California responsible for 12% of the world’s sulfuryl fluoride emissions

A new study by John Hopkins University has found that California puts more sulfuryl fluoride into the atmosphere than all the other American states combined, and 12% of the global total.

This relatively obscure gas is widely used as a fumigant for treating termite infestation in buildings and ships. It was first approved by the U.S. Environmental Protection Agency for use as a pesticide in 1959 and went on to replace a number of more environmentally pernicious treatments – such as methyl bromide – that had been previously popular.

However, as the researchers point out, sulfuryl fluoride is itself problematic because while it does not damage the ozone layer, it is a potent greenhouse gas that can contribute to climate change, remaining in the atmosphere for around 40 years. 

The research was lead by Scot Miller, an assistant professor of environmental health and engineering, and Dylan Gaeta, a PhD candidate both at Johns Hopkins University.

They analysed data more than 15,000 air samples collected between 2015 and 2019 by NOAA Global Monitoring Laboratory scientists, factoring in wind speed, direction, and other meteorological variables to trace the chemicals back to their point of origin. 

Miller says: ‘When we finally mapped it out, the results were puzzling because the emissions were all coming from one place. Other greenhouse gases like carbon dioxide and methane are found everywhere across the U.S. On our sulfuryl fluoride map, only California lit up like a Christmas tree.’

Their results suggested that up to 85% of sulfuryl fluoride emissions across America originate, not just in California, but more specifically Los Angeles, Orange, and San Diego counties.

Thanks to the state’s efficient record keeping, the team could see that the vast majority of these emissions were from the practice of structural fumigation, in which a termite infested building is enclosed in a tent and the gas pumped in. Because of year-round warm weather, properties in California find themselves particularly susceptible to such infestations.  Once fumigation is complete, the gas is released into the atmosphere. 

From this point, the gas remains in the atmosphere for decades, contributing to global warming by trapping heat and sending it back down to the Earth’s surface, and while the average concentrations in the atmosphere are low it is being emitted at a rate faster than it breaks naturally.  

Gaeta said: ‘Without some form of intervention, sulfuryl fluoride is going to keep accumulating in our atmosphere. For most greenhouse gases, California has been very intentional about how it’s going to reduce emissions, this one has slipped under the radar.’

Miller added: ‘It really is a double-edged sword. Sulfuryl fluoride is less harmful than the banned fumigants, but it also contributes to global warming. California’s track record shows that it’s been looking at out-of-the-box, creative ways to reduce its greenhouse gas emissions. I think knowing better what the emissions are and what impact they have will give the state the information it needs to help holistically develop greenhouse gas reduction strategies.’