What’s in your drinking water?

What’s in your drinking water is worrisome enough these days, but the documentary “What Lies Upstream” will also have you wondering what’s in the minds of corporations, regulators and politicians who seem unconcerned with appropriate oversight of the first issue.

Filmmaker Cullen Hoback, who last probed internet privacy with “Terms and Conditions May Apply,” starts his expose in West Virginia, where a notorious 2014 chemical spill left hundreds of thousands of citizens without potable water. With camera in tow, Hoback is there to cover bottled water runs, tortured news conferences with obfuscating and/ or dumbfounded officials, and angry West Virginians who may defend coal to the death as a homegrown industry but at least expect their water to be safe.

As the story unfolds, though, Hoback discovers just how easy it’s been for companies and the government to sidestep public health issues through the lax enforcement of environmental regulations, corporate secrecy regarding under-tested chemicals, and powerful lobbying that stymies lawmakers from holding companies accountable. Shaking one’s head at the corruption and ineffectuality on display becomes a near constant reaction to what Hoback uncovers. His curiosity and doggedness produce results — including a memorable exchange with a feckless West Virginia state senator after a compromised vote to roll back hard-won regulations he’d spearheaded only a year prior.

And like any honest, factbased exploration of a flawed system, it allows for complexity about the humans most deeply involved.

By acknowledging what isn’t known about drinking water, but what should be illuminated about the mechanism behind it, “What Lies Upstream” proves an exemplary piece of advocacy filmmaking. Outrage is a given, but more urgently, you’re left wanting to learn more. — Robert Abele

“What Lies Upstream.” Not rated. Running time: 1 hour, 25 minutes. Playing: Arena Cinelounge Sunset, Hollywood.