A study has found that most of the human population is breathing unsafe air with the poorest communities taking the hardest hits. As more people move into cities, they are exposing themselves to unsafe air, particularly in developing countries. But in more rural areas, indoor pollution is dangerously high mostly caused by the burning of fossil fuels. However, one-third of the world’s population suffers from pollution indoors and outdoors. By using satellite data and improved monitoring technology, the Health Effect Institute can receive a better estimate of people exposed to air pollution. Some pollutes levels are much higher than what the World Health Organization has deemed safe.

Now, air pollution is the fourth highest cause of death globally behind high blood pressure, die and smoking. Last year experts concluded that exposure contributed to more than six million deaths and played a key role in increasing the risks of stroke, heart attack, lung cancer, and chronic lung disease. While developed countries are cleaning up their pollution, developing countries are falling further behind. An increase use of road traffic has increased the amount of dangerous emissions into the air. Diesel fuel is leading in emission pollution, but even more in predominantly poor countries that use petrol-driven engines. There has been positive moves on the matter. China, one of the most effected country, is pushing harder each year to clean their air by implementing stronger controls and cutting the use of coal. The number of people exposed to indoor pollutes has gone from an estimated 3.6 billion in 1990 to 2.4 billion today, even though the world’s population continues to grow.