Inclusion Criteria:  All:  Signing the informed consent form Adults over 18 years of age  Indoor air pollutant groups:  Exposed to indoor air pollutants Neurological symptoms  Neurological symptoms groups:  Neurological symptoms possibly due to adverse external exposure  Healthy controls:  Reported healthy person  Exclusion Criteria:  All:  Pregnancy or breast-feeding Corticosteroid treatment within 4 weeks of imaging Patients with claustrophobia, or a history of moderate to severe anxiety disorder or panic attacks (which could potentially lead to preterm termination of the imaging) Contraindication to PET scan and MRI investigations Exposure to experimental radiation in the past 12 months such that radiodosimetry limits would be exceeded by participating in this study. Intolerance to previous PET scans; i.e. previous hypersensitivity reactions to any PET ligand or imaging agent or failure to participate in and comply with previous PET scans.  Neurological symptoms groups and healthy controls:  Exposure to indoor air pollutants