ARVIN, Calif. — In the Central Valley of California, hundreds of wells that provide water to a million people are tainted with a chemical that some experts say is one of the most powerful cancer-causing agents in the world.

The state is poised to take the first step Tuesday to regulate the substance — called 1,2,3, TCP — but test data compiled by an activist group show it’s also been detected by utilities across the country.

Some who live in this lush farmland believe it’s to blame for the health problems of their family members and neighbors.

“The word that really captures all of it is ‘outrage,'” said Jerry Tinoco, 45, who is from the city of Arvin and says at least three close family members have been diagnosed with cancer. “It’s a man-made chemical, so someone is to blame.”

There’s no research showing the chemical has caused cancer spikes in specific communities, but some residents and experts told NBC News that research simply has yet to be done in towns like Arvin.

How dangerous is TCP? The Environmental Protection Agency has concluded it’s “likely to be carcinogenic to humans,” and the California water board warns residents not to shower with tainted water because they might inhale the chemical.

Paul Tratnyek, a professor at the Institute of Environmental Health at Oregon Health and Science University who studied TCP for the Defense Department, said few other chemicals match its toxicity.

“Even the slightest amount of TCP in the water would be considered to be a potential health effect,” Tratnyek said. Continue reading.