The article was doing so well until the conclusion.

> Does this rule out the idea of contaminants? No. Even if it’s 97% pure d-meth, there could be something very nasty lurking in that last 3%. But I don’t see the need for such an explanation. We know there are many more heavy users, so there’s no need to go beyond the idea that quantity has a quality all its own.

It's fine if the author finds it an uninteresting problem because the probable answer is staring us in the face, but still, he only has a plausible hypothesis.

If Sam Quinones is correct in that there is a fundamental difference in meth then and now that is causing major issues for addicts, it would certainly be in society's interest to figure that out and rectify it.