Studies are beginning to show that pollution from shipping may have been underestimated up until now. It is estimated that pollution from the world's 90,000 cargo ships leads to 60,000 deaths a year in the US alone and costs up to $330bn per year in health costs from lung and heart diseases. It is estimated that 15 of the world's largest container ships emit as much cancer and asthma producing pollution as all the world's cars.