Though PFOS and PFOA can occur in water repellents as
impurities or by-products of degradation, most water repellents
on the market today are PFOS-free. There also are some “PFOAfree”
water repellents made with perfluorinated molecules that
have shorter carbon chains than the 8-carbon chain structure
(C8) that is typically used. The benefit? By-products from shorterchain
compounds also have shorter chains, and break down faster
in the environment than PFOA. Unfortunately, the shorter-chain
structure also tends to perform less effectively in repellency tests.