Table 3.

Comparison of literature on exposure to indoor NO₂.

Study	Location	Air Quality Assessment	Sample Size	Socio-economic Data	Socio-economic Measure	Pollutant	Results	Significance
Zota et al. (2005)	Boston, US	Home measurements.	77	Household questionnaire.	Household occupant density.	NO2	Occupant density was a significant predictor of indoor NO2 concentrations, with a univariate coefficient of 3.2.	p = 0.01*
Esplugues et al. (2010)	Valencia, Spain	Home measurements.	352	Study questionnaire, (INMA study)a.	Mother’s educational attainment.	NO2	For mothers with a primary education or lower, indoor NO2 levels were 0.07 μg/m3 higher than in the homes of mothers with a university education.	p = 0.04

*values shown in bold were significant at the 95% confidence level.

^aRibas-Fitó et al. (2006).