By Chris H. Miller, PhD
Engineering and work practice controls can eliminate or reduce your exposure to workplace hazards.
OSHA's approach to preventing exposure to bloodborne pathogens in the workplace falls into seven basic categories: provide training on the general nature; routes of spread and modes of prevention of bloodborne diseases; immunize against hepatitis B; prepare a specific plan for prevention of occupational exposure to bloodborne pathogens; use engineering and work practice controls to eliminate or minimize exposure to bloodborne pathogens; use personal protective equipment to protect workers from exposure; and provide medical evaluation and follow-up if exposure occurs. I will describe the primary prevention aspects of the standard: Engineering and work-practice controls.
The OSHA Bloodborne Pathogens Standard requires employers to institute engineering and work-practice controls as a primary means of managing employee exposure. The standard states: "Engineering and work-practice controls shall be used to eliminate or minimize employee exposure. Where occupational exposure remains after institution of these controls, personal protective equipment (gloves, masks, eyewear, clothing) shall also be used." (http:// www.osha.gov/Osh_data/1910_ 1030.html.)
Engineering controls isolate or remove the hazard from the workplace. In dentistry and hygiene, this means the use of devices that eliminate or reduce chances of exposure to blood and saliva. These include sharps containers, needle safety devices, red-bags, rubber dam, high-volume evacuation, instrument cassettes, and mechanical instrument cleaners. The controls used must be examined and maintained or replaced on a scheduled basis.
Sharps containers isolate contaminated sharps from the working environment so they can be safely removed from the office. For this isolation to be successful, the containers must be puncture-resistant, closable upon transport, and of a design that is not easily knocked over. Red-bags do the same for nonsharp solid waste that is saturated or dripping wet with blood or saliva. Needle safety devices (shielded needles) also isolate the hazard (contaminated needle), but are much more readily available in medicine/head/neck surgery arenas than in nonsurgical dentistry.
The rubber dam places a barrier between the dental team and the saliva/blood in the patient's mouth, thus isolating the team from the hazard. Although the dam does not seal perfectly around the teeth, it does greatly reduce exposure to organisms present in the oral fluids of patients during use of the high-speed handpiece and air/water syringe (Cochran, Miller, Shelldrake: "The efficacy of the dental dam as a barrier to the spread of microorganisms during dental treatment." J. Amer. Dent. Assoc. 1989; 119:141-144).
The high-volume evacuator is a very important engineering control used to remove much of the hazard (oral fluids, spatter, and aerosol created by handpieces and air/water syringes) by drawing it down the drain for final disposal.
Sometimes-forgotten engineering controls are instrument cassettes and mechanical instrument cleaners. Instrument cassettes isolate the sharp hand instruments by stabilizing them in protective metal or plastic resin containers.
Since these cassettes are designed to contain (isolate) the instruments through the entire cleaning and sterilization process, they reduce exposure injuries by reducing the direct handling of sharp, contaminated instruments. Also, mechanical instrument cleaners, such as the ultrasonic cleaner, instrument washer and washer/disinfector, isolate the sharps hazard and replace hand-scrubbing of the instruments.
Work practices can be used to reduce the likelihood of exposure by altering the manner in which a task is performed. All procedures must be performed in such a manner as to minimize the spraying and spattering of oral fluids. Examples of work practices include:
• Washing hands as soon as feasible after skin contact with oral fluids and after removing gloves or other personal protective equipment
• Flushing mucous membranes as soon as feasible if contaminated with infectious materials
• Recapping dental needles by a mechanical means such as forceps or other cap-holding device, or using a one-handed "scoop" technique
• Prohibiting the recapping, bending, or removing of contaminated needles from disposable (medical-type) syringes
• Disposing of medical-type disposable syringes and needles as a single needle/syringe unit
• Prohibiting the cutting, bending, or breaking of contaminated needles before disposal
• Discarding contaminated needles and other disposable sharps in proper sharps containers
• Prohibiting the overfilling of sharps containers
• Placing contaminated reusable sharp instruments in containers that are puncture-resistant, leak-proof, colored red, or labeled with the biohazard symbol until properly processed
• Eliminating hand-to-hand passing of contaminated sharp instruments
• Prohibiting eating, drinking, smoking, applying cosmetics, and handling contact lenses in areas where there is occupational exposure such as in the dental operatory or instrument processing areas
• Eliminating the storage of food and drink in refrigerators, cabinets or shelves, or on countertops where blood or saliva may be present
• Storing, transporting, or shipping blood or saliva and items contaminated with blood or saliva (extracted teeth, tissue, impressions that have not been decontaminated) in containers that are closed, prevent leakage, colored red, or labeled with a biohazard symbol
Engineering controls to remove or isolate hazards are used in concert with work practice controls as the primary means of preventing occupational exposure to potentially infectious agents.
Chris H. Miller, PhD, is professor of oral microbiology and executive associate dean at the Indiana University School of Dentistry.