Mostly I just work in a well ventilated area. Oh and for sure disconnect power before desoldering anything.

Other than that, I avoid taking apart microwaves (beryllium, high voltage), anything with a CRT (imploding glass, high voltage), and high voltage transformers (transformer oil, high voltage). Also any medical equipment (chemical hazard, radiation hazards, biohazard, high voltage, imploding glass). Oh and no unexploded munitions for reasons that should be obvious (people still salvage these in my country and it sometimes doesn’t end well).

I find a hot air rework station+tweezers a much faster way to salvage than jamming a hot iron into boards. Also lets you salvage SMT components, which are most of the better parts these days. For 1970s stuff, it’s mostly through-hole, I’d test the parts before trying to reuse them. Capacitors especially. Got to love those big transistors from our side of the Iron Curtain though.

Some old electronics use asbestos in heating elements or for shielding. Be careful when dealing with old hair dryers, coffee makers, stoves etc.

I don’t see how there could be any in your tape recorder though. It’s just what came to my mind when I read the title.

There is the old thermal paste made of Beryllium oxide. Best not to eat it.

Discharge capacitors before fucking with them.

Any bubbled up and leaking condenser may be acidic, don’t touch it.

Soldering fumes are bad.

That’s all I can think of.