Researchers propose an improved model of indoor pollution produced by cooking

Stir-fries yield more than just savory dishes like Kung Pao Chicken and Hunan Beef. It also emits an invisible mixture of gases and particles that pollute indoor air and can harm human health. Properly estimating these cooking emissions in various settings is critical to simulating exposure and informing health guidelines to keep people safe.

A team of researchers including an air quality expert from Johns Hopkins University has developed a new model that can more accurately estimate and predict the concentration of particles produced during stir-frying. Their approach improves on traditional methods, which have limitations when applied to real-world settings such as private homes and restaurants.

“This new method used detailed particle measurement data to develop a model that incorporates dynamic changes in particle concentration and composition as emissions from cooking move from where cooking takes place to other areas of our interior spaces.”

“With this improved model, we can better understand the potential for exposure to cooking emissions in homes or commercial cooking areas,” said Peter DeCarlo, associate professor of environmental health and engineering at Johns Hopkins.

The team’s results appeared in Environmental science and technology.

Stir-fries originated in China in the 14th century. Today, billions of people around the world use it as a quick, easy, and relatively healthy way to prepare a meal. However, cooking food this way – in sizzling oil in a hot wok or other pan – causes tiny particles of oil and other chemicals in the food to become suspended in the air.

These particles contain a wide range of organic materials, including triglycerides, fatty acids, and proteins, as well as a variety of chemicals and compounds that emerge when the substances are exposed to heat and hot oil.

Other chemical compounds resulting from stir-frying are emitted directly as gases, and some chemicals can move between the gas phase and particles depending on their volatility.

Numerous studies have shown that exposure to outdoor particles can contribute to cardiovascular and respiratory diseases. Whether indoor particles, especially those related to cooking, have the same impact remains an unanswered question.

DeCarlo’s team made detailed measurements of the composition of cooking particles resulting from sautéing a variety of vegetables in soybean oil in a nonstick wok or cast iron skillet on electric and gas stoves when of repeated cooking sessions over a day.

Using real-time measurements of particle concentrations and chemical composition, the team identified two main types of emissions: a dominant type chemically similar to cooking oil and a second chemically similar to particles from from wood burning containing partially burned sugars, which probably came from cooking vegetables and stir-frying sauce.

The two-zone computer model the team developed to simulate data from these experiments was intended to match the conditions of a laboratory “house” at the University of Texas at Austin, where a 2018 collaborative field study called House Observations of Microbial and Environmental Chemistry (HOMEChem) examined how daily activities influence emissions, chemical transformations and the removal of trace gases and particles in indoor air.

When previous models noted that air pollution levels were higher than expected even after cooking stopped and stoves were turned off, the assumption was that even if the action of cooking had stopped, the particles and gases emitted were static and persisted.

DeCarlo and the team recognized that this was an error and that natural thermodynamics (the way particles and gases dissipate when air moves) can cause concentrations and composition to change pollutants once cooking is finished.

“We know that cooking emissions travel through an indoor space; that’s why you can smell what someone is cooking from a few rooms away. What we did with this model is to better characterize how the Thermodynamics changes the composition as these cooking particles spread through a space,” DeCarlo said.

The new model not only provides details and estimates on pollution levels, airflow patterns and particle concentrations in homes and buildings, where individuals and families could be affected, but can also be used as input data to assess potential exposures and risks of a broader population. level.

“While this detailed model can better characterize potential exposure to cooking-related emissions in indoor spaces, the public health guidelines and recommendations remain the same. Ventilating cooking emissions to the outdoors is the best way to reduce exposure, while air filtration and other measures also help. reducing the exposure of people inside homes and businesses,” DeCarlo said.