Gloves for Chemical Protection
Published: 15th Feb 2016
In many workplaces it is common to find gloves being worn to protect workers against the hazards represented by the chemicals they may be exposed to.
Unfortunately, it is also all too common to find that the level of protection that they are receiving is inadequate. Indeed, if the wrong gloves are being used, or even if the right gloves are not being used correctly, the effect for the wearer may be worse than had no gloves been worn at all. Why is this?
The reality is that the selection and use of gloves for protection against chemical hazards is far more complex than many realise. This article will explain some of the factors that need to be recognised when considering whether gloves should be worn, which are the correct gloves and how well they will work. Space limitation does not permit a full explanation of all the many factors, but guidance on where to find further information will be given at the end.
When to use gloves for chemical protection
In most industrialised countries the regulations require that the prevention of skin exposure to a chemical hazard is controlled by means other than the use of personal protective equipment, such as gloves. There are several reasons for this.
So, other than as a temporary measure, gloves should only be used where other means of preventing exposure to chemicals cannot achieve an adequate standard of exposure control.
Why is the selection and use of gloves so complex?
Perhaps we should start by considering the four main reasons why gloves fail. These are:
1. Misuse - Using the incorrect glove; using it incorrectly, in particular not removing the glove with the correct method resulting in the hands becoming contaminated with the hazardous chemical.
2. Physical damage - Should the glove develop a hole or cut then it can no longer ensure that the wearer is protected.
3. Degradation - The chemical attacks the actual glove material. This is usually obvious to the wearer as the glove will show visible signs of the damage that is occurring.
4. Permeation - The chemical is absorbed into the glove and migrates through at a molecular level, emerging as a vapour on the inside of the glove. This is undetectable by the wearer. What is required here is to know with the particular glove and chemical how long this will take.
How we incorporate these into the decision as to which glove to use for a particular task and how long it will protect the wearer is not as simple as many assume.
What actually happens when gloves are worn for a particular task can have a major effect on how long the glove will protect the wearer. In a study carried out by the author in conjunction with a UK university, small detector pads were used underneath the protective glove to establish the extent to which the in-use factors might affect the time for which the glove would protect. The results were surprising. For example, a nitrile glove with a permeation breakthrough time (determined using the EN374-3 test) of 36 minutes when tested against xylene, showed for one task with this chemical no permeation breakthrough for in excess of two hours, but for another task showed permeation breakthrough in just five minutes.
Mixtures also present a problem in that the mixture can have a surprising effect on glove performance. A glove that had been tested for permeation breakthrough with methyl ethyl ketone and toluene, showed for each on its own no permeation breakthrough for at least 240 minutes. However, when tested against a mixture of the two chemicals in equal parts, the permeation breakthrough time was just nine minutes.
One significant factor is that of temperature. Indeed, the test for EN374-3 specifies that it is carried out at room temperature, stated as 23ºC ±1ºC. Yet hands tend to be warmer than this and gloves, when worn, will tend to adopt the skin temperature. The table shows permeation breakthrough times at the stated test temperature and at a temperature similar to that of a hand inside an occlusive glove.
What is apparent from these measurements is that there is no simple equation which states that for a certain increase in temperature there will be a defined reduction in permeation breakthrough time.
One common reason why gloves so often fail to protect is mishandling of the gloves by the wearer. It is often assumed that everyone knows how to put on and take off a pair of gloves. Yet simply observing someone removing gloves that have been in contact with a chemical – or biological – hazard shows clearly that this is not the case. Unless the correct method of removal is adopted it is almost inevitable that the wearer’s hands will contact the outer surface of the glove, resulting in the skin becoming contaminated with the very chemical hazard against which it was intended to protect.
“Forty-three hairdressers and apprentices were asked to remove gloves after washing hair. UV tracer was used to identify hand contamination before and after a training session on glove removal. All the participants (100%) had their hands contaminated during the first round. In the second round 55.8% were contaminated. There were no significant differences between hairdressers and apprentices.” - Glove use among hairdressers: difficulties in the correct use of gloves among hairdressers and the effect of education, Oreskov KW, Søsted H, Johansen JD, Contact Dermatitis, 2015.
Note that although there was a significant reduction in the number of persons who contaminated their hands after treatment, this was still around half the total number of glove wearers. The author’s experience is that repeat training is something that has to be considered if acceptable standards are to be achieved and that this is particularly important where the effect of contact between skin and hazard would be severe.
Which gloves do we choose?
In most countries gloves for protection against chemical hazards must comply with a number of standards. The following information relates to the regulations that apply within the European Union. Similar regulations and standards will exist in other countries and the person deciding whether and how gloves should be used for protection in a workplace will need to ensure that they are familiar with these.
