Exposure to the fumes emitted from solvents and cleaning products at home may increase the risk of childhood asthma, suggests a study by Australian researchers from Curtin University and the University of Sydney.
The authors base their findings on 88 toddlers with asthma, and 104 without, who had been identified from emergency care records at one hospital in Perth, Western Australia.
Their parents completed a detailed questionnaire on the children's health, and the children were tested for allergic reactions (atopy), using a skin prick test.
The levels of volatile organic compounds (VOCs) in all the children's homes were assessed twice - within two weeks of the children's visit to the emergency care department in the winter, and during the summer.
VOCs are found in solvents, paints, floor adhesives, cleaning products, polishes, room fresheners, fitted carpets and cigarette smoke.
The indoor temperature and relative humidity (both of which affect the activity of house dust mites, a known asthma trigger) were also assessed.
Three quarters (77%) of the children with asthma were atopic; only half of the children without asthma were. Similarly, three quarters of the children diagnosed with asthma had at least one parent with an allergy, and over half had at least one parent with asthma. These are significant risk factors for the development of asthma.
But the authors also found that the levels of indoor VOCs were significantly higher in the homes of the children with asthma.
The highest risks were for benzene, followed by ethylbenzene and toluene. For every 10 unit increase in toluene and benzene, the risk of asthma increased by almost two times and three times, respectively.
Those children exposed to total VOC levels of 60 ug/m3 or more were four times more likely to have asthma than those who were not. And these levels were lower than maximum recommended thresholds.
The authors conclude that although their study is small, it supports their theory that exposure to indoor pollutants during early life might be important in the subsequent development of asthma.
A second preliminary study from another research group, assessed the impact of indoor heating appliances that emit fumes on the development of respiratory symptoms.
The authors included a cross sectional sample of 627 children between 8 and 11 years of age. They also surveyed the parents and tested the children for allergy and airway hyper-responsiveness (rapid narrowing), which is a feature of asthma.
They found no association between the current use of heaters emitting fumes and the development of respiratory symptoms. But children who had lived in a home with this type of heater during the first year of their life were 47% more likely to have hyperactive airways and wheezing than those who had not.
Gas appliances, in particular, emit higher levels of nitrogen dioxide than would be found outdoors, say the authors. And some epidemiological studies have linked nitrogen dioxide with an increased risk of respiratory symptoms and illnesses.
If their findings are confirmed by other research, the authors suggest the range of heating appliances used in households with young children should be reviewed.
The research is reported in Thorax - an international journal of respiratory medicine.