“CDC identifies a mystery cluster of deaths among dentists.” This recent headline from CNN, which cites a Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report from March 2018, is just one example of the growing concern for the health and safety of employees working in the dental industry. Another article published by Business Insider, “The 15 Jobs That Are Most Damaging to Your Health,” lists work in the dental industry as one of the unhealthiest occupations. Dentists, dental hygienists and assistants, and dental laboratory technicians appear on the list along with occupations one might expect to be unhealthy, such as nuclear equipment operation technicians and derrick operators in the oil and gas industry. The U.S. Department of Labor data on which the Business Insider article is based accounts for exposures to physical, chemical, biological, and radiological hazards as well as other hazardous conditions. The article lists exposure to disease and infections, exposure to contaminants, and time spent sitting and standing as the top three health risks for workers in the dental industry.
Some hazards associated with dentistry are easily recognized while others may be more subtle. For example, sitting and standing for extended periods were key factors in Business Insider’s ranking of the unhealthiest jobs in the United States. The nature of work in the dental industry requires workers to remain in a stationary position for long periods of time, often followed by a brief break between patients or tasks before returning to the same stationary activity. While technological advances have made work easier and, in some instances, safer for the workers, repetitive-motion injuries and musculoskeletal disorders associated with prolonged static posture are common. And the risks are not limited to MSDs. Randall J. Nett, MD, lead author of the study summarized in the 2018 MMWR report, told CNN that dentists and dental personnel face unique occupational exposures, including bacteria, viruses, dusts, gases, radiation, and other respiratory hazards. In addition, many dental offices are small employers that may be exempt from some OSHA requirements and are often located in commercial office buildings where the employer may have little or no control over the building-related occupational risks. What does all this mean for dental workers when it comes to workplace hazards? PHYSICAL AND CHEMICAL HAZARDS Silica. One hazard most people do not typically associate with dentistry is exposure to respirable crystalline silica. According to an OSHA fact sheet published in 2013, more than 41,000 workers in dental laboratories were exposed to respirable crystalline silica. Crystalline silica is an ingredient in alginate impressions, dental porcelains, and dental models or casts. Exposures occur when these materials are small enough to reach deep into the lungs. This often occurs during activities such as mixing dry materials, sandblasting (investment material itself or the blasting media), grinding, and general cleaning and maintenance of the workspace, including the ventilation system. Exposures can happen in dental laboratories, where these tasks are performed daily, as well as in dental offices to a lesser degree. These exposures put workers at risk of contracting silicosis, a lung disease caused by breathing in fine dust containing crystalline silica. Silica exposures have also been linked to other illnesses such as kidney disease and lung cancer.  Metals: dental amalgams and crowns. A dental amalgam is a material used to fill cavities caused by tooth decay. Amalgams are a mixture of metals, consisting of liquid (elemental) mercury and a powdered alloy composed of silver, tin, and copper. Approximately 50 percent of the dental amalgam is elemental mercury. The chemical properties of elemental mercury allow it to react with and bind together the silver, copper, and tin alloy particles to form an amalgam. Exposure to mercury can occur when mercury vapor is released during procedures that involve the manipulation of both old and new amalgams. Exposures can affect both the patient and staff and can be higher in poorly ventilated spaces. Exposures to other heavy metals can occur during work with dental alloys associated with crowns and bridges. Beryllium is often used in porcelain-fused metal crowns. In 2002, federal OSHA released a hazard information bulletin titled “Preventing Adverse Health Effects from Exposure to Beryllium in Dental Laboratories” to inform the dental community about the risk of developing chronic beryllium disease, or CBD, while working with alloys containing beryllium. The bulletin describes ways to reduce beryllium exposures. Exposure to beryllium generally occurs in dental laboratories during crown and bridge production. Laboratory technicians who work with beryllium- containing alloys or those who work in the same facility are also at risk for developing beryllium sensitization and CBD.  Hard metal lung disease, or HMLD, a rare form of occupational lung disease, has also been linked to work in the dental industry. HMLD is associated with exposures to tungsten carbide-cobalt used in tools for cutting, grinding, drilling, and machining.  