In a recent study published in Advances in Scienceresearchers quantified indoor nitrogen dioxide (NO2) emissions from gas and propane stoves and assessed their health effects and demographic disparities in exposure among United States (US) populations.
Study: Nitrogen dioxide exposure, health outcomes, and associated demographic disparities from gas and propane stove combustion in the US. Image credit: M-Production/Shutterstock.com
Record
Gas and propane stoves, used in more than 50 million U.S. homes, emit pollutants such as NO2 and benzene (C6H6), often exceeds health safety levels. Long term NO2 Exposure is linked to serious health problems, including asthma and chronic obstructive pulmonary disease.
Traditional studies lack precision in exposure assessment due to variations in stove use and ventilation.
Further research is needed to improve exposure assessments and understand the full range of health effects in various demographics, improving mitigation strategies and policy interventions.
About the study
In the present study, different terms were clearly defined to standardize the terminology used throughout the research. A “stove” was identified as a flat surface that has two to six cooking elements, while “burners” refer to elements that use a gas or propane flame.
“Stoves” or “stoves” were described as self-contained units that combined both a cooktop and an oven. The team also distinguished between “external ventilation hoods”, which expel kitchen air outdoors, and “recirculation hoods”, which filter and return air back into the kitchen.
For measurement purposes, the term “concentration” was used for its accessibility, with standard conversions applied based on an assumed temperature of 25°C and atmospheric pressure.
The Multizonal Contaminant Transport Analysis Model (CONTAM), developed by the National Institute of Standards and Technology (NIST), has been instrumental in modeling indoor NO2 concentrations. The model was validated through comparisons with measured NO2 levels in various “validation dwellings”, then applying these validated models to other non-measurable dwelling types.
The methodology incorporated detailed NO measurements2 concentrations using advanced analytical equipment. Emission rates from gas and propane stoves were calculated for a diverse population of residences, including both private and rental properties, in several states.
The study carefully calculated the NO2 and carbon dioxide (CO2) emission rates using closed kitchen volumes, using a tracer gas method to adjust air exchange in the calculations.
Finally, the validated CONTAM model was used to estimate NO2 exposure to different environmental, behavioral and demographic conditions.
These estimates were linked to epidemiological data to assess health effects, especially the burden of childhood asthma attributable to long-term NO2 exposure from gas and propane stoves.
Study results
The present study evaluated the accuracy of the CONTAM indoor air quality model by comparing its predicted NO2 concentrations relative to actual readings taken from 18 different residences.
These included a mix of apartments and single-family homes, ranging in size and located in various urban areas such as the San Francisco Bay Area, Los Angeles, Denver, Houston, New York City, and Washington, DC.
Different scenarios were tested, including windows open or closed and external air vent hoods activated or deactivated. The results showed a strong correlation between modeled and actual NO2 concentrations, with no significant bias detected in the model predictions.
In addition to validating the model, the study also examined NO2 emission factors from gas and propane stoves. The measurements showed NO2 emissions are directly related to the amount of fossil fuels burned, as evidenced by the corresponding CO2 emissions.
Interestingly, no NO2 emissions from electric or induction stoves were detected. Propane and natural gas stoves showed similar NO2 emissions per joule of fuel burned, likely due to the similar flame temperatures of methane and propane.
Further testing in bedrooms showed NO2 Levels could exceed health-based guidelines within minutes when ovens were used without hoods involved.
The effectiveness of externally vented range hoods varied, with some reduction in peak NO2 concentrations significantly while others had minimal effect. On average, these hoods reduced the kitchen NO2 concentrations by about 35%.
The study also modeled long-term and short-term NO2 exposures from stove use, incorporating factors such as duration of cooking, frequency of hood use and the effectiveness of these hoods.
The findings showed that long- and short-term exposures to NO2 were significantly higher in smaller dwellings and households with lower incomes, highlighting socioeconomic disparities in exposure risks.
Racial and ethnic disparities were also evident, with American Indian or Alaska Native, Hispanic or Latino, and Black households experiencing higher levels of NO2 exposure compared to white and Asian households. This was partly attributed to the smaller average dwelling size among the most affected groups.
Behavioral factors such as duration and intensity of stove use played an important role in determining NO2 exhibition. For example, residences with high stove use saw dramatically higher NO2 short and long term exposure.
Sensitivity analysis of the study confirmed that total gas or propane combustion was the most critical factor for predicting NO2 exposure levels, followed by ventilation practices and kitchen residence time.
