuzin, simazine, trifluralin, and 2,4-D. The EPA also has found that about one out of ten public water supply wells contains pesticides; the EPA infers from these data that nearly 10,000 community drinking water wells and about 440,000 rural domestic water wells contain pesticides, although most apparently do not exceed the EPA’s existing drinking water standards for pesticides.
A recent report published by the Environmental Working Group (EWG) found that about 4.3 million Americans in 245 communities are exposed to levels of carcinogenic herbicides in drinking water that exceed the EPA’s benchmark of acceptable cancer risk (one case in a population of a million). Commonly used agricultural herbicides contaminate the tap water of 374 Midwestern towns. Over ten million Americans in the Midwest and Chesapeake Bay region are exposed to carcinogenic herbicides in their drinking water. In addition, mixtures of herbicides were found in tap water: one sample from a suburb of Cincinnati contained ten different herbicides and metabolites, and samples from five other towns in Ohio and Illinois contained six or more herbicides and metabolites.
A 1994 report from EWG also found that drinking water is commonly contaminated with two or more of the five herbicides atrazine, cyanazine, simazine, alachlor, and metolachlor. For example, 61 percent of samples taken at the Kansas City, Missouri, water utility intake contained two or more of these five herbicides, 47 percent of samples collected from four northern Ohio rivers that serve as drinking water sources contained three or more herbicides, and 38 percent of samples from 27 Midwestern drinking water reservoirs were contaminated with four or more of these five herbicides.
Due to the presence of these chemicals in drinking water, more than 3.5 million people in 120 cities and towns face cancer risks more than ten times the federal benchmark for acceptable cancer risk (one case in a population of one million), based on average annual exposure to five common herbicides. People in small rural communities are at particularly high risk; over 400,000 people in 98 rural communities face cancer risks from 10 to 116 times the federal benchmark. In all, some 67 different pesticides and pesticide metabolites have been detected in Midwestern sources of drinking water.[*]
Earlier studies by the U.S. Geological Survey (USGS) had found that 98 to 100 percent of the 150 streams tested in the Mississippi River Basin during 1990 contained herbicides. In 1991, the USGS survey of selected herbicides in eight rivers in the Mississippi River Basin found atrazine in all the samples taken, with concentrations exceeding the federal drinking water standard, or Maximum Contaminant Level (MCL), in 27 percent of the samples. Alachlor was detected in 88 percent of the samples, with levels greater than the MCL 4 percent of the time.
Nitrate appears in groundwater from fertilizer use, natural soil nitrogen, rare geologic nitrogen deposits, manure, sewage, and other organic wastes. Very high concentrations of nitrate in the drinking water can be fatal to infants, particularly in the first three months of life. The primary public health concern related to elevated levels of nitrate in drinking water is the development of a potentially fatal condition called methemoglobinemia, sometimes known as “blue baby syndrome.” This condition develops when nitrate is converted to nitrite by bacteria in the gastrointestinal tract. Increasing levels of nitrite decrease the blood’s capacity to transport oxygen. Though deaths from methemoglobinemia in the United States are rare, several cases of the disease have been documented in the western Corn Belt.
The medical community and the U.S. Department of Health and Human Services have determined that lead poisoning is the primary environmental threat to children. The EPA has found that lead in drinking water is one of the leading sources of exposure, typically contributing 20 percent of total lead exposure for an average person. In some cases, a higher percentage comes from drinking water; for example, the EPA found that more than 85 percent of the blood-lead in bottle-fed infants may derive from drinking baby formula made with lead-contaminated water. Indeed, studies by Harvard University doctors at a lead poisoning clinic in Boston found that the primary source of lead in the bloodstreams of about 15 percent of the lead-poisoned infants treated at the clinic was from lead-tainted drinking water used to make the babies’ formula. Research shows adverse health effects from lead at ever lower levels of exposure. There is a wide range of serious health problems that can result from lead poisoning; these are discussed in Chapter 3.
Lead can be present in service lines, solder, and faucets. The lead in plumbing leaches into water as it stands in pipes and taps. Boiling does nothing to eliminate lead. Babies have been poisoned when tap water was boiled to make their formula.
Every home may have a different level of lead in its drinking water, and every faucet may deliver a different level of lead. Lead in tap water usually originates between the water main in the street and the household plumbing. Adding lime or other corrosion inhibitors at the treatment plant can sometimes solve the problem because it can reduce acid in water, build a limestone precipitate that coats the pipes, and reduce leaching of lead from lead pipes and solder. The best first step to avoiding exposure to lead in drinking water is to have your household water tested for lead. A good rule of thumb for those who do not know the lead content of their water is to run the water at least 30 to 60 seconds (until temperature changes indicating that water is coming from outside) from each faucet that has not been used for several hours. (Catch this water for plants or dish washing.) Also, never use water from the hot tap for making infant formula or cooking purposes, since the chances for lead contamination increase with the use of hot tap water.
While lead, when present, is a serious health threat, there is a very good chance that you do not have a lead problem. The nation’s leading water-lead research program, at the University of North Carolina at Asheville has tested the water from more than 60,000 homes. It found that 83 percent of the homes tested had very low levels of lead. Another 15 percent could solve their problem by running the water briefly before using it. In 1993, Consumer Reports announced the results of their nationwide drinking water sampling for lead. Sixty-one percent of the households had no detectable lead (detection limit 2 parts per billion (ppb)).
Trihalomethanes and Other Disinfection By-Products
Disinfection of water supplies has substantially reduced the incidence of many waterborne diseases. But there are risks associated with this process. Trihalomethanes (THMs) and other disinfection by-products (DBPs), which are formed when chlorine or other similar disinfectants are used to purify water that has not been treated to remove organic matter before disinfection, are found at significant levels in the drinking water of 80 to 100 million Americans. Animal studies have long shown that these chemicals are likely to cause cancer in people.
