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Handle With Care

Thu, 04/01/2010 - 12:00am
Vince McLeod, CIH

A primer on protective gloves

Probably the single most common item of personal protection in any laboratory, even forensic ones, is the glove. Yet, it is also most likely to receive the least amount of thought or consideration and may be the most misunderstood. In the forensic laboratory, when we need to protect our hands, we often reach for whatever is closest, put it on, and think we are good to go. We are protected from…anything, everything. Whoever put that box of gloves on the shelf must have known the hazards faced and selected the proper type. Right? Why else would they be there?

Not so fast. Recall the highly publicized fatality of the New Hampshire researcher in 1997? She was working with dimethyl mercury. While transferring the material in a hood, a few small drops spilled onto the back of her latex gloved left hand. She cleaned up the spill, removed and disposed of her gloves, and didn’t give any more thought to the incident until being hospitalized five months later. Almost three hundred days post-exposure and after three months of aggressive treatment, she died from mercury poisoning.1,2 Latex offers no protection for this organic substance and glove permeation occurred in about fifteen seconds.

Assess the Job and the Risks
Granted, this tragic accident is an extreme example and one not encountered in forensic labs, but thousands of accidents occur every year due to improper hand protection. Given the myriad glove types and materials, it is imperative that both employees and supervisors know which gloves are suitable for the task at hand (no pun intended). This brings us to the first step in a good hand protection program—conduct a detailed and thorough glove audit and job hazard analysis. We have written articles on this previously, but it boils down to simply identifying the hazard and the employees at risk, then selecting the right control measures, which include personal protective equipment, for the job. Things to keep in mind when performing the audit and hazard analysis are questions like:

  • Can the procedure or process be changed to prevent or eliminate the hazard?
  • Can a less hazardous material or substance be substituted?
  • Will personal protective equipment solve the problem?
  • Is the risk acceptable?

Identify the Hazard(s)
Hazards faced in a forensic laboratory span a wide array. Physical hazards such as cuts or punctures from broken glassware or burns from hot equipment or containers demand a much different protective glove than chemical hazards such as dermatitis, corrosive burns, or absorption. Fortunately, innovations in materials and technology have produced a huge selection of protective gloves for nearly any purpose. Advanced polymers and fibers provide superior protection from abrasion, punctures, and lacerations compared to the old standbys cotton and leather. These new materials provide even more protection when various coatings are applied.

When we enter the realm of the typical forensic laboratory though, the characteristic most needed is resistance to chemicals. Chemicals take all forms—liquids, dusts or powders, gases and vapors—and selecting the right glove will require a little homework. Lucky for us there are excellent manufacturer’s web sites available to help. (A few of these resources are given below.) But, before we leap into cyberspace we should know the terminology or lingo so we can decipher the mountain of information out there.Here are the most important ones:

  • Contamination: occurs when the inside of the glove is contaminated either prior to or during donning (putting the glove on). Manufacturers cannot prevent this. Only careful and conscientious employees can. Make sure everyone is trained and follows good, safe housekeeping procedures.
  • Penetration: happens when a substance passes through a seam or damaged glove, e.g. a pinhole or tear. Employees must be very attentive. Double-glove when handling extremely hazardous materials. Change to fresh gloves at the first sign of a problem or if in doubt about integrity.
  • Degradation: happens when a chemical breaks down or damages the glove material. Manufacturers usually provide a rating over time. Selecting the best or most appropriate glove material, providing the highest rating for the longest time, is key to preventing exposures from degradation.
  • Permeation: occurs when a substance passes through the intact glove material at the molecular level. This is commonly referred to as “breakthrough” and usually given in minutes. The larger the number the longer the glove material can be in contact with the chemical before breakthrough.

Choose the Best Glove for the Job
As we mentioned above the internet resources provided below will help you select the best glove and provide the most protection. For chemical mixtures or multiple hazards pick the glove with the highest resistance to the most toxic substance or consider a double-glove protocol. If in doubt, do not hesitate to call the manufacturer’s representative for technical assistance. To get you started, here is a brief summary of the major glove materials.

  • Nitrile: Nitrile is a synthetic polymer made from acrylonitrile, butadiene, and any one of many carboxylic acids. It is a very good substitute for natural rubber, vinyl, and neoprene. Nitrile gives excellent protection from many corrosives, solvents, oils, and grease. Nitrile is generally more resistant to cuts, snags, punctures, and abrasions than neoprene or PVC gloves of the same thickness. Nitrile gloves do not contain latex, the source for many allergic reactions. Dexterity is considered very good.
  • PVC: polyvinylchloride gloves are typically resistant to petroleum hydrocarbons, oils, acids, and caustics. They also may provide protection from alcohols and glycol ethers, but not ketones, aldehydes, or aromatics. They provide very good abrasion resistance, but dexterity is poor to fair depending on the specific product.
  • Butyl: Butyl rubber is a copolymer of isobutylene (usually 98%) and isoprene. It was first developed for tire inner tubes as this material generally has the highest permeation resistance to gases and water vapors. Butyl rubber provides good chemical resistance to alcohols, aldehydes, amines, bases, and glycol ethers. Butyl rubber does not do well against halogenated compounds, aliphatic or aromatic hydrocarbons. Flex and dexterity can be very good with the right product.
  • Viton®: Viton is a Dupont trademark for a fluoroelastomeric material. Viton was developed specifically for handling chlorinated and aromatic solvents. Viton gloves are also reported to provide excellent resistance to PCBs. Abrasion resistance is very good as is flexibility and dexterity.
  • Silver Shield®: Silver Shield is a trade name for a flexible laminate made of polyethylene/ethylene-vinyl alcohol. This material offers resistance against permeation and breakthrough for the widest range of hazardous and toxic chemicals. Silver Shield material is excellent against aromatics, chlorines, esters, and ketones. Abrasion resistance is very good. Dexterity and flexibility are fair to good depending on the product.

Wrap Up
Choosing the right protective glove for the job is critical to safe handling of hazardous and toxic chemicals. The descriptions above should be used for general guidance. We must stress that you match the individual glove by manufacturer and style to the required task and exposure particulars. No single glove will protect against all harmful substances. Nor will one glove suit all applications. No matter which glove is used, they can all potentially leak or become punctured or torn. No glove can offer 100% protection either as permeation and degradation take their toll during use. To ensure the highest level of protection train employees to know the hazards of the substances they handle and the estimated breakthrough times for the gloves selected. Always handle toxic and hazardous chemicals with utmost care.

References

  1. “Dimethyl Mercury Hazard Information Bulletin,” OSHA. March 1998. http://www.osha.gov/dts/hib/hib_data/hib19980309.html
  2. Nierenberg, David W., et.al., “Delayed Cerebellar Disease and Death after Accidental Exposure to Dimethylmercury.” New England Journal of Medicine, June 1998. http://content.nejm.org/cgi/content/full/338/23/1672?ijkey=576bbde99ab04c2945a8286ebe7b275c6c057a72&keytype2=tf_ ipsecsha

 

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Vince McLeod is an American Board of Industrial Hygiene Certified Industrial Hygienist and the senior IH with the University of Florida’s Environmental Health and Safety Division. He has 22 years experience in all facets of occupational health and safety and specializes in conducting exposure assessments and health hazard evaluations.

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