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Outpatient Practice Public Health

A Pulmonologist’s Opinion About Gas Ranges

Recently, there have been health concerns raised about gas ranges. This has led some cities to prohibit their installation in new homes, including Los Angeles, New York and San Francisco. I am interested in these health concerns for two reasons. First, as a pulmonologist, I want to be sure that the people in our community are safe from health risks. Second, I am getting ready to buy a new range for myself. So, what are the health risks of gas ranges and should you be worried about them?

The basics of cooking ranges

First, some definitions. Many people use the terms “range”, “stove”, and “oven” interchangeably. Technically, an oven is the enclosed box that you bake in. A stove is the surface heating area that you heat pots on. A range is when a stove and an oven are combined into a single appliance. Sometimes the term “cooktop” is used when the stove is separate from the oven. For the purpose of this post, I will use the term “range” for the appliance that combines an oven with a stove.

In the United States, there are essentially four types of ranges: electric, gas, duel fuel, and induction. Electric ranges work by passing an electric current through a metal coil that heats up as it creates resistance to that current. These electric coils (“burners”) can be exposed on the top of the stove or covered underneath a flat sheet of glass. Electric ranges also use electric heating elements inside the ovens. Gas ranges work by igniting a jet of natural gas. The resultant flame is used to heat pots and pans on the stove. Gas ranges also use gas flames inside the oven for baking purposes. Duel fuel ranges use gas flames for the stove to heat pots and pans but use electric heating elements in the oven for baking purposes. Induction ranges work by using electricity to create a magnetic field on the stove that then heats up any pot or pan placed on the stove that contains iron or steel. Induction ranges generally use a standard electric heating element in the oven for baking purposes.

For many years, electric ranges dominated the U.S. appliance market. However, gas ranges are preferred by many cooks because of the better control over the amount of heat generated, for example, allowing the cooking surface to instantly increase or decrease in temperature. Duel fuel ranges combine the advantages of the gas stove for surface cooking with the more even heating of an electric oven for baking. Induction ranges offer the advantages of using electricity, thus avoiding an open flame, while also offering the advantage of being able to instantly control the temperature applied to the pot or pan. Consumer Reports found that induction ranges out-performed electric and gas ranges in cooking tests.

As a general rule, when things burn, the resultant products of combustion are bad for our lungs. Whether that be burning cigarettes, military burn pits, house fires, or indoor wood/charcoal cooking. Natural gas is often called “clean-burning” because it does not produce visible smoke, unlike a wood fire or charcoal fire. However, just because we cannot see or smell the products of combustion from natural gas does not mean that those products of combustion cannot hurt us.

What is natural gas?

Natural gas is a type of fossil fuel produced by the decay of long-dead plants. It accumulates in large gas pockets deep underground and then can be removed by drilling gas wells into those pockets. The main component of natural gas is methane which in pure form, creates water and carbon dioxide when it burns. However, natural gas is not pure methane and instead contains small amounts of other gases and chemicals. The typical components of natural gas include:

  • Methane
  • Ethane
  • Butane
  • Propane
  • Hydrogen sulfide
  • Carbon dioxide
  • Oxygen
  • Nitrogen
  • Trace elements: helium, hydrogen, Xenon, and Neon

When natural gas is burned, these components produce new gases, including carbon dioxide, nitrous oxide, methane, carbon monoxide, formaldehyde, nitrogen dioxide, and particulate matter. Many of these gases can cause lung disease.

Carbon dioxide

It is estimated that a typical U.S. family cooking with a gas stove produces slightly less than a pound of carbon dioxide each day from the combustion of natural gas. This is about the same amount of carbon dioxide produced by coal or gas power plants to generate the amount of electricity required to cook using an electric range or an induction range. So, we don’t really produce more carbon dioxide by using a gas range but we do concentrate that carbon dioxide inside our homes. To illustrate this, I measured the concentration of carbon dioxide in my kitchen before and during the use of my gas range. At baseline, the carbon dioxide level in my kitchen was 646 parts per million.

After turning on 4 burners on the gas stove for five minutes, the carbon dioxide level increased to 1609 parts per million.

I then turned on the overhead exhaust fan for five minutes and the carbon dioxide level fell to 821 parts per million.

Carbon dioxide is a by-product of living animals. Our bodies normally produce carbon dioxide that we exhale with every breath. If the levels of carbon dioxide in our bloodstream builds up, it can be toxic to the human body. Similarly, if the level of carbon dioxide in the air increases and then we breath that air, we can suffer ill health. NIOSH considers breathing air containing over 5,000 parts per million over the course of a 10-hour day to be toxic and over 30,000 parts per million for a 15-minute period to be toxic. It would require cooking for a long period of time in a poorly ventilated kitchen to reach these levels using a gas range.

