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.[39]
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.[40] 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)).[41]
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.[42] Animal studies have long shown that these chemicals are likely to cause cancer in people.[43]
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.[44] 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.[45]
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.[46] 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.
Arsenic
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.[47] Bladder, lung, and other types of cancer have also been observed at elevated rates in populations exposed to arsenic in tap water.[48] 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.[51]
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.[52] 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.[53]
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.[54] Another study found a link between this widespread drinking water contaminant and diabetes mellitus.[55] 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.[49] 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.[50] 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.
Radiation
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.[56]
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.[57] It also is in the water of 81 million people at an average of about 246 pCi/L, posing significant health risks.[58] 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.[59] The EPA has also found that the ingestion of radon and its decay products poses significant cancer risks.[60] 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.[61]