Health risk assessment of inhalation exposure to dry fogging of hydrogen peroxide in a dental clinic during the COVID-19 pandemic.

After the outbreak of COVID-19, many dental clinics use dry fogging of hydrogen peroxide (H2O2) to disinfect the air and surfaces. Inhalation of highly concentrated solutions of H2O2 may cause severe respiratory problems. This study aimed to estimate the health risk assessments of inhalation exposure to dry fogging of H2O2 in a dental clinic. This cross-sectional, descriptive-analytical study was performed to determine the inhalation exposure and health risk of 9 dental clinic staff with H2O2 in six rooms. Occupational exposure to H2O2 was assessed using the OSHA VI-6 method and a personal pump with the flow rate of 500 mL/min connected to the midget fritted-glass impinger containing 15 mL of TiOSO4 collecting solution. The health effects of H2O2 exposure were assessed using a respiratory symptoms questionnaire. The health risk assessment of inhaled exposure to H2O2 was also performed using the method provided by the Singapore occupational health department. The mean respiratory exposure of clinic staff to H2O2 was ranged from 1.3 to 2.83 ppm for six rooms which was above the limits recommended by international organizations. Dyspnea (44.4%), cough (33.3%), and nasal burning (22.2%) were the most prevalent health problems. The results also showed a medium risk for endodontics and surgery, and lower risk for periodontics, restorative care, orthodontics, and prosthetics. The results of this study indicate that when using an automated hydrogen peroxide-vapor fogger, calculating the spraying time based on room volume and using the rooms after 30 min of fogging is very important and can greatly reduce the risk ranking.

Pt-, Rh-, Ru-, and Cu-Single-Wall Carbon Nanotubes Are Exceptional Candidates for Design of Anti-Viral Surfaces: A Theoretical Study.

As SARS-CoV-2 is spreading rapidly around the globe, adopting proper actions for confronting and protecting against this virus is an essential and unmet task. Reactive oxygen species (ROS) promoting molecules such as peroxides are detrimental to many viruses, including coronaviruses. In this paper, metal decorated single-wall carbon nanotubes (SWCNTs) were evaluated for hydrogen peroxide (H2O2) adsorption for potential use for designing viral inactivation surfaces. We employed first-principles methods based on the density functional theory (DFT) to investigate the capture of an individual H2O2 molecule on pristine and metal (Pt, Pd, Ni, Cu, Rh, or Ru) decorated SWCNTs. Although the single H2O2 molecule is weakly physisorbed on pristine SWCNT, a significant improvement on its adsorption energy was found by utilizing metal functionalized SWCNT as the adsorbent. It was revealed that Rh-SWCNT and Ru-SWCNT systems demonstrate outstanding performance for H2O2 adsorption. Furthermore, we discovered through calculations that Pt- and Cu-decorated SWNCT-H2O2 systems show high potential for filters for virus removal and inactivation with a very long shelf-life (2.2 × 1012 and 1.9 × 108 years, respectively). The strong adsorption of metal decorated SWCNTs and the long shelf-life of these nanomaterials suggest they are exceptional candidates for designing personal protection equipment against viruses.

Evaluation of hydrogen peroxide and ozone residue levels on N95 masks following chemical decontamination.

BACKGROUND: Hydrogen peroxide and ozone have been used as chemical decontamination agents for N95 masks during supply shortages. If left behind on the masks, the residues of both chemicals represent a potential health hazard by skin contact and respiratory exposure. AIM: Characterization of hydrogen peroxide and ozone residues on mask surfaces after chemical decontamination. METHODS: Various N95 masks were decontaminated using two commercial systems employing either aerosol spray or vaporization of hydrogen peroxide in the presence of ozone. Following the decontamination, the masks were aired out to eliminate moisture and potential chemical residues. The residual hydrogen peroxide and ozone were monitored in the gas phase above the mask surface, and hydrogen peroxide residue directly on mask surfaces using a colorimetric assay. FINDINGS: After decontamination, hydrogen peroxide and ozone were detectable in the gas phase in the vicinity of masks even after 5 h of aeration. Hydrogen peroxide was also detected on all studied masks, and levels up to 56 mg per mask were observed after 0.5 h of aeration. All residues gradually decreased with aeration, likely due to decomposition and vaporization. CONCLUSION: Hydrogen peroxide and ozone were present on N95 masks after decontamination. With appropriate aeration, the gaseous residue levels in the vicinity of the masks decreased to permissible levels as defined by the US Occupational Safety and Health Administration. Reliable assays to monitor these residues are necessary to ensure the safety of the mask users.