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Cooking on a gas hob unlikely to increase cancer risk

With proper ventilation, cooking on a gas hob unlikely to increase cancer risk

Don’t panic. Despite this morning’s headlines suggesting that cooking on a gas stove could lead to cancer, it’s not exactly time to abandon your pots and pans or to trade the gas oven in for an electric one.

As we’ll discuss below, this shouldn’t be a problem for anyone with decent ventilation in their kitchen. And even so, the study showed that chemicals given off by cooking on a gas stove fall well below accepted workplace safety limits.

What did the study find?

The research comes from a Norwegian group, who wanted to see if they could detect cancer-causing chemicals in the fumes from frying steaks. They did their experiments in a model, tailored to resemble a typical Western European restaurant kitchen.

They fried 17 steaks, each weighing 400g, for 15 minutes, and measured the chemicals given off within the “breathing zone of the cook”. To cook the steaks, they used either a gas or an electric hob.

They detected a couple of potentially problematic substances including:

  • naphthalene, one of a group of chemicals called “polycyclic aromatic hydrocarbons (PAH) ”that could potentially cause cancer. Napthalene itself is only a “possible” cause of cancer in humans, a conclusion based on “inadequate evidence”
  • several large aldehydes, including some that can damage DNA
  • very small “ultrafine” particles that could damage the lungs if inhaled

Using the gas stove resulted in higher levels of these substances.

But are the levels of these chemicals dangerous?

And that’s where the story ends. This study only measured levels of chemicals. That’s certainly valuable data to have but they tell us nothing about the effect that these chemicals have on the body. It’s not enough to show the presence of substances that have been linked to cancer and conclude that our health is in jeopardy.

The authors say that the accepted safety threshold for PAHs in a workplace is 40 micrograms per square metre. But even frying steaks on a gas hob only produced 0.27 micrograms per square metre – around 150 times below the threshold!

Likewise, the safety threshold for particles in the air is 10 milligrams per metre square, and the gas stove gave off just 7.2.

They authors note that we don’t know the levels at which chemicals like aldehydes would become dangerous to humans.

What have other studies found?

Some studies have tried to compare the risk of cancer, particularly lung cancer, in people exposed to different levels of cooking fumes.

The International Agency for Research into Cancer (IARC) recently reviewed existing studies and concluded that “emissions from high-temperature frying are probably carcinogenic to humans”. IARC classified these emissions in “Group 2A”, their second-highest risk category.

But if you look at the studies themselves, you’ll see that almost all of them have a few things in common:

  • They all come from China, Taiwan or Hong Kong, and most focus on people living in rural communities
  • They’re all very small, typically including a few hundred participants or fewer
  • They’re all ‘case-control studies’, which compare lung cancer patients with healthy people and ask them questions about their exposure to cooking fumes. This type of study is notoriously vulnerable to bias, because it relies on people accurately remembering aspects of their lives that may have happened years ago.

What does this mean?

It is particularly important to note where these studies were carried out. People in the UK aren’t exactly exposed to cooking fumes in the same way that they would be in rural China, where people fry food more often and where ventilation is often poorer. For example, one of the earliest Chinese studies found a higher risk of lung cancer only among women who were stir-frying 30 dishes every week!

The bottom line is that in the UK and other Western countries, it is unlikely that the small fume exposures that people get from cooking in their homes would significantly affect their risk of cancer.

Even though this new study simulated a restaurant kitchen, where cooking fumes are probably at their greatest, most of the dangerous chemicals they identified were found at concentrations well below accepted occupational safety guidelines.

As long as you have a decent extractor fan in place, it shouldn’t be a problem. Good ventilation is particularly important for professional chefs and cooks.

- Ed

Reference: Sjaastad, A., Jorgensen, R., & Svendsen, K. (2010). Exposure to polycyclic aromatic hydrocarbons (PAHs), mutagenic aldehydes and particulate matter during pan frying of beefsteak Occupational and Environmental Medicine DOI: 10.1136/oem.2009.046144

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Comments

Jasmine P, Norwich UK March 1, 2010

I have been trawling the internet for a balanced comment on this research, and am very pleased to have finally found one, as opposed to the sensationalised, scare-mongering stance that seems to have been adopted by most of the media reviewers. For that I thank you.

Ed February 22, 2010

The evidence on cooking fumes and lung cancer, as described above, is based on small case-control studies conducted mainly in one part of the world. The link between passive smoking and lung cancer is a large number of studies (including large cohort studies), conducted in several continents. This far stronger body of evidence made it clear that the introduction of smokefree legislation in workplaces and public places would protect the lives of workers, a move widely backed by the majority of the UK public.

We have never suggested that smokers should not receive medical treatments. In relation to the story on third-hand smoke, we said, “This is an interesting piece of research that adds the possibility of an extra level of harm from tobacco smoke. However, this study doesn’t tell us what threat, if any, third-hand smoke could pose to our health.”

Jonathan Bagley February 22, 2010

Your dismissal of the cancer hazard from cooking fumes is not consistent with other claims made by CRUK.
The studies conducted in China, to which you refer, often find an increase in risk comparable to that claimed for environmental tobacco smoke. Here, you adopt the scientific approach that levels of the suspected carcinogens are well below those considered hazardous, and that adequate ventilation should suffice to make any increase in risk negligible. Yet, when you pronounce on ETS, you give the impression that you agree with the anti-smoking propaganda of the anti-smoking lobbyists, who claim that there is no safe level of ETS and use this to support their campaigns for smoking bans, including a ban on private members’ smoking clubs. I’m assuming you don’t support the relaxation of the smoking ban to allow private smoking clubs; but on what grounds, apart from fascistic or moralising, I don’t know after reading your statement regarding cooking fumes.
Furthermore, last week, you failed to dismiss as ridiculous the claims that so-called third hand smoke can cause an increase in cancer risk. If you had taken the trouble to investigate, you would have found that this is pure nonsense – an invention of the anti-tobacco industry.
By adopting such a non-scientific stance, you are not furthering the cause of your charity. I stopped my donation some time time ago when I heard one of your spokesmen suggest that smokers should not receive certain medical treatments; and I’m sure I’m not alone. Quite often you are now referred to as a “fake charity,” which is a shame.

Tsu Dho Nimh February 19, 2010

I bet they ate the steaks after the experiment.