(British Medical Journal: Occupational & Environmental Medicine) Experiments showed that substantial concentrations of nitrogen oxides were generated during cooking on gas, more so than with electric stoves. The study concluded that cooking in a poorly ventilated kitchen may give rise to potentially toxic concentrations of particles and that very high concentrations nitrogen oxides may be generated by gas cooking.
Dennekamp M, Howarth S, Dick CAJ, et al (2001) Ultrafine particles and nitrogen oxides generated by gas and electric cooking Occupational and Environmental Medicine; 58:511-516. https://oem.bmj.com/content/58/8/511.short