Hard, non-porous surfaces in public facilities that receive the most hand contact, such as door handles, elevator buttons, light switches, counters, and touchscreens, can be hot spots for the transmission of pathogenic microorganisms which can lead to infections in people.
Normal disinfectants intended for such surfaces are an important part of providing a hygienic environment. The cleaning process removes soil and microorganisms, and the disinfection process kills or inactivates remaining microorganisms. However, they are only effective immediately and offer no ongoing protection. To address this limitation, a range of chemical products can be applied to the surface on a regular basis to provide continued efficacy between cleaning and disinfection events. These products are referred to as having residual efficacy.
Manufacturers claim that residual efficacy reduces the hygiene risk for surfaces by continually protecting the surface with active biocidal compounds.
A common approach is to regularly apply the residual product which includes the biocidal agent (typically a chlorine-releasing compound or a quaternary ammonium chloride or ‘quat’ compound). It may also include a removable film (siloxane polymer or polyvinyl alcohol) or another agent to help attach the biocidal agent to the surface.
Dr Claire Khosravi, Diversey Europe’s EU IP & PC application and technical team lead, says: “Our Degragerm 24 Shield product features an innovative advanced polymer technology based on a polymer-binding film. This film provides a reservoir of quat near the surface, meaning that over the next 24 hours, any contamination of the surface is exposed to a fresh supply of biocidal quat.
“Through this mechanism, the surface retains the antimicrobial ability, limiting microbial contamination between applications of the product.”
However, products like this and Proctor & Gamble’s Microban 24, which both claim to “kill 99.9% of bacteria and viruses for up to 24 hours” including “the viruses that cause flu, colds, and COVID-19”, only do so if used correctly and do “not provide 24-hour residual virus protection”. They also contain harmful chemicals which require protective equipment to be worn during use, and could even cause health and environmental issues.
As well as these issues, quats can be adversely affected by water hardness (during dilution), fat-containing substances, and anionic surfactants.
In addition, cotton and gauze may absorb the active ingredients of quat-based products and significantly reduce their effectiveness.
Under the Workplace (Health Safety and Welfare) Regulations 1992, employers have a legal duty to ensure, as far as is reasonably practicable, the health, safety, and welfare of employees. Furthermore, the Management of Health and Safety at Work Regulations 1999 require employers to assess and control risks to protect their employees. A key element of this is the requirement to comply with the COSHH Regulations. The COSSH Regulations cover dust, mist, vapour, fumes, and chemicals. In addition to their health and environmental risks, hazardous cleaning and disinfection chemicals therefore also incur an additional administrative burden.
On the other hand, the COVID pandemic has caused increased pressure on the healthcare sector to maintain proper sanitisation and hygiene in facilities. Companies in the hypochlorous acid market have been developing efficacious disinfectant products that are more effective and more environmentally friendly than bleach, to combat COVID in hospital and healthcare settings.
One such British company has produced ‘Nemesis eH2O’ which it claims is a superior ‘natural’ alternative that features stabilised hypochlorous acid (weak HOCl) as its active ingredient. It contains no harmful chemicals or alcohol, so no personal protective equipment (PPE) is necessary for normal use, and it can be applied by spraying or fogging any surface.
A further advantage of HOCl is that it rapidly degrades to salt and water after application, so it is not persistent in the environment.
What’s more, eH2O offers an order of magnitude better protection than bleach at 99.99% protection, which may not sound like much, but Adrian Gee-Turner, from L’Eau Limited, says that the difference is enormous. “Most bleach manufacturers claim 99.9% kill (Log-3) of harmful micro-organisms, so Nemesis eH2O can claim to be 1,000 times more effective. This means that bleach could be expected (in the right conditions) to reduce 1 million colony forming bacterial units (CFUs) to 1,000 CFUs, whereas a Log-6 disinfectant (such as eH2O) would be expected to reduce the same size colony down to just one single CFU. Bleach is therefore mainly suitable for the low-cost disinfection of non-porous, unpainted surfaces such as floors and toilets.
“What you really need is something that kills a broad spectrum of pathogens with a high level of efficacy, but without toxic effects for users or the environment. That’s what HOCl is,” Gee-Turner says. “It’s actually more effective than having something that’s longer lasting.”
He says that products that claim to be longer lasting can be problematic because cleaning is the vital first stage of any disinfection programme.
“The biggest problem in the cleaning industry is people want a single product that you can spray and wipe straightaway,” Gee-Turner explains. “The problem with that is that it is necessary to clean a surface before disinfection so that the disinfectant is not neutralised by soil. What we teach is to clean with any kind of degreasing, dirt removing substance – a degreaser or soap – and then spray using an electrostatic gun.”
ELECTROSTATIC SPRAYING
L’Eau Limited’s ‘Atom Electrostatic Sprayer’ uses electrostatic technology to attract HOCl to a surface. The fine, positively charged droplets are attracted to the negatively-charged environment. When released from the sprayer as a mist, the droplets lock together on a surface and form a very thin film on an object. These handheld devices are said to be used infields including medical, industrial, military, laboratories, agriculture, in brewing and food processing to preserve the life of produce.
Hospitals in North Wales, North Tees and Hartlepool are changing from using hydrogen peroxide to HOCl because not only is it not poisonous but can also kill
C. diff, a so-called ‘superbug’, effectively. NHS Scotland carried out a retrospective revue that found the cost of cleaning to combat C. diff in hospitals was around £240 million per year across the UK.
HOCl can also be used to sterilise and disinfect equipment, which is important to reduce incidences of common hospital-borne infections such as MRSA and clostridium bacteria, which are highly common in healthcare environments.