Our results suggest that in homes using NGCBs without venting range hoods, a substantial proportion of occupants experience pollutant concentrations that exceed health-based standards and guidelines. Using simulations of Southern California households cooking at least once per week, we estimate that pollutant levels exceed ambient air quality standards for NO2 and CO in 55–70% and 7–8% of homes during a typical week in winter (
Table 2). Approximately half of homes in California and 34% of homes nationally have natural gas cooking burners, and assuming that the critical parameters of pollutant emission rates from appliances, homes sizes, and cooking patterns have similar distributions throughout the state as occur in the SoCal cohort, we estimate through extrapolation that approximately 12 million and 1.7 million Californians routinely could be exposed to NO2 and CO levels, respectively, exceeding ambient air standards in a typical week in winter. Additional work is needed to estimate the frequencies at which air quality benchmarks are exceeded in the tens of millions of U.S. homes that have natural gas cooking burners.
The U.S. EPA and California outdoor health standards, NAAQS (
U.S.EPA 2012b) and CAAQS (
CARB 2010), respectively, are legally enforceable regulations. If outdoor concentrations exceed these standards in specific areas they are referred to as “nonattainment” areas. The health impacts of being in nonattainment are thought to be significant enough to warrant a wide array of fiscal and regulatory penalties to achieve compliance. Our model-based estimates suggest that during the winter in Southern California, 55–70% of homes that have and use natural gas burners without venting have indoor air pollution levels consistent with ambient outdoor levels in nonattainment areas.
The hazard posed by natural gas cooking burners can be mitigated substantially through the use of venting range hoods that capture cooking burner pollutants—as well as pollutants generated from cooking activities—at the point of emissions and exhaust them to the outdoors.