**3.1 Case-control and biomarker studies on the effect of fine particles in the ambient air on atopic allergic and eosinophilic non-allergic phenotypes of the T2-endotype of bronchial asthma in adults**

The results of the "case-control" study [33] indicate the role of fine particulate matter in the ambient air in the development of bronchial asthma in adults (18– 65 years old), and also suggest the involvement of various underlying mechanisms in the formation of the clinical picture of eosinophilic non-allergic and allergic phenotypes of bronchial asthma: in non-allergic asthma —the reaction of the epithelium to the deposition of particles in the respiratory tract, and in allergic asthma—a reaction to the composition of the aerosol. An increased risk of the eosinophilic non-allergic phenotype of bronchial asthma and its more severe course were noted at higher average annual concentrations of the PM2.5 fraction averaged over 2014–2020. The concentration of bacterial endotoxin had a statistically significant effect on the odds of developing an BA allergic phenotype and was associated with a more severe course of the disease; the odds of an allergic phenotype also increased with an increase of carbon in the composition of the aerosol.

The medians of the average and maximal annual concentrations of PM2.5 fraction averaged over the period 2014–2020 in the areas of residence of patients with bronchial asthma exceeded the maximum allowable levels applied in the Russian Federation (25 and 160 μg/m3 ) by 1.2 and 1.1 times, respectively. For the PM10 fraction, the average annual concentration exceeded the maximum allowable level (40 μg/ m3 ) by 2.3 times, and the maximal annual concentration exceeded the maximum allowable level (300 μg/m3 ) by 1.2 times. In the comparison group, the levels of fine PM fractions did not exceed exposure limits, except for the maximum annual concentrations. The chemical composition of the fine PM fractions was represented mainly by carbon (from 36.9–100%) with minor metallic impurities. Contamination with bacterial lipopolysaccharides ranged from 0.0139 to 0.0694 EU/m3 . Microbiological examination of ambient air samples (in the areas of residence of 45 patients with

bronchial asthma and 45 persons from the comparison group) showed the growth of bacteria and fungi. Differences in pollution levels between both groups of patients and the comparison group were statistically significant, indicating a higher level of pollution by fine particles, as well as a higher content of carbon and bacterial endotoxin in the areas of residence of patients with bronchial asthma; no differences were found in the total number of microbes.

The study showed the important role of the PM2.5 fraction for patients with eosinophilic non-allergic phenotype of bronchial asthma (**Table 1**): the risk of this bronchial phenotype in adults statistically significantly increases with an increment of the average annual concentration averaged over the period 2014–2020 by 10 μg/m3 —the odds ratio adjusted by confounders (heredity for asthma, age, concentration of bacterial endotoxin


**Table 1.** *Effect of air pollution with particulate matter on the risk of non-allergic and allergic phenotypes of bronchial asthma (case–control study).*

#### *Fine Particles in the Ambient Air as a Risk Factor of Bronchial Asthma in Adults DOI: http://dx.doi.org/10.5772/intechopen.112419*

in the fraction with a particle size of less than 3.2 μg) was 4.76 (95% CI: 1.67, 24.40); odds ratios characterizing the effect of the PM10 fraction were below 2.0. No statistically significant relationship was found for the allergic phenotype of bronchial asthma and mass concentrations of fine particles in the ambient air. At the same time, the role of bacterial and chemical air pollution in allergic asthma formation was shown: the adjusted odds ratio for an increment of passive smoking duration by 1 hour was 3.24 (95% CI: 1.28, 14.79); for an increment of bacterial endotoxin found in the fraction with deposition in the tracheobronchial region of the respiratory system (3.2–18 μm) by 0.01 EU/ m3–1.32 (95% CI: 1.08, 2.00); for an increment of carbon in the chemical composition of the aerosol by 1%—1.45 (95% CI: 1.02, 2.52).

Eosinophilic non-allergic bronchial asthma was better controlled at lower average annual concentrations of the PM2.5 fraction (**Figure 1**), while in the case of allergic asthma, bacterial contamination of the aerosol mattered (**Figure 2**), which may

#### **Figure 1.**

*PM2.5 average annual concentration (monitoring data for residential zones averaged over the period 2014–2020 in the city of Kazan) for patients with non-allergic and allergic bronchial asthma, depending on the degree of bronchial asthma control. Model 1: PM2.5Avr (mg/m3 ) ~ b1i \* Degree of control of non-allergic asthma (1 – controlled, 2 – partially controlled, 3 – uncontrolled, Asthma Control Test) + b2 \* Age (years) + b3 \* Heredity for asthma (no/yes) + b4 \* BMI (kg/m<sup>2</sup> ); b1,1–2 = 0.012, p = 0.09, b1,1–3 = 0.013, p = 0.02. Model 2: PM2.5Avr (mg/ m3 ) ~ b1i \* Degree of control of allergic asthma (1 – controlled, 2 – partially controlled, 3 – uncontrolled) + b2 \* Age (number of years) + b3 \* Heredity for asthma (no/yes) + b4 \* BMI (kg/m<sup>2</sup> ) + b5 \* Passive smoking (hours/ week); p > 0.1 for coefficients b1(1–2) and b1(1–3).*

#### **Figure 2.**

*Bacterial endotoxin (BE) in the 3.2–18 μm size fraction of ambient particles at the residential zones of patients with non-allergic and allergic bronchial asthma, depending on the degree of disease control. Model 1: BE (EU/m3 ) ~ b1i \* degree of control of non-allergic asthma (1 – controlled, 2 – partially controlled, 3 – uncontrolled) + b2 \* age (years) + b3 \* heredity for asthma (no/yes) + b4 \* BMI (kg/m2 ); p > 0.1 for coefficients b1,1–2 and b1,1–3. Model 2: BE (EU/m3 ) ~ b1i \* degree of control of allergic asthma (1 – controlled, 2 – partially controlled, 3 – uncontrolled) + b2 \* age (years) + b3 \* heredity for asthma (no/yes) + b4 \* BMI (kg/m<sup>2</sup> ); b1(1–2) = 0.020, p = 0.04, b1(1–3) = 0.027, p = 0.01.*

indicate the importance of various physicochemical characteristics of the suspended solids aerosol in pathogenesis and influence on the clinical course of different phenotypes of the T2-endotype of bronchial asthma.

The data obtained indicate the presence of eosinophilic inflammation in patients of both groups (allergic and eosinophilic non-allergic bronchial asthma) [34]. For patients with eosinophilic non-allergic asthma, an increase in the production of epithelial cytokines IL-33 and IL-25 (alarmins), as well as IL-13 and DPP4, being depended on average annual concentrations of PM2.5 and PM10 averaged over the period 2014–2020. For patients with allergic asthma, similar dependencies were not found. Despite the presence of common signs of T2-type eosinophilic inflammation, the immune patterns of atopic allergic and eosinophilic non-allergic phenotypes of bronchial asthma differed significantly: with a comparable high level of the absolute number of eosinophils in the blood, patients with an allergic phenotype showed pronounced features of the T2-endotype, while with a non-allergic phenotype, there was a lower intensity of T2-type inflammation (IL-4) and an increased expression of genes of cytokines associated with a T17-type response (IL-6, TGF-beta1), being related to the mass of the deposited aerosol. These findings are important for the choice of therapy in different phenotypes of bronchial asthma.
