By Aditya Kalra

NEW DELHI (Reuters) - India has launched a new air quality index to help citizens understand complex pollution data and its implications for their health, the environment minister said on Friday.

A World Health Organization (WHO) study of 1,600 cities released in May found India's capital New Delhi had the world's dirtiest air with an annual average of 153 micrograms of small particulates, known as PM2.5, per cubic meter.

Thirteen of the dirtiest 20 cities worldwide were in India, the WHO said. India rejected the report.

The new index, launched as part of Prime Minister Narendra Modi's 'Clean India Mission', will provide one consolidated number after tracking eight pollutants and will use color coding to describe associated health impacts.

"In our cities air pollution is increasing ... we need to stop it," Environment Minister Prakash Javadekar said.

"This (index) will provide the common citizen one color, one number and one description so that he can understand what is the level of air pollution."

Currently, India's air quality status is reported through "voluminous data", the government said. This makes it difficult for people to understand particle names such as PM2.5 or PM10.

"People don't know what these pollutants are and what happens when they reach a certain level. This index will help people understand air quality better," said Anumita Roychowdhury, head of air pollution team at the Center for Science and Environment.

The environment minister said the government would also start action-oriented programs in collaboration with the states to improve air quality, but he gave no details.

Roychowdhury said India needed to do more and should have emergency measures in place when pollution levels are high. In China, for example, primary schools are shut when pollution levels are at "red alert" levels, she said.

Air pollution killed about seven million people in 2012, making it the world's single biggest environmental health risk, the WHO, a United Nations agency, said in March.


(Editing by Gareth Jones)