Two or three dozen times each winter, plow trucks head out onto Maine’s highways and byways to remove snow from the pavement and throw down sand, salt and chemical mixes to try to make it safer and easier for drivers.

The billion pounds of the stuff dumped on Maine roads each winter manage to melt away much of the white stuff, but not without imposing hidden costs that affect everything from the lifespan of cars to the possible extinction of some aquatic life.

The most talked-about result of all that salt — sodium, calcium or magnesium chloride — is that it tends to munch metal. They don’t call the Northeast and Midwest the Rust Belt for nothing.

Between the salty winds off the ocean and the harsh, frigid months when tourists are scarce, Maine gets a double dose of the corrosion that can eat away everything from brake lines to bridge supports. Here, at least, rust never sleeps.

Some worry the slushy salt the state sprays on its roads before and during snowstorms to combat ice may be contributing to the speed in which steel gives way over time.

Most controversial is the use of liquid calcium or magnesium, which many in the car repair field say is making a bad situation worse.

“It sticks to everything,” said Sherry Lavoie, the location manager for Moody’s Collision & Auto Body Repair Center in Lewiston.

She said rust “has always been an issue,” but the new liquids being used on icy roads have “definitely sped up the rust process,” in part because people don’t wash them off after driving through wintry conditions.

“When you leave that stuff on your vehicle,” Lavoie said, “it rusts.”

She said, though, that despite the damage it can do, there’s no doubt the anti-icing chemicals leave roads “a lot better” for traveling in the snow.

The statistics back her up.

SALTY ROADS, SAFER ROADS

A 2010 study by the Margaret Chase Smith Policy Center at the University of Maine, which remains the most comprehensive look at anti-icing issues, found that improved road clearing in the winter led to greater mobility for Mainers and “significantly fewer crashes.”

Years ago, crews would plow and sand during storms, often leaving behind packed snow that bonded to the roads for days. New Hampshire got the idea of adding salt to the equation in 1938 and other states, including Maine, quickly followed.

The next big change came after the turn of the century when Maine shifted to more salt and less sand.

In the 1990s, it used 455,000 cubic yards of sand in an average winter, but soon sliced that to less than 25,000 cubic yards in a bid to help the environment, save money and clear the roads more. In its place, the state relied on liquid salts to tackle ice better, particularly since rock salt doesn’t melt much once temperatures get below 15 degrees.

By spreading the new mixes early on in a storm, crews normally can prevent snow and ice from adhering to the pavement so that roads are wide open much more quickly.

Because that’s done, the study said, there’s been a significant reduction in the number of fatalities during winter months on state highways, something that didn’t hold true for town and city roads, where municipal crews more often stick with rock salt and sand.

In a typical year, the state puts down 115,000 cubic yards of rock salt, 3,000 cubic yards of salt brine, 690 cubic yards of liquid magnesium and 1,700 cubic yards of a brine and liquid magnesium blend. In short, a lot of salt.

The Maine Department of Transportation readily admits the chlorides it uses “accelerate corrosion on most bare metals,” but isn’t as convinced as some that rust has become a bigger problem in recent years because of liquid calcium or magnesium chlorides.

The University of Maine study acknowledged that corrosion from deicing salts is widespread and costly. By increasing the number of “freeze-thaw cycles,” it likely accelerates the deterioration of concrete and pavement as well.

“Abundant anecdotal evidence in Maine tells us that vehicle corrosion on cars and trucks is more prevalent than a decade ago,” it said, affecting family vehicles, commercial fleets, school buses and government-owned road equipment.

“Bridges are subject to corrosion from road salts through impacts on exposed steel, concrete and the steel reinforcing within concrete,” it said.

It found, though, that “all chloride salts contribute to corrosion” and “none is consistently shown to cause more corrosion than another in actual field conditions.”

The study said it’s impossible to rank the salt options by risk because there are too many variables, including the reality that each may be worse for some things than others.

In a written overview of the issue, the state transportation department said sodium chloride, normally called rock salt, remains by far its most commonly used material to tackle snow and ice.

Liquid calcium or magnesium chlorides are merely supplements used during cold storms to wet down the roads, typically at a rate of about two gallons per mile.

To combat corrosion, the state pays 40 cents a gallon extra to add rust inhibitors that are designed to make the briny mix no worse than distilled water.

The transportation department uses a product called Magic Minus Zero that bills itself as an environmentally friendly magnesium chloride blend. The department hasn’t used straight calcium chloride in a dozen years.

But if the new liquid salts are not causing the additional corrosion that anecdotal evidence suggests, what is?

