ABC of Safety in the Biological Sciences
GLOVES - HELP OR HAZARD?
Millions of gloves are used as protection every year by people at work in the UK. These gloves have two purposes. Either they are to protect the user from hazards in the workplace or to protect a product or person from the user. Of course, the glove may be expected to perform both functions. Examples of the former would be where sharp, hot or cold objects have to be handled or where exposure to a hazardous chemical is inevitable. Examples of the latter would be, for example, in health care to prevent cross infection, in the food industry to prevent contact with the food being handled or in the electronics industry to prevent the product being contaminated by human skin cells and lipids.
Of all of these, probably the most problematic is the provision of protection against hazardous chemicals, since each will have its own characteristics. Different gloves will perform in different ways. In a number of cases there is simply no glove which will provide adequate protection and still enable the work to be carried out.
In addition, we have to take into account the effect on the wearer of covering the skin with an impermeable membrane.
The question has to be asked: Are gloves a help or a hazard?
My studies indicate that many gloves used in industry do not provide the protection that the employer and user believe they are getting. In some cases, the glove may actually be increasing the risk of damage to health from contact with the chemical. There is also the possibility that the glove may, itself, cause damage to health.
For a start, we need to consider the various factors which affect the way in which a glove performs. In the rest of this article we will concentrate on gloves being used as protection against chemical and biological hazards.
Gloves sold for this purpose come in many different materials, of which the main ones are: Natural latex rubber, Nitrile rubber, Polychloroprene (Neoprene™), Polyvinyl chloride (PVC), Polyvinyl alcohol (PVA), Butyl rubber, Viton rubber, and various mixtures and laminates.
Each of these has its own particular characteristics and applications. None could be considered a universal glove suitable for all applications. To appreciate why selection is important we could consider how gloves actually fail.
There are four main reasons why gloves do not always provide the protection needed if damage to the health of the worker is to be avoided: Misuse, Physical failure, Degradation, Permeation and Misuse.
We assume that the worker will know how to don or remove a pair of gloves. This is simply not the case. If the untrained worker is asked to demonstrate the correct technique he or she will usually manage to contaminate either their hands or the inside of the glove.
Dirty gloves stuffed into an overall pocket or place in contact with clean clothing in a locker overnight are other causes of failure. Basic training on the correct use of gloves, including an understanding of the other factors described below, is essential (and a legal requirement) if gloves are to perform adequately.
It is important that the correct glove is worn. Chemicals underneath the glove may cause more damage than were a glove not worn at all, since they will be held in contact with the skin in a micro-climate where the skin's natural barrier cannot operate effectively.
It is not uncommon to see workers wearing gloves with holes, splits or cracks. It is also not uncommon to see workers wearing gloves from which they have removed the fingers so as to improve dexterity. They still seem to assume that the glove is protecting them!
Usually this damage is obvious. More insidious are the tiny imperfections (pinholes) which are often impossible to detect other than by sophisticated testing techniques. Frequently these holes are large enough to permit the penetration of a chemical, bacterium or virus.
Since there is no material known to man which is suitable for use as a glove and which is resistant to all known chemicals, it follows that many chemicals will attack and destroy a glove. For example, all hydrocarbon solvents will degrade natural latex rubber. The material will usually show visible signs of this in the form of swelling, tackiness, loss of flexibility etc.
Less easy to detect is permeation. Almost all chemicals have the ability to permeate some glove material. Permeation is a diffusion through the glove at a molecular level, the chemical then being emitted as a vapour from the interior surface of the glove. In itself, permeation does not involve any change in the appearance of the glove and is generally undetectable by the wearer - that is, until some damage to his health from exposure occurs.
What we need to know is how long it will take for a particular chemical to permeate through a particular glove. This is generally known as the permeation breakthrough time (BTT). Traditionally this was expressed in minutes, although the new EU regulations now stipulate six different categories.
Selection of a suitable glove
Reputable glove manufacturers provide performance data in the form of tables showing degradation and permeation factors for each of their gloves, for a range of chemicals. Unfortunately, this information alone is not sufficient to enable the selection and use of a glove. Surprisingly, there is at present no standardised test for degradation, so each manufacturer will have his own method. This makes comparison extremely difficult. Permeation is carried out in a static laboratory test at room temperature. This bears little relationship to what happens in the workplace when the glove is actually used. Neither factor can be taken on its own. For example, a natural rubber glove may show 120 mins. breakthrough time with 60% nitric acid, yet degradation will cause the glove to split within 30 mins.
As the diagram shows, many different factors interact to determine how well a particular glove will perform under normal working conditions. At present there is no simple way of evaluating these to produce a safe working time for a glove. Recently it has become possible to actually test gloves under actual working conditions for chemical breakthrough. This enables a safe working practice to be established. The results of such tests indicate that glove performance may vary widely from the manufacturers' data.
Some gloves are sold as "cotton lined" or "supported" gloves. These have a cotton internal surface. Where this surface shows seams, then the glove started as a cotton glove that was subsequently dipped or coated with the chemically resistant coating, usually rubber or PVC. Such gloves generally offer only limited resistance to chemicals.