Waste anesthetic gases. Common anesthetic gases used in dentistry include nitrous oxide and halogenated compounds such as halothane, enflurane, isoflurane, desflurane, and sevoflurane. Employees working in dental offices can be exposed to waste anesthetic gases, or WAGs, when systems intended to scavenge the gases leak. They can also be exposed by patients’ exhaled breath. According to OSHA, exposure to WAGs can result in “nausea, dizziness, headaches, fatigue, and irritability, as well as sterility, miscarriages, birth defects, cancer, and liver and kidney disease.” Halogenated compounds may be used during dental surgery where a patient requires general anesthesia. These procedures are typically conducted in operating rooms with specialized WAG scavenging systems and enhanced ventilation. Nitrous oxide is commonly available for use during in-office dental procedures, particularly with pediatric patients. These procedures are often conducted in dental offices equipped with HVAC systems designed for general room dilution. One of the challenges of managing WAG exposure is the lack of detectable odor until very high concentrations are reached. These exposures may impair workers’ judgment and ability to recognize exposure. WAG exposures are primarily managed by using scavenging systems or with local exhaust ventilation. Masks must be properly sized when using scavenging systems. It’s also important to maintain proper flow rates to minimize WAG escape from masks. Equipment should be routinely inspected and maintained, and personnel should be properly trained.  Sterilants and disinfectants. Cleaners, disinfectants, and sterilants are used extensively in dental offices. Surface disinfectants used in dentistry should be EPA- approved disinfectants with proven efficacy against the pathogens encountered. CDC recommends—and federal OSHA requires—that surface disinfectants be efficacious against either human immunodeficiency virus (HIV) and  hepatitis B virus, or tuberculosis.
American Academy of Pediatric Dentistry: Reference Committee Hearing Materials (PDF, May 2010). American Dental Association: “Safety Tips to Prevent Hearing Loss.” ASHRAE: ANSI/ASHRAE Standard 188-2018, Legionellosis: Risk Management for Building Water Systems (2018). Business Insider: “The 15 Jobs That Are Most Damaging to Your Health” (December 2013). CDC: “Infection Prevention & Control Guidelines & Recommendations.” CDC: Morbidity and Mortality Weekly Report, “Dental Personnel Treated for Idiopathic Pulmonary Fibrosis at a Tertiary Care Center—Virginia, 2000–2015” (March 2018). CNN: “CDC Identifies a Mystery Cluster of Deaths among Dentists” (March 2018). OSHA: OSHA Fact Sheet, “OSHA’s Proposed Crystalline Silica Rule: General Industry and Maritime.” OSHA: “Preventing Adverse Health Effects from Exposure to Beryllium in Dental Laboratories.” OSHA: “Waste Anesthetic Gases.”
Chemicals used may include alcohols, chlorine compounds, formaldehyde, glutaraldehyde, ortho-phthalaldehyde, hydrogen peroxide, iodophors, peracetic acid, phenolics, and quaternary ammonium compounds. Exposures to these chemicals can result in irritation and, in some cases, employee sensitization. In addition to protecting workers, industrial hygienists must also consider proper disposal of waste related to cleaning chemicals. Ergonomics. Dentistry is a profession that generally leads to musculoskeletal pains and soreness. Frequent and prolonged sitting and standing combined with awkward bending, twisting, and reaching places stress on the musculoskeletal system and can lead to discomfort and injury to the hands, wrists, elbows, and shoulders. Advances in dentistry and increased understanding of the importance of ergonomics has led to improvements in dental equipment, training, and work practices. Ionizing radiation source: X-rays. When researching exposure to X-rays in dentistry, most available literature is geared toward the patient—not the operator of the equipment or those in the work area. However, it is important to remember that there are potential radiation exposures that dental staff may encounter during a typical shift. Exposures can occur through direct impact with the primary X-ray beam, via scatter radiation, or from leakage from X-ray equipment. Regulatory exposure limits for X-rays are expressed differently than daily values such as time-weighted averages or short-term exposure limits. Maximum permissible dose, or MPD, equivalents are regulatory annual exposure limits established to prevent injury from occupational exposure to ionizing radiation. MPDs are established for the whole body, the skin and extremities, and the eye lens. These limits are based on the health risk of ionizing radiation and its cumulative effect on the system, and the concept of “as low as reasonably achievable” is always advised. MPDs are expressed in Roentgen equivalent man, or rem. Due to the cumulative effect of ionizing radiation, personal monitoring devices such as dosimeters must be worn every shift when X-ray equipment is used. Dose equivalents are set lower for pregnant employees. Requirements vary state by state, and staff must follow the U.S. Food and Drug Administration and American Dental Association guidelines (PDF) for prescribing dental radiographs.  