Government budgets for fighting wildfires have soared in recent years, reflecting a more assertive approach that critics say places too much emphasis on putting out fires that occur naturally in arid parts of the West.

“It’s just bombs away,” said Timothy Ingalsbee, a former wildland firefighter who now heads Firefighters United for Safety, Ethics and Ecology.

Still, many people who fight wildfires say that some of the resources that people are concerned will be damaged by retardant could potentially be lost to fire. Even in national parks, where some officials have called off the use of retardant to protect historic structures or wildlife from the chemicals, others have requested more retardant. And in more developed areas, particularly in California, the loudest critics of fire policy are those who want more use of retardant, not less, fire officials say.

“The second we don’t, they’re calling us: ‘Where are you?’ ” said Mr. Payne, of the state fire department. Speaking of the environmental threats of retardant, he said, “It’s the people whose houses are not on fire that are concerned about it.”

In the federal lawsuit in Montana, the Forest Service is being sued by a group of current and former employees and others who are demanding that the agency conduct a comprehensive environmental study of the impact of retardant under the Endangered Species Act. The suit cites a 2002 retardant drop on a river in central Oregon that killed 20,000 fish.

Current federal policy encourages pilots not to drop retardant within 300 feet of a body of water, but it allows for exceptions if flying conditions require it or if lives or property are in danger. By 2011, according to officials with the Forest Service in Montana, the most common type of retardant will have lower amounts of ammonia and will therefore be less harmful to fish and aquatic environments. Private companies have also used other chemicals to develop gels and foams that are popular among some firefighting agencies, though retardant is used by most.

The Forest Service says that the number of cases it has found where retardant affected waterways is so small  14 out of thousands of retardant drops since 2000  that mitigation measures already in place suffice.