actually, there is more care taken in that. slowly poisoning resilient humans is not detectable for some time, maybe even decades, so its easy to get away with it and cover your tracks. however, you know if a cleaner works immediately or if it has a different action like staining what youre cleaning or breaking it down, etc. chemistry is more exacting than biology. thats why a chemical certified ACS (american chemical society) is guaranteed to have half or less of the contaminants than USP(united states pharmecopia) certified specifically for human consumption.