Plastic pollution and climate change are orthogonal issues. The latter is much more immediate and serious. The former, we're not even sure how much of an issue is it.
Again: problem with plastic pollution isn't climate-related, it's about (hypothetical! [0]) food chain poisoning. Disposable plastics are just a tiny fraction of petrochemical industry's emissions.
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[0] - That is, we know the compounds get into the food chain, but in most cases we don't know what, if any, negative impact it has on living things.
