April 3, 2015

expert reaction to study linking household bleach and infection rates in children

A new study has investigated a potential link between the use of household bleach and rates of infection and respiratory problems in children.

Prof. Peter Openshaw, President of the British Society for Immunology and Professor of Experimental Medicine at Imperial College London, said:

“Although the authors acknowledge that cross-sectional studies raise questions rather than show causality, they conclude that domestic exposure to bleach may increase the risk of respiratory infections. The effect is not large (about a 20% increase), and it is possible that other benefits of domestic hygiene (that are not assessed) may outweigh the adverse effects on respiratory infection that they report. It’s important to recognise that the study relies on self-reported use of bleach and illness rather than objective measurements of exposure and health outcomes. Households that report the use of bleach may well have different thresholds for reporting illness compared to those that don’t.

“What is needed now is a study that comprehensively measures indoor air pollution (including chlorine and other volatiles from cleaning products), uses validated objective measures of respiratory infection and investigates the possible immunological mechanisms by which use of cleaning products might influence the frequency of respiratory infection. The study is interesting, but given these limitations the findings should be treated with caution. I will continue to (sometimes) use bleach at home.”

Dr Glenis Scadding, Consultant Physician in Allergy & Rhinology, Royal National Throat, Nose and Ear Hospital, said:

“This study helpfully highlights that we need more work in this area – the results are interesting but not yet conclusive. It was a large study, investigating household bleach use and childhood infections in three different countries.

“It would be interesting to know the reason behind the use of bleach in different households, and this could be relevant to the results – for example, might some families use more bleach after their child or children have had infections? This could potentially mean the children in some high bleach use households were already prone to infections for other reasons, before bleach use was measured.

“Finland is especially interesting because they tended to use less bleach than other countries but had quite high infection rates overall – low levels of one bout of sinusitis but high levels of recurrent sinusitis, and the same pattern for tonsillitis. This is an interesting finding and one that merits further investigation.

“Households in Spain had higher use of bleach than the other countries, which reduced overall statistical power because numbers in each level of bleach use were small.

“The levels of flu reported might warrant further study because the levels diagnosed are surprisingly high – 11% recurrent flu overall among children is higher than would be expected.

“Overall, this is an interesting study and will hopefully lead to further research in this area. There are some limitations and the authors are clear about these. We can’t tell from this study whether or not using bleach in the home leads to childhood infections.”

Dr Colin Michie, Paediatrician, Ealing Hospital Integrated Care Organisation, said:

“Do bugs on our children and their homes need to be eradicated? Bleach and other disinfectants may not always be beneficial.

“Children with staphylococcal colonisation that makes their eczema worse, for instance, are recommended to add bleach or disinfectant to their bathwater. Bleach has been used for the eradication of antibiotic resistant bacteria such as MRSA for many years. In these situations a reduction in bacterial numbers is effective. Clean homes and kitchens will also reduce the risk of food poisoning.

“However successive studies such as this one appear to alert us to potential harms from bleach. There are many problems with this study, as outlined by its authors. The most significant is that no information was collected relating to other cleaning agents used in the homes. Further, as this was an observational study, the responses could not be checked or validated. However the findings challenge paediatricians to decide just how clean children should be in order to stay healthy.”

Prof. David Coggon, Professor of Occupational and Environmental Medicine, University of Southampton, said:

“This study reports a modest association between frequency of respiratory infections in children and use of bleach in the home. The study was well-conducted, but has limitations which the authors rightly acknowledge. It is plausible that inhalation of the irritant gases which can be released when disinfectants are used, could in some way impair the body’s defences against infections. However, it is currently unclear to what extent the use of bleach in the home impacts on such exposures. To be exposed, a child would have to be in the relevant part of the house at a time when significant concentrations of the irritant gases were present. Until we understand better what levels of exposure result from use of bleach, how frequently, and whether the excess of respiratory infections is specifically in children who are exposed to the irritants, it is difficult draw very strong conclusions.

“Another possible explanation for the observed association is that parents who perceived their children to have more frequent infections were, as a consequence, more inclined to use bleach in the home.

“Importantly, it should be remembered that use of bleach to maintain good hygiene can have important benefits for health.”

Prof. Sally Bloomfield, Honorary Professor, London School of Hygiene & Tropical Medicine, said:

“This study tends to ask more questions than it answers and is clearly intended to make the case for further research rather than show there is a real effect. By the authors’ admission, the reported health effects are rather modest, and were self-reported rather than medically diagnosed.

“Demonstrating an epidemiological link does not demonstrate cause and effect. The authors note various potentially important confounding factors which they were not able to control for which could explain the results.

“There was no quantitative assessment of the possible level of bleach exposure in different homes in different countries in relation to health effects (the dose:response relationship) i.e. what concentrations were used, where the product was used, how much was used and how often, all of which would affect the extent of exposure and any response.

“Importantly, the authors provide limited biological evidence to support the proposed mechanism by which bleach exposure might damage the respiratory epithelium and thereby lower resistance to infection.

“We should be very careful in reporting these results. Oxidising microbiocides such as chlorine bleach are used at concentrations ranging from 0.5 up to 50,000 ppm, and are a vital part of our armoury to prevent infections in healthcare settings, water treatment, the food and pharmaceuticals industries – and also in the home when used in a targeted manner to prevent the spread of infectious germs. The vital importance of bleach to protect against infection was demonstrated in the recent and ongoing fight against Ebola in West Africa.”

‘Domestic use of bleach and infections in children: a multicentre cross-sectional study’ by Lidia Casas et al.  published in Occupational & Environmental Medicine  on Thursday 2 April 2015.

Declared interests

Prof. Peter Openshaw’s research is funded by the Wellcome Trust, the MRC, BBSRC and the European Union. He has received honoraria or consultancy fees from GSK, Janssen, Johnston and Johnston and Sanofi.

Prof. Sally Bloomfield is also on the Scientific Advisory Board of The International Scientific Forum on Home Hygiene (IFH), which is a not-for-profit, non-commercial, educational trust, which is supported through contributions from various sources which includes the householdcare industry.