It has been noted for many years that Asian women appear to be particularly predisposed to lung cancer despite a low frequency of smoking. Many of the series from resected NSCLC series have never-smoker rates of 30-50%, with the majority of these never-smokers as women. As we've struggled to understand and explain risks, hormonal differences between men and women have emerged as a possibility, as has genetic differences. One other idea that has been the subject of several studies is that exposure to fumes from cooking oils at a high heat, such as wok cooking, may expose Asian never-smoking women to a mutagenic toxin that could explain some of the high incidence of lung cancer among Asian never-smokers.

Several aspects of cooking may be relevant, including the method, such as deep frying vs. stir frying, as well as the question of whether fume extractors were present, and the number of years that a person has been cooking and therefore potentially exposed. There are also many limitations to these studies, because they tend to be retrospective reviews of patients with lung cancer that are compared to prior exposure of similar patients (age, sex, socioeconomic status, etc.), called a case-control study. There is a risk of recall bias, in which someone now with lung cancer is likely more likely to remember some remote exposure to a potential toxin than a random happy and health person now challenged to think of some prior exposure to some questionable toxin. Also, because this is an observational study of outcomes for real people interacting in many complex ways, there could be confounding variables that make it possible that some variable not related directly to cooking but potentially traveling with exposure to cooking fumes -- perhaps exposure to toxic dishwasher detergent (I doubt it, but who knows?).

One interesting study, for instance, looked at exposures of 672 Chinese women with lung cancer (among whom 65% were never-smokers) compared with 735 control women without lung cancer (abstract here). Although there were many factors that could be relevant, including a history of TB or other lung diseases, and also late menopause, there was a considerably higher risk of lung cancer associated with exposure to cooking with high heat cooking oil; rapeseed oil was identified in particular, and it is used at a high heat that can produce toxic fumes (abstract here). Stir frying 30 or more dishes per week was also associated with a 2.6 higher risk of developing lung cancer than in people who did not stir fry frequently. In fact, other case-control studies have also identified cooking oils as a risk , particularly in Chinese women (abstracts here and here).

It's not really possible to measure exposure to toxic fumes from cooking, and something like this is definitely subject to recall bias. In Seattle, I see a rather large proportion of Asian never-smoking women with lung cancer. A few have stood out in my mind as supporting the role of cooking fumes -- young women who have worked as wok cooks, or otherwise in a restaurant -- but this only applies to perhaps a couple of the 60-80 Asian never-smoking women with lung cancer I've treated over the last 5 years. It may be a component, but I doubt it provides a major explanation for most of the cases of lung cancer in never-smoking women, Asian or of other races. However, if you are a never-smoker with lung cancer and have a significant exposure to high heat cooking oils, please leave a comment. It may be a more common direct link than I've been able to discern.