Covid, museums are the safest places, schools and offices the most dangerous. German study

Museums and theaters are the places safest from Covid-19 infection, while schools and offices are conversely the most dangerous. This is the assessment that emerged from the study conducted by theHermann-Rietschel-Instituts of Berlin ’s Technische Universität in collaboration with the Robert Koch-Institut (the counterpart of our Higher Institute of Health) and theCharité University Hospital of the German capital. The study bears the signatures of Martin Kriegel, director of the Hermann-Rietschel-Instituts and an expert in ventilation, and Anne Hartmann, an engineer, also an expert in ventilation and aeration.

Kriegel and Hartmann studied the risk posed by the amount of aerosol particles emitted into an environment by potential infected persons (the dose depends on the intensity of the source, i.e., the infected individual, his or her and the respiratory activity of people in the environment, the concentration of aerosol in the environment, and the duration of his or her stay inside the room). Several assumptions are made: wearing a mask reduces aerosol emission and also the amount inhaled; respiratory activity varies with the type of physical activity followed, which changes the amount outgoing, but consequently also the amount others can inhale; and proper air exchange regulates the number of aerosol particles.

What the Technische Universität Berlin study aims to show is that one does not get infected everywhere in the same way and that there are places that are less safe than others: these are situations that need to be evaluated very carefully, especially when deciding which activities to close and which to keep open, while still following the rules (wearing a mask, in fact, is considered essential to stem the spread of coronavirus).

The risk indices

The paper (link here) by Kriegel and Hartmann states that although it is not possible to make an absolute assessment of the risk of infection (i.e., in a nutshell, we cannot know for sure how many people can become infected with a given amount of infected aerosol in the air: in fact, there is a lack of sufficient scientific data to be able to tell), it is possible, however, to determine the aerosol dose based on the type of activity and the premises within which the infected people are located.

Based on this data, a risk assessment was developed with an index where 1 is the risk of one person infecting no more than one person. According to the study, going to the supermarket has a risk value of 1, while, for example, going to the museum or theater with the audience wearing masks and the capacity reduced to 30 percent and two hours of attendance, results in an index of 0.5 (the lowest). This means that going to the museum or theater under these conditions is half as risky as going to the supermarket (with one hour’s stay), according to Kriegel and Hartmann. Conversely, the absolute most dangerous places are offices that are 50 percent occupied where workers (eight-hour stay) do not wear masks (index 8, meaning it is 8 times riskier than the supermarket) and high schools with full classes and students who do not wear masks over a six-hour stay (index 11.5).

Right after museums and theaters we find the hairdressing salon, wearing a mask, index of 0.6 with two-hour dwell time. In second place tied, theaters and museums with 40 percent occupancy and masking (also two-hour dwell time): 0.6. In fourth place is local public transportation, with masking and assuming an average dwell time of half an hour: 0.8. Next, in fifth place, is the supermarket with masking (1, one hour) tied with the movie theater, no masking, two-hour stay and 30 percent occupancy (1). Next: shopping with masking in 10 square meters per person and two hours occupancy, movie theaters without masking at 40% occupancy and two hours occupancy and restaurant at 25% occupancy and one and a half hours occupancy (1,1); sports arenas at 50% without masking in one hour occupancy and trains and long-distance buses on 3 hours of travel, 50% occupancy and masking (1,5); multi-person offices, 20% occupancy, masking and eight hours’ stay (1.6); swimming pool, two hours, obviously without masking (2.3); restaurant at 50%, one and a half hours (2.3); high schools at 50% with masking, six hours (2.9); gymnasiums at 50 percent without a mask, one and a half hours (3.4); high school at 50 percent without a mask, six hours (5.8); office at 50 percent without a mask, eight hours (8); full high school without a mask, six hours (11.5).

Pictured below: visitors to the Borghese Gallery on the day of reopening (ph. Credit Borghese Gallery)

Covid, museums are the safest places, schools and offices the most dangerous. German study

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