Keywords: carbon dioxide (CO2) exposure, toxicity, personal protective equipment, masks, N95 face mask, surgical mask, risk, adverse effects, long-term adverse effects, health risk assessment, MIES-syndrome, children, adolescents, pregnant women
1. Introduction
Approximately 77% of the countries in the world introduced the requirement to wear masks in public spaces to contain SARS-CoV-2 making it commonplace in 2020. Simultaneously, it is one of the most important ubiquitous environmental factors directly affecting human breathing. Government data from the end of the year 2021 show that an estimated 4 496 149 755 people worldwide (58% of world population) have been confronted with a mask obligation. Given this and the significant role masks have played as a non-occupational, non-pharmaceutical public health intervention for the past 2 years, a rigorous scientific toxicological consideration is required. Children in schools in particular are heavily exposed to the mandatory wearing of masks for long periods. In this paper, we highlight the toxicological aspects of wearing a mask for special user groups resulting from a low level CO2 exposure.
In medical environments, masks have been mandatory self-protective and third-party protective equipment for healthcare workers prior to COVID-19. There is no doubt about the efficacy of this medical device in reducing transmission of pathogens, especially bacteria. Masks belong in the hands of professionals in medical facilities and environments where symptomatic individuals are common. It should be noted that the authors of a recent systematic review evaluating six studies on antiviral mask efficacy concluded that wearing a mask might reduce the risk of COVID-19 infection, but predominantly in healthcare workers [1]. However, the evidence was limited due to the low statistical power and strength of the studies analysed. The topic of general mask mandates is currently the subject of much scientific debate, especially in the USA. It is widely believed that the use of masks – including in the general population – could be an important measure to combat SARS-CoV2 [2]. Yet moderate or strong empirical scientific evidence for the effectiveness of masks when used by the general population is lacking, and there is solid data questioning the definite antiviral effectiveness of masks [3-6], even from the Cochrane database analysing systematic reviews [7]. And even mask-supportive reviews include statements such as: „wearing a mask could reduce the risk of COVID-19-infection “, but „ more evidence is still needed to better define the protective effect of the mask on the wider population“[1]. An overview of systematic reviews on mask use against airborne viral diseases [8] found only one high quality study, which concluded „that compared with no facemask use, wearing a facemask may make little to no difference in how many people that catches a flu like illness“[7]. Furthermore, they stated: “It may seem that it makes little to no difference, what type of facemask is used“. Current evidence suggests that SARS-CoV-2 may be also transmitted via fecal transmission and fomite [9] between infected individuals and others. Altogether, from an evidence-based perspective, masks for the public are overrated in a pandemic response [10].
In contrast, it is known that masks bear several side effects and risks [11]. Among the many symptoms and physiological changes, an elevated blood carbon dioxide level is an important cornerstone of the so-called Mask-Induced Exhaustion Syndrome (MIES) [11]. There is a high risk of improper handling when the mask is used by the general population and by children [12,13]. Children and pregnant women are a special subgroup more susceptible to potential negative environmental factors [14].
There are several general short-term effects on human health due to low level CO2-inhalation: Physiological changes occur already at levels between 0.05% and 0.5% carbon dioxide showing increased heart rate, increased blood pressure and overall increased circulation with the symptoms of headache, fatigue, difficulty concentrating, dizziness, rhinitis and dry cough [15]. While the effects of short-term exposure on cognitive performance begin at 0.1% CO2 levels, with reduced cognitive performance, impaired decision-making and reduced speed of cognitive solutions, many other long-term effects are known at concentrations above 0.5% [15,16]. Exceeding the limit of 1% CO2 the harmful effects include respiratory acidosis, metabolic stress, increased blood flow and decreased exercise tolerance [15]. Therefore, regarding low level CO2 exposition an EN149:2001+A1 (European Standard Norm) and a NIOSH (National Institute for Occupational Safety & Health) norm exists. A health-critical limit is set at 15 minutes for 3% for short periods, while the 8-hour limit is set at 0.5% CO2 [17].