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WASHINGTON -- Living near an oil refinery was tied to increased risk of bladder cancer, according to a study in Texas, home to the most refineries in the nation.

After adjusting for various demographic and socioeconomic variables, individuals living within 10 miles of a refinery had 12% higher risk of bladder cancer compared to those living 21 to 30 miles away (risk ratio 1.12, 95% CI 1.07-1.17), reported Stephen Williams, MD, MS, of the University of Texas Medical Branch in Galveston.

The findings, presented here during a poster session at the Society of Urologic Oncology annual meeting, showed that even living 11 to 20 miles from a refinery raised the risk for bladder cancer somewhat (RR 1.06, 95% CI 1.02-1.11).

To validate the results, Williams' group used incidence of fractures and cataracts as negative controls, and this showed no association with close proximity to a refinery after controlling for confounders, which included age, race, sex, income, education, smoking status, and levels of atmospheric particulate matter.

"It's not causative," he said. "It doesn't say everyone should move away from Texas, or out of the state of Texas, but supports further research."

But he told MedPage Today that there is a "biological plausibility" for the link observed in the study and data supporting that. Amines -- diethanolamine, monoethanolamine, methyl diethanolamine, diisopropanolamine, and others -- are used in oil refineries during production, and aromatic amines (a byproduct of this production) have been shown to be a causative agent for bladder cancer.

"Whether that's disseminated in the air, food, water supply -- that remains to be determined," said Williams.

For their study, the researchers used the Texas Cancer Registry to identify patients diagnosed with bladder cancer from 2001 to 2014, and matched this with 2010 census data. In all, 14,924 cases of bladder cancer occurred within 30 miles of a refinery. Bladder cancer incidence was highest among densely populated areas in the state, such as Dallas, Houston, and Galveston.

At their time of diagnosis, patients living within 10 miles of a refinery were less likely to have localized disease compared to those living 21 to 30 miles away (74.8% vs 78.1%) while being more likely to have regional (7.3% vs 7.1%) and distant disease (4.8% vs 3.6%).

Overall, they found bladder cancer rates of 25.0 cases per 10,000 individuals living within 10 miles of a refinery, 23.1 per 10,000 for those living 11 to 20 miles away, and 22.8 per 10,000 for people living 21 to 30 miles away.

Limitations of the study included that it relied on population-based data and that various confounders were unable to be accounted for (radiation and cyclophosphamide exposure, occupational history, residency duration). Furthermore, the capacity of oil refineries was not factored into the analysis and many variables were measured at the county or zip-code level rather than for individuals.

Williams said further research will examine whether living in close proximity to an oil refinery puts individuals at risk for a host of other cancers, and emphasized that examining food and water supplies will also be key, as their study identified regions with higher bladder cancer incidence despite being nowhere near an oil refinery.

"What I think is imperative is to do our best to deduce causation but also to stimulate further research in this area," he said.