Every other Friday, the Outside/In team at NHPR answers listener questions about the natural world. This week's question came from Devon in Wyoming:
“When I was out of high school I worked on a summer ski camp on Mount Hood in Oregon. And, in the summer time, to keep the surface of the snow cold enough so we could ski on, we would throw bags of salt onto the snow. And I was thinking that like, multiple years in a row, it had to add up. So I was just wondering what kind of impact that might have had on the surrounding environment."
Our producer Felix Poon looked into it.
Transcript
Felix Poon: Americans use a lot of salt – and not just in the kitchen. If you spend winters in cold parts of the country, you’re probably used to seeing salt on the road to melt ice and snow. In fact 44% of salt consumption in the US is for de-icing roads. When we add road salt, it lowers the freezing point of water. The idea is to prevent ice from forming in the first place. When ski resorts sprinkle salt on the slopes, they’re relying on that same chemistry. Except the idea there is to melt the very top layer of wet snow so it can refreeze into a hard, uniform surface that’s better for skiing. But where does all that salt go?
Sujay Kaushal: Even though we think of it as something that gets dissolved in water and washes away, it actually stays in the environment and sticks around.
Felix Poon: This is Sujay Kaushal, a professor of geology at the University of Maryland. Sujay says we tend to overdo it with road salt, using more than we need.
Sujay Kaushal: If you keep applying salt to an area, it's going to eventually build up in the soils and in the groundwater beneath the soils.
Felix Poon: And that has impacts on plants and wildlife. For example…
Sujay Kaushal: They started finding that there were salt tolerant plants that are in roadside wetlands by highways where they shouldn't be.
Felix Poon: Besides creating opportunities for invasive species to take over, research has found that too much salt can be toxic to fish and other aquatic organisms and plants, and it can mess with the whole food web of an ecosystem. Salt also causes property damage because it corrodes vehicles as well as roads and bridges. Plus there’s the impact on human health.
Sujay Kaushal: It's having a major impact on major drinking water supplies in the United States.
Felix Poon: Hypertension is already a concern for many Americans. And now, drinking water supplies are getting saltier, to the point where people can actually taste it.
Sujay Kaushal: There are drinking water treatment plants on the East coast that do get complaints during the winter months of that salty taste, actually. So people do recognize it. The problem is, is that when there's kind of a creeping normalcy. It's kind of like a lobster in progressively warmer water, you know, it's like it's just used to it and it keeps rising.
Felix Poon: Elevated salt can even cause heavy metals to leach into drinking water. For example in Flint Michigan, lead leached out of city pipes when they switched to a new water supply that had elevated salt levels caused by, you guessed it, road salts. So, with all these environmental and health problems from salting our roads, I asked Sujay if there’s anything else we could use instead.
Sujay Kaushal: There are different alternatives that people have proposed with salt, for example beet juice based deicers, or cheese brines, or beer maybe.
Felix Poon: But don’t go pouring your leftover lager on the street quite yet. The beer deicer is actually an industrial byproduct from brewing beer mixed with salt brine. But, Sujay says, there are so many roads and parking lots, that no matter what we use, it’s going to have an effect on the environment, like toxic algae blooms for example. Plus, in places that have tried out beet juice based deicers, some residents complain about the smell. So, the best way forward, according to Sujay, is to be strategic with salt, and just use less of it, both on our ski slopes and on our roads. Road salt only actually does its job when it's dissolved in water. In other words, if you can still see it after you’ve put it down, you’ve probably used too much.
