Equally important in the context of air pollution, the cerebellum has high dopamine levels with midbrain dopaminergic afferents having a wide distribution of the dopaminergic receptor subtypes (DRD1-DRD5) [137] and is compromised in PD patients, as evidenced by a reduction in cerebellum WM integrity, i.e., assessed by fractional anisotropy, mean diffusivity, radial diffusivity, and axial diffusivity measures [138]. The gene discussed is DRD1; the disease is Parkinson disease.