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Cancer risks of cooking on a gas hob overplayed

Posted Feb 18 2010 12:00am
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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