Background: In two regions of Sydney where sewage treatment facilities with high temperature sludge burning incinerators are installed, there was concern that the resultant emissions were causing a local increase in symptoms of asthma and other allergic diseases.
Aim: To investigate whether living in a region with high temperature sludge burning incinerators was associated with an increased prevalence of childhood asthma or allergy.
Methods: We studied 713 children aged eight-12 years in two regions close to incinerators and 626 children in a control region with no sludge burning incinerator. We measured respiratory illness in the previous year by questionnaire, airway hyper-responsiveness (AHR) by histamine inhalation test, and atopy by skin prick tests. 'Current asthma' was defined as AHR and recent wheeze.
Results: Recordings of oxides of nitrogen and sulphur, hydrogen sulphide, ozone and particulates during the study period showed that the level of pollutants did not vary in any major way between the study regions and the control region. The prevalence of current asthma, atopy, symptom frequency or any category of severity of asthma illness was not significantly different between the control and study regions.
Conclusions: This suggests that factors other than intermittent or industrial air pollutants are responsible for the high prevalence of asthma symptoms, asthma medication use, asthma morbidity and AHR in the study of children.