Since this article is specifically about pm 2.5, I’m going to chime in and say I have a gas range with no extractor, and the only time my pm2.5 sensor picks anything up is when frying generates smoke and oil aerosols. That’s more a function of cooking temperature than fuel, and my induction hotplate will generate just as much.

CO2? Definitely more with gas. Trace chemicals? Probably more with gas, but all the studies I’ve seen are just about running the cooktop, with no food, in a sealed room. Run the extraction hood or open a window when you cook - it’s not just heat source.