Textile disinfection in laundry processes

Although the main purpose of laundry processes is the removal of visible stains and soiling, textile disinfection is particularly important for ensuring that micro-organisms are reduced to hygienically safe levels, as it reduces microbiological contamination present in the fabrics, thus avoiding cross-contamination phenomena that act as routes of transmission and contagion for diseases.

This feature is particularly relevant in the hospital and geriatric sector, in terms of textiles for at-risk groups and those that have a high presence of bodily residue (dead skin, blood, faeces, urine, vomit, etc.) from people who may be infected.

 

Trend for low temperature washing

In recent years, an increase in environmental awareness has led to the development and implementation of low-temperature textile washing programs that optimize energy efficiency. However, lowering the washing temperature means that the antimicrobial efficacy of the process is significantly reduced.

In order to ensure that the laundry process reduces microbiological contamination levels to hygienically safe levels, it is essential to have a broad knowledge of the disinfection mechanisms that are applicable in textile washing processes, allowing for the application of new approaches which are compatible with current energy saving trends, and which are necessary to guarantee the environmental sustainability of the process.

 

Laundry processes that have a disinfectant effect

In order to restore contaminated fabric to a hygienic state, preventing it from acting as a source of contagion and transmission of disease, laundry programs should be specially designed for this purpose. It will be possible to achieve a disinfectant effect for a washing process with an appropriate combination of the following three parameters: Temperature, Time and Chemical Action.

Understanding the great importance of textile hygiene, the main international health organisations (the Centers for Disease Control and Prevention (CDC) in the United States, the European Centre for Disease Prevention and Control (ECDC) in Europe and the World Health Organization (WHO) on a global level) have published numerous technical guidelines to define the necessary requirements to guarantee adequate textile disinfection during a washing process. These organizations have agreed that textile disinfection should be carried out through the application of washing programs that include one of the following mechanisms:

• Thermal Disinfection.
• Thermochemical Disinfection:
  • In the washing phase.
  • In the independent decontamination phase.

 

Thermal Disinfection

The thermal disinfection or thermodisinfection process allows the contaminant load of fabrics to be reduced through the combination of appropriate Temperature (high) and Time conditions, during one or more of the stages of the washing process.

The conditions that enable thermodisinfection to be achieved have been thoroughly studied and defined by the international health organisations mentioned above, establishing the following:

• According to the CDC, thermal disinfection can be achieved with a minimum temperature of 71ºC and a minimum time of 25 minutes.
• According to the ECDC, thermal disinfection can be achieved by washing at a high temperature (90ºC) and adding a detergent.
• According to the WHO, thermal disinfection can achieved with detergent or disinfectant at a temperature of 70ºC for at least 25 minutes.

Operationally, as part of a textile washing process, thermodisinfection is usually carried out in the washing phase, by adding a dose of a detergent that is suitable for high temperatures. Additionally, when it is necessary to obtain a bleaching effect on the fabric, the washing phase itself can also be used as a bleaching phase, combining the detergent with an oxygenated chemical bleaching agent. With the high temperatures of a thermodisinfection phase, active oxygen releasing agents such as hydrogen peroxide or sodium percarbonate can be used as chemical bleaching agents. Due to the oxidizing capacity of these ingredients, they provide the process with an additional disinfectant effect by chemical action.

 

Thermochemical Disinfection

For situations in which it is not possible to achieve temperatures of more than 70- 71ºC, washing programs that incorporate an antimicrobial agent should be implemented, in order to complement the disinfectant effect obtained by the conditions related to temperature and contact time. Thermochemical disinfection consists of a combination of Temperature, Time and Chemical Action.

 

 Complementary chemical actions

Depending on the phase of the washing process in which the complementary chemical action takes place, the following thermochemical disinfection mechanisms can be differentiated:

 

In washing/bleaching phase

Disinfection is achieved through the combination of Temperature (medium), Time and Chemical Action during the washing/bleaching phase, making use of the chemical disinfectant action provided by the oxidizing capacity of the chemical bleach used in the process.

Although the main purpose of chemical bleach in the washing process is to act as a detergent, removing stains that are sensitive to oxidants (such as tea, coffee, etc.), its high oxidizing capacity makes it particularly effective in the elimination of micro-organisms, providing the process with a disinfectant effect.

