Prof Roy Harrison, Professor of Environmental Health, Birmingham University, said:

"There are no big surprises in this work. Cooking, and especially frying, have long been known to be a source of carcinogenic chemicals and ultrafine particles. The health consequences (if any) remain uncertain."

Dr Deborah Jarvis, who works at the National Heart and Lung Institute and within the MRC-HPA Centre for Environment and Health, based at Imperial College London, said:

"There have been large scale studies to see whether people who cook with gas have more breathing problems - such as coughs, infections and asthma - than those who cook with electricity. Results from these studies are inconsistent. This new study may help us understand why these inconsistencies occur. The public health message to the general public remains the same – keep your kitchen well-ventilated when cooking, and make sure all your gas appliances are well maintained."