SECTION 6C: Controlling Chemical Exposure

• Personal Protective Equipment
• Eye Protection
• Protective Clothing and Footwear
• Gloves
  • Proper Glove Removal
• Hearing Protection
• Respiratory Protection

 

Personal Protective Equipment (top)

Personal protective equipment (PPE) is special gear used to protect the wearer from specific hazards of a hazardous substance. It is a last resort protection system, to be used when substitution or engineering controls are not feasible. PPE does not reduce or eliminate the hazard, protects only the wearer, and does not protect anyone else.

 

 

PPE includes gloves, respiratory protection, eye protection, and protective clothing. The need for PPE is dependent upon the type of operations and the nature and quantity of the materials in use, and must be assessed on a case by case basis. Workers who rely on PPE must understand the functioning, proper use, and limitations of the PPE used.

 

Eye Protection (top)

Safety Glasses

Safety glasses look very much like normal glasses buy have lenses that are impact resistant and frames that are far stronger than standard streetwear glasses. Safety glasses with proper impact and shatter resistance will be marked "Z87" on the frame or lens. Safety glasses must have side shields and should be worn whenever there is the possibility of objects striking the eye, such as particles, glass, or metal shards. Many potential eye injuries have been avoided by wearing safety glasses. See Anecdotes for accounts of a few of these incidents.

Standard streetwear eyeglasses fitted with side shields are not sufficient. Workers who are interested in obtaining prescription safety glasses should contact EHS at 8-5294. Safety glasses come in a variety of styles to provide the best fit and comfort, including some designed to fit over prescription glasses.

Safety glasses do not provide adequate protection from significant chemical splashes. They do not seal to the face, resulting in gaps at the top, bottom and sides, where chemicals may seep through (see Anecdotes for an actual incident where this occurred). Safety glasses may be adequate when the potential splash is minimal, such as when opening eppendorf tubes.

Safety glasses are also not appropriate for dusts and powders, which can get by the glasses in ways similar to those described above. Safety goggles are best used for this type of potential exposure.

Chemical Splash Goggles

Chemical Splash Goggles should be worn when there is potential for splash from a hazardous material. Like safety glasses, goggles are impact resistant. Chemical splash goggles should have indirect ventilation so hazardous substances cannot drain into the eye area. Some may be worn over prescription glasses.

Goggles come in a variety of styles for maximum comfort and splash protection. Visorgogs are a hybrid of a goggle and safety glasses. They offer more splash protection than safety glasses, but not as much as goggles. They fit close to the face, but do not seal at the bottom as goggles do.

Face Shields

Face shields are in order when working with large volumes of hazardous materials, either for protection from splash to the face or flying particles. Face shields must be used in conjunction with safety glasses or goggles. A few incidents where a face shield would have prevented injury are described in Anecdotes.
 

Contact Lenses

Contact lenses may be worn in the laboratory, but do not offer any protection from chemical contact. If a contact lens becomes contaminated with a hazardous chemical, rinse the eye(s) using an eyewash and remove the lens immediately. Contact lenses that have been contaminated with a chemical must be discarded.

This particularly recommendation runs counter to what most of us were taught previously.  However, studies have shown that contact lenses are safe to wear in the laboratory environment.  For more information, see the American Optometric Association guidelines.

Protective Clothing & Footwear (top)

Protective Clothing

When the possibility of chemical contamination exists, protective clothing that resists physical and chemical hazards should be worn over street clothes. Lab coats are appropriate for minor chemical splashes and solids contamination, while plastic or rubber aprons are best for protection from corrosive or irritating liquids. Disposable outer garments (i.e., Tyvek suits) may be useful when cleaning and decontamination of reusable clothing is difficult.

Loose clothing (such as overlarge lab coats or ties), skimpy clothing (such as shorts), torn clothing and unrestrained hair may pose a hazard in the laboratory.

Footwear

Closed-toed shoes should be worn at all times in buildings where chemicals are stored or used. Perforated shoes, sandals or cloth sneakers should not be worn in laboratories or where mechanical work is conducted. Such shoes offer no barrier between the laboratory worker and chemicals or broken glass.

Chemical resistant overshoes or boots may be used to avoid possible exposure to corrosive chemical or large quantities of solvents or water that might penetrate normal footwear (e.g., during spill cleanup). Leather shoes tend to absorb chemicals and may have to be discarded if contaminated with a hazardous material.

Although generally not required in most laboratories, steel-toed safety shoes may be necessary when there is a risk of heavy objects falling or rolling onto the feet, such as in bottle-washing operations or animal care facilities.

 

Gloves (top)

 

 

Choosing the appropriate hand protection can be a challenge in a laboratory setting. Considering the fact that dermatitis or inflammation of the skin accounts for 40-45% of all work-related diseases, selecting the right glove for the job is important.

