India's air pollution is the worst in the world and the national capital is the globe's most polluted city, said a new study. According to the study by Yale University, India has the worst air pollution in the world in terms of the proportion of population exposed to average air pollution levels exceeding the World Health Organization thresholds, local media reported Wednesday. And, the Indian capital, with 810 million registered vehicles, has the highest particulate matter pollution of 2.5 levels in the world, the Hindustan Times newspaper quoted the study that is based on a comparative analysis of 178 countries on nine environmental parameters as saying. It also said that India has overall slipped 32 ranks in the global Environment Performance Index 2014, and that the pollution has been affecting the health of ordinary Indians. "A bottom performer on nearly every policy issue is included in the Environment Performance Index (EPI) 2014 with the exception of forests, fisheries and water resources and India's performance lags most notably in the protection of human health from environmental harm," said a statement issued by Yale University.