According to the State of Global Air 2018 report by Health Effects Institute (HEI), released in April 2018, more than 95% of the world’s population (7 billion people) live in areas of unhealthy air.
The report states that air pollution is the leading environmental cause of death worldwide. “Long-term exposure to outdoor and indoor air pollution contributed to 6.1 million premature deaths from stroke, heart attack, lung cancer, and chronic lung disease.” This means that air pollution is the 4th highest cause of death among all health risks, exceeded only by high blood pressure, diet, and smoking. It is a major global public health challenge according to Dan Greenbaum, President of HEI.
Read more about the report at https://www.stateofglobalair.org/whats-new/press-release.