## 1 Introduction  
With economic development the negative health effects of air pollution are becoming more severe. According to data reported by the World Health Organization (WHO), 99% of the world's population breathes poor-quality air [1]. According to a report in 2019, air pollution ranked fifth among the global mortality risk factors in 2017 [2]. Therefore, given the survival pressure brought by the deteriorating air environment, it is crucial to understand the mechanism of pollutant-induced disease, which is of great significance for preventing disease and reducing the medical burden. As we know, the respiratory system is susceptible to pollutants [3, 4], yet research on the association of pollutants with respiratory diseases is still lacking. Many of the pollutants we are familiar with, such as particulate matter with aerodynamic diameter less than 2.5 \(\upmu\)m (PM\({}_{2.5}\)), nitrogen dioxide (NO\({}_{2}\)), and sulfur dioxide (SO\({}_{2}\)), have been widely reported to exert adverse health effects [5, 6, 7, 8, 9]. Previous studies revealed a relationship between exposure to air pollution such as PM\({}_{2.5}\) and chronic respiratory disease [10], however, limited information is currently available on the relationship between exposure to polycyclic aromatic hydrocarbons (PAHs) as constituents of particulate matter (PM) and respiratory symptoms. Rhinitis is a common respiratory disease, and interestingly, research on its association with air pollution was inconsistent. A longitudinal study demonstrated that exposure to air pollution was not associated with rhinitis in adults [11], while another cohort study showed that only NO\({}_{2}\) correlated with rhinitis [10]. In a study conducted in Changsha, China, exposure to traffic air pollution significantly increased the risk of developing allergic rhinitis in the early stages of life [12]. Furthermore, a European cohort study that focused on adults with rhinitis revealed the potential of PM\({}_{2.5}\) and NO\({}_{2}\) to increase the severity of rhinitis [13]. Nasal symptoms often occur in patients with rhinitis, whether allergic or nonallergic [14] and include nasal congestion, rhinorhea and sneezing, etc. Many factors can cause nasal symptoms [15], and air pollutants are one of them. However, the mechanism by which air pollutants cause nasal symptoms is unclear. One of the possible explanations is that due to non-allergic rhinitis and allergic rhinitis being associated with inflammation, manifested by an increase in inflammatory cells [16], Air pollutants might be a potential cause of rhinitis because of their role in the onset of inflammation [17; 18]. In a study on children, PM\({}_{2.5}\) was shown to be associated with nasal allergic inflammation in children with allergic asthma, as eosinophils were significantly increased in their nasal lavage after exposure to PM\({}_{2.5}\)[17]. Moreover, after exposure to dose-related NO\({}_{2}\), asthmatic patients had increased eosinophils in their sputum, which may exacerbate their airway inflammation [18]. But studies on whether PAHs are associated with airway inflammation are still scarce. Although some studies have found that some PAHs may be related to asthma markers such as Immunoglobulin E (IgE), interleukin (IL)-4 and IL-5 [19], the mechanisms by which exposure to PAHs affects nasal symptoms in adults currently remain unknown. Polycyclic aromatic hydrocarbons (PAHs) are mainly produced by incomplete combustion of fossil fuels or biomass, and emissions from industrial metal production and vehicle exhaust are also sources of PAHs [20]. PAHs have been proved to have a negative effect on the respiratory system, with one study showing that exposure to PAHs exacerbates chronic obstructive pulmonary disease [21], and a case-control study demonstrating that elevated levels of urinary PAH metabolites increase the risk of asthma in adults [22]. However, there are few reports of PAHs that mentioned an association between PAHs and rhinitis or nasal symptoms.