Carbon monoxide

Like carbon dioxide, carbon monoxide is produced when things burn. However, carbon monoxide is much more toxic to humans than carbon dioxide. It is an invisible, odorless gas. When inhaled, it tightly binds to the hemoglobin molecules in our red blood cells thus preventing oxygen from binding to those hemoglobin molecules. Without oxygen, the cells in our bodies suffocate. We all inhale small amounts of carbon monoxide from our environments so there are always low levels of carbon monoxide in our blood stream. Cigarette smokers have higher levels of blood carbon monoxide than non-smokers. Very high levels of carbon monoxide are fatal. This is how most people die in house fires or die by suicide from running their car in a closed garage. Lower levels of carbon monoxide can cause headaches, ringing in the ears, and confusion. Every house with a gas range should have a carbon monoxide detector installed.

Nitrogen dioxide

The air we breathe is mostly made up of nitrogen – it constitutes about 80% of the gases in air. Nitrogen gas is considered inert – it does not cause any direct harm to the body except when nitrogen dissolved in the bloodstream “boils” and creates nitrogen gas bubbles in the tissues when SCUBA divers ascend too rapidly and get the bends. But when gases are burned, pure nitrogen can be converted into nitrogen oxides. One of these is nitrogen dioxide, which can be very toxic and poses the greatest health risks to our lungs from gas ranges.

Nitrogen dioxide can also build up from decay of certain types of plant materials. In pulmonary medicine, an important result of nitrogen dioxide toxicity is in “silo-filler’s disease”. This occurs when nitrogen dioxide builds up inside of poorly ventilated silos storing silage. If a farm worker enters that silo and inhales high concentrations of nitrogen dioxide, the lungs can become injured. In the short-term this can result in ARDS (acute respiratory distress syndrome), where the lungs are damaged and fill up with inflammation and fluid, thus blocking air from getting into the lung’s alveoli (air sacks) where oxygen normally transfers into the bloodstream. In the long-term, small airways in lungs exposed to high concentrations of nitrogen dioxide can fill up with scar tissue, resulting in permanent blockage of air getting to the alveoli. This is called “bronchiolitis obliterans“. A famous event resulting in pulmonary nitrogen dioxide toxicity occurred in Cleveland in 1929. At that time, a fire arose in the Cleveland Clinic in a room where large amount of old x-rays films that were made of nitrocellulose were stored. The resultant nitrogen dioxide gas produced by the burning x-ray films resulted in 129 deaths, including one of the Clinic’s founders, Dr. John Philips.

In lower concentrations, nitrogen dioxide can irritate small airways causing asthma. This can be particularly insidious because nitrogen dioxide does not cause allergic reactions, unlike many allergic triggers of asthma such as cats dander or pollens. For this reason, most people with asthma worsened by nitrogen dioxide do not realize that it is their gas cooking range that is making them sick. A 2013 meta-analysis of 41 studies found that indoor gas stove use increases the incidence of asthma in children. A recent study estimated that 12.7% of childhood asthma is due to nitrogen dioxide and other by gases produced by gas ranges. Adults with asthma may be less affected by gas ranges than children based on a 2003 study of 445 subjects.

Formaldehyde

Every middle school student who accidentally opened the jar of preserved frogs in biology class knows how noxious inhaling formaldehyde is. It is another toxic by-product of natural gas combustion. Formaldehyde is also produced by burning cigarettes and can be released by wood adhesives in newly constructed houses. It is often one of the suspected culprits in patients with “sick building syndrome”. When inhaled, formaldehyde can cause eye irritation, nose irritation, throat irritation, and cough. Meta-analyses in 2010 and 2018 showed that environmental formaldehyde in homes is associated with asthma in children. Formaldehyde is also considered a carcinogen. A 2018 study found that using even 1 gas burner turned on low increased air formaldehyde levels above safe thresholds.

Particulate matter

Natural gas is often called “clean-burning” but that is not exactly true. Tiny particles (< 10 μm) of soot are produced when gas is burned, even if those particles cannot be easily seen with the naked eye. Breathing particulate matter can cause cough and worsened asthma. It is one of the main causes of respiratory symptoms when outdoor air quality is poor, due to air pollution. Some particulate matter is produced from food as it is cooked, however, gas ranges produce particulate matter even if there is no food being cooked.

Fire

Accidental house fires are another harmful consequence of gas ranges. It surprises me that there are not more of these. Spilled cooking oil or a dishtowel accidentally dropped onto an open flame can quickly develop into a kitchen fire. The National Fire Protection Association estimates that there are 179,500 fires due to cooking in the United States, accounting for 49% of all house fires. Ranges account for 61% of cooking-related house fires and 87% of cooking-related fire deaths. Interestingly, electric ranges are more likely to cause house fires than gas ranges. There is very little research in fire risk from induction ranges compared to electric or gas ranges but given that induction cooktops produce no heat if a pan is removed, it would seem that there would be less risk of fire if the induction range was accidentally left on after cooking. Grease fires may also be less frequent given the absence of a flame (gas ranges) or hot electric coil (electric ranges).

