Average lifespan differs by up to 19 years between suburbs in Sydney

This is not really a surprise, public health varies greatly even within one country/city. In the UK, there is a similar phenomenon between certain areas of Glasgow and the rest of the country / continent, it is called the "Glasgow effect" [1]. Although the gap is not as wide, "only" 7 years, it is explained by poverty, unbalanced population, low-quality estate and pollution.

[1] https://en.wikipedia.org/wiki/Glasgow_effect