Just the wells themselves are prone to leaking lots of toxic gases, and a lot of the modern extraction procedures have additional risks too.

https://www.latimes.com/environment/story/2020-03-05/deserte...

Modern epidemiology also enables really accurate tracking of the increase in asthma and other health problems near wells:

https://www.usnews.com/news/cities/articles/2021-06-02/urban...