Water slowly dripping from the tap is a common scene in horror movies—but this can be scary for reasons that go beyond cinematic effect. The Environmental Working Group has found that much of America’s drinking water contains naturally occurring elements and agricultural and industrial contaminants that have been linked to hormone disruption, brain and nervous system damage, fertility problems, cancer, and other health harms.

Let’s take a look at some of the scary contaminants that may be lurking in your tap water. 

7 Common Scary Contaminants found in Tap Water


PFAS, or per- and polyfluoroalkyl substances, encompass more than 4,700 different manmade substances that are used for a wide variety of purposes. From the coating on non-stick pots and pans to food packaging and cosmetic products, many of our common household products either contain, or have been made with, PFAS. 

Because of their nearly ubiquitous use, PFAS have infiltrated our soil, air, and water. Worse, they’re long lasting chemicals. Known as “forever chemicals,” PFAS can take hundreds—if not thousands—of years to break down. Their link to a range of serious health complications is why the EPA announced a 2021 PFAS Roadmap to protect us from these chemicals, and they’ve continued to ramp up their efforts since then. 

Exposure to PFAS has been linked to fetal development harm, reduced effectiveness of vaccines, and increased cancer risk. Nearly all Americans have blood that is contaminanted with PFAS. Very frightening, indeed. 


Arsenic may be naturally occurring, but this doesn’t make it any less terrifying. The metalloid can be found in many minerals and most of it comes from natural rock formations; and it’s small enough to make its way into drinking water. 

It’s been estimated that more than 25 US states have drinking water that contains dangerously high levels of arsenic, possibly exposing more than 2.1 million people to its harms—namely, the fact that the EPA has classified arsenic as a “human carcinogen” that’s associated with liver, skin, bladder, kidney, and lung cancers. We’d hide under the bed from this drinking water contaminant. 


Lead is a toxic metal that can be found in natural deposits that infiltrate food, dust, soil, and air. But it also makes its way into drinking water through old plumbing materials. Up until 1986, homes and cities used lead pipes, fixtures, faucets, and service lines. As these lead-containing plumbing fixtures corrode (chemically react with water), lead can enter the water. 

Because it’s so spooky, the EPA has set the maximum contaminant level goal for lead in drinking water at ZERO. Even at low levels, lead can be harmful to human health. This is especially true for fetuses, infants, and young children, for whom it can lead to permanent detrimental physical and behavioral effects. 

Worse, this monster in our drinking water is persistent, meaning it can bioaccumulate in the body. Continued exposure can lead to decreased kidney function, reproductive issues, and cardiovascular effects in adults. In children, it can be responsible for hearing problems, learning problems, seizures, coma, or even death. 

Chlorine and Chloramine

Across the country, chlorine and chloramine are used as a disinfectant to kill disease-causing microorganisms in our water sources. Unfortunately, it can react with many of the materials in dirty water—fallen leaves, manure, sewage—to form toxic chemicals that may be harmful for people. 

The process of chlorinating water to make it safe may inadvertently be creating something just as toxic: trihalomethanes. This family of toxic contaminants includes chloroform, a “probable” human carcinogen in the US (a “known” human carcinogen in California). This group of trihalomethanes is largely unregulated, but has been linked to birth defects and cancer. 

Like a zombie outbreak in our tap water, trihalomethanes are just the tip of the iceberg. The’re just some of more than 600 potentially dangerous chemicals created by the interaction between water pollutants and water treatment disinfectants. 


Nitrates occur naturally and also come from many human-made sources. As one of the most common drinking water contaminants, it has been linked to more than 12,500 cases of cancer every year. 

Quite often a result of agricultural fertilizer and manure runoff, children, infants, and pregnant women are at increased risk of nitrate dangers. Because it can’t be seen, smelled, or tasted, nitrates are like a scary ghost that could be hiding in your tap water. 

Radioactive Elements

Radioactive elements, like uranium, barium, radom, and radium, are stored in Earth’s bedrock. As they decay, they can be released into groundwater as “decay products.” Mining and oil and gas drilling can also unearth these elements, allowing them to enter groundwater.

Unfortunately, about 170 million Americans have radioactive tap water that’s hiding in the dark. What’s worse, the EPA has deemed all ionizing radiation as carcinogenic. The fact that they can contribute to cancer in various organs is reason enough for anyone to let out a scared shriek. 


When it comes to the scariest toxins lurking in your tap water, there are few more notorious than fluoride. The controversial contaminant has been used in tap water to ward off dental caries (cavities) and tooth decay—yet scientists are wondering if the potential developmental neurotoxin is even effective in doing that. 

The really scary consideration, though, is that even low doses of fluoride have been linked to IQ reductions in children. While the jury’s still out on whether there are more pros and cons to fluoride, it’s got many households hiding under the bed from it.