There is a bill currently in the CA legislature on the topic of polyester microfibers. They have proposed legislation mandating by 2020 that garments with 50% or more polyester or other synthetic fiber warn you to wash them by hand and not wash them by machine.
This is on the heels of studies indicating that the combination of polyester and washing machines is particularly damaging to the environment and that microfibers are pervasive and harmful to aquatic life in and around the US. You can read about it in this Patagonia article or this article in the Guardian.
You can see a copy of the bill here.
and here it is:
The people of the State of California do enact as follows:
(a) The Legislature finds and declares all of the following:
Chapter 6 (commencing with Section 42368) is added to Part 3 of Division 30 of the Public Resources Code, to read:
CHAPTER 6. Microfiber Pollution Education and Reduction
For purposes of this chapter, the following definitions apply:
(a) Clothing made from fabric that is more than 50 percent polyester shall bear a conspicuous label that states: “This garment sheds plastic microfibers when washed. Hand washing recommended.”