Fresh water is a resource that’s likely to become increasingly scarce in the coming years, even without corporations buying up water supplies. The Great Salt Lake of Utah was already on track to dry up before global warming really got going, simply because of how much water is taken from the rivers that feed into the lake. Add in warmer temperatures, and you have a body of water that’s evaporating much faster than it’s being replenished.

The big danger here is not that people will run out of water, though. It’s worse than that. See, the reason the Great Salt Lake is so salty is that, unlike the Great Lakes further east, it doesn’t drain into the sea. That means that all the minerals carried into it by its tributary rivers just stay there, concentrating as water evaporates, and new minerals arrive. The problem is that sodium chloride isn’t the only mineral that’s been concentrating there over the last 16,000 years or so. There’s also arsenic in the mix, and other toxic chemicals.

In the areas where the lake has already dried, the lakebed is protected from the wind by a crusty layer of salt, but that layer is pretty thin, and once it’s gone, northern Utah starts getting toxic dust storms.

The terror comes from toxins laced in the vast exposed lake bed, such as arsenic, mercury and lead, being picked up by the wind to form poisonous clouds of dust that would swamp the lungs of people in nearby Salt Lake City, where air pollution is often already worse than that of Los Angeles, potentially provoking a myriad of respiratory and cancer-related problems.

This looming scenario, according to Ben Abbott, an ecologist at Brigham Young University, risks “one of the worst environmental disasters in modern US history”, surpassing the partial meltdown of the Three Mile Island nuclear reactor in Pennsylvania in 1979 and acting like a sort of “perpetual Deepwater Horizon blowout”.

Salt Lakers are set to be assailed by a “thick fog of this stuff that’s blowing through, it would be gritty. It would dim the light, it would literally go from day to night and it could absolutely be regular all summer,” said Abbott, who headed a sobering recent study with several dozen other scientists on the “unprecedented danger” posed by lake’s disintegration.

“We could expect to see thousands of excess deaths annually from the increase in air pollution and the collapse of the largest wetland oasis in the intermountain west,” he added.

There is evidence that plumes of toxic dust are already stirring as the exposed salt crust on the lake, which has lost three-quarters of its water and has shriveled by nearly two-thirds in size since the Mormon wagon train first arrived here in the mid-19th century, breaks apart from erosion. Abbott now regularly fields fretful phone calls from people asking if Salt Lake City is safe to live in still, or if their offspring should steer clear of the University of Utah.

“People have seen and realized it’s not hypothetical and that there is a real threat to our entire way of life,” Abbott said. “We are seeing this freight train coming as the lake shrinks. We’re just seeing the front end of it now.” About 2.4 million people, or about 80% of Utah’s population, lives “within a stone’s throw of the lake”, Abbott said. “I mean, they are directly down wind from this. As some people have said, it’s an environmental nuclear bomb.”

I feel like we need metaphors other than nuclear disaster for this sort of thing. I get that radioactive fallout is the go-to way to describe this kind of long-lasting damage to the environment, but I think it’s a bad comparison. The long-term health effects might be similar, but this isn’t an event with lasting effects – it’s just… lasting effects. This is also a problem that is both foreseeable (obviously), and preventable, at least in the short term. Water conservation and finding a water source other than the rivers feeding the lake would allow it to start growing again, and water seems to be an effective “seal” on the nasty stuff. This is a make-or-break moment when it comes to ecosystem services – the water draining into that lake is literally protecting people from taking in poison with every breath.

The Great Salt Lake’s predicament is often compared to that of the dried-up Owens Lake in California, one of the worst sources of dust pollution in the US since the water feeding it was rerouted to Los Angeles more than a century ago. But the sheer heft of the Great Salt Lake, sometimes called ‘America’s Dead Sea’ but in fact four times larger than its counterpart that straddles Israel and Jordan, presages a loss on the scale of the Aral Sea, once the world’s fourth largest lake but strangled to death by Soviet irrigation projects.

The demise of the Aral Sea was dumfounding to many Soviets, who thought it virtually impossible to doom a lake so large just by watering some nearby cotton. “But these systems are actually very, very delicate,” said Abbott, and they can quickly spiral away. The Great Salt Lake, its equilibrium upended by the voracious diversion of water to nourish crops, flush toilets and water lawns and zapped by global heating, could vanish in just five years, a timeline Abbott admits seems “absurd”.

“History won’t have to judge us, not even our kids will have to judge us – we will judge ourselves in short order,” said Erin Mendenhall, the mayor of Salt Lake City, who is now regularly bombarded with questions about the toxic dust cloud from mayors of other cities. “The prognosis isn’t good unless there’s massive action. But we have to start within one year, we have have to take the action now.”

With the climate warming, I have to say I’m worried that letting the rivers flow might not be enough, but there’s no question that it should be done. That, in turn, should be part of a national conversation about water policy. It may be that areas with an over-abundance of water can help to supply those with less (though not for a profit), or it may be that places like Salt Lake City need to be abandoned altogether. Climate change is just one part of it, but we’re rapidly approaching a point where places we’re used to inhabiting will no longer support human life, and I don’t think we’re doing enough to prepare for that.