Our paving proclivities have many well-known deleterious effects on our environment (urban heat island, capping off aquifer recharge areas, energy intensive construction, car promotion, ugly places, etc). Direct health effects on humans can be somewhat difficult to establish (e.g., high correlation between chronic diseases and car-mandatory, over-paved places, but direct causal links sometimes too diffuse to nail down).

But one emerging health threat might end up being the biggest direct killer of them all:  Road salt in drinking water (You didn’t think the salt just magically disappeared come March, did you?). The New York Times just published an article about the mounting scientific & public health concerns about salt in our diets vis-a-vis hypertension.

And think about it: the more the city paves, the more it must de-ice. And that means more road salt forevermore.

And that salt does eventually make its way into our drinking water.

Though road salt was never mentioned in that NYT article as a possible culprit, hydrogeologists and water utility operators in the US and Canada have been alerting us to the rising levels of NaCl in our drinking water sources for some time. This 2001 article from Stormwater: The Journal for Surface Water Professionals surveyed studies from across the US and Canada about road de-icing practices and the resulting build up of NaCl in drinking water supplies. They came to this conclusion:

Applying road salt in deicing operations could create significant adverse health, environmental, and infrastructure problems. Equally troubling is the fact that New York State applies up to 298 tons of road salt/lane-mi./yr. in the unfiltered drinking-water—supply watersheds for more than 9 million citizens. This level of salt use jeopardizes the health of consumers having heart or kidney disease, destroys protective vegetation and soil, and corrodes automobiles, bridges, and other infrastructure.

Apparently Canada has even declared road salt a toxic substance for the very same reasons:

Based on the available data, it is considered that road salts that contain inorganic chloride salts with or without ferrocyanide salts are entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity or that constitute or may constitute a danger to the environment on which life depends. Therefore, it is concluded that road salts that contain inorganic chloride salts with or without ferrocyanide salts are “toxic” as defined in Section 64 of the Canadian Environmental Protection Act, 1999 (CEPA 1999).

Wow. And according to that same Health Canada report, here’s how it happens:

Road salts enter the Canadian environment through their storage and use and through disposal of snow cleared from roadways. Road salts enter surface water, soil and groundwater after snowmelt and are dispersed through the air by splashing and spray from vehicles and as windborne powder. Chloride ions are conservative, moving with water without being retarded or lost. Accordingly, all chloride ions that enter the soil and groundwater can ultimately be expected to reach surface water; it may take from a few years to several decades or more for steady-state groundwater concentrations to be reached. Because of the widespread dispersal of road salts through the environment, environmental concerns can be associated with most environmental compartments.

So we won’t experience the full effect of Mayor Pave’s paving spree on our heart health for a few years, though we do know that salt concentrations in Wisconsin’s drinking water have been going up right along with increased salt applications.

The [US Geological Survey] study found the rising levels were consistent over the past two decades with more use of road salt and the expansion of road networks and parking lots that get deicing.

More paving = More salt.

More salt = Decreased heart health.

How many reasons do we need to scale back the paving?