Tap Water FAQs

What types of contaminants are commonly found in tap water?

Tap water contaminants can be broken down into two broad categories: non-toxic and toxic. Non-toxic contaminants are relatively harmless and typically include copper, iron manganese, and sulfate. Some common toxic contaminants in tap water are arsenic, chlorine, fluoride, hydrogen sulfide, lead, nitrates and nitrites, and radon.

While some toxic substances in tap water will produce no ill health effects when ingested in small amounts for short periods of time, many of these toxins accumulate in the body over time. Long-term exposure to these toxins may cause cancer, reproductive difficulties, or gene mutation.c Recent studies show that many regulated and unregulated contaminants pose a greater risk in even smaller concentrations than previously thought.a

Where do tap water contaminants come from?

Some contaminants come from natural sources and include radon gas and certain types of salts and minerals, which leach from the ground into the water. Human activity is responsible for the majority of other tap water contaminants. Major types of tap water contaminants come from mining, drilling for oil and natural gas, agriculture and forestry, city drainage systems, landfills, water and sewage treatment plants, domestic septic tanks and cesspools, and underground gasoline storage tanks.c

How do I know what is in my tap water?

Because the quality of tap water and the way it is treated depends on the region, the best source for specific information about contaminants in your tap water is your local water supplier. Water suppliers are required to provide a consumer confidence report (annual water quality report) annually before July 1st. The report indicates what contaminants are in your tap water and at what levels.

Many water suppliers also post their annual water quality report online.b Online reports can be found on the EPA Web site or by simply typing the name of your city and the words “annual water quality report” or “consumer confidence report” on Google.

If my city’s water quality report shows that it meets all EPA guidelines, does that mean the water is safe?

Among the thousands of pollutants found in drinking water, the EPA’s Safe Drinking Water Act (1974) requires maximum standards for only 91 of them. What this means is that the EPA regulates only a small percentage of a wide range of potentially dangerous contaminants, and these contaminants are legally allowed in tap water until they reach a maximum level as defined by the EPA. Additionally, scientists claim the EPA’s Safe Drinking Water Act is so out of date that American drinking water poses serious health risks—legally. The EPA itself has admitted that millions of Americans have been exposed to unhealthy tap water.a

Where does tap water come from?

According to the CDC, approximately 40-45% of the United States’ tap water is from ground water wells and 55-60% is from surface water. Surface and ground water are fundamentally interconnected and, consequently, pollutants (such as fertilizer) in one will contaminate the other. Both surface and ground water are treated at municipal water treatment centers before traveling, often over long distances, through main water pipes to reach your faucet.d

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