The most common road and sidewalk de-icer in use today is rock salt (aka halite, aka sodium chloride). While there are more effective de-icers, NaCl’s predominance is because it’s cheap, which is very relevant at the scale street de-icer is used. It has two primary mechanisms of action: one, the uneven surface increases traction; and two, the freezing point of salt water is -17C (0F) rather than 0C (32F), so at temperatures between -17C and 0C, less ice actually forms.

Salt’s cheapness is extra funny from a historical perspective. Salt was an essential trade good whose importance is clear from the salt mines of Salzburg (literally, “salt castle”) to the Classical Latin noun salarium (literally, “saltiness”), the ancestor of English salary. It’s not just that you will literally die if you don’t eat enough salt; it’s also an important way to preserve food in the millennia before refrigeration.

Salt deficiency’s mechanism of action of causing death turns out to be the same as what you die from if you drink too much water, hyponatremia. Water is the substance with the highest known LD50: an average person has a 50% chance of dying after drinking about 7 liters (2 gallons) of water in one sitting. The least deadly substance known to man is somehow still the cause of most deaths by drowning.