EN420 - General standards for protective gloves:
- This standard defines the general requirements for protective gloves in terms of construction, fitness of purpose, safety, etcThe gloves themselves should not impose a risk or cause injury
- The gloves themselves should not impose a risk or cause injuryThe pH of the gloves should be as close as possible to neutral
- The pH of the gloves should be as close as possible to neutralThe highest permitted value for chromium is 3 mg/kg (chrome VI)
- The highest permitted value for chromium is 3 mg/kg (chrome VI)ecific details of any substance used in the glove which is known to cause allergies
- Secific details of any substance used in the glove which is known to cause allergies
- Sized by reference to an agreed common European hand size; for example, minimum length
EN374 - Gloves giving protection from chemicals and microorganisms:
- This is the main standard of concern to those who have to decide which gloves to use for protection against chemical hazards
Protective gloves must also fit into one of three ‘categories’. For chemical protection only categories I and III are relevant. Different symbols then indicate into which category the gloves fit.
To comply with the requirements for classification as a category III glove it must be shown to provide a permeation breakthrough time of at least 30 minutes when subjected to the standard permeation test (EN374-3) for three of a specified range of chemicals. To achieve this, samples of the gloves must have been tested by an independent, accredited laboratory.
Manufacturers wishing to sell their gloves as category III gloves will then need to arrange for them to be tested against a range of chemicals and make this information available to the purchaser. This is usually done by classifying the level of protection achieved by the time taken for the chemical to permeate when tested. In theory this allows the purchaser to identify the optimum glove, i.e. one that has been classified as class 6 for the chemical in question.
A further factor now comes into play, the AQL (Acceptable Quality Level). This is the number of faulty gloves that are to be expected per 100 gloves. There are three levels, as shown in the table. Where biological hazards are concerned caution is advised here, as the test applied is not necessarily adequate to detect holes down to a diameter that will prevent the passage of microorganisms. It may be necessary to arrange for additional, more stringent testing to be carried out.
If a particular type and make of glove is to be used as protection against one or more chemicals the user must then obtain the permeation data for both this particular glove and these chemicals from the manufacturer or supplier. This forms the basis for deciding which glove is acceptable and the level of protection afforded. However, EN374 actually states: “The chemical data information does not necessarily reflect the actual duration in the workplace.” Given the factors already described that affect a glove’s performance it may be prudent to obtain specialist advice.
In some situations it may be advisable to conduct actual ‘in use’ testing to establish the real performance level that the glove is providing for the actual workplace and task for which it is being used. This can be done using small pads of activated carbon cloth attached to the skin underneath the glove. These are replaced at pre-determined intervals, then analysed. The time taken for the chemical to appear in the analysis is then the maximum time for which the glove will penetrate for that chemical in that task. Ideally a safety factor will then be applied to ensure that the wearer is not exposed.
Gloves as a hazard to health
Yet another consideration is the effect that wearing occlusive gloves will have on the wearer’s skin. All such gloves will cause changes in the condition of the skin of the hands that can, of their own, result in what one eminent dermatologist has called hydration dermatitis. This is due to the increase in moisture content in the outermost layers of the skin. It is common to refer to this as sweat, but this is not correct! There are two causes for the hyperhydration, namely what is referred to as trans-epidermal water loss (TEWL) and sweat. TEWL is a continuous loss of water through our skin. A person with a normally functioning skin can lose up to 700 mg of water each day in this way. Normally this evaporates from the skin surface, but underneath the glove this is prevented and the water is absorbed back into the skin.
Sweat only occurs where the sweat glands are activated, normally due to an increase in body temperature. One can provide a person with occlusive gloves and then place them in a cold room where sweating will not occur. There will still be an increase in skin moisture content in the gloved hands. This is one reason why claims that a cream applied to the skin that will prevent sweating will prevent hyperhydration are not correct, since the cream will have no effect on TEWL. What is needed is a layer on top of the skin, underneath the occlusive glove, that will absorb and retain the moisture so that it is not absorbed back into the skin.
“The negative effect on skin barrier function from occlusive gloves was prevented by the use of a cotton glove.” - Effect of glove occlusion on human skin - Long-term experimental exposure, Ramsing DW, Agner T, Contact Dermatitis 1996, 34, 258-262.
A recommended approach is now that if occlusive gloves are worn for more than two hours in total in an eight hour shift, cotton gloves should be worn underneath the protective glove and changed as and when they become saturated.
Considerable concern is often apparent about allergic reactions to chemical protective gloves. Experience indicates that provided gloves of high quality are selected this risk is actually relatively minor, often being mistaken for an allergic reaction, whereas the reality is that it is irritated due to the hyperhydration.
This article illustrates that the selection and use of gloves as protection against chemical hazards is frequently not as simple as many assume. Of course, there will be situations where determining which glove to use is simple. For example, for washing dishes a good quality natural rubber latex glove will provide adequate protection. However, where more hazardous chemicals are in use the creation of an effective glove selection and use system that ensures the glove user is adequately protected may be much more complex and may require the support from someone with the appropriate specialist knowledge.
Published: 15th Feb 2016 in Health and Safety International