Ratings for each category were averaged into an overall grading scale from zero to 10, where zero was the best and 10 the worst. India emerged the worst overall with a score of 8.31. It was followed by China with 8.03, Vietnam with 7.63, the Philippines with 7.55, Indonesia with 7.33 and Hong Kong with 7.28. India's major cities have among the highest levels of sulfur dioxide and nitrogen oxide, PERC said. A fifth of its urban households have no access to safe drinking water, just 23 percent have toilets and only 48 percent have sanitation coverage.
China has one of Asia's most polluted environments.
Singapore emerged top with a grade of 3.38, beating Japan with 3.63 and Malaysia with 4.50 to become the only three countries with a score better than the average of five. Thailand had an overall grade of 7.02, South Korea 6.25 and Taiwan 5.84. Hong Kong came next with 8.47, China with 8.38 and India with 8.13. For water quality, Vietnam scored the worst with a 9.0, worsening from 8.30 last year. It was followed by India and China with scores of 8.63 and 8.25, respectively.