# Indoor Air Quality Assessment in Grocery Stores
## 1 Introduction  
Unlike other resources, air is not scarce, rather, its vulnerability lies mainly in its risk of deterioration [1]. Indoor Air Quality (IAQ) has a significant impact on our well-being and health, with several adverse impacts on health being found, such as respiratory and cardiovascular illnesses, among others [2]. Indoor air hosts a complex mixture of non-biological and biological contaminants along with outdoor and indoor pollutants. Outdoor pollutants are mainly associated with vehicular traffic and industrial activities, whereas indoor pollutants are influenced by the behavior of occupants, building and furniture materials, consumer and cleaning products, and pollutants that manage to get inside through ventilation systems [2; 3; 4; 5]. Changes in lifestyle have made us more subjected to these pollutants, as we spend most parts of our days in indoor environments (for instance, for Portuguese children, it is estimated that they spend 86% of their time indoors [6]), from public to private environments, namely home, workplace, leisure, building and commuting, where we are exposed to a panoply of pollutants that may negatively affect health welfare and productivity [3; 7]. Studies by the United States Environmental Protection Agency (EPA) ranked indoor air pollution as a top five environmental risk to public health [8]. Efforts have been done tounderstand IAQ complexity and its impact on human health specially focused on exposure levels in different environments and activities [9; 10]. As a result of the energy crisis in the 1970s, many changes in building design have been implemented, including in construction and operation, focused on making buildings as airtight as possible, to prevent \"leaks\" and minimize thermal energy losses. Moreover, along with these building design advancements, numerous new sources of air pollutants emerged, based, for example, on changes in lifestyle and building materials used. A change in composition and complexity of pollutants in the indoor air has been acknowledged, due, for example, to the use of more synthetic materials and chemicals in construction, decoration, cleaning agents, and consumer products [7; 11]. These changes have led to low ventilation rates that impact IAQ since it promotes the indoor accumulation of pollutants, which leads to high indoor pollution levels, often 2 to 5, or even 100, times higher than the levels found in outdoor environments [7]. Moreover, indoor exposure to different indoor air pollutants may have a significant impact on occupants' health, even at low concentrations [12]. Therefore, in the 1980s, IAQ started to be an issue of public interest when buildings' occupants started to exhibit several sick building syndromes and efforts were conducted to understand, minimize, and/or correct those issues. According to the United Nations Environment Programme, in 2020, IAQ was responsible for nearly 3.2 million premature deaths, and, in 2021, around 4 million [13]. In 2020, the Eurostat statistical atlas estimated that a regular person has an average duration of working life in the European Union of 35.2 years, while in Portugal, the estimative is 38.2 years [14]. Considering that an adult spends around 8 h per day at work (5 days of the week), and considering the lifetime working period, a Portuguese individual spends, on average, around 71,800 h (considering 47 working weeks per year) at work, and in some cases, even more, depending on the profession and type of work. Therefore, IAQ at workplaces may have a significant impact on worker well-being, productivity, and health due to prolonged exposure [15]. It is also important to highlight that, according to the International Labour Organization (ILO), it is estimated that around 2.3 million people endure work-related accidents and diseases every year, with around 160 million a victim of work-related illnesses [16].