Not only can many chemicals cause skin irritation or burns, but also absorption through the skin can be a significant route of exposure to certain chemicals. Dimethyl sulfoxide (DMSO), nitrobenzene, and many solvents are examples of chemicals that can be readily absorbed through the skin into the bloodstream, where the chemical may cause harmful effects.

When Should Gloves Be Worn

Protective gloves should be worn when handling hazardous materials, chemicals of unknown toxicity, corrosive materials, rough or sharp-edged objects, and very hot or very cold materials. When handling chemicals in a laboratory, disposable latex, vinyl or nitrile examination gloves are usually appropriate for most circumstances. These gloves will offer protection from incidental splashes or contact.

When working with chemicals with high acute toxicity, working with corrosives in high concentrations, handling chemicals for extended periods of time or immersing all or part of a hand into a chemical, the appropriate glove material should be selected, based on chemical compatibility.

Selecting the Appropriate Glove Material

When selecting the appropriate glove, the following characteristics should be considered:

• degradation rating
• breakthrough time
• permeation rate

Degradation is the change in one or more of the physical properties of a glove caused by contact with a chemical. Degradation typically appears as hardening, stiffening, swelling, shrinking or cracking of the glove. Degradation ratings indicate how well a glove will hold up when exposed to a chemical. When looking at a chemical compatibility chart, degradation is usually reported as E (excellent), G (good), F (fair), P (poor), NR (not recommended) or NT (not tested).

Breakthrough time is the elapsed time between the initial contact of the test chemical on the surface of the glove and the analytical detection of the chemical on the inside of the glove.

Permeation rate is the rate at which the test chemical passes through the glove material once breakthrough has occurred and equilibrium is reached. Permeation involves absorption of the chemical on the surface of the glove, diffusion through the glove, and desorption of the chemical on the inside of the glove. Resistance to permeation rate is usually reported as E (excellent), G (good), F (fair), P (poor) or NR (not recommended). If chemical breakthrough does not occur, then permeation rate is not measured and is reported ND (none detected).

Manufacturers stress that permeation and degradation tests are done under laboratory test conditions, which can vary significantly from actual conditions in the work environment. Users may opt to conduct their own tests, particularly when working with highly toxic materials.

For mixtures, it is recommended that the glove material be selected based on the shortest breakthrough time.

The following table includes major glove types and their general uses. This list is not exhaustive.
 

Where to Find Compatibility Information

Most glove manufacturers have chemical compatibility charts available for their gloves. These charts may be found in laboratory safety supply catalogs such as Fisher Scientific and Lab Safety Supply. Best Gloves offers copies of their glove compatibility charts upon request. To obtain a copy, call them directly at 800-241-0323. Best Gloves also has a great deal of information available on their web site, including a downloadable glove selection program.

Most safety data sheets (SDS) recommend the most protective glove material in their Protective Equipment section. There are MSDSs for many laboratory chemicals available on the web through the EHS home page.

EHS also has a computer program with glove compatibility information for hundreds of chemicals. Contact EHS at 258-5294 for more information.

Other Considerations

There are several factors besides glove material to consider when selecting the appropriate glove. The amount of dexterity needed to perform a particular manipulation must be weighed against the glove material recommended for maximum chemical resistance. In some cases, particularly when working with delicate objects where fine dexterity is crucial, a bulky glove may actually be more of a hazard.

Where fine dexterity is needed, consider double gloving with a less compatible material, immediately removing and replacing the outer glove if there are any signs of contamination. In some cases, such as when wearing Silver Shield gloves, it may be possible to wear a tight-fitting glove over the loose glove to increase dexterity.

Glove thickness, usually measured in mils or gauge, is another consideration. A 10-gauge glove is equivalent to 10 mils or 0.01 inches. Thinner, lighter gloves offer better touch sensitivity and flexibility, but may provide shorter breakthrough times. Generally, doubling the thickness of the glove quadruples the breakthrough time.

Glove length should be chosen based on the depth to which the arm will be immersed or where chemical splash is likely. Gloves longer than 14 inches provide extra protection against splash or immersion.

Glove size may also be important. One size does not fit all. Gloves which are too tight tend to cause fatigue, while gloves which are too loose will have loose finger ends which make work more difficult. The circumference of the hand, measured in inches, is roughly equivalent to the reported glove size. Glove color, cuff design, and lining should also be considered for some tasks.

Glove Inspection, Use and Care

All gloves should be inspected for signs of degradation or puncture before use. Test for pinholes by blowing or trapping air inside and rolling them out. Do not fill them with water, as this makes the gloves uncomfortable and may make it more difficult to detect a leak when wearing the glove.

Disposable gloves should be changed when there is any sign of contamination. Reusable gloves should be washed frequently if used for an extended period of time.

