(Bloomberg) -- Drive up to any gas pump in Cambridge, Massachusetts, and you’ll see a yellow label slightly bigger than a greeting card. In red lettering, it tells drivers, “WARNING: Burning Gasoline, Diesel and Ethanol has major consequences on human health and on the environment including contributing to climate change.”The labels are the first of their kind in the United States, and have been in place since early 2021, with one upgrade this spring to incorporate larger lettering and an updated ordinance number. The Cambridge City Council first mandated gas warnings at self-serve pumps, and later expanded the mandate to full-service gas stations. The progressive city is home to Harvard University and the Massachusetts Institute of Technology.

“The fight to reverse climate change requires that everyone take action to change their behavior,” the council noted in its policy order for the labels, “and the City must underscore the fact that each individual’s behavior can make an impact on the environment and on public health.”Transportation is the sector with the biggest greenhouse gas footprint in the US, and driving cars and trucks makes up a lion’s share of those emissions, according to Environmental Protection Agency data from 2020. That means weaning drivers off of gas-powered cars will be critical for the clean-energy transition needed to fight climate change. And while the increasing availability and affordability of electric alternatives will help, so too might reminding drivers of the climate stakes at the pumps.

“It’s relatively easy to do,” said Patricia Nolan, the Cambridge City Council member sponsoring the labeling effort. “I don’t understand why it hasn’t taken off.”

How to warn people at the pump

Robert Shirkey was one of the first people to propose putting climate warning labels on gas pumps. In the summer of 2010, he was stuck in traffic on a major Toronto highway, listening to people call into a radio show and lambaste BP for its disastrous Deepwater Horizon spill in the Gulf of Mexico.

“It dawned on me,” Shirkey said, “[that] the only reason BP was there drilling however far deep down into the ocean for fossil fuels is because here I am on this highway consuming this product.” In 2013, he launched the Canadian nonprofit Our Horizons (the name is a play on the oil spill) to get climate warning labels on gas pumps. 

North Vancouver ended up agreeing to the idea first, and in 2016 became the first Canadian city to put climate labels on its pumps. But local officials opted not to go with a graphic warning about climate change proposed by activists and instead chose a label that the energy industry helped design. The word “warning” doesn’t appear. Instead, the labels state “Reducing Emissions Help Fight Climate Change” and also offer tips on how to do so through things like maintaining tire pressure and not idling your car. “I’d call it cowardice,” said Shirkey. “[North Vancouver officials] kind of caved to industry.” 

British Columbia’s City of Terrace adopted similar labels in 2017, but the campaign didn’t last. Around this time, the oil industry was also fighting off proposals for warning labels on the West Coast. “It’s been debated by the city of San Francisco and Berkeley and Santa Monica and Seattle,” said activist James Brooks, who started on the issue as a member of the green group 350 Bay Area and  kept with it after moving  to Hawaii. “It didn’t go anywhere because of fears of constitutionality.” Indeed, in 2015 oil industry trade group Western States Petroleum referred to gas pump labels as “the type of forced speech that the United States Supreme Court has ruled is absolutely unconstitutional.”

Since passing in Cambridge, where they have yet to face any industry or legal challenges, the labels have been tentatively discussed by governments in Newton, Massachusetts, and in Hawaii. But across the Atlantic, things have moved much faster. In Sweden, a campaign to put climate labels on gas pumps launched in 2013 and was passed by parliament in 2018. Now color-coded labels can be found in most fueling stations across the country; they compare the carbon intensity of fossil fuels, biodiesel, and electric vehicle chargers.

Do gas pump labels work?

Brooks said the biggest obstacle to wider implementation of gas pump labels may not be resistance, but fear — “that we’re going to do this and then it won’t be effective.” 

Cambridge’s Nolan conceded that the city isn’t tracking whether the labels are working, and has no idea if they are. Nor has there been much research into labeling efficacy overall. Brooks last year published a paper along with Kristie Ebi, a climate health expert at the University of Washington, that involved a literature review of label studies. It concluded climate warnings like the one in Massachusetts had the potential to shift public opinion in support of climate-friendly solutions.

Perhaps the closest parallel are the warning labels on cigarettes; but even there, the effectiveness remains unclear. “Do the warnings on cigarette packs actually prevent people from smoking? We don’t know,” Nolan said. For her, the point of the gas labels is “educating the public. The science is very clear: burning gasoline hurts people’s health and the environment.”

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