An analysis in American Journal of Public Health of more than ten epidemiological studies found that DBPs may be responsible for 10,700 or more rectal and bladder cancers per year. Colorado researchers recently completed another study of human populations exposed to DBPs. That study confirmed the findings of previous studies that exposure to DBPs is significantly associated with bladder cancer.
Another study concluded that analyses of the health effects of exposure to THMs and possibly other DBPs may have substantially underestimated risks due to understatement of exposure. The researchers found that overall lifetime cancer risk associated with exposure to THMs in shower water is underestimated by about 50 percent if the concentration of THMs in cold water is used in a risk assessment. The level of THMs increases substantially when water is heated, but most studies have measured concentrations of THMs in cold water. When steam is inhaled during use of hot water, such as showering, exposure to DBPs is increased, and the risks are higher than generally assumed.
By improving water treatment – such as physically removing precursors to DBPs – water systems can control DBPs while reducing microbiological risks. Modern treatment technologies known as “precursor removal,” such as granular activated carbon, can be employed without harming the ability of water systems to disinfect their water. However, only a relative handful of U.S. water systems use this technology. In light of strong evidence that DBPs pose serious health risks, the EPA is required to issue rules in late 1998 to reduce THM levels. More stringent requirements are due in 2002.
The most significant non-occupational exposure to arsenic now occurs through the contamination of drinking water. There are numerous studies of populations with exposure to high levels of arsenic through drinking water (at levels above the current EPA standard – unchanged since 1942 – of 50 ppb). In humans, skin cancer has long been associated with chronic ingestion of arsenic. Bladder, lung, and other types of cancer have also been observed at elevated rates in populations exposed to arsenic in tap water. In the United States, more than 50 million people drink tap water containing arsenic, mostly at levels below EPA’s current standard of 50 ppb. It has been estimated, however, that 25 million people in this country are exposed to at least 25 ppb of arsenic in their drinking water and that as many as 350,000 people may be exposed to levels greater than the 50 ppb standard.
California state experts found that water containing arsenic at the level of the EPA’s current drinking water standard (set in 1942 before arsenic was known to cause cancer) presents a risk of more than one cancer in every one hundred people exposed – 10,000 times higher risk than the EPA’s standard “acceptable” cancer risk of one in one million. This is extremely troubling because 35 million people in the United States drink water every day from their community water systems that contain arsenic at a level of over 1 ppb, which presents a very significant cancer risk.
While numerous studies in other countries have demonstrated arsenic’s carcinogenicity at moderate to high doses, a handful of very small studies done on U.S. populations have failed to show a statistically significant increase in the risk of developing skin cancer at low dose exposures. The difficulty of demonstrating adverse health effects may be due to the type of study design and the small populations studied, both of which decrease the statistical power of a study to detect adverse health effects.
Researchers from the University of California recently found increased rates of death from vascular diseases such as arteriosclerosis, aortic aneurysms, and other diseases of the arteries, arterioles, and capillaries among Americans living in areas with relatively higher levels of arsenic in their drinking water. Another study found a link between this widespread drinking water contaminant and diabetes mellitus. According to the study of large populations in Taiwan, people who receive significant levels of arsenic in their drinking water have a six to ten times greater risk of developing diabetes mellitus. The researchers found that there was a dose-response relationship – that is, the more arsenic in the drinking water, the more likely the person was to be diabetic – reinforcing the weight of their findings. The researchers concluded that chronic arsenic exposure “may induce diabetes mellitus in humans.”
Bottled Water and Home Water Filters
Though Americans try to ensure the safety of their drinking water by paying nearly $2 billion each year for bottled water and home treatment units, the quality of the water they receive may not be any better than tap water. Home treatment units, which can cost hundreds of dollars, are virtually unregulated, and while many companies test their filters voluntarily, others fail to do so. There also is no requirement that home treatment units be independently tested to ensure that they meet their claims and provide safe water.
Hundreds of times more expensive than tap water, bottled water is often no safer. In fact, one study estimated that as much as one-quarter to one-third of all bottled water sold in the United States comes from water supplied by public water utilities. Bottled water is governed by an often less stringent set of regulations set by the Food and Drug Administration (FDA). While the FDA is required to set contaminant standards at the same levels for bottled water as for tap water, these standards in some cases still fall short. The FDA generally requires only one chemical test per year, making it unlikely that some important problems will be detected. The standards also fail to account for decreases in microbiological quality caused by long-term water storage, and the results are often not required to be reported to public health authorities.
Radon is an odorless and colorless radioactive gas that generally occurs in drinking water derived from groundwater as a result of the underground decay of naturally-occurring radioactive rock. It is considered to be a known human carcinogen by the National Academy of Sciences and others.
Drinking water contaminated with radon in excess of the EPA’s proposed standard of 300 picocuries[*] per liter of water (pCi/L) flows from the taps and showerheads of over 19 million people according to available EPA data. It also is in the water of 81 million people at an average of about 246 pCi/L, posing significant health risks. As required by the 1996 amendments to the SDWA, the EPA must establish an enforceable standard for radon in tap water by the year 2000.
Radon in drinking water poses significant threats due to inhalation during and after water use. The EPA has also found that the ingestion of radon and its decay products poses significant cancer risks. The EPA has acknowledged that the cancer risks from radon in both air and water are high and that while the airborne risk typically exceeds that arising from water, the cancer risk in water is higher than the cancer risk estimated to result from any other drinking water contaminant.
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