While wearing gloves, be careful not to handle anything but the materials involved in the procedure. Touching equipment, phones, wastebaskets or other surfaces may cause contamination. Be aware of touching the face, hair, and clothing as well.

Before removing them, wash the outside of the glove. To avoid accidental skin exposure, remove the first glove by grasping the cuff and peeling the glove off the hand so that the glove is inside out. Repeat this process with the second hand, touching the inside of the glove cuff, rather than the outside. Wash hands immediately with soap and water.

Follow the manufacturer’s instructions for washing and caring for reusable gloves.

Proper Glove Removal

Gloves should be removed avoiding skin contact with the exterior of the glove and possible contamination. Disposable gloves should be removed as follows:

• Grasp the exterior of one glove with your other gloved hand.
• Carefully pull the glove off your hand, turning it inside-out. ............ The contamination is now on the inside.
• Ball the glove up and hold in your other gloved hand.
• Slide your ungloved finger into the opening of the other glove. ........ Avoid touching the exterior.
• Carefully pull the glove off your hand, turning it inside out again. .... All contamination is contained.
• Discard appropriately.

 

 

Latex Gloves and Related Allergies

Allergic reactions to natural rubber latex have been increasing since 1987, when the Centers for Disease Control recommended the use of universal precautions to protect against potentially infectious materials, bloodborne pathogens and HIV. Increased glove demand also resulted in higher levels of allergens due to changes in the manufacturing process. In addition to skin contact with the latex allergens, inhalation is another potential route of exposure. Latex proteins may be released into the air along with the powders used to lubricate the interior of the glove.

In June, 1997, the National Institute of Occupational Safety and Health (NIOSH) issued an alert Preventing Allergic Reactions to Latex in the Workplace (publication number DHHS (NIOSH) 97-135).

Latex exposure symptoms include skin rash and inflammation, respiratory irritation, asthma and shock. The amount of exposure needed to sensitize an individual to natural rubber latex is not known, but when exposures are reduced, sensitization decreases.

NIOSH recommends the following actions to reduce exposure to latex:

• Whenever possible, substitute another glove material.
• If latex gloves must be used, choose reduced-protein, powder-free latex gloves.
• Wash hands with mild soap and water after removing latex gloves.

 

Hearing Protection (top)

Most laboratory equipment and operations do not produce noise levels that require the use of hearing protection, with the exception of some wind tunnels, as described below. Princeton University has a Hearing Conservation Program in place for individuals who are exposed to noise levels equal to or exceeding the OSHA action level of 85 decibels (dBA) averaged over eight hours, per the OSHA Occupational Noise Standard. This program includes workplace monitoring, personal exposure monitoring, annual audiometric testing, use of hearing protection and annual training.

Laboratory workers who would like to use hearing protection for noise levels below the action level may do so without enrollment in the Hearing Conservation Program. Using hearing protection, such as earplugs, earmuffs or hearing bands, can improve communication or provide comfort to the worker in a noisy environment.

The most common noisy equipment in the laboratories are ultrasonicators and wind tunnels. EHS has measured noise levels of several ultrasonicators used in the laboratories and found that noise levels were well below 85 dBA, averaged over eight hours. Some of the wind tunnels, particularly the supersonic wind tunnels, are capable of very high noise levels. Users should check with the principal investigator or EHS to determine whether they need to be enrolled in the Hearing Conservation Program.

For more information about the Hearing Conservation Program, see Section B5, Noise and Hearing Conservation, of the Princeton University Health and Safety Guide. Contact EHS at 258-5294 to request noise monitoring.

Respiratory Protection (top)

A respirator may only be used when engineering controls, such as general ventilation or a fume hood, are not feasible or do not reduce the exposure of a chemical to acceptable levels. Since the use of a respirator is regulated by the OSHA Respiratory Protection Standard, respirator use at Princeton is subject to prior review by EHS, according to university policy.

Any worker who believes that respiratory protection is needed must notify EHS for evaluation of the hazard and enrollment in the Respiratory Protection Program. This program involves procedures for respirator selection, medical assessment of employee health, employee training, proper fitting, respirator inspection and maintenance, and recordkeeping.

Use of a paper or cloth dust mask (left-most in above picture) is allowed without enrolling in the Respiratory Protection Program. However, if you believe you need to upgrade to a tight-fitting respirator, you must contact EHS prior. Tight fitting respirators are typically made of silicone or rubber and have filter cartridges or supplied air for breathing.

Self-contained breathing apparatus (SCBA) is available in E-Quad for use by only trained individuals for changing out cylinders of highly toxic gases and cleaning up chemical spills. They are not to be used for response to a fire. Training is offered every Spring and Fall in E-Quad. Contact EHS (8-5294) if you are interested and are not on the mailing list for this training.

For more information, see Section C4, Respiratory Protection, in the Princeton University Health and Safety Guide.