We often feel safe in our homes, protected from external pollution. But the reality is that even within the home we can breathe harmful substances without even realizing it. Let’s think for example of the seemingly harmless gas stoves, even cooking could compromise the quality of the air we breathe within the home.
This is said (or rather confirmed) by new research, published on PNAS Nexus by a team at Stanford University, who analyzed nitrogen dioxide (NO₂) exposure in more than 133 million U.S. homes, combining direct measurements, outdoor air quality data, and building characteristics. The findings show that gas stoves contribute substantially to indoor pollution, putting many homes above the World Health Organization’s safety thresholds.
What the study found
According to the study, households that use gas or propane stoves are exposed on average to around 10.1 parts per billion (ppbv) of nitrogen dioxide, almost double the long-term safety threshold indicated by the WHO (5.2 ppbv). Of this total exposure, approximately 2.4 ppbv comes directly from combustion during cooking, while the remaining 7.7 ppbv comes from external sources such as vehicular traffic.
For those who cook with electric stoves, however, exposure stops at around 8 ppbv, coming exclusively from external sources, given that these appliances do not produce nitrogen dioxide.
The most alarming data concerns families who cook more frequently or in small spaces: for those in the 95th percentile of use of gas stoves, exposure can exceed 18 ppbv, with over half of the total pollution attributable to the kitchen itself.
The study estimates that about 22 million Americans would exceed WHO safety limits due to gas cooking alone. In nearly half of the U.S. zip codes analyzed, the combination of outdoor and stovetop pollution pushes total residential exposure above recommended thresholds.
Of particular concern is acute exposure: researchers have found that gas cookers are responsible for virtually all exceedances of the WHO hourly threshold (100 ppbv) recorded in domestic environments. Those who regularly cook with gas may be exposed to concentrations above this limit for 7-15 days a year.
Why nitrogen dioxide is dangerous
Nitrogen dioxide is not a pollutant to be underestimated. Prolonged exposure has been linked to numerous health problems such as worsening of asthma, especially in children; increased risk of chronic obstructive pulmonary disease (COPD); greater vulnerability to respiratory infections; possible effects on fetal development and cardiovascular health.
Children, the elderly and people with underlying respiratory conditions are particularly vulnerable to these effects.
We take it for granted that the air we breathe at home is healthy – commented Robert Jackson, one of the authors of the study – Our research shows that with a gas stove you can breathe the same amount of NO₂ into your home as comes from all external sources combined.
This study represents the first attempt to systematically map nitrogen dioxide exposure at a national level in the US, integrating both internal and external sources. The researchers hope this data can guide more targeted public policies, including incentives for replacing gas appliances in the most vulnerable communities.
How to defend yourself
The good news is that there are practical solutions to reduce home exposure to nitrogen dioxide:
