Workers in nearly 70% of commercial kitchens that are equipped with gas and propane appliances are exposed to high levels of air pollution and heat at levels that health limits, finds a US study. Propane appliances are devices that use propane gas— the liquefied petroleum gas or LPG—as their primary fuel source instead of electricity or utility-line natural gas.
The research, conducted by PSE Healthy Energy, the Stanford Doerr School of Sustainability and New York University Grossman School of Medicine, in collaboration with Chef Christopher Galarza, monitored 27 commercial kitchens across California, Pennsylvania and New York in the US. Among them, 24 were fuelled by natural gas or propane and three were all-electric.
“We measured nitrogen dioxide (NO2), benzene, carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and air temperature at multiple worker-relevant locations during both active service and overnight idle periods,” says a statement from the researchers at PSE Healthy Energy as available with The Plurals. PSE Healthy Energy is an independent, scientific research institute based in California, US. “This is the first US study to systematically compare air quality and heat exposures in gas, propane, and all-electric commercial kitchens as workers actually experience them,” says the statement.
An estimated 15.7 million workers are employed in the US restaurant and food service industry and about five million of them spend all of their working hours in the kitchen, the researchers estimate.
Kitchens turning gas chambers
Gas kitchens demonstrated far higher levels of air pollution than all-electric kitchens, shows the research.
The study found that commercial ventilation hoods reduced, but did not eliminate, workers’ exposure to pollutants during cooking. “…In roughly two-thirds of commercial kitchens with gas-fired appliances, concentrations at worker-relevant locations exceeded health-based benchmarks,” says PSE Healthy Energy.
In 70% (17 of 24) of gas kitchens monitored, the hourly average of NO2 concentrations during cooking hours measured outside ventilation hood systems were above the EPA (Environmental Protection Agency)’s 100 ppbv air standard. One kitchen recorded a 15-minute average above 1,000 ppbv, exceeding the National Institute for Occupational Safety and Health (NIOSH)’s short-term occupational exposure limit for NO2.
Other combustion-related pollutants, such as Carbon monoxide concentrations, exceeded exposure guideline (20 ppm) in three gas kitchens. The carcinogen benzene exceeded a local exposure benchmark in five gas kitchens.
“None of the all-electric kitchens exceeded any pollutant thresholds during cooking hours,” says PSE Healthy Energy.
Heat benchmarks breached
“In 68% of gas kitchens (13 of 19 with temperature measurements), we recorded temperatures exceeding both California’s indoor heat illness prevention regulations and OSHA (Occupational Safety and Health Administration)’s proposed high heat trigger of 90°F (32oC),” say the researchers.
Ten of the gas kitchens recorded maximum temperatures above 37°C and four exceeded 50°C. Even on days when external temperatures were below 23°C, 10 of 13 gas kitchens exceeded 32°C indoors, “indicating that extreme heat is driven primarily by gas combustion in the kitchen rather than outdoor temperature”.
Chefs under heat, literally
The chef himself or herself was monitored. “Personal temperature monitoring of a chef (via monitor on chef’s shoulder) during a roughly five-hour service averaged 33°C and peaked at 41°C, well above OSHA’s proposed heat regulations,” the researchers write.
In contrast, all-electric kitchens were much cooler. Two electric kitchens recorded two of the three lowest in-service temperatures observed throughout the research.
Off-work hours hotter at a few places
The research measures the impact of gas appliance pilot lights that remain lit overnight. While many kitchens experienced high pollution and heat during working hours, over two thirds of kitchens (16 of 22 gas/propane kitchens) recorded higher levels of NO2, CO, CO2, CH4 and benzene overnight. Then ventilation was off and appliance pilot lights remained lit.
The study found seven kitchens exceeding the 100ppbv NO2 standard during off-work hours, raising concerns for cleaning crews and early-arriving staff.
“None of the all-electric kitchens exceeded any pollutant thresholds at any time of day or night,” the researchers found.