* RANIPET, INDIA -- potentially affected: 3,500,000

-- Tannery waste from the leather tanning industry in Ranipet, a medium-sized town about 100 miles (160 kilometres) upstream from Chennai, poses a pollution risk to surrounding populations. Uncovered waste made up of chemicals such as sodium chromate could easily leach into ground water supplies, the report says.

-- Clean-up: A factory responsible for about 1.5 million tons of untreated sludge was shut down in 1996, but the report says no real progress has been made to clean up the site.

* LINFEN, CHINA -- potentially affected: 3,000,000

-- Carbon monoxide, sulphur dioxide, arsenic and lead are among the cocktail of air pollutants circulating in Linfen, Shanxi Province, which has the country's worst air quality. Residents in the city, located in the heart of China's enormous coal industry, have reported high rates of bronchitis, pneumonia and lung cancer.

-- Clean-up: Linfen plans to close 160 of 196 iron foundries and 57 of 153 coke and coal processing plants by the end of 2007, and replace small polluting plants with larger cleaner facilities.

* LANZHOU, CHINA -- potentially affected: 3,OOO,000

-- Heavy industrial emissions from petrochemical manufacturing and oil refineries, as well as rising automobile emissions, have dragged down air quality in highly industrialized Lanzhou, the capital of Gansu province. Respiratory ailments are common in the town, which is located in an arid valley with little wind circulation.

-- Clean-up: Various efforts are under way, including a shift from polluting fuels to natural gas, and pollution has been substantially reduced since 1998.

* SUKINDA, INDIA -- potentially affected: 2,600,000

-- Toxic chromium contaminates waterways, air and soil in southeast Orissa state's Sukinda Valley, which contains 97 percent of India's chromite ore deposits, and one of the largest open-cast chromite ore mines in the world. Pollution-induced diseases such as gastrointestinal bleeding, tuberculosis and asthma are commonly reported ailments.

-- Clean-up: Miners have installed treatment plants to stop mine waste being spread over large areas, however, state audits say they so far fail to meet agency regulations.