The atmospheric pollutants are currently the most serious concern in the field of environmental health, with outdoor air pollution causing 1.3 million fatalities in urban areas around the world and indoor air pollution causing 2 million premature deaths in developing nations (WHO, 2014). Many air pollutants are significant contributors to human disease. Anthropogenic air pollution is one of the world's most serious public health threats, causing around 9 million deaths yearly (WHO, 2019). Vehicle emissions produce particle and gaseous pollutants such as particulate matter (PM2.5 and PM10) and carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2), volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs)(Straif et al., 2013). Outdoor air pollution is a significant factor in the global disease load (GBD, 2017), including cytogenetic abnormalities, somatic and germ cell mutations, and altered gene expression, all of which have been associated with increased cancer risk in humans (Cohen et al., 2004; Smith et al., 2004; Chen et al.,2015; Bray et al.,2018; Klompmaker et al., 2020). Several studies reported that the majority of human cancers are sporadic and are caused by environmental factors, which have a substantial risk factor for various diseases (Lichtenstein et al., 2000; Wogan et al., 2004; Seilkop et al., 2012; Drakaki et al.,2014; Abdel-Shafy et al.,2016; Turner et al. 2017). Furthermore, various studies witnessed the link between air pollution and lung cancer, female breast, astrocytoma, acute lymphoblastic leukaemia and brain tumors (Pedersen et al. 2017; Wei et al. 2012; Lavigne et al. 2017; Jorgensen et al. 2016). Non-lung cancers have been linked to indoor air pollution based on cigarette smoking for short- or long-term exposure, including cancers of the brain, kidney, colorectal, gallbladder, bladder (Whiteman and Wilson 2016; Carter et al. 2015).
COVID-19, a unique coronavirus disease, was discovered in Wuhan, China, at the end of 2019 (Zhu et al.,2020). On January 23, 2020, the Chinese government-initiated lockdown measures in the epicenter to stop it from spreading. Soon after, the lockdown was extended to the rest of the country (Lau et al.,2020). Several countries have taken measures to flatten the coronavirus curve, such as closer of non-essential businesses and residents confined at home (He et al.,2020; Ji et al.,2020; Sun et al.,2020). Anthropogenic sources associated with traffic and industrial emissions are the most significant contribution in urban areas (Lelieveld et al., 2015); hence COVID-19 shutdown will result in a decrease of anthropogenic air pollutants emissions sources (Li et al., 2020). COVID-19 shutdown has a significant impact on air quality in China (Chen et al., 2020; Li et al., 2020), the United States (Zangari et al., 2020), Europe (Menut et al., 2020), India (Singh & Kumar, 2021), and other regions, according to recent research articles.
During the COVID-19 lockdown, several studies reported that the concentrations of gaseous and particulate pollutants significant declined in many cities (Bauwens et al., 2020; Chauhan and Singh, 2020; Rodriguez-Urrego and Rodriguez-Urrego, 2020; Zangari et al., 2020), while surface ozone (O3) pollution increased (Sicard et al., 2020; Zhao et al.,2020). Although volatile organic compounds (VOCs) are key precursors of O3 and PM2.5 (Atkinson et al., 2006), the effects of the COVID-19 lockout on ambient VOC levels have remained unknown till now. The pandemic provided a once-in-a-lifetime opportunity to look into the origins and consequences of human activities on air quality and pollution emissions.
VOCs are released into the environment from both natural and anthropogenic sources. VOCs are essential in atmospheric chemistry because they contribute to the formation of ground-level ozone and have an impact on the amounts of hydroxyl radicals (OH) and nitrogen oxides (NOx). These contribute to the formation of hazardous oxidants, which can have negative consequences for human health, the environment, and the atmosphere (Atkinson, 2000). According to Ho et al. (2009), tropical forests are the biggest sources of biogenic VOCs globally, whereas automobile emissions account for the majority of VOCs in metropolitan regions. Several studies reported that BTEX species (benzene, toluene, ethylbenzene, and xylene) had gotten a lot of attention because of their health effects (Alghamdi et al., 2014; Miller et al.).
The use of volatile organic compounds (VOCs) in the detection of several cancers, including lung (Rudnicka et al.,2019), colon (Mozdiak et al.,2019), breast (Phillips et al.,2018), pancreatic (Princivalle et al.,2018), prostate (Bond et al.,2019), and head and neck (Opitz et al.,2018), has piqued (Phillips et al.,2018; Markar et al.,2018; Chang et al.,2018). Benzene, toluene, ethylbenzene, and xylene (BTEX) are among the most common VOCs and a significant class of air pollutants (Hwang et al., 2011; Pegas et al., 2010;). Many studies reported that BTEX species are a significant association with negative health consequences since they are abundant in the interior environment (Luengas et al., 2015; Baghani et al., 2018; Golkhorshidi et al., 2019; Ceron Yousefian et al., 2018; Lin et al., 2017; Zhang et al.,2020; Smith et al., 2020). In addition, a rise in the number of occupants combined with insufficient ventilation rates might increase indoor pollutant concentrations (La Vecchia et al., 2003). BTEX compounds account for up to 60% of non-methane VOCs in metropolitan areas around the world. As a result, these mono aromatic hydrocarbons serve as a marker for organic pollutants originating from numerous sources of air pollution, such as vehicles (Hajizadeh et al., 2018). Vehicle emissions, including petroleum refineries and cigarette smoking, are also potential sources of BTEX (Garg and Gupta, 2019; Hajizadeh et al., 2018; Rad et al., 2014). As a result, indoor and outdoor BTEX concentrations in diverse contexts have been examined in numerous investigations (Sarigiannis et al., 2011; Masih et al., 2021). BTEX is a collection of harmful chemicals that have been a hot area of research around the world (Hazrat et al.,2015; Dehghani et al.,2018, El-Hashemy et al.,2018; Baberi et al.,2022).
Although various studies have been reported on improving air quality in various countries during the lockdown periods (Singh et al, 2021, Singh et al., 2022); a few studies reported on Indian cities because more concern has been paid to the health risks of atmospheric particles but very few studies reported on BTEX species associated with their health. However, the details analysis of BTEX associated with health risks during the lockdown is lacking. None of the previous studies have investigated on the analysis of BTEX species for pandemic periods in Southern India. The major objectives of the current study were (i) to quantify temporal variation in TVOC concentrations and (ii) to estimate the health risk assessment of BTEX in different age groups.