The characters of plastics (2024)

"Modern nonstick pans are often regarded with suspicion; but the old mainstay in that department, cast iron, gets its nonstickness by being “seasoned”: coated with a layer of burnt, polymerized oil, no doubt containing many carcinogens." - interesting, I hadn't thought of it that way. Still I won't get any more PTFE pans

Properly cleaning the white residue that builds up on some plastics (game pads, cameras from the 80s onwards) is still an open problem in conservation and restoration circles. You can remove it with some solvents (isopropyl alcohol, lighter fluid) but they may "pull" whatever that white stuff is faster afterwards, worsening the degradation.

If it's PP, it's probably just talc or a slip agent such as erucamide or oleamide. They migrate over time.

When heated it de-polymerizes and gives off styrene, which has a distinctive acrid smell.

That sounds like the styrene itself is decomposing into something else; but most descriptions of its smell (and what I'd also describe it as) are "sweet and flowery", not surprising given what it was originally isolated from: https://en.wikipedia.org/wiki/Styrene#Natural_occurrence