In 1921, General Motors engineers discovered that tetraethyl lead could make internal combustion engines run more smoothly and reduce engine knock. For the next 100 years, the toxic additive in automobile gasoline contaminated the environment and endangered public health. As of this week, however, lead has finally been phased out of all global gasoline use — a nearly two-decade effort led by the United Nations Environment Programme, or UNEP, involving a coalition of scientists, nongovernmental organizations, fuel and vehicle companies, and governments, including the U.S. Environmental Protection Agency.

Despite the success of the UNEP-lead coalition in eliminating the use of leaded gasoline across the globe, however, the coalition was unable to clearly identify plans to address what scientists say is a continued public health threat: the legacy of leaded particles from gasoline emissions that settle in the soil and continue to haunt urban centers around the world. Countries that most recently phased out leaded gasoline will face challenges similar to those in U.S. cities, where researchers have found that residents of highly trafficked urban centers are exposed to lead particles in the soil that are resuspended into the atmosphere during the summer and fall, particularly during hot, dry weather.

“The same patterns that we were seeing of soil lead contamination in [U.S.] urban areas is likely to have occurred internationally in every city which has used leaded gasoline,” Mark Laidlaw, a geologist and environmental scientist.

The UNEP estimates that eliminating the use of leaded gasoline globally will prevent more than 1.2 million premature deaths from heart disease, strokes, and cancer each year. It will protect children from the irreversible effects of lead poisoning and save as much as $2.44 trillion per year in costs that otherwise would have been spent to address the effects of lead poisoning.

Read the full article about the lingering effects of leaded gas by Yvette Cabrera at Grist.