This Synthetic Rubber Coating could have been used
to prevent from contamination.
http://www.plastidip.com/home_solutions/Plasti_Dip
i dont know if below statment is true though, because i've never used this staff but looks promising.
.
Plasti Dip is a multi-purpose, air dry, specialty rubber coating. It can be easily applied by dipping, brushing, or spraying. Plasti Dip protective coating is ideal for a broad array of do-it-yourself projects around the home, garage, garden, and elsewhere. It protects coated items against moisture, acids, abrasion, corrosion, and skidding/slipping, and provides a comfortable, controlled grip. Plasti Dip remains flexible and stretchy over time, and will not crack or become brittle in extreme weather conditions. It has been tested and proven in temperatures from -30°F
.