The Secret Life of Drinking Water

Water scarcity will be one of the defining features of the 21st century. The U.N. predicts that by 2025 two thirds of the world’s population will suffer water shortages. Here CNN takes a look at what we do with the water we can drink.

There is a deep disconnect between what people care about and what the government is willing to act on. From agricultural pollution to industrial waste to pollution stemming from sprawl and urban runoff, a lack of political will means poor planning and scarce funding and ultimately leads to pollution that begins upstream and ends up at the tap. 1)National Drinking Water Database – EWG

Natural Resources Defense Council’s (NRDC) 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. 2)Common Tap Water Contaminants – NRDC

Since 2004, testing by water utilities has found pollutants in the tap water Americans drink, according to an Environmental Working Group (EWG) drinking water quality analysis of almost 20 million records obtained from state water officials.

More than half of the chemicals detected are not subject to health or safety regulations and can legally be present in any amount. The federal government does have health guidelines for others, but 49 of these contaminants have been found in one place or another at levels above those guidelines, polluting the tap water for 53.6 million Americans. The government has not set a single new drinking water standard since 2001.

Source of pollutant Number detected Number of states where detected Total number of people exposed Number of people exposed over health-based guidelines
Total chemical contaminants found 315 45 256,000,000 252,000,000
97 46 215,664,000 127,498,258
204 46 241,437,000 204,950,207
Sprawl and urban areas
86 46 236,933,000 177,124,541
Water treatment, storage, and distribution
42 45 240,744,000 235,606,510
Naturally Occuring 48 46 239,961,000 198,613,659
Source: EWG analysis of water utility test data for 2004-2009, compiled and provided to EWG by state drinking water offices.
Some pollutants stem from multiple sources and are included in all relevant categories.

EWG’s analysis of tap water test results revealed 42 pollutants that are residues of water treatment, storage and distribution, including chemical byproducts of water disinfection, in water supplied to 237 million people in 45 states. The water provided to 97 percent of them contained one or more of these contaminants at concentrations above non-mandatory, advisory health guidelines issued by government agencies. Moreover, 24 of these disinfection byproducts are unregulated, with no enforceable health-based limits for drinking water.

Nearly two-thirds of the 315 chemicals found in the nation’s drinking water over the last five years — a total of 201 — are unregulated. Public health officials have not set safety standards for them, even though millions ingest them in their tap water every day. Among the most common are some that have been linked to serious health concerns:

  • Bromochloroacetic acid, a tap water disinfection byproduct, was found in the water supplied to 40 million consumers. It induces gene mutations and is associated with damage to DNA.
  • Perchlorate, a rocket fuel ingredient, was found in water provided to 26 million people. It is toxic to the thyroid gland.
  • MTBE (methyl tert-butyl ether), a gasoline additive and groundwater pollutant scheduled to be phased out nationwide, was found in water supplied to 12 million people. It is associated with liver and kidney damage, and nervous system effects.
  • Di-n-butylphthalate, a chemical from a group of industrial plasticizers called phthalates, was found in water used by 5 million people. Phthalates have been linked to birth defects and reproductive toxicity.


Tap water disinfection is crucial for controlling waterborne disease, but the chemicals used can form harmful, DNA-damaging or cancer-causing byproducts in the treated water. These byproducts form when disinfectants react with organic pollution from agriculture or urban and sprawl runoff. EPA requires testing and restricts levels for 11 disinfection byproducts: four trihalomethanes, five haloacetic acids, bromate and chlorite. This is a tiny fraction of the more than 600 chemicals that can form as disinfection byproducts in tap water, according to scientists from EPA, academia and water utilities (Boorman 1999; Chowdhury 2009; Krasner 2006, 2009; Richardson 1998, 1999a,b, 2003, 2007). Neither the states nor the federal government require testing for the vast majority of these compounds, and most water systems do not test for them.

  • Nationally, two groups of disinfection byproducts — trihalomethanes (chloroform, bromodichloromethane, dibromochloromethane) and haloacetic acids — top the list of the most commonly detected tap water contaminants. Disinfection byproducts are associated with damage to DNA and elevated risk of cancer (Richardson 2007; EPA 2005d; EPA 2007f).
  • The fifth frequently detected water pollutant is nitrate. Excess nitrate (and/or the related chemical nitrite) in water used to make infant formula can cause “blue baby syndrome,” a potentially fatal condition in which an infant’s blood is less able to carry oxygen (Knobeloch 2000; Manassaram 2006; National Research Council 1995). The greatest use of nitrates is as a fertilizer in agriculture (USGS 1999; EPA 2009b).
  • Many commonly detected contaminants have been found at concentrations exceeding mandatory federal drinking water standards.
  • Water quality varies widely from one community to the next (Figure 4). For two groups of regulated disinfection byproducts, trihalomethanes and haloacetic acids, mid-sized utilities serving between 10,000 and 250,000 people had the highest average contaminant levels, while the smallest and largest utilities fared better.

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