The Presidents 2008-2009 cancer pannel reports more than 260 contaminants in drinking water.

Source:
2008-2009 Annual Report ~ Presidents Cancer Panel
Environmental Working Group ~ Preventing Cancer: 9 Practical Tips for Consumers

Americans’ drinking water comes from groundwater and rain that fills streams, reservoirs, rivers, lakes, and ultimately, the oceans. Chemicals improperly stored and disposed of by industry and individuals alike soak into the soil and eventually leach into groundwater. As clouds and rain, water absorbs chemicals in the air. As a result, the water we drink is steeped in varying mixtures of chemicals and other substances. Some of these contaminants are not harmful to human health in trace or extremely small amounts, while others can cause or contribute to numerous diseases, including cancer.

Assessing health hazards due to drinking water contamination is difficult, since it typically is challenging to estimate the levels and timing of exposures and the specific chemicals involved. It also can be difficult to define exposed populations clearly and select the most appropriate disease endpoints or intermediate biologic markers for study. Further, it often is not possible to identify the cause of observed health effects when there are multiple exposures or to link specific health effects with individual chemicals that occur in mixtures.

Public water filtration and treatment plants remove some contaminants, but current technologies cannot remove them all.
 
Water treatment systems vary significantly across the country since they are tailored (to the extent practicable) to treat the water contaminants that are found in each vicinity. Arsenic, microbes, nitrates, radium, uranium, selenium, antimony, sulfate, magnesium, calcium, iron, manganese, potassium, phosphorous, and other metals are among the substances commonly removed from drinking water supplies. 264 Because of concerns about water pollution, some people use home filtration systems to further treat water from public supplies or wells and/or use bottled water for drinking and cooking.

…in a country where I work hard and I vote, I feel like I have been involuntarily exposed to things that could have made me sick and I can’t make informed decisions when that’s the situation. ~ Breast cancer survivor, Indiana
 
Public Systems:
Most Americans rely on public systems for the water they use for drinking, cooking, irrigating crops (including feed crops) and ornamental plants, and watering livestock. As Table 4 shows, the U.S. population is served by more than 52,000 community water systems. The quality of drinking water is regulated by the Safe Drinking Water Act (SDWA) of 1974, but enforcement takes place at the state level. The legislation authorizes EPA to establish standards (Maximum Contaminant Levels, or MCLs) to protect tap water and requires that owners and operators of public water systems comply with these standards. Regulated chemicals in drinking water include 53 organic chemicals (e.g., atrazine, benzene), 16 inorganic chemicals (e.g., arsenic, nitrate), 7 disinfection by-products (e.g., trihalomethanes), 6 microorganisms (e.g., cryptosporidium), and 4 radionuclides (e.g., alpha particles from radon, radium).
 
However, an analysis of more than two million drinking water test results acquired from 42 state water offices found 260 contaminants in tap water. Of these, 141 contaminants have no safety standards. Forty (40) of the unregulated contaminants were detected in tap water consumed by at least one million people.
 
“EPA typically sets a level that they would call safe, which is as close to zero risk as they can get, and then they say, well, we can’t do that because that costs money, so let’s come up with another number that allows a certain amount of risk as a trade-off for cleaning up the water… I think our public policies need to be revisited because we’re trading disease for costs probably unnecessarily”.~ Richard Wells, Environmental Working Group
 
Private Wells:
It should be noted that the population distribution shown in Table 4 does not account for the 10–15 percent of the U.S. population that uses wells or other private water supplies. Water from wells is not subject to SDWA standards, but usually is regulated by state programs. In 2009, the U.S. Geologic Survey (USGS) released a report on the quality of water from about 2,100 domestic wells throughout the United States;46 samples were collected between 1991 and 2004. The analysis found that 23 percent of sampled domestic wells contained one or more contaminants at a concentration greater than EPA MCLs for public water supplies, or USGS Health‑Based Screening Levels.

Contaminants most often above benchmark levels were inorganic chemicals, with all but nitrate primarily from natural sources. Higher nitrate concentrations were more common in areas with intense agricultural land use, due primarily to fertilizers, livestock, and septic systems. Man-made organic compounds were detected in 60 percent of sampled wells, but concentrations seldom were above EPA MCLs. Contaminants usually co-occurred with other contaminants as mixtures, with the most common mixture consisting of nitrate, arsenic, radon, and uranium.
 
Bottled Water
Many bottled water users assume that it is cleaner than tap water. Bottled water is regulated by the FDA, and while standards for lead content are more stringent than Federal public water standards, other quality standards are the same as Federal limits for public supplies. Bottlers, however, are not required to disclose either the content or the source of their water, as is the case for public supplies. Some bottled water is simply drawn from municipal supplies and receives no additional filtration or other treatment.

One study has shown that the contaminant levels in bottled waters vary widely. Some of the 10 brands tested were found to be of no better quality, and in some cases were worse, than water available from municipal water systems. The testing found an average of eight contaminants in each brand. Half of the brands tested contained bacterial contamination. Two carcinogens were found in some of the samples at levels exceeding California and/or industry standards. Also detected were caffeine, the pharmaceutical acetaminophen, arsenic, radioactive isotopes, nitrates and ammonia from fertilizer residue, and industrial chemicals including solvents, degreasing agents, and propellants. Trace amounts of acetaldehyde, isobutane, and toluene also were found, but the investigators could not ascertain health effects at the low levels detected.

