Because of the name of this thread, there's one warning I feel compelled to throw in here: Neither of these tablets 'purify' water, they only 'disinfect' it to some degree.
I get what you are saying about chemical contamination, but I wanted to point out that in most of the reading I've done, mostly in the context of backcountry water treatment, I've noticed the term purification is usually applied to solutions capable of rendering water safe from viruses in addition to protozoa & bacteria. See
this article for an example of this usage of the term.
For example SteriPens (UV), the MSR Purifier System (filter + chemical) and AquaTabs (chemical) are all considered purifiers in this context (as a side note, the full product name of the latter is actually Aquatabs Water Purification Tablets).
I've never noticed any the products I've looked at marketing themselves as rendering water safe from industrial pollutants, but really they are are geared for primarily for backcountry use. Frankly, based on the product information and other reading I've done I don't know which, if any, solutions would be a good defence against industrial or chemical contamination.
As a side note, I've found the following chart (taken from the article I linked to above) helpful:
