Odds ratios for symptoms reported by questionnaire in 2007 and in 2008 relative to 2006 adjusted for change in the control zone.

aAdjusted for: asthma, gas cooker or oven.bAdjusted for: age, age2, gender, asthma, smoker, unflued gas heater.cAdjusted for: age, age2, asthma, smoker, unflued gas heater.dAdjusted for: age, age2, asthma, smoker, ETS at home.eAdjusted for: asthma, unflued gas heater.fAdjusted for: age, age2, asthma, unflued gas heater.gAdjusted for: age, age2, asthma, smoker, gas cooker or oven.hAdjusted for: age, age2, gender, asthma, smoker, gas cooker or oven.