In addition to the contaminants indicated above, plastics such as BPA can leach from the bottle itself into the water it contains.
 
“Wherever you chlorinate water, you have chlorination by-products… there is strong evidence that disinfection by-products are carcinogenic for bladder cancer”. ~ Kenneth Cantor, National Cancer Institute
 
Water Disinfection By-Products (DBP):
Disinfection of public water supplies has dramatically reduced the incidence of waterborne illnesses and related mortality in the United States, with unquestionable public health benefit. However, chemical by-products are formed when disinfectants such as chlorine react with organic matter, and long-term exposure to these chemicals may increase cancer risk.

Hundreds of disinfection by-products have been identified; the most common of these are trihalomethanes (THMs, including chloroform, bromoform, and others) and haloacetic acid. Only a small percentage of identified DBPs have been tested for carcinogenicity. Some rodent studies have been positive for cancer, and some DBP components have shown mutagenic effects in in vitro testing, suggesting carcinogenicity.267

The Federal standard for disinfection by-products in public water supplies is 80 parts per billion of THM as an annual average.  THMs are measured because they generally reflect levels of other chemicals in DBP mixtures. If not controlled, DBPs in water systems can range up to several hundred parts per billion. In addition, a recent study suggests that THM levels vary within a water system, with the highest levels found in water that stays in the system the longest after disinfection. In this study, rectal (bromoform THM only) and bladder cancer risks were highest among those who consumed the greatest amount of water at points within the distribution system with the oldest post-disinfection tap water.

People are exposed to DBPs through consumption and through inhalation and absorption through the skin during bathing, showering, and swimming in chlorinated pools. Relatively little research has been done on DBPs and cancer; the strongest data show increased bladder cancer risk with long-term (up to 40 years) exposure to DBPs, particularly among men. In addition, several metabolic pathways and key genes have been identified that may increase bladder cancer risk among individuals with common variants in these genetic factors. Other very limited research suggests possible DBP associations with colon and rectal cancer, renal cell carcinoma, and glioma. One speaker underscored the need for further research on DBPs and cancer, noting that exposure assessments should account for at least 35 years of exposure prior to a cancer diagnosis. DBPs represent a situation in which observed relative risks are modest, but because of the high numbers of people exposed, such risks may translate into potentially significant public health problems.

Metals such as beryllium, cadmium, and lead from industrial sources are found in U.S. water supplies, usually under 100 micrograms per liter (μg/L), but can increase or decrease due to water treatment. Little research has been conducted on possible cancer risks associated with these trace minerals in drinking water.
 
To Read the full report click here: http://deainfo.nci.nih.gov/advisory/pcp/pcp08-09rpt/PCP_Report_08-09_508.pdf

  EWG’s Recommendations to reduce your exposure:
 
1. Filter your tap water. Common carcinogens in tap water include arsenic, chromium, and chemical byproducts that form when water is disinfected. A simple carbon filter or pitcher can help reduce the levels of some of these contaminants. If your water is polluted with arsenic or chromium, a reverse osmosis filter will help. Learn about your tap water and home water filters at EWG’s National Tap Water Database.

2. Seal outdoor wooden decks and play sets. Those built before 2005 are likely coated with an arsenic pesticide that can stick to hands and clothing. Learn more from EWG.

3. Cut down on stain- and grease-proofing chemicals. “Fluorochemicals” related to Teflon and Scotchgard are used in stain repellants on carpets and couches and in greaseproof coatings for packaged and fast foods. To avoid them, avoid greasy packaged foods and say no to optional stain treatments in the home. Download EWG’s Guide to PFCs and learn more about PFCs.

4. Stay safe in the sun. More than one million cases of skin cancer are diagnosed in the United States each year. To protect your skin from the sun’s cancer-causing ultraviolet (UV) radiation, seek shade, wear protective clothing and use a safe and effective sunscreen from EWG’s sunscreen database.

5. Cut down on fatty meat and high-fat dairy products. Long-lasting cancer-causing pollutants like dioxins and PCBs accumulate in the food chain and concentrate in animal fat.

6. Eat EWG’s “Clean 15.” Many pesticides have been linked to cancer. Eating from EWG’s Clean 15 list of the least contaminated fruits and vegetables will help cut your pesticide exposures. (And for EWG’s Dirty Dozen, buy organic.) Learn more at EWG’s Shopper’s Guide to Pesticides.

7. Cut your exposures to BPA. Bisphenol-A (BPA) is a synthetic estrogen found in some hard plastic water bottles, canned infant formula, and canned foods. Some of these chemicals cause cancer in lab studies. To avoid them, eat fewer canned foods, breast feed your baby or use powdered formula, and choose water bottles free of BPA. Get EWG’s tips to avoid it.

8. Avoid carcinogens in cosmetics. Use EWG’s Skin Deep cosmetic database to find products free of chemicals known or suspected to cause cancer. When you’re shopping, don’t buy products that list ingredients with “PEG” or “-eth” in their name.

9. Read the warnings. Some products list warnings of cancer risks – read the label before you buy. Californians will see a “Proposition 65” warning label on products that contain chemicals the state has identified as cancer-causing.

Read EWG’s news release about the President’s Cancer Panel report.