Solvents

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

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 Environmental Protection Agency (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. 

 

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 fever (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 United States, 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 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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