According to the World Health Organization, only about 73% of the global population has easy access to clean drinking water, leaving billions without this essential resource. Alarmingly, around 1.7 billion individuals have to rely on water sources tainted with human waste.

While specific instances, like the Flint water crisis, raise concerns, most people in the U.S. can trust their drinking water. “Compared to the risk of illness in many other countries, our drinking water is relatively safe thanks to sophisticated testing methods that help ensure it is free from both chemical and microbial contaminants,” explains Rachel Noble, a prominent marine sciences professor at the University of North Carolina at Chapel Hill.

Is tap water safe to drink?

In the United States, the U.S. Environmental Protection Agency (EPA) heavily regulates tap water sources through the Safe Drinking Water Act of 1974. This legislation allows the EPA to create standards and guidelines for public drinking water, which helps shield the population from harmful germs, pollutants, and toxic chemicals. Therefore, “the majority of American tap water is clean and suitable for drinking and other daily uses,” says Noble.

The EPA not only establishes standards for what can be in public drinking water, but it also guarantees that treatment facilities use advanced technologies to eliminate contaminants and safeguard water quality, according to Rianna Murray, the director of the graduate studies program in Global, Environmental, and Occupational Health at the University of Maryland’s School of Public Health.

These treatment plants effectively filter out more than 90 known contaminants, including pathogens, various pollutants, heavy metals like arsenic, and both inorganic and organic chemicals along with their dangerous byproducts. This ensures that “the water is microbially safe for drinking,” states Susan Richardson, the executive editor of the peer-reviewed journal “Environmental Science & Technology” and a chemistry professor at the University of South Carolina.

It’s important to remember that all these standards are applicable only to public drinking water and do not extend to bottled water, which is regulated by the U.S. Food and Drug Administration and has its own set of rules.

How can tap water become unsafe?

Despite stringent measures to ensure the safety of public water supplies, contaminants can occasionally infiltrate and compromise drinking water safety.

This contamination can happen when hazardous levels of heavy metals, harmful bacteria, or chemicals enter the water at its source—whether from groundwater or from lakes, reservoirs, or rivers—or while the water travels through the distribution system after it has been treated, according to the Centers for Disease Control and Prevention.

Ways in which contaminants might enter public water systems include “accidents that leak industrial chemicals or fracking wastewater into water supplies,” says Richardson.

Murray adds that lead contamination often arises from aging infrastructure or from older homes with outdated lead pipes, service lines, or plumbing fixtures. “Microorganisms such as bacteria, viruses, and parasites can also contaminate drinking water, potentially leading to waterborne illnesses,” she notes. Contamination can originate from sewage spills, agricultural runoff, animal waste, or other pollution sources that seep into public water supplies.

“While instances of contamination or water quality issues do happen, we have mechanisms ready to tackle concerns swiftly, which include regulatory oversight, public alerts, and swift actions by water utilities,” emphasizes Noble.

How to know if your drinking water becomes unsafe?

Besides staying informed through news and notices, you can also identify potentially contaminated water by its appearance (look out for cloudy, foamy, or colored water), its smell (avoid water that has a sulfur-like odor, or smells of chlorine or swampiness), and its taste (refrain from water that tastes salty, oily, fishy, gritty, or metallic).

If you suspect your water may be contaminated, report it to your utility provider, your local health department, or directly to the EPA. “You can also assess your tap water’s cleanliness using at-home water testing kits,” suggests Murray.

Moreover, it’s wise to prevent any potential contaminants from entering your home in the first place. This does not mean relying on bottled water, “because bottled water lacks the rigorous testing that tap water undergoes and contributes to the plastic waste dilemma,” Richardson explains. Instead, consider installing a water filtration system, a reverse osmosis filter, or an ultraviolet water purification system.

“Although it may not be financially feasible for all Americans, I often recommend countertop filtration systems for those who can afford it,” says Noble.

She reiterates that “the frequency of outbreaks linked to tap water in the United States is relatively low per capita, but by keeping informed and utilizing available filtration options, people can mitigate their risk of exposure to chemicals and biological contaminants in tap water.”