COVID-19: Are airborne particles media for human exposure to coronavirus (SARS-COV-2)?

Indoor Air Cartoon Journal, May 2020, Volume 3, #105

The main goal of any public health efforts is to reduce or eliminate exposure to hazards, e.g., air pollutants, and resulting health implications. Source of an air pollutant, medium carrying the pollutant, and the environment in which the medium exist should be managed to reduce or eliminate exposure to the pollutant.

If exposure occurs or anticipated to occur, public health efforts will focus on reducing the inhalation dose of the pollutant. Efforts will also be made to increase immunity or improve any pre-existing conditions to reduce the physiological vulnerability of the exposed person to suffering from health implications.

If there is no source of a pollutant, there won’t be any exposure. If there is no exposure, health implications due to the pollutant will not occur. However, in real life, identifying and eliminating the source of a pollutant can be very challenging, like in the case of coronavirus – SARS-COV-2 – causing COVID 19. Thus, managing the medium and the environment in which a person could be exposed to the coronavirus become essential to reduce exposure and potential health implications.

Coronavirus is released into the indoor air through activities such as coughing, sneezing, talking, and breathing. Some schools of thought believed resident time of coronavirus in the air (a medium) is very short. Thus, they dismissed the potential contribution of airborne transmission to a large outbreak of coronavirus (SARS-COV-2) infections. The focus of precautionary measures was largely towards mitigating fomite transmission.

The large global outbreak of the number of people tested to be coronavirus positive prompted many experts and policymakers to rethink their stands on the potential role of airborne transmission. Although, research articles published before the COVID 19 pandemic have already suggested the potential contribution of airborne transmission of viruses to respiratory diseases.

Many aerosol scientists sprang into action to provide the evidence needed to sway policymakers to take airborne transmission seriously and recommend precautionary and mitigating measures necessary to abate the significant rise in the number of infected people and fatality rate.

Emerging evidence in the literature suggests that the resident time (amount of time spent) of and distance travelled by coronaviruses in the air can be far more than initially thought. The resident time of coronavirus in the air could be several days, and distance travelled could be several meters, especially in indoor environments, if appropriate measures like ventilation, filtration, or air cleaning strategies are not adopted. More research efforts are needed in this area to quantify the impact the engineering solutions could have on resident time and distance travelled by coronaviruses.

What could increase the resident time and distance travelled by coronaviruses in the air? Research works referenced in the comics below suggest particles could be media for viruses to be airborne for a considerable period and travelled long distances. Thus, air and particles suspended in it could be media through which humans are exposed in environments they occupied.

While the evidence is emerging, it will suffice to say it is essential to take precautionary measures against environmental degradation caused by coronavirus seriously. Article 15 of the 1992 Rio Conference on precautionary principle states that “where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.”

Thus, it is essential to stay at home as much as possible, away from environments or situations where one might be exposed to coronavirus, its source or media carrying the virus. The potential risk of being infected due to exposure also reinforces the need for mask usage and engineering solutions mentioned above.

105. PM virus media_105

Do you want to learn more about this topic? Read Ma et al. (2017), Qin et al. (2020), Setti et al. (2020), and Wu et al. (2020) papers. You may also want to read a book titled “Healthy Buildings…” written by Allen and Macomber (2020) to learn more about “conceptual model for exposure-related disease”.

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