Researchers are starting to focus on dioxane, a potential carcinogen that’s starting to show up in tests of tap water.

You probably haven’t heard of the chemical dioxane.

But there’s a good chance you’ve been drinking it.

The chemical, 1,4-dioxane, is an industrial solvent used in the production and manufacturing of a whole range of common products, including cosmetics, varnishes, dyes, and detergents.

The U.S. Environmental Protection Agency (EPA) classifies the chemical as “likely to be carcinogenic in humans.”

And it’s found its way into water supplies in the United States.

According to a report released last month by the Environmental Working Group, a nonpartisan advocacy group, dioxane was found in tap water samples that affect 90 million Americans in 45 states.

In August, the New York State Department of Health passed legislation requiring all water systems, regardless of size, to begin testing for dioxane.

New York joins a handful of other states, including New Jersey, Massachusetts, and Connecticut, that have established dioxane tolerance standards in water.

There’s currently no federal standard for dioxane levels in water.

Dioxane is one of many contaminants that the EPA has been monitoring since the mid-1990s. But the agency has yet to regulate it.

The 1996 amendment of the Safe Drinking Water Act introduced the Unregulated Contaminant Monitoring Rule (UCMR). It requires the EPA to monitor a list of no more than 30 unregulated contaminants in water.

Based on its findings, the EPA uses data and survey information from the UCMR to make regulatory decisions about potentially harmful contaminants.

So far, dioxane hasn’t been directly linked to any major health events in the United States.

There also hasn’t been any “smoking gun” incident in which a group, community, or water system contaminated with dioxane resulted in people getting seriously ill.

So, why are people starting to pay attention to dioxane now?

“To the best of my knowledge, it’s not that people have gotten sick from 1,4-dioxane,” Wendy Heiger-Bernays, PhD, a professor of environmental health at Boston University, told Healthline. “The reason why these things start to get looked for is because people start to measure them.”

“This has been going on for many, many years, but it wasn’t until our analytical tools got good enough to be able to detect 1,4-dioxane at fairly low levels,” she explained.

Dioxane has previously been detected in high concentrations in and around landfills. That’s because it’s common in so many different products that it tends to accumulate in areas filled with garbage.

Among other things, dioxane is a byproduct of sodium laureth sulfate, a foaming agent found in shampoo, soap, detergent, and toothpaste.

It’s also water-soluble and can travel rapidly through soil to permeate groundwater supplies.

As far as a public health risk and a toxicity threshold in water, there still needs to be more research.

However, dioxane is known to affect the liver and kidneys. It’s also been identified as a probable carcinogen.

The National Institute for Occupational Safety and Health previously established dangerous toxicity levels for dioxane, but those were based on inhalation (as in a manufacturing environment) and not consumption.

Less serious health effects of dioxane exposure can include eye, nose, and throat irritation, as well as cracked, dry skin and eczema.

“I think this is one in a series of chemicals that we have not been looking for,” said Heiger-Bernays. “If we don’t look for things, we don’t find them.”

“There is a whole suite of chemicals that we are finding in water supplies because they have not been adequately regulated, and the ones we are finding are those that are either used in manufacturing of something or are a byproduct of a manufacturing process,” she added.

Despite the attention dioxane has received in recent months, federal regulation of the chemical may not be a priority under the current administration.

Michael Dourson, President Trump’s nominee for the EPA’s chemical safety office, has been accused of downplaying the risks of some chemical contaminants.

Dioxane in particular has already been brought up in testimony between Dourson and Democratic senators.

In a tense exchange, Sen. Ed Markey (D-Mass.) stated that Dourson’s proposed level of acceptability for dioxane was thousands of times higher than EPA levels.

For dioxane and the other chemicals included on the UCMR, additional EPA regulation can be tricky, requiring additional money, monitoring, and resources.

However, according to Heiger-Bernays, we’ll inevitably begin to find new and different chemical contaminants in our water supplies.

“People are unaware that many of these chemicals that are being found are unregulated, although they are in our water supply,” she said. “We really need a comprehensive way of looking at water and doing a better job of screening what’s in the water and then figuring out what are the priorities for regulation.”