Non-ionizing radiation source: lasers. Another form of radiation increasingly used in dentistry is lasers. Lasers typically emit optical ultraviolet, visible light, infrared (non-ionizing) radiation. Lasers are now used in a variety of dental work such as tooth decay removal, teeth whitening, treating gum disease, and treating hypersensitivity. Dental lasers belong to category IV, which includes the most hazardous of commercial lasers, and are generally classified according to tissue applicability (either soft tissue or hard tissue lasers). Each type of laser has specific associated biological effects and procedures. Potential hazards for dental staff while using lasers include ocular hazards, tissue injury, inhalation of vapor or surgical smoke plumes, and fire and explosion hazards. While the use of lasers is highly controlled in hospitals and traditional medical centers, less focus has been placed on dentistry, where enforcement of regulations related to lasers is limited. The level of training and experience dental staff receive is generally far less than the typical laser surgical nurse or hospital laser safety officer. Noise. According to the American Dental Association, dentists are exposed to the noise of handpieces and ultrasonic scalers at levels of 60 to 99 decibels. While this level of noise may present a minimal risk of hearing loss, sustained exposure can result in sensorineural hearing loss. Exposure to high- frequency, noisy equipment is unavoidable in a dental practice, so prevention is the key to protect and preserve hearing. BIOLOGICAL HAZARDS Bloodborne pathogens. Exposures to infectious bloodborne pathogens such as HIV and viral hepatitis can present significant risk. Dental staff can be exposed to bloodborne pathogens during routine treatments that impact skin and tissues or during contact with dental materials or instruments. Skin and tissue exposure incidents are the primary concern in dentistry. Needlesticks and cuts or punctures pose a high risk to dental workers due to the frequency with which they use tools and instruments and the close quarters in which they work. Preventing these exposure incidents and their consequences should be part of a safety plan that includes infection prevention practices, continuing education, and vaccinations. Infection prevention programs should make workers aware of individual protective measures and appropriate sterilization or other high-level disinfection practices.  Dental workers often find themselves in very close contact with the breath of their patients and have frequent contact with patients’ saliva. These can be additional sources of exposure if a patient arrives with a cold, the flu, hepatitis C, or other airborne or fluid-borne contagions. Legionella and other waterborne bacteria. Illnesses associated with exposures to Legionella bacteria are on the rise. Aging infrastructure and demands for reduction in water usage are just two factors that may contribute to these increases. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and CDC have developed standards and guidelines to help building owners manage waterborne pathogen risks in domestic water systems. However, requirements to follow these standards are limited, and many building owners are not proactively managing these risks. Often, the dental office or clinic does not have the responsibility or authority to manage the building’s domestic water systems. Numerous activities in dentistry may result in the aerosolization of building water, often directly in the breathing zone of the worker, which is an important risk factor in the transmission of these pathogens.  Legionella is only one of the waterborne pathogens that may be of concern. Pseudomonas and Mycobacterium species can also be present in and colonize domestic water systems. For example, in 2016 potentially deadly Mycobacterium abscessus was found in several samples that a county healthcare agency took from the water system in a children’s dental clinic in Orange County, Calif. The agency was investigating multiple infections that led to a lawsuit.  GUIDANCE DOCUMENTS AND STANDARDS CDC has developed guidelines for infection control in dental healthcare settings, which are available on its website. Topics covered in the agency’s guidelines include the application of standard precautions (for example, all body fluids except sweat, regardless of whether blood is present, are presumed to be infectious); work restrictions for healthcare personnel infected with or occupationally exposed to infectious diseases; and management of occupational exposures to bloodborne pathogens. The guidelines also discuss selection and use of devices with features designed to prevent sharps injury; hand-hygiene products and surgical hand antisepsis; contact dermatitis and latex hypersensitivity; sterilization of unwrapped instruments; dental water-quality concerns (for example, dental unit waterline biofilms; delivery of water of acceptable biological quality for patient care; usefulness of flushing