The reason is that the fibres from the cotton inner glove may reach up into the coating, this reducing the effective thickness. There have been cases where the fibres have been detected on the surface of the glove, thus rendering it totally ineffective as protection against chemicals.
Gloves as a hazard to health
Quite correctly, the current health and safety legislation stresses that gloves are, in effect, a last resort. Regulation 7(2) of the COSHH Regulations states:
So far as is reasonably practicable, the prevention or adequate control of exposure of employees to a substance hazardous to health, except to a carcinogen or a biological agent, shall be secured by means other than the provision of personal protective equipment.
Regulation 7(3) then goes on to state that where personal protective equipment is used it must only be in conjunction with the other means. How many employers can genuinely claim that they have actually exhaustively investigated all other practicable means of control before providing their workforce with gloves?
One good reason for this approach to PPE is simply that if personal protective equipment fails it almost invariably fails to danger, whereas with engineering controls it is often possible to create a "fail-to-safe" situation. Thus, where short terms exposure to a substance may result in serious damage to health, a glove should only be considered as back-up protection rather than as the main means of controlling exposure.
In addition the occlusion of the skin by an impermeable glove will inevitably have an effect on the skin. Sweat from the skin will not be able to evaporate and will the reabsorbed into the skin. The warm, moist environment creates an ideal situation for the growth of bacteria, fungi etc. The skin's barrier will be impaired so that any soiling on the skin or permeating through the glove may be more readily absorbed into the skin, enhancing its potential to cause damage to health. Even sweat, itself, has been found to be an irritant to the skin.
The damaging effect on the skin can be substantially reduced by the use of separate cotton gloves worn underneath the main protective glove. These will have to be changed at regular intervals as they become saturated with sweat. Not only will the damaging effect on the skin be reduced but wearer comfort is improved. Where dexterity is important the fingertips of the cotton gloves can be removed.
In addition, some gloves, notably those manufactured from natural latex rubber, contain substances capable of causing allergic (type IV) reactions. Many gloves contain chemicals such as thiurams, mercaptobenzothiazoles and dithiocarbamates. These are sensitizers capable of eliciting an allergic contact dermatitis. Reputable manufacturers take great pains to reduce the amount of these substances in their gloves so as to largely eliminate the possibility of a reaction. This, of course, costs money, resulting in a more expensive glove. Cheaper gloves often show high levels of free chemicals thus increasing the risk of skin reactions. It may be prudent to ask the manufacturer to state the total free protein in his gloves when evaluating different makes.
With the increasing use of gloves as protection in the medical and health sectors there has been an increase in the numbers of people reporting latex allergy. Natural latex contains proteins which can trigger a type I (contact urticaria) reaction. This can be accompanied by a phenomenon known as anaphylaxis, which can result in unconsciousness and cessation of breathing, which has actually resulted in several fatalities. The problem is most common with the disposable latex gloves used by doctors, nurses, first aiders etc.
High quality latex gloves will have undergone several additional processes in manufacturing to reduce the amount of protein left in the glove. They will not show the same potential to cause this problem as cheaper latex gloves. Powdered latex gloves should be avoided. The powder (an ethoxylated corn starch) can bind to the protein and remove this from the glove, presenting it to the skin in an easily absorbed form. During donning the powder will become airborne and can trigger an asthmatic reaction.
Creating an effective glove system
Merely providing the correct gloves and expecting these to be used correctly will seldom achieve the levels of control required by COSHH. The employer will need to consider how to ensure that the glove he is providing are actually working.
This will require a careful analysis of the chemicals, the working practices and the performance data on the gloves in question. He will then need to create a system, which ensures that only the correct glove is used and only in accordance with the correct procedure.
|A glove usage chart,
such as that shown in the diagram, may be an effective
method of ensuring the use of the correct glove. Glove usage
should be incorporated into any working practice documents.
Adequate training is not only a legal requirement, it ensures that the user understands the limitations of the gloves in question and thus is able to use the correctly.
Gloves should be evaluated in the same way as all other PPE, such as respirators, fall arrestors etc. Performance is the most important criteria. User acceptability is essential; otherwise the PPE will simply not be used. Price may be a consideration but only after the other criteria have been met. It makes little sense to provide an expensive respiratory and then negate its effect by exposing the worker to heavy contact through inadequate gloves. Purchasing cheap gloves, which do not work, is a waste of money, not a saving.
Within the scope of this paper it has not been possible to cover all aspects of glove selection and use. However, it should, by now, be clear that this is not a simple matter. As the diagram shows, a careful evaluation of all the many factors is needed. Relying on CE marking and pictograms or purely on manufacturers' data will often not be sufficient to ensure that the employer is meeting his responsibilities under health and safety legislation.
Gloves should only be used in accordance with carefully designed working procedures to ensure that they are not used for longer than they actually provide protection. This may involve changing gloves frequently, resulting in a relatively high cost. In many cases it makes good economic sense to invest more time and money in engineering controls since not only will these provide more reliable protection but will almost certainly prove to be more cost effective in the long term. Obviously this will not always be possible. Gloves will always have a role to play in ensuring a safe and healthy workplace, but only if selected and used correctly.
Article by Chris Packham. For more information contact Chris or Hilary Packham at EnviroDerm Services, e-mail: firstname.lastname@example.org