The Denka Performance Elastomer plant on River Road in Laplace, 2019.

Cancer in all its manifestations is a deadly disease and rightly feared. While medical science has made great strides against it, fear of the disease continues.

But if the causes of cancer are becoming clearer with time, it remains difficult to justify criticisms of careful scientific studies that do not prove activists' assertions about the impact of industrial emissions.

A new example: LSU found that its Louisiana Tumor Registry has accurately reported cancer cases around a chemical plant much-criticized by environmentalists. But the cautious statements of statisticians amount to a “not proven” verdict about whether the emissions caused cancers, or that the Denka plant’s production of chloroprene has caused elevated levels of cancer in St. John the Baptist Parish.

''This report in no way implies that there are no health effects from long-term exposure to chloroprene,'' the report carefully notes. While the substance in sufficient doses over sufficient time may be cancer-causing, there is no evidence that there are specific cancers arising from the emissions from the plant.

What the tumor registry does show is that there aren’t more cancers in the general area of the plant than elsewhere.

Not-proven isn’t enough for activists.

All too often, the results of careful study are waved away by environmentalists and community groups angry at the all-too-visible smokestacks.

“They answered a question that I'm not sure anybody was asking,” sniffed Kimberly Terrell, director of community outreach for Tulane Environmental Law Clinic.

Lawyers who argue past the facts so blithely in a courtroom would be admonished by a judge. In the court of public opinion, though, there’s a guilty-until-proven-innocent character to these debates.

We commend the LSU School of Public Health for the searching study and careful conclusions. The tumor registry is the best data we’ve got. We want it to be as complete as possible.

The U.S. Environmental Protection Agency says chloroprene causes cancers, in sufficient doses over sufficient time — the qualification that is too often overlooked — but industry spokesmen argue that the EPA conclusions are disputed by new research.

We don’t buy that industrial emissions are surely not causing health problems. That’s why we need environmental regulations. We want to see emissions reduced, even as the benefits of the petrochemical industry are reaped by parishes like St. John, in jobs and taxes.

It is common sense that people living near a smokestack might get more exposure, and that poor residents — maybe even without air-conditioning in Louisiana’s brutal summers — may be much more at risk.

Poverty is a cruel carcinogen in society. It’s probably worse than a dozen Denkas. Parsing out what’s caused a specific case of a specific cancer may be proven one day by science. But not yet.

Our Views: In 'cancer alley,' we've got a health problem we must diagnose properly