An alarming new investigation has revealed that over half of the drinking water in the US contains radioactive elements.

The Environmental Working Group (EWG) have found that a good portion of the drinking water in all 50 states contains radioactive elements that may increase one's risk of cancer. The EWG analyzed almost 50,000 public water systems and discovered that the water supply consumed by 170 million Americans contains radioactive elements. In 27 states, water supplies were found to exceed the EPA's legal limits.

The most common radioactive element the EWG found was radium. Radium enters groundwater naturally though deposits in the Earth's crust. Levels are higher when activities such as oil gas drilling disturbs the deposits from the rock and the soil. When this occurs, it releases ions and is known as "ionizing". The EPA categorizes all ionized radiation as carcinogenic and sets safe levels, which are then enforced.

Desoto was found to have higher levels of radium in their water. EWG.

In 158 public water systems used by 276,000 Americans, the EWG found that radium levels were above legal limits.

Unfortunately, EPA guidelines aren't as stringent as they could be. In 2006, California state scientists set public health goals for radiation that are much more strict in response to the elevated risk of cancer posed by radiation and the potential harm to fetuses during pregnancy. These guidelines are hundreds of times stricter than the standards set by the EPA.

If the California standards were adhered to, it would mean that no more than one case of cancer per million people was down to the water supply. The EPA's levels allow for 70 cases per 1 million people.

The study, conducted between 2010 and 2015, found that around 122 million people are drinking water that contains levels of radium above what is considered safe by the Californian scientists' guidelines, Newsweek reports

The EWG warned that levels of radiation in US water supplies could be harmful to those drinking it.

“Most radioactive elements in tap water come from natural sources, but that doesn’t take away the need to protect people through stronger standards and better water treatment,” Olga Naidenko, senior science adviser at EWG, said in a statement. “Millions of Americans are drinking water with potentially harmful levels of radioactive elements, but the outdated federal standards mean many people don’t know about the risk they face when they turn on the tap.”

Of all the states, Texas was the region where radium was found in the most water supplies. Around 80 percent of residents in the Lone Star state have radium in their water.

The EWG put together this interactive map with the data, so that you can search for the radium levels in your zip code.