A study has found that pollution is the world's biggest killer. It caused one in six deaths in 2015. This was 16 percent of all global deaths. Most of these deaths were from diseases like heart disease, lung cancer and stroke. The study is in the medical journal 'The Lancet'. Researchers said about 92 percent of pollution-related deaths were in poorer countries, especially countries with a lot of economic development, like India and China. Bangladesh and Somalia were the worst affected countries. Brunei and Sweden had the lowest numbers of pollution-related deaths. A researcher said: "Pollution, poverty, poor health, and social injustice are deeply linked." He added: "Pollution threatens fundamental human rights, such as the right to life." He said air pollution was the biggest killer. It led to 6.5 million premature deaths. The second biggest killer was water pollution. The next largest killer was pollution in the workplace. A scientist said: "Air pollution is reaching crisis point." She said the people who pollution hit the hardest are those with breathing and lung problems, children and the elderly.