I don't know the numbers, but the premise here is not (a) that gas is bad or that (b) cooking releases particulate, but rather that gas stoves are actually constantly leaking very small amounts of particulate that in aggregate can cause harm along the same lines of other sources of PM2.5 pollution.
https://80000hours.org/ (conceptually related to GiveWell) can help you figure out ways to use your career to do good, aside from simply earning a lot and donating. They also do free 1:1 coaching along these lines.