Among the wide variety of chemical oxidisers currently used in washing processes at medium temperature (between 40 and 60ºC), the following can be highlighted:

• Oxygen Bleaches, such as:
  • Peracetic acid
  • Sodium percarbonate (activated with TAED, to achieve an effect at low temperatures)
  • Organic peracids, such as phthaloimidoperoxyhexanoic acid (PAP)
• Chlorine Bleaches: usually based on sodium hypochlorite.

 

All these chemical compounds are correctly reported as active biocidal ingredients within the European regulatory framework established by Regulation (EU) No. 528/2012 relating to biocidal products, specifically for uses designed for fabric disinfection (product type PT2).

 

In the independent decontamination phase

If it is not possible to achieve sufficient temperatures in the washing/bleaching phase to achieve the thermochemical disinfection effect with the bleaching compounds used, textile disinfection can be carried out in an independent decontamination phase. The combination of Temperature (Low), Time and Chemical Action provided by a specific biocidal product may be used. This biocidal product must be correctly reported as a PT2 disinfectant, in accordance with the European regulatory framework for biocides or the equivalent state regulation.

Although there are a lot of different biocidal active ingredients that can achieve the effect of textile disinfection at low temperatures, among the most widely used at present, quaternary ammonia should be highlighted. They have a broad disinfectant spectrum which works on all types of organisms, a low sensitivity to any dirt that may be present in the process, and a good ecotoxicological profile.

This disinfection process is carried out at low temperatures (below 40ºC), in an independent phase after the washing and oxidising phases, ensuring that the fabrics are already clean and thus obtaining the maximum performance of the disinfectant product.

 

Conclusions

Laundry processes must not only remove the dirt present on the textile, they must also reduce the levels of microbiological contamination present on the fabrics until they are at hygienically safe levels, breaking infectious chains and thus preventing the transmission of infections. In order to achieve the disinfectant effect, it is essential to have a broad knowledge of the disinfection mechanisms that can be applied in the laundry processes in order to select the optimum combination of temperature, time and chemical action.

Due to the great variety of existing micro-organisms, and their different degrees of sensitivity to disinfection conditions (especially temperature and chemical action), it is advisable to adjust the process conditions (time, temperature and concentration of the disinfectant agent used) in order to achieve the desired biocidal effect against the organisms that are to be controlled. The data available from studies of biocidal efficacy (usually EN standards) on the target micro-organisms (bacteria, viruses, fungi, yeasts, etc.) should be used as a reference.

 

Bibliographic references:

(1) Centers for Disease control and Prevention (CDC). Guidelines for Environmental Infection Control in Health- Care Facilities. Updated July 2019. [Fecha de consulta: 14 septiembre 2020]. Disponible en:
https://www.cdc.gov/infectioncontrol/guidelines/environmental/index.html

(2) Centers for Disease control and Prevention (CDC). Disinfection and Sterilization Guideline. Updated May 2019. [Fecha de consulta: 14 septiembre 2020]. Disponible en: https://bit.ly/2VKyfj7

(3) European Centre for Disease Prevention and Control (ECDC). Interim guidance for environmental cleaning in non- healthcare facilities exposed to SARS-CoV-2. Updated February 2020. [Fecha de consulta: 14 septiembre 2020]. Disponible en: https://www.ecdc.europa.eu/sites/default/files/documents/coronavirus-SARS-CoV-2-guidance-environmental-cleaning-non-healthcare-facilities.pdf

(4) Organización Mundial de la Salud (WHO). Infection prevention and control of epidemic- and pandemic- prone acute respiratory infections in health care. Updated 2014. [Fecha de consulta: 14 septiembre 2020]. Disponible en: https://www.who.int/csr/bioriskreduction/infection_control/publication/en/

(5) Bockmühl DP, Schages J, Rehberg L. Laundry and textile hygiene in healthcare and beyond. Microb Cell. 2019 Jul 1;6(7):299-306. doi: 10.15698/mic2019.07.682. PMID: 31294042; PMCID: PMC6600116.

 

AUTHOR: Carles Bertrana