Recent consecutive research results have shown that gas combustion emissions and cooking oil vapors generated in kitchens can affect not only the respiratory system but also overall systemic health. In U.S. commercial kitchens, harmful substances such as nitrogen dioxide and benzene were detected.

In mouse experiments, the overlapping exposure to atopic dermatitis and oil vapor prominently induced inflammation and metabolic changes in various organs, including the heart and kidneys. However, additional verification is needed to determine whether the same health impacts appear in humans.

◇ Accumulation of Harmful Substances in Restaurant Kitchens Even at Night When Ventilation is Off

A research team consisting of the U.S. non-profit research organization PSE Healthy Energy and Stanford University recently published a study measuring air quality and temperature in commercial kitchens in the international journal Environmental Research Letters.

The researchers investigated 27 kitchens in California, Pennsylvania, and New York. Among 24 kitchens using gas cooking appliances, 17 (approximately 71%) exceeded the researchers' comparative benchmark of 100 ppb (1 ppb = 1 part per billion) for the 1-hour average concentration of nitrogen dioxide (NO₂) during cooking hours. In some kitchens, instantaneous concentrations exceeded the National Institute for Occupational Safety and Health (NIOSH) short-term exposure limit of 1000 ppb. In 5 kitchens, the concentration of the carcinogen benzene exceeded the researchers' comparative benchmark of 8.4 ppb, and carbon monoxide was also detected at high levels in some spaces.

Notably, in 16 out of 22 gas kitchens, the median concentrations of nitrogen dioxide, carbon monoxide, methane, and benzene were higher during nighttime hours when ventilation systems were turned off than during cooking hours. If combustion and gas emissions continue after business hours—such as through pilot lights maintained to keep burners ready for ignition—pollutants can accumulate in spaces where ventilation has stopped.

Thermal environment was also an issue. Among 19 gas kitchens, 13 exceeded 32.2 degrees Celsius (90 degrees Fahrenheit), and high temperatures of 37.8 degrees Celsius (100 degrees Fahrenheit) or more were observed in 10 kitchens. On the other hand, 3 kitchens using exclusively electric cooking appliances showed no cases of exceeding the target pollutant standards and had relatively low indoor temperatures. However, point is raised that for electric kitchens, the sample size was small, and electric cooking processes can also generate pollutants while heating food and oil.

◇ Oil Vapor, Skin Barrier Damage, and Systemic Metabolic Changes

A research team from Fudan University in China and Queensland University of Technology in Australia recently published a study in the international journal Environmental Science & Technology analyzing the combined exposure to cooking oil fumes (COF) and atopic dermatitis.

The researchers applied dermatitis-inducing conditions and exposure to oil fumes generated by heating cooking oil either individually or simultaneously to mice for a period of 6 weeks.

As a result, changes in inflammatory cytokines such as IL-6 and TNF-α were prominent in the group exposed to both factors simultaneously. These substances are proteins that regulate inflammatory responses in the body.

Further analysis observed metabolic changes not only in the lungs but also in the blood, heart, and kidneys. Succinate, associated with inflammation, increased, while purine metabolites such as xanthine and uric acid decreased. Changes also appeared in pathways involved in cellular antioxidant defense and energy metabolism, and the distribution and metabolic patterns of phospholipids constituting cell membranes changed in the heart and kidneys.

This suggests that when skin barrier damage and oil vapor exposure overlap, biochemical processes in multiple organs may be affected. However, this study alone does not prove that the metabolic changes observed in mice will lead to heart disease or kidney disease in humans.

◇ Ventilation Before Business Hours and Gas Management are Essential... Electrification is Also an Alternative

These two studies demonstrate the necessity of managing kitchen air quality not only during cooking hours but also outside of business hours. In gas kitchens, the necessity of maintaining pilot lights after business hours should be verified, and unnecessary combustion and gas emissions should be reduced in accordance with the manufacturer's safety guidelines. Before resuming business operations, it is advisable to inspect the operating status of ventilation facilities and gas equipment and ensure sufficient ventilation.

Electric and induction cooking appliances can reduce nitrogen dioxide, carbon monoxide, and other pollutants directly generated from gas combustion, and improve the thermal environment of the kitchen. However, they cannot eliminate pollutants generated when heating food and oil, so appropriate exhaust and ventilation facilities are still required.

The kitchen is a workspace where food is prepared, while at the same time being a workplace where pollutants are generated by combustion and high-temperature cooking. To protect the health of culinary workers, it is necessary to comprehensively manage not only ventilation during cooking, but also nighttime equipment operation and indoor temperature.

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