By Valerie Volcovici

WASHINGTON, Sept 14 (Reuters) - A district court judge in Louisiana on Wednesday vacated air permits for a plastic and petrochemical plant proposed along Louisiana's industrialized coast, delivering a major blow to a project that has faced years of fierce opposition by local residents.

Baton Rouge District Judge Trudy White ruled in favor of environmental and local community groups, who appealed the decision by Louisiana's Department of Environmental Quality to issue air permits to Formosa Plastics for its enormous Sunshine Project.

She said state regulators used "selective" and "inconsistent" data in evaluating the permit application and failed to consider the air quality impacts of the project on the predominantly black local community of St James Parish.

"Because the agency's environmental justice analysis showed disregard for and was contrary to substantiated competent public evidence in the record, it was arbitrary and capricious," the judge wrote in her opinion.

The decision is the latest blow to the proposed $9 billion petrochemical and plastics complex in a Louisiana region nicknamed “Cancer Alley,” home to several major petrochemical facilities and refineries where black residents suffer high rates of cancer.

If approved, it would have become one of the world’s largest production facilities for plastics and plastic feedstocks.

Last August, the U.S. Army ordered a full environmental review of the Taiwanese plastic firm's project after deciding the original assessment of the project failed to properly weigh the health impact of the project on the overburdened local communities. The new review could take years.

Formosa did not immediately respond to a request for comment.

Nikki Reisch, director of the climate & energy program at the Center for International Environmental Law, said the decision sends a clear message to companies that they cannot ignore the voice of local communities when proposing major fossil fuel projects.

"The Court’s decision affirms that the harms caused by an industrial facility, whether a plastics plant or a fossil fuel refinery, cannot be assessed in isolation from surrounding sources of pollution or from the broader context of the mounting climate emergency, disproportionately harming marginalized communities," said Reisch. (Reporting by Valerie Volcovici; Editing by Kim Coghill)