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A Network of Experts in Children’s Environmental Health


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Water Issues

 

The United States has one of the safest water supplies in the world. However, drinking water quality varies from place to place, depending on the condition of the source water from which it is drawn and the treatment it receives.

There is no such thing as naturally pure water. In nature, all water contains some impurities. As water flows in streams, sits in lakes, and filters through layers of soil and rock in the ground, it dissolves or absorbs the substances that it touches. Some of these substances are harmless. In fact, some people prefer mineral water precisely because minerals give it an appealing taste.

However, at certain levels minerals, just like man-made chemicals, are considered contaminants that can make water unpalatable or even unsafe. Some contaminants come from erosion of natural rock formations. Other contaminants are substances discharged from factories, applied to farmlands, or used by consumers in their homes and yards. Sources of contaminants might be in your neighborhood or might be many miles away.

Your local water quality report tells which contaminants are in your drinking water, the levels at which they were found, and the actual or likely source of each contaminant. Some ground water systems have established wellhead protection programs to prevent substances from contaminating their wells. Similarly, some surface water systems protect the watershed around their reservoir to prevent contamination.

Right now, states and water suppliers are working systematically to assess every source of drinking water and to identify potential sources of contaminants. This process will help communities to protect their drinking water supplies from contamination, and a summary of the results will be in future water quality reports.

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Please expand the subtopics below to learn more.

          
 Water--Solvents  

In Tucson, Arizona, a study of 707 children born with heart defects revealed that 35% of them were born to parents living in a part of the city where the water supply was contaminated with industrial solvents (trichloroethylene [TCE], and dichloroethylene).

 

The rate of birth defects of the heart was three times as high among people drinking the contaminated water, compared to people in Tucson not drinking contaminated water. Exposure to solvents and other organic liquids is one of the most common chemical health risk at places of work.

 

Most of the organic solvents are combustible, often highly volatile and extremely flammable and they should always be handled with care. Some solvents produce vapors, which are heavier than air. These may move on the floor or ground to a distant ignition source, such as a spark from welding or caused by static electricity.

The vapors may also explode from smoking. Vapors of solvents can also accumulate in confined places and stay there for a long time, presenting risks for health and property. Solvents enter the body by inhalation, by swallowing and through the skin.

  

          
 Water--Fluoride  

Many communities add fluoride to their drinking water to promote dental health. Each community makes its own decision about whether or not to add fluoride. The EPA has set an enforceable drinking water standard for fluoride of 4 mg/L (some people who drink water containing fluoride in excess of this level over many years could get bone disease, including pain and tenderness of the bones).

 

The EPA has also set a secondary fluoride standard of 2 mg/L to protect against dental fluorosis. Dental fluorosis, in its moderate or severe forms, may result in a brown staining and/or pitting of the permanent teeth. This problem occurs only in developing teeth, before they erupt from the gums.

 

Children under nine should not drink water that has more than 2 mg/L of fluoride.

 

  

          
 Water--Bacteria  

If there are enough tiny particles suspended in water it becomes cloudy or turbid. Light bounces off the suspended particles giving the water a milky or muddy appearance. Gasses dissolved in water can also cause turbidity if they begin to come out of solution or "degas" (like the bubbles that form when a carbonated drink is opened).

Gas bubbles will eventually rise to the surface and disappear - the water will clear, other materials suspended in water neither rise nor settle, so the water does not clear. 100+ years ago cholera (caused by Vibrio cholera) and typhoid feaver (caused by Salmonella typhi) were responsible for epidemics (caused by drinking contaminated water) that killed many thousands of people.

Today, in most parts of the world, because of chlorination and other water purification processes, we do not usually hear about cholera outbreaks unless an accident or natural disaster has disabled water purification plants. Today in the US, the pathogenic bacterial contaminant most often encountered is fecal bacteria, or E. coli {MCL=0.0 bacteria}, which enters the water supply from human or animal wastes.

The EPA regulates the maximum allowable levels for these bacteria in drinking water, and most people most of the time either do not encounter these bacteria in their drinking water or do not get sick. The article, Tap Water at Risk by the Houston Chronicle, reported that in the USA in 1994-1995, there were 3,641 water purification utilities in the US that reported violating the federal health standards for fecal bacteria contamination.

These utilities together served 11.9 million people. Despite these statistics, disease outbreaks (in people on municipal water) linked to E. coli in the U.S. appear to be quite rare. According to a note in the Denver Post (p. 4B), July 18, 1998 reporting that an E. coli outbreak that sickened at least 50 people in Alpine WY (population 470) was probably caused by a contaminated town water supply, the state epidemiologist said that it was only the second outbreak in the nation that has been linked to municipal water.

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