This poster presents a newly linked UK oncology–environmental dataset combining electronic health records from The Christie with residential air-pollution data to examine how environmental exposure relates to comorbidity burden at cancer diagnosis. In 55,380 patients, higher exposure to mixed pollutants (NO₂, PM₂.₅, O₃, SO₂) was associated with greater odds of severe comorbidity, demonstrating a scalable, policy-relevant approach to studying environmental determinants of cancer outcomes.