Figure 4.

Representative light microscopy sections of lung tissues of BALB/c mice 72 h after repeated PM $\left({\text{PM}}_{\text{2.5}}^{+},{\text{PM}}_{\text{2.5}}^{-},{\text{PM}}_{\text{10}}^{+},{\text{\hspace{0.17em}and PM}}_{\text{10}}^{-}\right)$ stimulation. Normal histopathology can be observed in control groups (A,B), the lung sections of heat-treated PM₁₀ $\left({\text{PM}}_{\text{10}}^{-}\right)$ group (C), the lung sections of non-heat-treated PM₁₀ $\left({\text{PM}}_{\text{10}}^{+}\right)$ group (D), the lung sections of heat-treated PM_2.5 $\left({\text{PM}}_{\text{2.5}}^{-}\right)$ group (E), and the lung sections of non-heat-treated PM_2.5 $\left({\text{PM}}_{\text{2.5}}^{+}\right)$ group (F). The experiment was performed using six BALB/c mice per group.