Effectiveness of laundering processes used in domestic (home) settings

Author: 

Professor Sally F. Bloomfield, Professor Martin Exner, Professor Carlo Signorelli, Dr Elizabeth A. Scott.
International Forum on Home Hygeine

Abstract: 

The aim of this review is to summarise and evaluate the scientific evidence on the effectiveness of domestic machine laundering in reducing the risks of transmission of infections and of antibiotic resistant strains amongst family members.

• In order to save energy, increasingly over the past few years, home laundering has been carried out at lower temperatures (30-40°C). A key aim of this review is to evaluate whether and to what extent the effectiveness of domestic laundering may be compromised by laundering at temperatures of 30-40°C, as opposed to 60°C. Throughout this report the term “effectiveness” is used to describe this process.

• The literature was searched to identify peer-reviewed published data on the effectiveness of machine laundering processes. The 29 publications which were identified were evaluated and data extracted on the effectiveness of laundering (expressed as log reduction in the microbial levels on contaminated fabrics) under different conditions. In particular the impact of temperature, detachment and rinsing, and detergent formulation on hygiene effectiveness was recorded for each study. Other determinant factors which were evaluated were the impact of soiling, details of the machine wash process (wash time, volumes of wash water, number of rinse cycles etc.) and the impact of drying and ironing.

• From studies where the impact of temperature, detachment and rinsing, and detergent formulation was evaluated systematically, it was concluded that each of these factors significantly contribute to the effectiveness of laundering. The data shows that decrease in temperature can significantly increase numbers of survivors on contaminated fabrics, and the transfer of microbes to other items included in the wash. The inclusion of detergent in the wash is associated with a significant decrease in numbers of microbes found on laundered fabrics and decreased transfer of contamination within the wash load. This reduction can be further enhanced where activated oxygen bleach (AOB) is included in the detergent formulation.

• A major difficulty of interpreting the data in this report is the extent of the variability in the results obtained from different studies under any given set of condition e.g laundering at 30°C. The most likely source is the lack of standardisation of test conditions in the published data. Particularly, the data suggests that the specified temperatures are not achieved in many current models of domestic washing machines. Because of the variability in methodology between studies, and gaps in methodological information, in many cases, interpretations about the extent of the impact of changes in temperature, detergent formulation, washing conditions must be regarded as relative indications rather than absolute values.

• In 2011 IFH carried out a detailed review of the potential infectious disease risks associated with clothing, household linens etc. The overall conclusion from the 2011 and this 2013 IFH report is that that clothing, household linens etc. are risk factors for transmission of potentially harmful microbes in the family home, although they may be less than those associated with hands or other frequent hand and body contact surfaces. It is concluded that these risks need to be properly investigated, assessed and suitably managed as part of a multibarrier approach to home hygiene. Tackling antibiotic resistance is a global priority, and since the publication of the 2011 IFH laundry report, there has been increasing awareness that infection prevention and control measure in hospital and hygiene practices in the home and community are a central part of reducing spread of drug-resistant organisms such as meticillin resistant S.aureus (MRSA) and faecal organisms carrying multidrug resistance determinants in the community as well as in hospitals. As persistent nasal, skin or bowel carriage of these strains in the healthy population spreads “silently” in the community, the risks of infections from drug resistant strains in both hospitals and the community increases. The risks are such that home laundering should be able to not only reduce the risk of transmission of infectious illnesses amongst family members, but also reduce the “silent” spread of antibiotic resistant strains such as MRSA or multidrug resistantgram negative species which may be carried (e.g on the skin or within the normal bowel flora) amongst healthy family members. Even with modern approaches, it is difficult to quantify the risks associated with domestic laundry. Because of this, and the lack of precision about LR values obtained, it is difficult to determine with any degree of confidence the likely effectiveness of laundering under any given conditions and thus give informed advice to consumers (and those involved with developing washing machines, laundry detergents etc.) on appropriate and optimum conditions for laundering of clothing to manage risks of spread of infection and/or colonisation with resistant strains.

• IFH recognises the need to move to low temperature (30°C) laundering in order to conserve energy usage, but this review together with the 2011 IFH report suggest that it is also advisable, in public health terms, that steps are taken to ensure that, this is achieved without compromising hygiene effectiveness. This report suggests that there are good possibilities to achieve this through one or a combination of approaches which include the use of AOB-containing detergents, optimizing detachment through enhance detergency, optimizing dilution through rinsing, or the use of “detergent”/microbicidal rinse products etc., It could also include targeted changes in drying and ironing practices.

• Further work is required to gain a better picture of the impact of laundering at reduced temperatures, and the ways in which this could be done without compromising laundry hygiene.

In response to current needs, IFH has developed guidance on home laundering of clothing and household linens. This is set out in Appendix 1. The proposed guidance is the consensus view of the IFH, based on the findings of this report, and the feedback of, and opinions expressed by, the other members of the panel of experts who examined the report. However, the inconsistency in the published data couple with the data showing that in reality many modern washing machines do not reach the temperature specified on the machine controls makes it extremely difficult to propose guidelines for home laundering with confidence, without first generating better data.