A layer of smog sits over Wazirabad in New Delhi, India. Credit: Sanchit Khanna/Hindustan Times via Getty In July 2025, Lily Nguyen was arranging a vase of flowers at her home in Los Angeles, California, when she felt a “radiating heat and numbness” sweep down the right side of her body. Moments later, she was wracked by violent muscle convulsions. She went to the emergency department, but the physician dismissed her concerns. When the convulsions happened again the next day, Nguyen filmed herself. She showed the footage to a different physician, who sent her for a magnetic resonance imaging (MRI) scan. The scan revealed three brain tumours. Five days later, Nguyen underwent surgery to remove them. Biopsies uncovered an unexpected and devastating cause: Nguyen had stage 4 lung cancer. “I was in shock,” she says. Nature Outlook: Lung cancer Nguyen is just 41 years old, has never smoked and has no family history of lung cancer.…