I was pretty surprised when I found this:
It’s In the Bag! Teenager Wins Science Fair, Solves Massive Environmental Problem

"Daniel Burd, an 11th grader at Waterloo Collegiate Institute, has discovered a way to make plastic bags degrade in as little as three months.."

Genious. Study how nature deals with the problem, isolate the main factors and amplify their effects in a recreated, controlled enviroment.

Now a company can patent the micobes and make us pay for the cleanup

This is rather old, the news is from May 2008.
Although the article is rather sketchy, the species (or rather the genus) used are very well known and studied, so if it was feasible economically to do it, we should be seeing the results of such efforts for a while now.

Note that the problem is just economical. A simple way to get rid of plastic and toxic pollutants is to ship it to the sun, but that's expensive! We already have solutions to many problems, the issue is generally how to do it economically