Concentration of droplets from patients during normal breathing and speech and their importance in protection from coronavirus sars-cov-2 (Covid-19) infection

Purpose: Coronavirus disease (COVID-19) has been declared a pandemic and the number of infected individuals and deaths continue to increase globally. COVID-19 is transmitted through airborne droplets formed during coughing and sneezing and from the saliva of infected patients. Medical healthcare workers are often at risk of infection. This study measured the aerosol derived from the droplets of patients during the conversation. Methods: Overall, 25 patients aged 21 to 87 years were enrolled. The amount of droplets from the patient was measured under the following four conditions: 1) no conversation with the mask on; 2) conversation with the mask on; 3) conversation without the mask; and 4) no conversation without the mask. Particulate matter (PM) with an aerodynamic diameter of 2.5 μm or less (PM2.5) and PM with a diameter of 10 μm or less (PM10) were measured as representative aerosols at a position of 1 meter from the patients. Results: The concentrations of PM2.5 (μg/m3) were as follows: 22.7 ± 10.2 before the conversation with the mask, 24.2 ± 10.2 during the conversation with the mask, 32.3 ± 14.7 during the conversation without the mask, and 23.1 ± 9.9 after the conversation without the mask. The concentrations of PM10 (μg/m3) were as follows: 39.8 ± 18.2 before conversation with the mask, 41.9 ± 18.5 during conversation with the mask, 55.5 ± 27.2 during conversation without the mask, and 40.4 ± 17.8 after conversation without the mask. The variations in the PM2.5 and PM10 correlated negatively with the age of patients (PM2.5: R = -0.51, p = 0.0009 and PM10: R = -0.53, p = 0.0063). Conclusion: Wearing a mask can prevent airborne droplet formation and reduce transmission of infection.