4.1 Results overview
Overall, compliance with wearing face masks by the general public in Poland was good in the beginning of the study period (74%), however, it decreased (to 66%) in the 2nd and 3rd week of the observation, with a predominance of cloth masks observed. Female gender, age >40 years, and closed space were each associated with higher mask usage. Those playing sports had about two times lower chance to use facial masks. The percentage of those using facial masks in the correct manner also decreased gradually over time, mainly due to a decreasing trend observed for medical and cloth masks; significantly more females correctly used masks. Breaches in nose covering and hanging masks around the neck were the most common incorrect practices while wearing a mask.
4.2 Trends in facial mask use
The willingness of the general public plays a decisive role in achieving the successful implementation of protective measures . However, it is still a problem to encourage the public to unconditionally and continuously follow these recommended preventive actions. The decreasing trend regarding facial mask usage by the general public in Poland through the three weeks of observation, which illustrates behavioral change, may be due to a gradual decrease in concerns about the pandemic over time, combined with a lowering in the perceived risk of infection. The strong association between respondents’ risk perceptions and taking comprehensive pre-cautionary measures against influenza, MERS and SARS infections has been reported previously [31-34]. Apprehensions about relatively high administrative penalties while not complying with governmental regulation on wearing masks could also play a role in the high percentage of those observed using face masks at the beginning of this study.
The number decreased in later weeks, possibly due to less strict supervision, monitoring and regulation enforcement by the relevant services . Numerous examples of political leaders, including the Polish president and the prime minister not using masks in public spaces, which was transparently reported by the media [35-37], could influence mask usage by the public, by simply signaling that fears related to the virus are overblown. Public officials should be acutely aware they are in position to lead by example, with the choices they make and how they carry themselves can send a powerful message; this also refers to the SARS-Cov-2 pandemic. Sadly, face masks have become one of the potent symbols in how poorly Polish leaders have responded to this public health crisis.
Of note, during the observation period of this study, the number of daily reported SARS-Cov-2 cases in Poland was rather stable (between 300-400), with the ongoing outbreak in the Silesian region among miners and their family members and smaller outbreaks in Lodz and Wielkopolska provinces. Basic reproductive number for those regions exceeded 1 . As such, the perceived risk of infection among the general public in those regions should be higher than the rest of Poland. However, the results of the study did not show significant differences in masks usage among the regions divided by pandemic risk. Thus, existing communication channels should be improved to increase general public awareness regarding infection risk.
4.3 Determinants of mask use
Various factors, including socio-demographic characteristics, social context, and individual values can affect the subjects' perception of their actual risk of disease, as well as influence their worries about a pandemic [3,38,39]. Based on recent studies, being older, female, more educated, are associated with a higher chance of adopting protective behaviors [3,32,40]. The results of this study show that males, traditionally risk takers, were significantly less likely to have appropriate practices regarding mask usage, and protecting themselves and others against SARS-Cov-2. These findings are consistent with other studies on SARS and MERS, showing that females are more health conscious and risk averse [32,33,41]. This was also reported during the current SARS-Cov-2 pandemic . It is suggested that health promotion messages sent through female mediators who are significant for young males, e.g. mothers, sisters or partners, could increase mask use for this vulnerable subgroup . In addition, there was a positive dose-response gradient with increasing age and mask usage. Older age was also found by other authors as a determinant of precautionary measures taken against respiratory infections [33,40]; elderly people might feel more susceptible to being affected by a pandemic .
Wearing masks to the cover mouth and nose when out in public was significantly lower in open spaces during the three-week observation, and decreased to a greater extent (10%) over time, when compared to enclosed spaces. During the study period government officials announced that in the upcoming weeks it would not be necessary to wear masks while walking on the street, in parks or during sport activities outdoors, e.g. riding a bike ; this could have influenced the behavioral change regarding the mask usage by the general public. The message that it would still be mandatory to wear masks in shops might have made the population consider its importance, which in turn influenced high compliance.
4.4 Type of mask used
To control the infection source, as well as to self-protect, cloth masks, as recommended by the WHO, CDC, and ECED [13-16] are likely to be adequate to minimize SARS-Cov-2 transmission in the community, especially if everyone wears a mask correctly. Cloth masks were predominantly used in the public space in this study, possibly due to the low price and the fact that they can be easily manufactured or made at home and reused after washing. The shortage of mask supply in the community and the integrated governmental and media message that medical masks and N95 respirators must be reserved for health-care workers might have influenced their poor usage by the public.
Notably, compliance of correct mask use was poor – only two thirds of those wearing facial masks (cloth and medical) wore them correctly at the first time point, this decreased over time, with 55% wearing cloth masks and 60% - medical ones. Although N95 respiratory masks were rarely used by the public, compliance with correct use was the best and increased over time. One of the possible interpretations of this observation could be that the potential N95 respiratory masks wearers were more health oriented and health educated. People with high health literacy skills are more competent in related to public health outbreak controls [3,40,44]. Due to the small number of observations regarding this type of mask usage, further qualitative and quantitative studies are needed to better assess this issue. Correct mask usage was gender dependent with more females using a mask in the proper manner. Interestingly, no differences were observed regarding the correct mask usage and age, residence, as well as location and type of activity.
At all 3 time points breaches in nose covering and hanging masks around the neck were the most common incorrect practices while wearing a mask. Such practices elevate infection risk regarding SARS-Cov-2 and other airborne respiratory pathogens. Notably, the pathogens may settle on the surface of used masks layers, resulting in mask contamination  which in turn highlights the risk of self-contamination to the wearer, particularly when fixing, elevating or doffing a mask.
4.5 Strengths and Limitations
To our knowledge, this is the first study to investigate facial masks use in the general population in Poland, as well as in the EU. One particular strength of the study is that participants were observed during an actual continuing outbreak - data collection started three weeks after an introduction of the regulation about obligatory mask use in the public space. Furthermore, by covert observation, the Hawthorne effect has been limited as the behavior of participants was not altered .
However, the study has some limitations which should be pointed out. Community-based national surveys were not feasible regarding the phase of SARS-Cov-2 pandemic in Poland in which the study had been conducted. As such, data were collected through students observations, depending on their place of residence. Therefore, the majority of the participants were observed in the western and central regions of Poland, where most of the students came from. Further research should cover all Polish provinces to better assess mask usage at a national level. Due to student sick leave, the numbers of observations were smaller at the first and third time point than at the second time point. Nevertheless, the response rate was still high which led to a relatively large sample size. Another limitation is that the study was administered over a short time period. Thus, the stability of the responses is unknown . Further observations are needed to track possible changes as the pandemic evolves. Age assessment was based on the subjective observations of students. However, the age range was categorized to “every 10 years”, which should have minimized any possible assessment mistakes. The implication is for future research to assess whether there is a relationship between mask usage and other variables, not covered by this study, such as education, knowledge on infection control, anxiety level, trust in the health authorities, etc. Finally, this study did not address causation. Therefore, the regression results should be interpreted with caution.