Though state officials stop short of blaming automobile manufacturers for what some think is a growing rust problem, the department pointed out that car makers stopped using a chemical called hexavalent chromium that used to serve as an effective corrosion coating. That’s a result of stiff environmental regulations, mostly in Europe, that bar the material because it contributes to lead and heavy metals in the water.

The department also said that some of the perceived increase in rust issues with vehicles is the result of stricter inspection laws for cars and trucks. It said mechanics who work on them say they see corrosion today that won’t pass under current standards that would have been allowed in years past.

RUST IS ONLY ONE ISSUE

In addition to the rust problem, there is growing research indicating many of America’s freshwater lakes are endangered by their increasing saltiness, the result of road salts flowing off nearby asphalt.

Those salts “are becoming an environmental contaminant,” said Hilary Dugan, a professor at the University of Wisconsin.

Dugan led a study this year that found nearly 8,000 freshwater lakes “may be at risk for elevated chloride concentrations” and that some may receive so much salt in the decades to come that it could kill some native species.

She said cities and states have been “heavily salting our roads for half a century now,” but only recently has the scientific community begun to focus on the problems that is creating.

Whether there’s too much salt in Maine lakes isn’t a new issue.

Donald Mairs wrote a scientific paper on “Chloride Distribution in Maine Lakes” 50 years ago for a journal put out by the American Geophysical Union that found higher salt levels in lakes closer to the coast, where more people lived.

It suggested the possibility that “highway salting in winter may affect surface chloride levels in Maine lakes.”

Dugan said the reality is that people want to build roads beside lakes. Bigger lakes with fewer people suffer least, she said, while smaller ones surrounded by lots of people are in particular trouble.

She said the tons of salt dumped on northern roads wash off into nearby soils and ultimately make their way into streams and lakes, some of which are seeing background levels of salts 100 times what they used to be.

The growing salinity of lakes is “probably hurting endemic species” and giving a leg up to nonnative invasive ones that originate in places with more brackish water than the pure freshwater lakes that stretch from Minnesota to New Brunswick, Canada, Dugan said.

“We’re just stressing species more and more,” she said.

There isn’t any one level at which the salt content is too high, Dugan said, because different species have more or less ability to cope.

Experts who have started looking into the issue say fish are generally more tolerant than invertebrates and microorganisms. But, of course, fish may get clobbered if the food they eat begins to vanish.

Every winter, road salts wind up contaminating some drinking wells, too, so it’s not just wildlife that winds up short of fresh water.

Experts cited in the University of Maine study said salt’s impact can be seen on trees and vegetation along the roads as well.

All that salt “can cause severe injury to the flowering, seeds, germination, roots, and stems of roadside plant species” when it comes in contact with roots and leaves, the study said.

Conifers such as pine trees are among the most sensitive to salt, which retards their growth and discolors their needles, researchers have found. A University of Washington scientist discovered that exposure to deicing chemicals killed each of the four types of trees in his experiment.

But that’s a small problem compared to salt’s impact on waterways.

One good thing about salt, Dugan said, is that it dissolves in water — unlike, say, a heavy metal such as mercury — so if people cut back on salt use, the chlorides will eventually be flushed out of the ecosystem.

But even in the best-case scenario, she said, it will take decades to lower the levels given how much salt is already piled up in the soil surrounding America’s roads.

Dugan said the growing use of brine mixtures actually helps, because crews put down less salt since the sticky mix adheres to the surface better than salt alone. She said today’s trucks are also generally calibrated better to spread less as they go along.

WHAT CAN YOU DO?

When it comes to reducing corrosion, rinsing is one of the few options.

State vehicles that are washed and used regularly during the winter “generally seem to have fewer issues” with corrosion, the transportation department said.

Those used only during storms and then parked until the next one “seem to fare the worst.”

Other experts said vehicles that are parked in warm garages appear to rust the fastest. That’s been a particular problem for firetrucks in New England.

Dugan also urged everyone to use less salt. She said people tend to put far more down on sidewalks, driveways and parking lots than is necessary or even helpful.

“They actually make up a huge percentage of the road salt that gets put down,” she said, and reducing it would help save threatened bodies of water.

scollins@sunjournal.com

A Lewiston Public Works truck lays down salt and sand as it makes its way up Pine Street in Lewiston during a past storm. (Sun Journal file photo)

Annual snow removal costs for Maine Department of Transportation. Quantities are for cubic yards.

Al Nadeau waits in his Lewiston Public Works sanding truck at the Operations Center in Lewiston in this 2014 Sun Journal file photo. (Sun Journal file photo)

Al Spencer dumps a load of sand into a plow truck at the Auburn Public Works garage in this Sun Journal file photo. (Sun Journal file photo)

Auburn Public Works plow truck poses for a photo. (Andree Kehn/Sun Journal)