[00N8]

In terms of microplastics, I would think 100 of the old flimsy single use bags would be much worse than 5 reusable plastic bags, even if the total mass is the same. The heavier reusables have less surface area per mass, so they'll be degraded more slowly by the sun. They also are less easily blown by the wind, so it's more likely someone will dispose of them properly or that they'll naturally end up buried somewhere that does a better job of containing the eventual microplastics. Fewer bags in total would probably be better for sea turtles than thinner bags as well.

I'm not sure if that makes the reusables better overall, but I don't think we can say they're 10-100x worse based on weight alone.

[kragen]

I agree with most of your comment, except that microplastics come from paint, tires, and washing synthetic garments, not plastic bags, and I'm dubious about your photodegradation point.