You’re getting ready to make a meal. You decided to cook because it’s cheaper and you got tired of Chipotle. I know, doesn’t seem possible but stay with me here. You groan to yourself because you know you’ll make a mess but decide to go for it anyway. What you don’t realize is…cooking in an enclosed space releases particles. Fine particles are inhaled through the respiratory system. The health risk of continuous inhalation in a lifetime can lead to cancer! But let’s not be alarmist. Why does this happen and can we prevent it?
The Department of Architectural Engineering in Yonsei University (Seoul, Korea) sought to quantify the concentration of cooking-generated particles and to assess the health risk of the occupants in the study: Measurement of Particulate Matter (PM2.5) and Health Risk Assessment of Cooking-Generated Particles in the Kitchen and Living Rooms of Apartment Houses. The study examined three different ventilation scenarios (see below) over a period of 30 minutes to measure the concentration of PM2.5 while grilling fish. Note: different food types and methods will generate pollutants of different concentrations.
Case 1: Single-sided natural ventilation (ventilation window was opened, range hood was operated)
Case 2: Cross-ventilation (southern window and the kitchen veranda window were opened to create the conditions for smooth air supply through the windows,range hood was operated)
Case 3: Mechanical Ventilation (heat recovery ventilation units were used, range hood was operated)
What are the particles?
The major particle or contaminant of concern for this study is PM2.5, which is a classification for particulate matter with a diameter less than 2.5 micrometers. The EPA defines particulate matter as:
“…the term for a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope.” (EPA 2018)
To give us some perspective, EPA also provides an example: the average human hair is about 70 micrometers in diameter. Particulate matter is generated through multiple sources, including dust, fly ash, soot, smoke, aerosols, fumes, mists and condensing vapors that are suspended in the air for extended periods of time. In the cooking-generated particles study, particulate matter was generated through the burning of food and oil.
Introduction to Risk Assessment
The risk assessment method includes four stages: (1) hazard identification, (2) dose response assessment, (3) exposure assessment and (4) risk assessment. For the purposes of this study, the hazard was identified as having a carcinogenic effect when these tiny particles are deposited in the lungs. The dose-response assessment used a slope factor, which is a value that, if exceeded, will increase the risk of cancer. It had units of mg/kg-day, to determine the slope of potential risk when a person is exposed to PM2.5. This slope factor is a value that, if exceeded, will increase the risk of cancer. The exposure assessment uses external/physical factors and scenarios such as inhalation rates, contaminant concentrations and exposure duration to determine a daily dosage of the contaminant. Risk assessment involves multiplying the slope factor by the average daily dose to estimate the cancer risk over a lifetime (the probability that a person will develop cancer).
Figure 1. Source: EPA Risk Assessment Process
What did they find in the study?
Concentration of Contaminants
In order to study the potential health effects on occupants in the house, the study compared the concentrations in the kitchen to the concentrations found in the living room adjacent to the kitchen as seen in Figure 2. The researchers found that the total amount of emissions was greater in the natural-ventilation case than in the mechanical-ventilation case, but the maximum value was larger in the mechanical-ventilation case (88.1 mg/m3) than in the natural-ventilation case (81.1 mg/m3). They suggested that the natural ventilation case had greater emissions due to the influx of the outside air contaminants.
Figure 2. Source: MDPI Open Access
In the kitchen, the highest concentration was found at about 16 minutes after the end of cooking. After 30 minutes, Case 1 (natural ventilation) and Case 3 (mechanical ventilation) showed similar results. Cross-ventilation, or Case 2, resulted in the lowest concentrations in the kitchen. Emissions in the living room had similar results, except Case 1 was more effective than Case 3.
Based on the risk assessment method, natural ventilation, or Case 1, showed the highest health risk in the kitchen. The cancer risk increased by 30.8% in the kitchen and by 26.2% in the living room when mechanical ventilation, or Case 3, was applied. Case 3 showed the highest health risk in the living room. Interestingly enough, Case 2 demonstrated similar health risk compared with no cooking being done. The health risks for all cases were not that different between the kitchen and the living room, but the generated heat in the kitchen allows quicker dispersion of the contaminants.
Should I still cook at home?
You certainly can! While there are multiple contaminants of concern that relate to indoor air quality, studies such as this one note the importance of adequate ventilation. The study warns that particulate matter (PM2.5) reduction is diminished if cross-ventilation is not performed properly. It also advises to discourage diffusion from the kitchen into other living spaces. Most importantly, find the sources of particulate matter and other contaminants and inform yourself on how to minimize exposure.