In the 1960s and ‘70s, acid rain became a central part of the environmentalist conversation when scientists tied deforestation and reef-bleaching to emissions from industrial centers whole continents away. The findings of their research implicated sulfur output mostly from coal power plants with the damage, as it contaminated falling rain and heavily altered soil and water pH wherever it fell. Those findings lead to the Clean Air Act in 1970, which regulated sulfur output among other pollutants.

Sulfur is naturally occurring and an important nutrient for plant growth. Even while regulations made dramatic reductions in its emission as air- and water-borne industrial waste, its use in agricultural activities has just increased.

Recently, a study led by Eve-Lyn Hinckley, assistant professor of environmental studies at University of Colorado, Boulder, indicated that the sulfur being used on U.S. croplands are often many times higher than the peak of acid-rain contamination.

Hinckley’s research team looked at trends in sulfur application on a variety of widespread, staple crops in the U.S., including corn, sugarcane, and wine grapes. They compared data on what was being applied to the fields with sulfur concentrations in downstream surface water. They found levels of sulfur unacceptable by the Clean Air Act, along with heavy concentrations of methylmercury, which, while a safe preservative in tiny concentrations, becomes a neurotoxin at higher doses. Methylmercury is a byproduct of sulfur. Heavy sulfur loads also cause disastrous algae blooms in affected waterways.

“It seemed like the sulfur story was over,” said Hinckley. “But our analysis shows that sulfur applications to croplands in the U.S. and elsewhere are often ten times higher than the peak sulfur load in acid rain. No one has looked comprehensively at the environmental and human health consequences of these additions. … Yet there is an opportunity to bring science and practice together to create viable solutions that protect long-term environmental, economic, and human health goals.”

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