Miasma

Definition: a foul smell or environment, once thought to be the source of disease.

Why I Looked It Up

I knew “miasma” from a book I read about a cholera epidemic in London which gave birth to the bacteria theory of disease and started to dispel notions of miasma.

However, I found the adjective form in a book about India in the early 20th century.

While you are [at a party], you forget the great, seething, miasmic city behind you.

Postscript

I was reading The Covenant, and found this:

[…] they would meet him at the railway station in central Johannesburg, and when they did they led him into a miasma of urban horror.

Again, it’s being used to describe an unpleasant urban environment.