By Bill Walker | April 25, 2024 | The New Lede

Among US states, California is a leader in efforts to cut emissions of the greenhouse gases that fuel the climate crisis. But just three counties in Southern California emit far more of one little-known greenhouse gas than all other US states combined.

Blame termites – and the tragic, too-frequent mistake of replacing one environmentally harmful chemical with another that turns out to be just as bad.

Sulfuryl fluoride is a fumigant pesticide first made by Dow Chemical Co., marketed since 1959 as Vikane. To kill western drywood termites, pest control companies cover infested houses with tents and then pump in Vikane. Houses tented for fumigation are a common sight in Southern California, where warm, dry weather leaves wooden buildings highly susceptible to infestations of the hard-to-exterminate species.

The colorless, odorless, highly neurotoxic gas that kills termites is also a danger to humans. That’s why Vikane must be spiked with another toxic pesticide gas called chloropicrin, which has an intensely irritating smell that is meant to warn people against entering a house until the fumigant has dispersed in 24 to 72  hours.

California Department of Pesticide Regulation (DPR) records show that between 1992 and 2017, at least 16 Californians died from sulfuryl fluoride poisoning after going inside fumigated houses too soon. In the same period DPR recorded more than 200 cases of human exposure that caused breathing problems, dizziness, nausea, and other symptoms.

But the biggest problem with Vikane is that, when fumigation tents are removed and sulfuryl fluoride disperses into the atmosphere, it is a greenhouse gas much more powerful than carbon dioxide (CO2).

Sulfuryl fluoride has more than 7,000 times the global warming potential of CO2 Fortunately, it lingers in the atmosphere less than 40 years, compared to 300 to 1,000 years for CO2.

Compared to CO2, emissions of sulfuryl fluoride are relatively small. But they are a growing problem that is getting the attention of scientists: An international team of researchers estimated that worldwide emissions rose by almost six times between 1978 and 2019.

California is the only state to record how much sulfuryl fluoride is used, and neither federal  nor state regulators track the sources of emissions. But earlier this month, a team led by researchers from John Hopkins University published a study using monitoring data from the National Oceanic and Atmospheric Administration (NOAA) and computer modeling to map where emissions are coming from.

When they fed the NOAA data into the model’s US map, “only California lit up like a Christmas tree,” Scot Miller, a professor of environmental health and engineering at Johns Hopkins, told the Los Angeles Times.  The worst hot spots were in Los Angeles, Orange and San Diego counties. The rest of the country showed barely any emissions.

The researchers estimated that California is responsible for up to 85% of US emissions of sulfuryl fluoride and up to 12% of global emissions. Actual emissions may be much higher: DPR says that in 2021, almost five times more sulfuryl fluoride was used in the state than the NOAA monitors detected, making the state by far the world’s largest consumer of the compound. 

In 2022, the nonprofit advocacy groups Center for Biological Diversity (CBD) and Californians for Pesticide Reform (CPR) formally petitioned the California Air Resources Board (CARB) to begin tracking sulfuryl fluoride emissions, so that the state’s legally-mandated greenhouse gas reduction goals don’t fail to account for them. (I have worked with CPR in advocacy coalitions.)

The petition also asked CARB to begin a phaseout of the pesticide, saying sulfuryl fluoride’s annual climate impact in California equals the CO2 emitted by 1 million vehicles. CARB denied both requests, saying the agency “lacks sufficient information” to decide whether tracking emissions or phaseout is warranted.

“On the one hand, the Air Resources Board is saying we need to do more to address climate change, and on the other hand, they’re failing to really take steps in the context of sulfuryl fluoride to reduce this highly potent greenhouse gas,” CBD senior attorney Jonathan Evans told Inside Climate News.

Exterminators used to fumigate for termites using a neurotoxic gas called methyl bromide. In 1992, it was targeted for phaseout under the global Montreal Protocol because it erodes the earth’s protective ozone layer, and its use as a termite fumigant ended in 2005. (California strawberry farmers also used huge quantities of methyl bromide to kill nematodes, and despite the threat of the nerve gas drifting into nearby schools and neighborhoods, DPR granted growers a series of  “critical use exemptions” that finally ran out in 2015.)

When methyl bromide use ended, sulfuryl fluoride was seen as a relatively harmless replacement that dissipated from the atmosphere in just a few years. But by 2008,  researchers found that it has a high global warming potential and stays in the atmosphere an average of 36 years.

It’s a classic case of “regrettable substitution” – what Joseph Allen, director of the Healthy Buildings program at Harvard University’s T.H. Chan School of Public Health, described as “a big game of Whack-a-Mole: Every time one (harmful) chemical is knocked out, another takes its place.”

In a commentary for The Washington Post, Allen cited disturbing examples: Swapping hormone-disrupting BPA in baby bottles for BPS, a hormone disrupter that may be even more harmful. Banning one formulation of flame retardants that harms embryos to a similar formula that decreases sperm production – and then banning that in favor of a chemical called tris, which can cause cancer.

The common thread is our over-reliance on chemicals.

There are non-chemical ways to treat houses for termites, such as heating the infested area to 120 to 150 degrees Fahrenheit for less than an hour.  This leaves no chemical residue, and occupants can return home in eight hours. It’s true that heat and other treatments are more expensive – but as Jonathan Evans of CBD told The Guardian, they are “certainly less costly than climate change.”

  • Bill Walker has more than 40 years of experience as a journalist and environmental advocate. He lives in California’s San Joaquin Valley.