A first-in-the-nation study hopes to answer questions about an emerging contaminant in Long Island water - and whether it can cause cancer.

News 12’s What’s In The Water offers an exclusive look at a Yale University study into 1,4 dioxane, and its impact on the island.

As News 12 previously reported, 1,4 dioxane was first found in Long Island’s water supply around 2015. 

Long Islanders, however, questioned drinking water safety for decades, especially after noticing a trend in the 1990s.

"My children's babysitter [was] very, very active with my children. And then all of a sudden, it was like flipping a light switch,” said Jack Delaney, of Bethpage. “She got very sick and died."

Delaney says similar news came from his contractor in the early 1990s.

"I met him down at 7-Eleven one morning and [...] he says, 'I got about three months to live,'" he said.

Many wonder how this potential carcinogen got into the drinking water.

Citizens Campaign for the Environment first released a study that put many on the island on notice about 1,4 dioxane.

CCE executive director Adrienne Esposito says groundwater test results in 2015 showed Long Island had the highest levels of 1,4 dioxane in the drinking water of anywhere else in the country.

1,4 dioxane is found in common household items, like shampoo and dish soap.

Esposito says several businesses across the island have also used products containing the man-made compound in much larger amounts over the last 50 years.

"Everything we dump on the surface seeps underground and taints that water supply,” she said. 

Researchers at the Yale Superfund Research Center began looking into 1,4 dioxane to determine, for the first time, what exactly the compound does to the human body.

Yale School of Public Health Superfund Center director Dr. Vasilis Vasiliou says the EPA has classified the compound as a potential carcinogen, and says it has been shown to cause damage to the liver and nasal tissue.

The concrete data showing that connection, however, does not exist.

"The major concern at this time is cancer,” he said.

The Superfund Center looks to gather that data as part of a four-part study into 1,4 dioxane.

Dr. Georgia Charkoftaki is one of the lead researchers for the Yale Superfund Center Project 1.

She says her particular project looks to answer one important question.

"The big question is how does dioxane cause liver cancer,” she said.

The only way they can get these answers is if Long Islanders participate in the study.

News 12 will give viewers an exclusive look at the extensive study and reveal what study participants have found out about the danger coming out of their tap.

What's in the water? (2018) Is tap water safe to drink on Long Island? What's in the water? (2019): Removing 1,4 dioxane from water could come at steep price for taxpayers