The magnesium chloride ice melt (which contains other compounds too) has lower toxicity than sodium chloride. That is particularly important for plants and pets.
Rust inhibitors were things in road salt spreads in the past, but it is found that they can be very harmful to aquatic life ( https://onepetro.org/NACECORR/proceedings-abstract/CORR96/Al... ) so now they're generally not used ( https://www.cga.ct.gov/2014/rpt/2014-R-0001.htm )