We hear about greenhouse gases, like carbon dioxide and methane emissions, a lot these days, but other types of air pollution are happening as well. One major problem is ammonia in the atmosphere, a major component in smog and a toxin to many freshwater aquatic organisms. Getting a handle on just how much ammonia humans are producing and where it’s entering the atmosphere has been difficult.

But a new study in the journal Nature used a decades-worth of satellite emissions tracking to pinpoint ammonia hotspots around the globe, most of which were previously unknown.

A team of researchers from the Université libre de Bruxelles and France’s CNRS used three European MetOp weather satellites to gather twice-daily readings on ammonia emissions over the last decade. Each satellite was fitted with an instrument that was able to measure ammonia concentrations down to the square kilometer. The team then overlaid that data with satellite imagery, which allowed them to identify 241 major hotspots of ammonia emissions.

According to the paper, 83 of the sources were linked to livestock, whose feces and urine break down and release ammonia and the remaining 158 sources linked to industrial activity. They also identified 178 larger emission zones—two-thirds of which had never been previously identified.

Over time, the researchers were able to observe livestock operations and industrial operations open and close, directly observing their impact on ammonia concentrations in their immediate area, according to a press release.

Brandon Specktor at LiveScience reports that only one natural source of ammonia, Lake Natron in Tanzania is included on the hotspot list. Decaying matter and algae may be the cause for the alkaline lake's output. Many of the industrial sites pinpointed by the study are plants producing ammonia-based fertilizer, which have enabled a global agricultural boom, but has also led to massive nutrient pollution of the world’s lakes, rivers and oceans.

The paper suggests that our current understanding of how much ammonia humanity produces is pretty far off. “Our results suggest that it is necessary to completely revisit the emission inventories of anthropogenic ammonia sources and to account for the rapid evolution of such sources over time,” the team writes in their paper.

The new study is significant and will allow nations to accurately monitor their ammonia emissions for the first time, Mark Sutton and Clare Howard of the International Nitrogen Management System, NERC Centre for Ecology and Hydrology in Edinburgh, write in a commentary on the paper.

“Their demonstration that global satellite observations can now detect such ammonia sources represents a historic moment for science,” they write.

Monitoring ammonia is one thing. Controlling it is another. Researchers are working on ways to reduce ammonia emissions from cows, including drugs that reduce the amount of ammonia in cattle waste and improved barn designs that could help reduce ammonia.