‘Water resistance’ is an ambiguous term, particularly when used in the context of medical protective clothing. Photo: US CDC.
Rain coats, ponchos and garbage bags are water-resistant, in fact waterproof. A recent YouTube video, entitled ‘Appropriate PPE use in different areas of the hospital’, advocates the use of water-resistant gowns to protect from COVID-19. This is wrong. The link for this video, which includes staff of the All India Institute of Medical Sciences, New Delhi, is listed on the homepage of the Ministry of Health and Family Welfare Website, under ‘Resources’.
The message about using water-resistant garments to keep the virus out is mistaken because the ‘guidelines on rational use of personal protective equipment’, issued by the health ministry, prescribes ISO 16603 Class 3 exposure pressure or equivalent (such as ASTM F1670/71-98, EN14126, NFPA1999, ISO 16604, IS16545/46, ASTM F1819-19) as minimum standards for coveralls and gowns. In its EU PPE Regulation 2016/425 and the EU MDD Directive 93/42/EEC, the WHO has also prescribed FDA Class I or II medical devices or their equivalent; EN 13795 (any performance level); or AAMI PB70 (all levels) as acceptable gown standards when dealing with COVID-19 patients.
(According to the International Organisation for Standardisation (ISO), the ISO 16603:2004 specification pertains to “a laboratory test method for measuring the penetration resistance of clothing materials to blood and body fluids. This test method uses synthetic blood in continuous contact with the material specimen at specified set of conditions using the ISO 13994 test apparatus”; source here.)
‘Water resistance’ is an ambiguous term, particularly when used in the context of medical protective clothing. There are different standards associated with this specification. For example, ISO 22958:2005 is, according to the ISO, “applicable to any textile fabric which may or may not have been given a water-resistant or water-repellent finish. It measures the resistance of fabrics to the penetration of water by impact, and thus can be used to predict the probable rain penetration resistance of textile fabrics.”
On the other hand, for the ISO 16603:2004 standard that hospital gowns need to meet, three additional ISO certifications are considered indispensable:
1. ISO 3801 (‘Textiles – Woven fabrics – Determination of mass per unit length and mass per unit area’),
2. ISO 5084 (‘Textiles – Determination of thickness of textiles and textile products’), and
3. ISO 13994 (‘Clothing for protection against liquid chemicals – Determination of the resistance of protective clothing materials to penetration by liquids under pressure’).
It’s a fallacy to think that if a fabric is impervious to water, it will also be impervious to blood (and the viruses it might contain). Many factors affect the wetting and penetration characteristics of body fluids, including surface tension, viscosity and polarity of the fluid’s particles, and the structure and relative hydrophilicity or hydrophobicity1 of the materials.
The surface tension is relevant because it determines the liquid’s wetting characteristics. Blood has a much lower surface tension than water.
Part of the ISO 16603:2004 test method relates to testing for physical stress by applying pressure to a textile sample. A fluid-resistant fabric will resist liquid penetration but may allow penetration with pressure. The ISO 16604:2004 standard includes more sophisticated barrier tests (e.g. using the Phi-X174 bacteriophage challenge suspension) for viral-resistance properties. This test associated with this standard is also used to screen protective apparel before they’re tested for viral-resistance ability.
The Government of India has resolved to use ISO 16603:2004 as the minimum standard.
The Ministry of Textiles has set up laboratories equipped with synthetic blood penetration resistance test facilities to test and certify body coveralls. These laboratories have uploaded a list of manufacturers whose fabric samples have passed the synthetic blood penetration test. The Bureau of Indian Standards also specified requirements for bio-protective coveralls in a meeting on April 3, 2020.
Wrong information about safety apparel could give the user a false sense of safety, and could contribute to panic in emergency situations. And in case it’s not possible for some reason to access a certification test, a prospective user should perform the qualitative elbow-lean test for blood penetration. This test simulates actual use conditions, and hospitals could use it to check for quality. There are also guidelines about what to do in case standard PPE is not available. The WHO has prescribed temporary measures in the context of severe PPE shortage or stock-out with feasibility considerations for all countries.
This said, resistance to blood and body fluids (and viruses) can only be ascertained through laboratory testing and certification, not by intuition and hope.
The WHO has noted that “health care workers are often viewed as ‘immune’ to injury or illness”. These workers are exposed to numerous occupational health hazards, so governments have a responsibility to protect their health and safety if the state can hope to mount an effective pandemic response.
Indeed, the COVID-19 pandemic has presented extraordinary occupational hazards for healthcare professionals. Their situation is precarious. On the one hand, they have to deliver patient care at all costs, and on the other hand, they have to expose themselves to the risk of contracting COVID-19. The only way to wriggle through this unfortunate situation is with the use of good-quality PPE.
Most equipment that the healthcare industry manufactures or purchases and is directed at patient care is mandatorily certified by the Bureau of Indian Standards, the EEA standards (CE), the US Food and Drug Administration, etc. to ensure patient safety. Similarly, it is essential to understand that certification of protective apparel is mission-critical for healthcare workers as well.
Dr Mrinal Barua is with the All India Institute of Medical Sciences, Rishikesh.
Tendency to attract or repel water↩