Asthma and Gas Stoves - What You Need to Know
Cooking with gas might be a fun way of saying you’ve achieved something, but did you know that 12 per cent of childhood asthma in Australia can be attributed to gas stoves? And that Australia’s prevalence of asthma is among the highest in the world, with 1 in 10 people having it?
Researchers from the University of Queensland published a study in the Medical Journal of Australia which used statistical analysis to predict the association of gas stoves and asthma. Nearly 13,000 households were used in the study which highlighted the effects of the by-products from gas cooking.
How do we get these by-products exactly? It’s simply a result of how gas stoves work!
This doesn’t mean we need to rush out and replace all gas stoves with electric ones to reduce exposure to gas stoves, necessarily. But more on that later – first we need to understand how gas stoves work in the first place to understand their impact on asthma symptoms.
How does a gas stove work?
The main components of a gas stovetop include the burner assembly and a small gas valve connected to your main gas line. When you turn the knob of your gas stove on, the valve opens and natural gas flows through.
The gas enters into a wide tube which becomes more narrow and increases the pressure of the gas. It follows through to a wider tube which causes the pressure to drop quickly, in effect sucking oxygen into the tube.
Oxygen mixing with the gas makes the perfect mixture to create a flame. This mixture flows into the burner and is lit from a pilot light or igniter. This creates the flame we all know and love for gas cooking. The chemical reaction of combusting the gas and oxygen produces carbon dioxide and water vapour, along with a few by-products.
By-Products of Combustion of Natural Gas
Despite being the cleanest burning fossil fuel available to us, natural gas still produces a range of by-products aside from carbon dioxide and water:
- Nitrogen oxides
- Carbon monoxide
- Sulphur dioxide
Very small soot particles can also be produced in the process of natural gas combustion. The worse ones are particulate matter smaller than 2.5 micrometres, also called PM2.5.
Gas Stove Health Effects on Childhood Asthma
Nearly 40 per cent of Australian homes have gas stoves and it is natural gas for stovetop cooking that is being attributed to 12 per cent of childhood asthma in Australia. With children spending up to three-quarters of their lives indoors, what are the asthma risks associated with stoves and indoor air quality?
There is a growing body of research showing the negative respiratory health effects of nitrogen oxides such as nitrogen dioxide. One study from 2011 found that high indoor nitrogen dioxide levels resulted in increased asthma symptoms including coughing and wheezing, and resulted in more frequent use of relievers.
Another study compared regular indoor environmental exposures to nitrogen dioxide to that from gas stoves. Their findings suggested that it was the short term increase in nitrogen dioxide associated with gas cooking that increased asthma symptoms rather than a long term exposure at low concentrations.
2.5 micrometres is so small that the human eye can’t even distinguish it. This particulate matter, PM2.5, is known to negatively impact the respiratory health of children and adults alike.
More and more researchers are focusing their efforts on PM2.5 and the risk factors it poses to public health. From overall lung health and increased risk of asthma, PM2.5 has also been linked to poor cardiovascular health and increased inflammation responses – a cause for many asthmatic attacks. Some PM2.5s have even been found to have absorbed into the bloodstream!
Sulphur Dioxide and Carbon Monoxide
More by-products associated with cooking with gas and asthma are sulphur dioxide and carbon monoxide. A study in Italy on adults with asthma found a decreased lung function caused by these by-products. The concentration of these was even within current air quality requirements, making this a concern for public authorities!
Another study demonstrated an increase in asthma exacerbation with increased carbon monoxide among children specifically.
Formaldehyde has been linked to a long list of health problems, one of them being asthma. A study focusing on childhood asthma found that those exposed to higher levels of formaldehyde were 3.5 times more likely to have asthma than those with no exposure.
More studies have also suggested that specifically indoor exposure to formaldehyde can also be attributed to a higher prevalence of childhood asthma.
So all these by-products associated with gas stoves have been quite clearly linked to childhood asthma, surely we should be ripping out all our gas stoves and swapping to an alternative energy source for cooking? Don’t get too ahead of yourself – there’s more to the story.
Gas cookers are only one source of these by-products that we’re exposed to daily. These same by-products are produced by driving a car, bushfires and can even be emitted from your furniture and carpets!
And who’s to say a different energy source won’t have similar emissions? The action of cooking alone can also release these by-products.
Any indoor exposures to these particles can increase the prevalence of asthma in children, not just cooking with gas. While 12 per cent of the burden of childhood asthma in Australia can be attributed to gas stoves, it’s much more complex than it appears on the surface.
What about other gas appliances?
While natural gas used for cooking is getting all the bad rap, what about other gas appliances in your home? Gas combustion is the same chemical reaction regardless of the appliance.
Gas space heaters actually have a very similar nitrogen oxide emission rates compared to gas stoves. Unflued gas heaters can produce more than four times as much nitrogen dioxide than gas stoves!
What about air pollution outside? Similar by-products have been found to be produced from bushfires, cars and even your carpet!
While exposure to gas stoves has been linked to poor respiratory health and childhood asthma in Australia, we also need to consider other gas appliances and their effects too. And we certainly can’t forget about dust mites, dampness, pollen and all the other asthma triggers for children.
How can we reduce this effect?
As complex and challenging it can be to determine the extent of the link between gas stoves and asthma, there is undoubtedly a link. So what are some ways to reduce gas stove exposure and these harmful by-products?
The answer is range hoods!
Range hoods or exhaust fans in the kitchen are specifically designed to remove pollutants and by-products from cooking. Rangehoods can collect upwards of 75 per cent of particles and gases released during cooking when on their high setting and reduce exposure to them in the first place.
Potentially the most important discovery from the Medical Journal of Australia study by the University of Queensland is that the burden of childhood asthma due to gas stoves could be reduced from 12 per cent to 3 per cent if all Australian homes had high-efficiency range hoods installed!
So why is there such a considerably large link between gas stoves and asthma if the solution is so simple? Only 44 per cent of people use their range hoods.
Insulation has gotten increasingly more effective over the years. While your wallet might be happy about that when the energy bill arrives, your home is also more effective at accumulating pollutants associated with gas cookers and much more.
While it might be impractical to install high-efficiency range hoods in every home, we can certainly try to improve its natural ventilation. Whether that’s simply opening a window or using an air conditioner that brings outside air in, we can reduce our exposure to indoor air pollution and gas stove by-products, in effect reducing the burden of childhood asthma.
The best course of action here for parents of children with asthma is to simply become more educated about the risks of poor indoor air quality and actually use our range hoods! As a matter of public health, we need to try and reduce indoor exposure to the use of gas for cooking in Australian homes, in effect decreasing the prevalence of asthma in children.
Published: 28 Jan, 2021