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.