May 2, 2024

NIOSH Evaluates Respirable Hazards in Dental Clinic

A new health hazard evaluation (HHE) report published by NIOSH outlines respirable hazards found in a dental clinic and lists controls the clinic may implement to protect workers. According to the report (PDF), clinic management requested the evaluation due to concerns about idiopathic pulmonary fibrosis (IPF), a serious, chronic disease that can cause permanent scarring in the lungs. IPF was first reported among dentists in 2018. The NIOSH evaluators visited the clinic in August 2022 to analyze possible exposures, assess the ventilation system, and interview clinic employees. Although agency staff found low levels of respirable hazards and employees did not report work-related symptoms, the report recommends that the clinic’s ventilation controls be significantly improved. Treatment rooms and staff offices did not meet ASHRAE standards for temperature and outdoor air intake. Staff members did not consistently use local exhaust ventilation (LEV) in the clinic laboratory, causing aerosols generated in the lab to flow into adjacent spaces.

NIOSH’s exposure assessment included air sampling for respirable dust, respirable crystalline silica, respirable metals, volatile organic compounds (VOCs), and aerosols. All personal air samples for respirable dust were below OSHA permissible exposure limits (PELs) and ACGIH threshold limit values, and all personal air samples for respirable crystalline silica were below the NIOSH recommended exposure limit (REL) and OSHA PEL. Area sampling found low levels of respirable dust, respirable crystalline silica, and respirable metals throughout the clinic, although metals were present in all or most areas. Nickel was detected in one sample at levels below the REL; NIOSH considers nickel dust to be a possible carcinogen and recommends reducing exposures to the lowest levels feasible.

Benzene and methylene chloride, also possible carcinogens, were measured during tasks such as grinding and molding a mouthguard and trimming a retainer. Other VOCs were found at low levels through full-shift area air sampling, but levels of ethanol, isopropyl alcohol, and acetone were elevated, likely due to cleaning and disinfecting. Although levels for all VOCs were below the respective RELs, the report notes that use of LEV lowered exposures further. Both an LEV tray and a downdraft table were available in the lab, but the LEV tray was not always used by workers.

The report recommends that the clinic reduce the risk of contaminants migrating from the lab into other areas by maintaining the lab under negative pressure and encouraging workers to use LEV while performing grinding, trimming, and soldering tasks. The clinic may consider implementing high-volume evacuation and allowing workers to voluntarily wear N95 respirators when performing dental procedures requiring nickel or silica. NIOSH’s recommendations also include bringing the clinic’s ventilation system in line with nationally accepted standards for ventilation, making N95s available and training staff in their use, ensuring that staff members understand the hazards of their workplace, and encouraging them to report work-related respiratory symptoms.

More information may be found in NIOSH’s report, which can be downloaded as a PDF from the agency’s HHE report library.

Related: A feature article published in the December 2019 Synergist titled “The Other Hygienists” discusses occupational health and safety in the dental industry.