Following a July study that found switching from a household gas stove to an electric one can improve asthma symptoms, a new peer-reviewed study published on Tuesday concluded that workers in restaurant kitchens using gas and propane appliances are exposed to air pollution and heat levels that exceed health guidelines.
The National Restaurant Association reports that over 15.7 million Americans work in the food service industry.
Published in the scientific journal Environmental Research Letters, and in collaboration with chef Christopher Galarza, the study was conducted by researchers from the Stanford Doerr School of Sustainability, the New York University Grossman School of Medicine and PSE Healthy Energy, an independent scientific research institute specializing in bringing science to energy policy.
According to a press release, this is the first US study to compare air quality and heat levels in restaurant kitchens that use gas appliances with those that use all-electric appliances under real-world working conditions. The study is part of PSE Healthy Energy’s Methane and Health Initiative, which uncovers air quality and health risks associated with methane sources to protect public health and the climate.
Researchers measured air temperature and air pollutants produced by gas stoves: methane, nitrogen dioxide, carbon monoxide, carbon dioxide and benzene. Measurements were taken in five employee work areas, both during service and overnight, in 21 gas kitchens, three propane kitchens and three all-electric kitchens in California, New York and Pennsylvania.
“Everyone likely has a favorite restaurant or fast food chain, but most people probably haven’t thought about the equipment being used and how that affects what the staff is experiencing in the kitchen area,” Drew Michanowicz, principal scientist at PSE Healthy Energy, told CNET in an email.
Air pollution findings
When kitchens are not properly ventilated, pollutants can build up and cause harmful health effects, though this depends on individual sensitivity and exposure level.
During the study, it was discovered that in kitchens with gas or propane appliances, at least one health guideline for pollutant exposure was exceeded during cooking hours.
About 70% of gas kitchens in the study surpassed the US Environmental Protection Agency’s 1-hour outdoor air standard for nitrogen dioxide. The outdoor standard was used because there is no comparable indoor standard in the US.
In kitchens with gas or propane appliances, about 170 cumulative hours (about four full work weeks) were recorded in which nitrogen dioxide concentrations exceeded the World Health Organization’s hour-averaged exposure recommendation. This recommendation is roughly equal to the EPA’s outdoor standard, and both apply to the general population.
One kitchen’s 15-minute average nitrogen dioxide level exceeded the National Institute for Occupational Safety and Health’s recommended short-term workplace exposure limit.
Nitrogen dioxide can cause reduced lung function, increased asthma attacks, increased airway inflammation, and worsened cough and wheezing. This gaseous air pollutant has even been tied to causing asthma in children.
The study also found that carbon monoxide and benzene concentrations exceeded California’s 1-hour exposure guidelines in three and five gas kitchens, respectively. Carbon monoxide poisoning symptoms can range from a headache and dizziness to passing out and death. Benzene, on the other hand, is a carcinogen that has been linked to a higher risk of leukemia and other blood cell cancers.
By comparison, no all-electric kitchen exceeded pollution-exposure health guidelines during cooking hours.
“This study emphasizes that the concentrations of pollutants in commercial kitchens with gas-fired appliances can reach levels even higher than what we’ve previously observed in homes with gas stoves,” Yannai Kashtan, an air quality scientist at PSE Healthy Energy, told CNET in an email.
Overnight levels matter too
Even outside cooking hours, exposure remains a concern, according to new evidence from the study.
When gas appliance pilot lights remain lit, and ventilation is turned off, cleaning crews and staff arriving early risk exposure to pollutants. About 71% of the gas kitchens with overnight monitoring recorded higher levels of nitrogen dioxide, carbon monoxide, carbon dioxide, methane and benzene overnight than during service hours.
Aside from contributing to climate change, high concentrations of methane can displace oxygen in the air, causing fatigue, rapid breathing, vomiting, collapse, convulsions, organ damage and death.
When you consider that commercial gas appliances are also used in hospitals, schools and other buildings, the health concerns extend beyond restaurant kitchens.
None of the all-electric kitchens exceeded pollutant guidelines overnight.
Temperature findings
When it came to heat health guidelines, about 68% of gas kitchens with temperature data exceeded 90 degrees Fahrenheit, the Occupational Safety and Health Administration’s proposed high-heat threshold.
Even when temperatures outside were below 75 degrees Fahrenheit, 10 of 13 gas kitchens exceeded 90 degrees Fahrenheit, meaning that high heat in commercial kitchens isn’t directly tied to the weather.
When a temperature monitor was attached to a chef’s shoulder during a 5-hour cooking session, the average temperature was 92 degrees Fahrenheit, with a maximum of 106 degrees Fahrenheit.
A guideline gap in kitchen worker protection
The study compared its findings with both EPA and WHO guidelines for the general population, which prioritize health protection, and with NIOSH and OSHA guidelines, which are occupational. Researchers found fewer instances of kitchens exceeding workplace thresholds.
“Compared to benchmarks for the general population, occupational thresholds are higher because they serve a different purpose by also accounting for industry cost and technical feasibility,” Kashtan said. “If work environments are exceeding health-based thresholds but are compliant with the occupational limits that govern enforcement, this points to a gap in health protection for commercial kitchen workers.”
The study’s limitations
Due to the scarcity of all-electric commercial kitchens, only three were used in this study. However, the researchers stated in the study that their findings remain consistent with prior research on nitrogen dioxide concentrations from gas versus electric appliances.
As about 80% of end-use energy in US commercial cooking is gas, the small number of all-electric kitchens used in the study also reflects the current restaurant industry.
Only restaurant kitchens in three states were used, so this may not reflect the broader US. Participation was voluntary and partly facilitated through professional partnerships, so selection bias may have been introduced, especially given that kitchens willing to participate likely had better working conditions.
While sampling locations were chosen to account for different worker roles in the kitchen, pollutant measurements may differ from actual exposure due to a worker’s movement, health, posture and proximity to emission sources. These locations also weren’t monitored continuously; instead, they were sampled for 5 to 12 minutes per cycle.
Particulate matter and WBGT, which measures occupational heat stress, were not measured.
Restaurant recommendations
Based on this study, Michanowicz has three recommendations for worker protections in commercial kitchens that use gas appliances.
First, it’s important to ensure that ventilation systems are properly maintained, as these are usually the first line of defense against pollution and excess heat. However, even with these systems in place, restaurant workers who work directly over a cooking surface can still be exposed to pollution and heat before they reach the ventilation system.
While converting a commercial kitchen from gas to electric can be challenging and costly, focusing on electrifying gas ranges and fryers first can yield the greatest benefits for indoor air quality.
“There are also additional benefits that chefs we worked with have mentioned, such as higher worker productivity due to more comfortable kitchen temperatures, reduced cleaning times and reduced burn and explosion risks,” Michanowicz said.
Lastly, for workers in commercial kitchens during off-hours, including cleaning crews, when pilot lights are still on, ventilation systems should be turned on. This applies to workers who arrive early in the morning, as pollution will have built up overnight.
Gas stove household advice
The recommendations for those with gas stoves at home aren’t dissimilar.
“The best way to reduce gas combustion pollution is to eliminate the source – the gas flame – and to get an electric radiant or induction stove,” said Kashtan.
However, if that’s not possible due to cost or because one is a renter, cooking can still be partially electrified with air fryers, electric kettles, rice cookers and portable induction hobs.
And when you do use your gas stove, always make sure your range hood is on, and consider putting an air purifier in your kitchen.
