Cooking can be one of the biggest indoor air quality hazards when proper precautions are not taken. Different cooking methods come along with different degrees of risk. Most of us are aware that burning natural gas to cook indoors will always have a bigger negative impact on air quality than cooking the same thing with an electric stove. Everyone should be cooking healthy food for all of the benefits offered, but there are a few good things to know to be sure your methods aren’t canceling out some of the vitamins and nutrients from your diet.
Fry with caution
When preparing healthy proteins and vegetables, frying on the stove where oil gets very hot releases the most unhealthy particles and gasses. Overheated oil forms toxic gasses and ultrafine particles while it emits those acrid smoke particles covered in free radicals.
A red hot electric burner is over 1,000 °F (540 °C), the flame of a natural gas burner is over 3,000 °F (1650 °C), and even a campfire is around 600 °F (315 °C), so overheated oil is an easy possibility. To examine the effect on air quality, some researchers in China conducted air quality testing when cooking twenty five different dishes with a combination of meat and vegetables. They tried boiling, steaming, deep frying, pan frying, and stir frying.
- Stir frying involves a small amount of oil and heat up to 450 °F (232 °C), and requires an oil with a high smoke point and even more careful attention to not overheating the pan.
- Pan frying uses just enough oil for a layer between the food and the pan, and if one part of the pan gets hotter than the oil’s smoke point, usually over 400 °F (200 °C), the oil will burn and fill the air with unhealthy smoke particles.
- Deep frying submerges the food in oil that is 350–375 °F (177–191 °C), any higher and the oil will start to burn and smoke.
- Boiling involves submerging the food in boiling water, which is always 212 °F or (100 °C).
- Steaming involves putting the food in a basket above boiling water and allowing steam to heat it, which is also no more than 212 °F or (100 °C).
Pan frying and stir frying were about the same in their high likelihood to spread particles and VOCs throughout the cooking space. Deep frying was not good but had a smaller impact, possibly because deep frying oil stays below its smoke point. Deep frying was a lot less likely to produce larger particles, but only somewhat less likely to produce ultrafine particles or the toxic gasses.
Boiling water is not very hot, and there are few particles associated with boiling or steaming, but still much more than when not cooking. Ultrafine particles in particular were much lower. Still, these methods are the safest go-to to combine healthy food and healthy air.
Here are a few smoke points for some of the more common cooking oils.
A few more points to consider for the healthiest oils:
- Refined oils are processed to remove some flammable solids, so refined oils have higher smoke points.
- You can use an oil with a higher smoke point than necessary, just don’t use one with a lower smoke point.
- Any oil can turn into smoke on any stove that is too hot.
- Don’t reuse oil for cooking. Oil degrades into unhealthy products with heat, and the repeated use of oil is linked with some cancers.
- Old oil that has developed an unpleasant plasticky or play-doh smell has gone rancid and should be thrown out.
If it smells overpowering smells also overpower air quality
There are many air quality hazards that have no smell, but a piercing bad odor like from smoke is usually an accurate indicator of unhealthy air. With all of the satisfying and pleasant fragrances and aromas that usually come along with cooking, it can be hard to know where to point your nose to figure out if your air quality has gone awry.
One study looked at some foods that are known for their odors, how much they stank during different preparation conditions and if that actually matched changes in air quality. The team fried and steamed cabbage; roasted and brewed coffee; and grilled and boiled clams. Like with cooking oils, the team found that higher temperatures resulted in worse air quality.
- Coffee is roasted up to around 450 °F (232 °C) and releases very potent smells that can be detected from very far away and is easily burnt. Roasting coffee had the worst air quality impact.
- Frying cabbage around 400 °F (204 °C) releases the sulfurous odors of cabbage into the air, and is only pungent in the room, unlike coffee roasting. Frying cabbage was bad, but not compared to coffee roasting.
- Grilling clams in their shells was next, which involves close proximity but no contact with a heating element and reaches up to 500 °F (260 °C). Shellfish like clams has a smell, but the impact on air quality was only a little worse than steaming or boiling.
- Brewing coffee, boiling clams, and steaming cabbage are methods with temperatures at or below 212 °F or (100 °C). Not only do these methods have the lowest impact on air quality, they also release less odor than the other cooking methods for each food.
Another looked at cooking mackerel at different temperatures and what kinds of gasses and particles result. While the air quality was worse as it burned, the mackerel released a lot of fishy VOCs at the beginning of the cooking process. These VOCs that rise from the pan early on are driven off at fairly low temperatures and aren’t associated with ultrafine particles or the presence of free radicals as a result.
In general, smells may indicate more VOCs in the air, which can lead to ultrafine particles but aren’t harmful in the short term but should be ventilated or removed soon. You can trust your nose that stronger bad or chemical smells, like the acrid or piercing smell from something very hot or burning, is a better indicator that the air is indeed bad and ventilation is required. Good smells that arise from room temperature foods or relative warm (instead of hot) cooking methods, like boiling, have less of an air quality impact.
Regardless, excessive VOCs in the air will eventually lead to ultrafine particles. Even the smells from cooking with extra spices can add gasses to the air that may become unhealthy particles later. The best solution is to ventilate with the hood over your stove or open a window. An air purifier can also help to reduce those smells and the particles associated as well.
Neutralize cooking fumes with food
How bad the air gets when cooking has a lot to do with what is being cooked in addition to the method used. We can avoid smoke by not letting our food burn, but what about all those gasses that both make smells and present a possible air hazard? It turns out there are some strategies to figure that out, too.
Among the most plentiful unhealthy gasses from cooking is a group called aldehydes, containing contaminants like formaldehyde and acrylamide. These chemicals usually result from the combination of fats or oils, heat, and oxygen. As you may have guessed, many aldehydes are unhealthy to be exposed to and should be avoided.
Figuring out how to stop aldehyde formation is difficult because it occurs in similar conditions to a favorable reaction. The Maillard reaction forms the delicious golden brown layer on the outside of breads, fried dishes, meats, and other foods when proteins and carbohydrates are heated just right. The aldehyde reaction is unhealthy but the Maillard reaction is a big part of what makes food worth cooking.
The worst aldehyde that comes from burnt food is probably acrolein, which can cause cardiovascular disease and prevent cell growth and healing from strokes and other injuries. Acrolein is also the smell of burning fat with a very pungent and piercing acrid odor. One study found that linoleic acid, a very common component of cooking oils, is the primary precursor for acrolein. Cooking with extra virgin olive oil, which is low in linoleic acid, can help to reduce acrolein formation.
Controlling acrolein at the source might be a little too challenging since it can form from countless combinations of foods and cooking methods. A different and tastier method is to mitigate acrolein’s ability to harm with antioxidants and sulfur compounds like in cruciferous vegetables such as cabbage, broccoli, and most other plants. These antioxidants can also serve to neutralize other reactive or free-radical laden airborne chemicals from any source that may enter your body or land on your skin.
In addition to eating fresh fruits and vegetables, you can get antioxidants as oral supplements or in lotions. Vitamins A, B3, C, E, coenzyme Q10 and other plant-based antioxidants like resveratrol have long been shown to mitigate oxidative damage from free radicals both in and on the body, just be sure to follow instructions on any products.