One-third of China's vast landmass is suffering from acid rain caused by its rapid industrial growth, while local leaders are failing to enforce environmental standards for fear of hurting business, said officials quoted Sunday by state media.

China's factories spewed out 25.5 million tons of sulphur dioxide — the chemical that causes acid rain — last year, up 27 percent from 2000, said Sheng Huaren, deputy chairman of the Standing Committee of parliament.

Sheng released a report Saturday that found pollution from factories and power plants was rising by 9 percent a year — an embarrassment for a government that promised this year to clean up China's air. The report said sulphur dioxide emissions were double safe levels.

"Increased sulphur dioxide emissions meant that one-third of China's territory was affected by acid rain, posing a major threat to soil and food safety," Sheng said, according to the Xinhua News Agency and newspapers.

Environmental protection has become a prominent issue in China following a string of industrial accidents that poisoned major rivers, forcing several cities to shut down their water systems.

Chinese cities are among the world's smoggiest following two decades of breakneck economic growth. The government says all of China's major rivers are dangerously polluted. Millions of people lack access to clean drinking water.

On Sunday, local officials said a tanker carrying 25 tons of caustic soda had fallen Friday into the Xuefeng River in China's northwest, poisoning a drinking water source for 100,000 people.

One person was killed in the accident, Xinhua said. Officials said the water quality had returned to normal by Sunday after the government dumped 10 tons of hydrochloric acid into the water to neutralize the caustic soda, also known as sodium hydroxide.

Premier Wen Jiabao publicly criticized officials in April after the government revealed it failed to meet most of its targets over the past five years in environmental areas ranging from containing pollution to stopping the loss of farmland. Wen said officials would be held personally responsible for future environmental disasters.

The government pledged this year to cut air pollution emissions by 10 percent by 2010.

Beijing plans to spend $175 billion on environmental protection over the next five years, up 60 percent from the previous five years, according to Mao Rupai, chairman of the parliament's environmental committee.

Lawmakers are considering raising fines for environmental violators in order to encourage companies to spend more on clean technology, Mao said at a news conference on Saturday.

Mao complained that local officials fail to enforce standards for fear of hurting businesses. He said some areas comply with as few as 30 percent of environmental regulations.

"It is true that in some areas, local governments focus more on economic development than on the environment," he said. "In the future, officials will be judged not just by their economic growth but by environmental protection as well."