Lung cancer. Coloured chest X-ray of a lung cancer (red) in a 59-year-old man's right lung. The lungs are the two black spaces. The chest bones and the heart (lower right) are yellow. Lung cancers are most often caused by cigarette smoking, exposure to asbestos, and pollution. Treatment includes radiotherapy, chemotherapy, and the surgical removal of all or part of the affected lung. SCOTT CAMAZINE / SCIENCE PHOTO LIBRARY.