BARCELONA, Spain, Oct. 12 -- Using common household cleaning sprays and air fresheners at least once a week may increase the user's asthma risk, European researchers reported.
On average, the asthma risk, which increased with frequency of use and the number of sprays, was about 30% to 50% higher in regular users, primarily women, Jan-Paul Zock, Ph.D., of the Municipal Institute of Medical Research here, and international colleagues, reported in the second October issue of the American Journal of Respiratory and Critical Care Medicine.
The results underscore an important public health issue for those who clean their own homes, Dr. Zock and colleagues said.
Many reports have found adverse respiratory effects and increased asthma among professional workers who clean homes or commercial and industrial facilities. However, the respiratory effects of nonprofessional home cleaning with cleaning sprays have rarely been studied, the researchers wrote.
To investigate the risk of new-onset asthma among individuals using common household cleaners, the researchers used data from the European Community Respiratory Health Survey, an epidemiological study that included 22 centers in 10 countries, plus interviews about nine years later.
The researchers identified 3,503 persons doing the cleaning in their homes and free of asthma at baseline.
Frequency of use per week of 15 types of cleaning products was obtained in face-to-face interviews. The participants were also assessed for current asthma, current wheeze, physician-diagnosed asthma, and allergy at the nine-year follow-up.
Two-thirds of the study population doing the cleaning and washing at home were women, ranging from 57% to 87% from country to country.
About 6% of participants had current asthma symptoms at the end of the follow-up, while the incidence of physician-diagnosed asthma was 2.3 per 1,000 person-years.
The use of cleaning sprays at least weekly (42% of participants) was associated with an almost 50% increase in those with asthma symptoms or medication use (relative risk 1.49; 95% confidence interval 1.12-1.99) and wheeze (RR, 1.39; CI, 1.06-1.80).
The incidence of physician-diagnosed asthma was twice as high among those using sprays at least four days a week (RR, 2.11; CI, 1.15-3.89). These associations were not modified by atopy, the researchers said.
Dose-response relationships (P<0.05) were apparent for the frequency of use and the number of different sprays.
The association between spray products and asthma was seen primarily with the most commonly used air fresheners, glass cleaners, and furniture-cleaning sprays.
Cleaning products, such as solvent stain removers and washing powders not applied in spray form, were not associated with asthma. Also products used infrequently, such oven sprays, did not pose a major risk.
This research may also have significant implications for public health, they said. Relative risks of 1.3 to 1.5 together with an overall proportion of 42% of spray users suggest that exposure to cleaning products could account for as much as 15%, or one in seven adult asthma cases, the researchers wrote.
However, this study, the researchers said, precludes strong conclusions about the biological mechanisms behind the risk. It is possible, they said, that asthma could have been partly induced by irritants. Also, cleaning sprays contain sensitizers, such as disinfectants, amines or pinene, so that specific sensitization resulting in asthma is possible.
It is also possible, they said, that a localized inflammatory response is involved. Further studies are needed to explain the mechanisms of the respiratory toxicity.
In discussing study limitations, they said it is possible that asthma was due to the scented component in the cleaning products. However, it is more likely that those with asthma avoided these products and therefore could have biased the finding toward the null. Analysis found that frequency of use of perfumed and scented products was not associated with asthma.
In an accompanying editorial, Kenneth D. Rosenman, M.D., of Michigan State University in East Lansing, wrote that companies are not required to test their products or the ingredients for the ability to cause type 1 immunologically mediated reactions, such as asthma.
Routine testing by these companies includes assessing the compound's irritant potential and sometimes testing for contact dermatitis. Accordingly, the number of potential sensitizers in cleaning products is unknown.
The methodology used in Dr. Zock's study is strong, Dr. Rosenman said, and clinicians should be aware of the potential for respiratory toxicity for these products.
The local studies in the European Community Respiratory Health Survey II were funded by institutions, health departments, and agencies in the various countries, as well as by several drug companies, including GlaxoSmithKline Italy, Glaxo Wellcome AS, Norway, and UCB Pharma (France).