Real-time Monitoring of Aerosol Generating Dental Procedures.

OBJECTIVE: We aimed to quantify aerosol concentrations produced during different dental procedures under different mitigation processes. METHOD: Aerosol concentrations were measured by the Optical Particle Sensor (OPS) and Wideband Integrated Bioaerosol Sensor (WIBS) during routine, time-recorded dental procedures on a manikin head in a partitioned enclosure. Four different, standardised dental procedures were repeated in triplicate for three different mitigation measures. RESULT: Both high-volume evacuation (HVE) and HVE plus local exhaust ventilation (LEV) eradicated all procedure-related aerosols, and the enclosure stopped procedure-related aerosols escaping. Aerosols recorded by the OPS and WIBS were 84 and 16-fold higher than background levels during tooth 16 FDI notation (UR6) drilling, and 11 and 24-fold higher during tooth 46 FDI notation (LR6) drilling, respectively. Ultrasonic scaling around the full lower arch (CL) or the full upper arch (CU) did not generate detectable aerosols with mitigation applied. Without mitigation the largest concentration of inhalable particles during procedures observed by the WIBS and OPS was during LR6 (139/cm3) and UR6 (28/cm3) drilling, respectively. Brief aerosol bursts were recorded during drilling procedures with HVE, these did not occur with LEV, suggesting LEV provides protection against operator errors. Variation was observed in necessary fallow times (49 - 280 minutes) without mitigation, while no particles remained airborne when mitigation was utilised. CONCLUSION: This data demonstrates that correctly positioned HVE or LEV is effective in preventing airborne spread and persistence of inhalable particles originating from dental AGPs. Additionally, a simple enclosure restricts the spread of aerosols outside of the operating area. CLINICAL SIGNIFICANCE: Employing correctly positioned HVE and LEV in non-mechanically ventilated clinics can prevent the dispersal and persistence of inhalable airborne particles during dental AGPs. Moreover, using enclosures have the additive effect of restricting aerosol spread outside of an operating area.

Assessment of Environmental and Occupational Risk Factors for the Mitigation and Containment of a COVID-19 Outbreak in a Meat Processing Plant.

Throughout the COVID-19 pandemic, meat processing plants have been vulnerable to outbreaks of SARS-CoV-2 infection. Transmission of the virus is difficult to control in these settings because of a combination of factors including environmental conditions and the specific nature of the work. This paper describes a retrospective outbreak investigation in a meat processing plant, a description of the measures taken to prevent or contain further outbreaks, and insights on how those with specific knowledge of the working environment of these plants can collaborate with public health authorities to ensure optimal outbreak control. The plant experienced 111 confirmed positive asymptomatic cases in total with an estimated attack rate of 38% during a five-week period. 4 weeks after the first case, mass screening of all workers was conducted by the public health authorities. Thirty-two workers tested positive, of which 16 (50%) worked in one particular area of the plant, the boning hall (n = 60). The research team prepared and carried out semi-structured interviews with the plant personnel who were charged with COVID control within the plant. They carried out assessments of operational risk factors and also undertook air quality monitoring in the boning hall and abattoir. The air quality measurements in the boning hall showed a gradual build-up of carbon dioxide and aerosol particles over the course of a work shift, confirming that this poorly ventilated area of the plant had an environment that was highly favorable for aerosol transmission of SARS-CoV-2. Assessment of operational conditions incorporated visual surveys of the plant during the working day. Prior to and during the first 2 weeks of the outbreak, multiple measures were introduced into the plant by management, including physical distancing, provision of educational material to workers, visitor restrictions, and environmental monitoring. After the implementation of these measures and their progressive refinement by plant management, the factory had no further linked cases (clusters) or outbreaks for the following 198 days. The tailored approach to risk mitigation adopted in this meat processing plant shows that generic risk mitigation measures, as recommended by public health authorities, can be successfully adapted and optimized by designated plant emergency response teams.