If that's the case, you have much bigger problems. Time to get your water tested.
The acidity of the water combined with the strong sun light, might be responsible for conditions that favor embedding of fine, fine particles. But yeah,
with people setting their well water on fire and such, I'd be worried there's some sort of solvent chemical or something in there too. Maybe some fuel station(s) have leaky tank(s).
Yeah the EPA has been underfunded, undermanned and virtually toothless in many cases. The companies know this and some take advantage to save a buck at the workers and communities' expense. But that's okay because we have an affordable health care system that will take care of us. Oh wait...
Like engine oil analysis, there are labs that test water samples sent to them. However I don't think it's as simple as testing a water sample and magically getting each and every foreign component. There are specific tests for specific contaminants and if you don't run that test, you don't necessarily find that contaminant. So they have to know what they're looking for; and it can get expensive to run a great many different tests.