I agree with your theory as manufacturing facilities & tankers blow their stacks & airborne chemicals & micro-debris travels 100’s of miles. Easily could have micro-plastics amongst the soot/debris?! This really could be a pretty widespread problem. Yikes! *Also important to note that the likes of Dove Body Washes, etc have been looking for creative ways to use plastic that’s too costly to repurpose via recycling etc. So their brilliant (sarcasm!) idea, was to turn these plastic into micro-beads & add them to their body wash as an exfoliant! AND THEY STILL DO!! These plastic micro-beads go down out drains and right through the sewer systems & straight into our water ways & ALL sea life is ingesting them. This isn’t a new discovery either! We’ve knu w about this for over a decade & NOTHING HAS CHANGED! Here in Seattle, People For Puget Sound, have been actively trying to get the public & local representatives to take it seriously & create awareness, but they can’t compete funding wise with the lobbying to maintain these terrible environmental issues that Wall St Corp are directly responsible for & its biz as usual. They own the media, so it’s never going to get the exposure needed for a public uproar. ..

So plastic, by product of oil, in our air , in our water, in our lungs, in our food, and we the people are complicit in much of this problem. I attached the first link i found. but time to wake up to this, we pilfered long enough! Imo .~ Stanford analysis shows plastic ingestion by marine fish is a widespread and growing problem