Chemical protective gloves

SECOND SKIN

By Hayley Chandler

Your "protective gloves" may not provide any protection at all if they are the wrong material for the chemical you’re working with -- and it’s up to you to pick the right ones

Would you take a sip from a cup of paint thinner the next time you’re painting with an oil-based paint? Of course not. But if you’re like most of us, if you paint without wearing protective gloves, or if you wear cotton work gloves that hold the solvent next to your skin, or if you actually wash your bare hands in the paint thinner, you might as well. That’s because paint thinner, like many other chemicals, can soak through your skin with astonishing ease and be carried throughout your body.

The skin is the second most common route by which occupational chemicals enter the body, after inhalation (see "The Final Frontier", April/May 1997, page 38). Certain things, such as detergents and organic solvents, can cause flaking and cracking of the skin. Others are so corrosive they can actually burn the skin. That’s an unpleasant prospect to say the least, but great harm can also be caused when chemicals penetrate our bodies without our even realizing it. Often, the exposure is small, the amount absorbed is low; but day-after-day exposure can have long-term effects six months or 20 years down the road.

The fact is, if you expose your hands to significant amounts of any hazardous chemical, you should wear protective gloves.

But not just any protective gloves will do. In the case of mineral spirits (paint thinner), gloves made of a material called "supported polyvinyl alcohol" would give excellent protection, while natural rubber gloves would provide virtually no protection at all. But if you were working with hydrobromic acid, the natural rubber gloves would do the job while the supported polyvinyl alcohol material would not.

The same considerations apply with virtually every hazardous chemical your hands might contact. Different kinds of protective gloves, depending mainly on their material composition, provide different levels of protection -- ranging from excellent to "not recommended".

Check the chart

The correct choice of protective gloves is not obvious at all. There are many different materials used to make protective gloves -- including laminated film, neoprene, nitrile, vinyl, supported polyvinyl alcohol, polyethylene, polyurethane, butyl rubber and natural rubber. No one material is resistant to all chemicals. So you must determine which glove will best protect against each specific hazard in your workplace. And you’re probably going to need some help.

A logical starting place is the material safety data sheet (MSDS) for the hazardous chemical in question. In Canada, every material controlled by the workplace hazardous materials information system (WHMIS) must have an MSDS that contains information on the potential health effects of exposure to a chemical, and information about how to work safely with the product. That document should specify the best type of protective glove. Unfortunately, the phrase commonly found on MSDSs is "Wear impervious (or impermeable) gloves."

But there ain’t no such thing.

Impervious or impermeable gloves do not exist. Some chemicals will travel through or permeate some materials in a few seconds, other chemicals may take days or weeks. But no glove remains impervious to a chemical forever.

If the MSDS for the chemical you are concerned about does not contain information specific enough to be helpful, you can turn to glove manufacturers or suppliers. Many of them provide charts and computer software listing hundreds of chemicals and matching them with test results for various gloves made of various materials. The American Society for Testing and Materials (ASTM) has developed several standards regarding the performance of chemical protective clothing. Manufacturers use ASTM test methods to determine how various glove materials perform when subjected to various chemicals. They measure four things: penetration, degradation, permeation and breakthrough.

Penetration occurs when the chemical leaks through seams, pinholes and other imperfections in the material. Tables of penetration data are rarely found. Gloves that fail this test because they can be penetrated cannot be used for protection against chemical hazards.

Degradation is a measurement of the physical deterioration of glove material due to contact with a chemical. The material may get harder, stiffer, more brittle, softer, weaker or may shrink or swell. Some materials actually dissolve when exposed to certain chemicals. If a chemical has a significant impact on a glove material, the gloves will be rated "poor" or "not recommended" for use with that chemical.

Permeation occurs when a chemical travels through intact material. The permeation rate is the rate at which the chemical will pass through the material. It is expressed in units such as milligrams per square meter per second. The higher the permeation rate, the faster the chemical will move through the material. 

Breakthrough time is the time it takes a chemical to permeate completely through the material. It is determined by applying the chemical on the glove exterior and measuring the time it takes to detect the chemical on the inside surface. The breakthrough time gives some indication of how long a glove can be used before the chemical will permeate through the material. Breakthrough time should exceed the duration of chemical exposure or the maximum amount of time the gloves will be worn.

But breakthrough is more complicated than it appears. A glove material may have a quick breakthrough time but a low permeation rate, or a long breakthrough time that is followed by a high permeation rate. A material with a shorter breakthrough time is sometimes given a better rating than one with a longer breakthrough time. That’s because a glove with short breakthrough time and a low permeation rate may expose a wearer to less chemical than a glove with a longer breakthrough time and a higher permeation rate.

Glove-material compatibility charts are available from suppliers and independent sources. However, because factors that have an impact the effectiveness of the gloves -- such as the thickness of the material, manufacturing methods and a company’s quality control -- can vary between manufacturers, generic information may be inadequate. For these same reasons, you cannot assume that one manufacturer’s test results will apply to all gloves made of the same material. Results of permeation testing can vary from one manufacturer to another even in cases where the glove materials have the same generic name. It is essential, therefore, that you check the manufacturer’s data for the performance figures on any particular glove.

