[Doe Eyes]

that’s why roads are deiced with mixtures of various salts.

And they use ethylene glycol on aircraft because salt is to corrosive.

[null and void]

Yes, ethylene glycol, and its proper disposal are expensive, worth it for a multimillion dollar aircraft deiced in a controlled area. It's prohibitively expensive over thousands of miles of roads and bridges. Salts, whether sodium, potassium or calcium based, are much cheaper and relatively benign.

Environmentally, pouring ethylene glycol onto a bridge and allowing it to run off untreated into a river would be a non-starter.

(Although 50 years ago, they might have thought that a flowing river would dilute it to safe levels.)