That was the difficulty with DNA: how do you make that control if everything is contaminated and minor variations in protocol (like wafting your hands over the samples one too many times) changes the baseline?

It took years to figure out proper methods and many subfields have their own adjusted procedures and sometimes even statistical models. At least with DNA you could denature it very effectively, I’m not sure how they’re going to figure out the contamination issue with microplastics.