The question was how to reduce your exposure, not eliminate it. Of course you can't be 100% clean from microplastics, but why not do what you can given what we currently know?
Yes, freeways are major sources of microplastics and yes, I drive on a major freeway daily. That's why I suggested getting a HEPA filter for your car. Does it make a huge difference? Probably not, but the cost of doing so is also very low.
Some studies suggest that indoor air can contain more microplastics than outdoor air [1]. I doubt this is true in busy metropolitan areas, but the point is that indoor air matters. If you're spending half of your time at home, why not get an air purifier and run it when you sleep?
All of the things I listed are small steps you can take to manage your long-term exposure. Even if it's only by a few percent, the cost of getting an air or water purifier is relatively lower. Like I said, we'd need top-down legislation changes to really reduce the presence of microplastics everywhere.
It seems like you agree that this is a problem, so what are you proposing we do?
do you go outside? cars on pavement roadways are one of the biggest sources of microplastics.
do you buy prepackaged food/drinks/groceries?
do you eat out?