Fire is a particular risk for people with lung disease who require supplemental oxygen. As pulmonologists, we caution our patients to never use their oxygen in the kitchen when using a gas range. However, there is no risk of fire when using supplemental oxygen around an induction range.

Thermal injuries

Both electric ranges and gas ranges produce high heat. Small children who don’t know any better can get severe hand and finger burns from reaching up to an electric or gas burner. Even experienced cooks often burn their hands from accidentally touching a hot burner. Induction ranges substantially reduce the risk of burns. Only the bottom of a pot or pan gets hot; the surface of the range does not heat up. So unless a toddler touches the bottom of a pan, there is no danger of thermal injury with an induction range.

So, what are the downsides of induction ranges?

The main problem with induction ranges is that they are expensive. The cheapest electric or gas range is several hundred dollars less than the cheapest induction range. However, a provision of the Inflation Reduction Act to discourage gas ranges provides a tax credit of up to $840 to replace gas ranges with electric or induction ranges. This only applies to Americans with lower incomes. Those with middle incomes can qualify for a reduced amount of the tax credit while those with higher incomes are not eligible for any tax credit. Although induction ranges can be expensive, it is anticipated that prices will come down in the future as the market for induction ranges increases. Consumer Reports recently rated ranges and found that the top rated induction ranges cost about the same as the top rated gas or electric ranges. The least expensive of the top four rated induction ranges costs $1,200.

A second problem with induction ranges is that the bottom of pots and pans must contain iron or steel. Copper, purely ceramic, aluminum, and glass cookware will not work with an induction range. If you have to buy all new steel/iron plated cookware, it can considerably add to the cost of a new induction range. An easy way to determine if a given pot or pan will work is to see if a refrigerator magnet sticks to the bottom.

A final problem with induction ranges is that you cannot generate extremely high heat. This is especially a problem for restaurants using very high heat output gas flames for wok cooking. These high heat levels are generally not achievable with an induction cooktop. However, there are now “induction woks” being marketed that surround the wok bowl with an induction element, thus permitting cooking temperatures similar as can be produced using high-output gas burners.

“I have a gas stove. What can I do to reduce the risk of harm?”

If you have a gas range, the most important step you can take is to ventilate the kitchen. This can mean opening kitchen windows when the weather outside permits. If you have a fan that you can put in that window, even better. If you have an exhaust hood above your range, then turn it on when cooking. An exhaust hood that blows air outside is optimal. If a child in the house has asthma, then try to keep that child out of the kitchen when cooking. If you are unsure of how effective your kitchen ventilation is, you can buy a home CO2 monitor for about $80. If the CO2 level increases significantly when you are cooking, then your ventilation is likely inadequate.

A second way of minimizing harm from a gas range is to use other kitchen appliances for cooking instead of the range whenever possible. For example, an electric kettle can be used to heat water rather than boiling water in a pot on the gas stove. An air fryer can replace the use of a gas oven for many foods. And a slow cooker can be used instead of the range range for chili, stews, and soups.

“Should I switch out my gas range for an induction range?”

The short answer is that most people do not need to ditch their gas ranges if they already have one. However, if your kitchen is poorly ventilated or lacks an exhaust fan over the range, then replacing your gas range with an electric or an induction range may make sense. Also, if there are children in the house, the health risks of a gas range increase significantly, especially if one of the children has asthma or another lung disease. If someone in the home uses supplemental oxygen, then getting rid of the gas range can reduce the risk of a house fire, particularly if the oxygen-user does the cooking.

For climate-conscious people, changing gas to electric or induction ranges can appear on the surface to be the more responsible choice. However, if your local electricity producer uses fossil fuel power plants, then there really is not much advantage in electric or induction ranges since the overall CO2 production is similar. Here in Ohio, we can choose our electricity provider and for several years, I have purchased electricity from providers that only produce electricity from wind and solar sources. So for me, an induction range will result in less overall CO2 production than a gas range. People in other parts of the country where the electrical grid sources electricity from hydroelectric power-plants can also reduce their CO2 footprint by switching from gas to electric or induction ranges.

For me, I don’t have any lung disease and no longer have children in the house. I like breathing clean air in the home and I like to minimize my personal CO2 footprint. However, I also like the ability to easily regulate the cooking temperature that in the past was only achievable with a gas stove but is now achievable with induction stoves. We are building a new house and had to decide what kind of appliances to install. So, I just ordered my new induction range.

January 15, 2023