Reference
Casas L, Espinosa A, Borràs-Santos A, et al. Domestic use of bleach and infections in children: a multicentre cross-sectional study. Occup Environ Med. 2015 Apr 2. [Epub ahead of print]
Study Design
Cross-sectional study
Participants
As part of the Health Effects of Indoor Pollutants: Integrating Microbial, Toxicological, and Epidemiological Approaches (HITEA) project, this study evaluated 9,102 children, aged 6-12 years, from schools in Spain, the Netherlands, and Finland.
Parameters Assessed
Parents of enrolled children completed a questionnaire, reporting the frequency of infections (influenza, tonsillitis, sinusitis, otitis, bronchitis, and pneumonia) over the past 12 months and reporting whether or not bleach was used to clean the home at least once a week.
Primary Outcome Measures
Relative risk (RR) ratios for childhood infections in relation to bleach use in the home were calculated for each country, and RR ratios were combined for meta-analysis.
Key Findings
Bleach use varied greatly among countries (7% of respondents from Finland and 72% of respondents from Spain). In all 3 countries, the overall prevalence of infections was higher in children exposed to bleach. Exposure to bleach was associated with significantly increased risk for influenza in the Netherlands (RR=1.27; 95% confidence interval [CI]:1.06-1.54), tonsillitis and sinusitis in Finland (RR=2.41; 95% CI:1.25-4.66 for tonsillitis; RR=2.18; 95% CI:1.19-4.00 for sinusitis), and any infection in Spain (RR=1.28; 95% CI:1.00-1.65). That's a 27% increased risk for influenza in the Netherlands, 141% increased risk for tonsillitis and 118% increased risk for sinusitis in Finland, and 28% increased risk for any infection in Spain. In combined analysis of all 3 countries, exposure to bleach was associated with increased risk for influenza, tonsillitis, and any infection.
Practice Implications
The current study using HITEA study participants finds a positive correlation between the use of bleach in the home and the incidence of infectious diseases in children. This relationship is scarcely explored in other studies, which more commonly examine the relationship between atopic disease and chlorine or bleach exposure. Wheezing in infants and small children, for example, has been associated with routine household use of chemical cleaners (including bleach and cleaning sprays).1-3 In addition, risk for bronchiolitis in infants and risks for allergies and asthma in children have been correlated with swimming in chlorinated pools.4,5 In contrast, according to a cross-sectional study of similar design to the study reviewed here, household use of bleach was associated with decreased risks for asthma, eczema, and dust mite allergies.6
Bleach exposure might increase the risk for infectious disease because aerosolized volatile chemicals released from chlorine bleach irritate the respiratory tract and make children more susceptible to respiratory illness.
Part of the challenge in assessing the relevance of any of these studies is their design. These are population-based studies, which are helpful to improve our understanding of environmental risk factors for disease but can only identify associations, not causal relationships. Results of population-based studies can be misleading if a variable that is not accounted for is the true cause of the observed effect. The study reviewed here adjusts for sex, age, mold in the home, passive smoke exposure, and parental education but does not account for household use of any other cleaning products that may expose children to chemical irritants. We must, therefore, be cautious in generalizing the findings.
If household use of bleach does, indeed, increase the risk for infectious diseases, the mechanism is uncertain. It is tempting to argue that the results of this study support the “hygiene hypothesis,” the idea that children’s immune systems become compromised by living in artificially sterile environments. However, the hygiene hypothesis more specifically states that atopic disease—not infectious disease—increases when children are deprived of microbial exposure, fail to develop natural immunity, and do not establish a healthy microbiome.7 A more feasible explanation for why bleach exposure might increase the risk for infectious disease is that aerosolized volatile chemicals released from chlorine bleach irritate the respiratory tract and make children more susceptible to respiratory illness.
Patients use bleach in their homes because it is a broad-spectrum disinfectant, thought to eliminate disease-causing microorganisms—making the results of this study somewhat of a paradox. For practical purposes, bleach is simply unnecessary for routine household cleaning. An unbleached home does not need to be a dirty home. Nontoxic cleaners can be purchased or made at home with vinegar, baking soda, liquid soap, essential oils, or other natural ingredients. We could wait for future studies to confirm the association between household use of bleach and childhood risk of infectious disease, or we could act on the assumption that, as this study suggests, the risks of bleach for routine household use outweigh its benefits.
