California wildfires grew worse. The Forest Service dropped more retardant. Did it help?

Some studies on aerial retardants conducted by a branch of the U.S. Department of Agriculture shows that they can slow the spread of a fire. But the conditions in which they are dropped have a huge impact on its efficacy; high winds, weather and the type of terrain take significant tolls on whether the retardant can properly impede a fire’s progress. Now at least one group is questioning if they work, and if the benefits of using them outweigh the costs of chemicals accidentally contaminating water.