A federal court has dismissed a suit by environmentalists pushing the Environmental Protection Agency (EPA) to decide whether lead emissions from general aviation aircraft engines endanger public health and welfare. The court said the issue is not one that it can take up under a provision of the Clean Air Act allowing “citizen suits.”

Friends of the Earth originally filed a petition with the EPA in 2006, detailing harms from lead emissions. The group alleged that by failing to make an endangerment finding, the EPA caused an “unreasonable delay.” The Clean Air Act allows citizens to sue the government if they feel the agency is delaying action without good cause.

The court found that Friends of the Earth’s request fell outside the bounds of the Clean Air Act’s citizen suit provision. “While the allegations raise significant concerns, they do not bear on the narrow jurisdictional issue now before the Court.”

EPA plans to initiate a public proceeding about whether the emissions are harmful, with any final decision expected in mid-to-late 2015.