It seems most likely that someone in the supply chain is adding this to attempt harm reduction, it has been studied in rats and showed some positive effects.
One example: "Effect of administration of the nicotinic acetylcholine receptor antagonist BTMPS, during nicotine self-administration, on lever responding induced by context long after withdrawal" https://pubmed.ncbi.nlm.nih.gov/19772864/
Also the dose they're actually detecting is tiny.
You probably inadvertently ingested more actual plastic today than a drug user would ingest from this.
This article like so many is being written in a way that is designed to incite fear instead of being informative or curious.
>As much as half of the fentanyl sold on Philly’s streets contains an industrial chemical used in plastics manufacturing.
I believe this is an entirely factual statement but the impression it will give nearly every reader is highly manipulative and false. The first sentence of the article.
The more interesting question is who is doing this and why, is some illicit drug manufacturer trying to make their drugs less dangerous? Could this be some clandestine "adulteration" of the drug supply to make it safer or less addictive?