Melbourne's general aviation airport (i.e. light planes like Cessnas) is Moorabbin, in the south east. The map shows the City of Kingston which contains it with a dark green dot, meaning safe. Planes often do a circuit south and then turn and follow the coast (over my house...) and all those places are shown as safe.

The neighbouring City of Casey to the east is shown as unsafe, but this contains a "noxious industries area". Planes usually take off and land on a roughly north–south alignment because of the prevailing winds.

Only "avgas" which is basically the same stuff we used to put in cars and is running the same sort of engines, a piston engine, driving a propeller roughly the same way your car engine turns the wheels. Most little things, from smaller airports.

JetA, which is basically kerosene (still terrible, don't drink it - but at least it doesn't have lead in it) is used by all the jet engines. That includes lots of things a casual observer wouldn't think of that way. A King Air, or a C-130, they've got propellers, but that's a turboprop engine, the propeller is spinning because there's a turbine behind it, and instead of kicking hot fast air out the back (like an A320) it's using that energy for turning the propeller really fast.

https://en.wikipedia.org/wiki/Turboprop

True, but unless you live really close to a busy airport, I doubt it's an issue. I live fairly close to a rural grass strip that sees moderate use. I have about 40ppm which is 10x less than the allowed limit for crops.

It sounds like accumulation from lead based paint and leaded car gas is the issue in the article. Which makes sense since you generally can't fly low over cities anyways (disperses) and small planes are not huge emitters (low in numbers).