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The debate between drinking tap water or bottled water seems to be endless.

In most parts of the United States and Canada, it’s safe to drink tap water from public water systems. Tap water that’s been properly filtered is equally safe as bottled water and provides you with essential minerals you may not get from bottled water.

Even though it’s usually safe to drink tap water, it’s still a good idea to keep an eye out for local water advisories in your area. Situations like a broken water line or equipment failure at the water treatment plant can lead to temporary contamination.

You may also want to stick to bottled water when traveling to developing countries that don’t have the same level of infrastructure or safety standards. For example, a 2017 research review showed that Mexico’s maximum allowable limit of arsenic in drinking water is 2.5 times higher than the World Health Organization’s recommendation.

Keep reading to learn everything you need to know about drinking tap water in North America.

Even tap water that’s safe to drink isn’t made up of 100 percent water. You can also find traces of minerals and small amounts of containments at levels deemed to be safe for human health.

Fluoride

The mineral fluoride is added to water in the United States to help strengthen your teeth. According to the Centers for Disease Control and Prevention (CDC), studies have found drinking fluoridated water prevents your risk of tooth decay by about 25 percent.

Chlorine and chloramine

Disinfectants like chlorine or chloramine are added to drinking water to kill germs that can make you sick. These disinfectants are added in very small amounts that haven’t been found to cause harmful health effects in humans.

For example, the CDC says that chlorine levels up to 4 parts per million are considered safe for human consumption.

Minerals

Tap water contains minerals that are essential for human health. Some of these minerals occur naturally and some are added.

According to a 2013 study, drinking a quart of tap water provides you with about 1 percent of your daily required copper, calcium, magnesium, and sodium. The researchers found no significant differences in the overall mineral content of water extracted from 144 sampling locations across the United States.

Tap water also contains other minerals, such as:

  • potassium
  • iron
  • phosphorous
  • zinc

The taste of tap water can differ depending on the amounts and ratios of minerals dissolved in it. For instance, high levels of iron may give your water a metallic taste.

Contaminants

Even water considered safe can contain traces of contaminants in amounts not deemed to be dangerous for human health.

The Environmental Protection Agency (EPA) has limits on more than 90 potential substances that may be unsafe for humans. For example, the limit for arsenic is 10 parts per billion.

There also might be a microscopic amount of other contaminants in your water that aren’t harmful to your health, such as soil or sediment.

According to the EPA, water can be contaminated with various types of pollutants that may make it unsafe.

Bacteria and parasites

Tap water can contain microorganisms like bacteria or parasites that make you sick. If potentially dangerous microorganisms are detected in tap water, your local health authority will likely declare a “boil water advisory.”

Cryptosporidium, E. coli, and Giardia are three harmful organisms that can leak into drinking water through sewage.

Chemicals

Both human-made and natural chemicals can make their way into drinking water. Pesticides, bleach, and bacterial toxins are some of the potential things that can have harmful health effects.

Other chemicals like bisphenol-A and pharmaceuticals are also sometimes detected in groundwater sources. Often these chemicals are filtered before reaching your tap.

Radioactive elements

Radioactive elements chemicals like uranium, cesium, plutonium are sometimes detected in drinking water. These elements can emit ionizing radiation that can harm cells in your body and raise your risk of developing cancer.

Other types of ionizing radiation people are exposed to include X-rays and ultraviolet light.

Heavy metals

Heavy metals like arsenic, mercury, or lead can enter your water supply through plumbing and service lines as well as through natural mineral deposits. The EPA says that people who consume a lot of these minerals may develop sudden or long-term toxicity that’s linked to:

Certain groups of people are more sensitive to containments. They include:

  • infants
  • young children
  • pregnant women
  • adults more than 65 years old
  • people undergoing chemotherapy
  • people with HIV or AIDS
  • people with other immunocompromising conditions

Children, babies, and fetuses have less blood volume than adults, and contaminants like heavy metals can have a greater effect on them. People who are immunocompromised may be more vulnerable to bacteria and parasites.

Congress enacted the Safe Drinking Water Act in 1974 to ensure the quality of public water systems in the United States.

According to the CDC, the United States has one of the safest water systems in the world. All public water systems follow guidelines set by the EPA. However, the EPA doesn’t monitor private wells.

The EPA says that more than 13 million homes in the United States get their water from private wells. It’s up to the well owner to make sure the water is safe for consumption.

Most of the time, your local health authority will send out an alert if your water supply becomes contaminated. In very rare cases, contaminants may enter public water systems and go unnoticed.

Like in the United States, Canadian drinking water goes through rigorous safety standards and is generally safe to drink. Health Canada’s Water and Air Quality Bureauworks with provinces, territories, and municipalities to develop guidelines for water safety.

Canadians and people visiting Canada should still keep an eye out for local water advisories.

The drinking water in many areas in Mexico isn’t safe to drink. A 2018 study found that only 7 percent of people in Guadalajara, Mexico’s third-largest metro area, drink the tap water.

Even in areas where water is purified, water can often be contaminated by pipes or water holding tanks. Travelers are often recommended to buy bottled water in Mexico.

Every year, you should receive a Consumer Confidence Report from your local water supplier by July 1, telling you your water source and what’s in it. You can also search for your local CCR from the EPA website.

According to the World Health Organization, you’re largely unable to determine the quality of your water using your own senses.

A strange taste, appearance, or odor may indicate pollution or malfunction during water treatment. But in some cases, these abnormalities may be caused by the mineral content.

Drinking tap water that’s contaminated with microorganisms can lead to gastrointestinal illness. Common symptoms include:

You can also develop hepatitis from contaminated drinking water, which is especially likely to cause severe health effects in people who are immunocompromised.

Microorganisms that cause life threatening conditions like typhoid or cholera are rare in the United States.

Exposure to chemicals can cause short-term or long-term effects. According to the EPA, high doses of chemicals can cause symptoms that include:

Local health officials sometimes issue boil water advisories to kill germs that may make you sick.

If you don’t have access to bottled water during a boil water advisory, the CDC recommends bringing tap water to a rolling boil for 1 minute and then allowing the water to cool before using it.

Bottled water and water filters are both potential alternatives to tap water.

Bottled water

The FDA oversees the safety of bottled water. Normally, bottled water and tap water are both considered very safe in the United States. Bottled water is the better choice in areas where tap water isn’t safe to drink or if there’s a water advisory.

Water filters

Many types of home water filters are available. Some filters attach directly to your sink, and some brands sell pitchers with filters in them.

Not all water filters make your water safer. Some water filters are only designed to improve the taste.

Tap water is generally safe to drink in the United States and Canada, but you should watch for water advisories released by your local health authority. A breakage in a water line or malfunction at the treatment plant can lead to temporary contamination.

When visiting developing countries such as Mexico, you may want to avoid the tap water to be safe.