According to OSHA’s guide to stairways and ladders, these following rules apply to all ladders:
Ladder rungs should be resistant to slippery elements in order to prevent accidents; the best way to eliminate slip and fall injuries is to coat the ladder rungs with a slip resistant coating. Slip resistant ladder rungs help provide the foot to surface security needed for workers to perform their jobs with ease.
Employers should make a point to keep their employees safe by incorporating slip resistant ladder rungs into new ladder construction to help keep them on their feet.
OSHA. “Stairways and Ladders. A Guide to OSHA Rules.” http://www.osha.gov/Publications/osha3124.pdf