18 months to 10 years, according to the first Google response.

I see no reason regulation to enforce like a 6-month breakdown time on a product. Seems very sensible.

They shouldn't be able to release products that are unhealthy for the environment.

Theoretically biodegradable, but not yet shown to be. As of 2015 the longest measured time was 2 years to break down about 30% of the acetate, with a diminishing breakdown rate and a dependence on soil nitrogen availability (ocean beaches lack it).