water lines; use of sterile irrigating solutions for oral surgical procedures; handling of community boil-water advisories); and dental radiology. Plumes from laser or electrosurgery and the evaluation of infection-control programs are also discussed. CDC’s document can help employers in the dental industry prepare task-specific health and safety programs. IHs can use the guidelines to better understand the risks and improve occupational health support of the industry. In 2018, ASHRAE revised ANSI/ASHRAE Standard 188, Legionellosis: Risk Management for Building Water Systems. This standard provides minimum legionellosis risk management requirements for the design, construction, commissioning, operation, maintenance, repair, replacement, and expansion of new and existing buildings and their associated potable and non-potable water systems and components. Federal and state OSHA standards cover exposures to other hazards such as radiation, silica, and chemicals. Ergonomics standards are also available. THE ROLE OF THE INDUSTRIAL HYGIENIST Most dental clinics and offices do not have an IH on staff to assist with recognition, evaluation, and control of the occupational health risks associated with dentistry, and many dental employers outsource the development of their safety plans. In many cases, a person whose primary function is either administrative or clinical is assigned to manage the safety plan. This person typically has minimal training on how to effectively manage these programs.  A qualified IH, armed with the resources mentioned in this article, can provide comprehensive health and safety plans that include our current understanding of the risks commonly faced by dental workers. Today’s IH can also provide training; conduct exposure assessments; review policies and procedures for chemical use, storage, and disposal; assess building-related environmental risks; and provide educational resources to help reduce or eliminate ergonomic injuries in dentistry.  A good place to start may be to engage with the American Dental Association on a local or national level. There might be opportunities to educate ADA members at association meetings and seminars about the role IHs can play in helping protect workers in the dental industry. IHs should look for ways to increase awareness of the industrial hygiene profession and establish partnerships to help move dental workers lower on the list of unhealthy occupations.    JOHN MARTINELLI, CAC, CDPH I/A, CHCPEW, is a principal consultant and the healthcare practice leader for Forensic Analytical Consulting Services. DAVID BRINKERHOFF, CIH, is a consulting industrial hygienist and the San Francisco Bay Area consulting director for Forensic Analytical Consulting Services. MICHELLE ROSALES, MPH, CIH, is a consulting industrial hygienist and senior project manager for Forensic Analytical Consulting Services. Send feedback to The Synergist.
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One hazard most people do not typically associate with dentistry is exposure to respirable crystalline silica.
Occupational Health and Safety in the Dental Industry
The Other Hygienists
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Disadvantages of being unacclimatized:
  • Readily show signs of heat stress when exposed to hot environments.
  • Difficulty replacing all of the water lost in sweat.
  • Failure to replace the water lost will slow or prevent acclimatization.
Benefits of acclimatization:
  • Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
  • Stabilization of the circulation.
  • Work is performed with lower core temperature and heart rate.
  • Increased skin blood flow at a given core temperature.
Acclimatization plan:
  • Gradually increase exposure time in hot environmental conditions over a period of 7 to 14 days.
  • For new workers, the schedule should be no more than 20% of the usual duration of work in the hot environment on day 1 and a no more than 20% increase on each additional day.
  • For workers who have had previous experience with the job, the acclimatization regimen should be no more than 50% of the usual duration of work in the hot environment on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.
  • The time required for non–physically fit individuals to develop acclimatization is about 50% greater than for the physically fit.
Level of acclimatization:
  • Relative to the initial level of physical fitness and the total heat stress experienced by the individual.
Maintaining acclimatization:
  • Can be maintained for a few days of non-heat exposure.
  • Absence from work in the heat for a week or more results in a significant loss in the beneficial adaptations leading to an increase likelihood of acute dehydration, illness, or fatigue.
  • Can be regained in 2 to 3 days upon return to a hot job.
  • Appears to be better maintained by those who are physically fit.
  • Seasonal shifts in temperatures may result in difficulties.
  • Working in hot, humid environments provides adaptive benefits that also apply in hot, desert environments, and vice versa.
  • Air conditioning will not affect acclimatization.
Acclimatization in Workers