Workers are often exposed to a product or formulation that contains ingredients in addition to a hazardous chemical or chemicals. In such cases, you should base your research on the particular product being used, not on the hazardous chemical in the product, advises Dave Shanahan, an occupational health and safety project manager for the CSA who has many years of experience working in the chemical industry. "Each product, of course, has all kinds of additives and different kinds of mixtures and they’re in different concentrations," he says. "You may think that you’ve got the gloves to cover yourself for one chemical whereas an additive that’s in there actually degrades the performance of the gloves."

Shanahan suggests asking the supplier of the hazardous product to specify the appropriate protective wear. He acknowledges that "they feel it’s too complicated an issue to give a simple statement in an MSDS." However, he says, most of the big chemical companies that have offices in Canada will give that type of information either over the telephone or on specific request. He says you’ll have to specify the conditions under which you are using the chemical. "As soon as they can get those type of specifics, they feel more comfortable telling the customer what type of gloves are appropriate under those conditions."

In addition to chemical resistance, you will also want to consider the type of glove material used in terms of resistance to abrasion, cuts, punctures, tearing, heat, and ozone.

Obviously, the best way to protect workers is to not expose them to hazardous chemicals at all -- perhaps a different, less dangerous substance or process can be used. Then there are engineering controls -- making sure workers don’t have to contact the hazardous materials. But, sometimes, it’s still necessary to work closely with chemicals, and that’s when workers need personal protective equipment. Such as gloves. Gloves that fit the hazard as well as the hand. 

Hayley Chandler is associate editor of safety purchasing for ohs canada.

BUYING TIPS

* Gloves must allow the worker enough flexibility and dexterity to do the required tasks. Otherwise, they are more likely to remove them and expose themselves to risk. A lining makes gloves more comfortable to wear, but it also adds bulk and can reduce dexterity.

* Workers may require gloves with a special finish to improve their grip. You will probably need to experiment with different textures and finishes to determine which surface performs best.

* Strength and durability is another important factor. You may need a glove that will stand up to exposure to rough surfaces or physical stresses. Generally, thicker gloves are stronger than thin ones, and gloves with liners are stronger than those without.

* The gloves must fit properly. Look for a wide range of sizes. Ensure that gloves are long enough so that no skin is exposed between the glove and the sleeve.

* Workers may be allergic to some glove materials. Where possible, be prepared to offer alternatives. Allergies to latex are increasingly common.

* Select a different coloured glove for each purpose. Workers will be less likely to use the wrong type of glove, and supervisors will be more likely to notice if they do.

* Many companies purposely buy low price gloves so they can be discarded after one use. If gloves are going to be reused, you have decontamination and training issues to consider.

* Non-disposable gloves must be cleaned after use. If the chemical is left on the glove, it will be permeating the material. Follow the manufacturer’s or supplier’s instructions for decontaminating gloves and remember that you may have to follow special procedures to dispose of the wash waste.

* The insides of gloves are often contaminated when they are taken off and then reused. "You have to train people how to remove gloves without putting a hand or fingers inside the gloves to pull them off," says Shanahan.

* The Canadian Centre for Occupational Health and Safety database CHEMINFO has recommendations for chemical protective clothing for some 1,300 chemicals. Their web site is at www.ccohs.ca.

* The American Conference of Governmental Industrial Hygienists (ACGIH) "Guideline for the Selection of Chemical Protective Clothing" is available for $52 (US) per copy. To order, write to ACGIH, 1330 Kemper Meadow Dr., Cincinnati OH 45240; 513/742-2020, fax 513/742-2020, or via the internet at www.acgih.org.

* A "Guide for Evaluating the Performance of Chemical Protective Clothing 90 109" can be downloaded at no charge from the NIOSH web site at www.cdc.gov/niosh/publistb.html.

In order to decide which chemical protective glove to purchase, the Canadian Centre for Occupational Health and Safety in Hamilton, Ontario, recommends that you gather and analyze information on a number of factors.

* A complete and accurate description of the task.

* Identification of all hazards that may require hand protection. This should include chemicals involved as well as physical hazards such as abrasion, tearing, puncture and temperature. The kind of hazards will also affect the decision to use other chemical protective clothing in addition to gloves.

* Flexibility and touch sensitivity needed for the task. This need may significantly limit the thickness of glove material that can be used. The requirement for textured or non-slip surfaces to improve grip must also be considered.

* Type of potential contact (such as occasional contact, splash protection or continuous immersion of hands). This will also help in choosing the appropriate length of the glove.

* Contact period. How long the worker could be in contact with the chemical (and which chemicals) may also influence the selection of type and thickness of the glove material and the choice of lined or unlined gloves.

* Potential effects of skin exposure. The immediate irritation or corrosion of the skin must be considered in addition to the potential health effects to the entire body from absorbing the chemical through the skin.

* Decontamination procedures. Consider whether the gloves should be disposed of or cleaned after use. If they are cleaned, consider the cleaning method, how often they can be cleaned, and any special procedures required for disposing of the "decontamination wash waste."

* Training required. This includes teaching about the hazards of skin contact with the chemical; the limitations of the gloves; what could happen and what to do if the gloves fail; and when to dispose of or to decontaminate gloves.

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