BEIJING - The rapid growth of the chemical industry has caused an increase in water pollution which is outstripping the government's ability to monitor it, a senior official said on Thursday.

The buildup of chemical plants along rivers, particularly the Yangtze River, threatens the quality of drinking water in cities already short of this essential resource, said Hu Siyi, vice-minister of water resources.

"Government authorities cannot respond quickly to every accident, due to the limited number of monitoring sites. In some areas, water is only monitored once a month," Hu said at a news conference organized by the State Council Information Office.

In 2011, a total of 542 environmental accidents were reported nationwide. Of these, nearly 60 percent were triggered by accidents in either production or transportation, according to the Ministry of Environmental Protection.

Earlier this month, phenol leaked by a cargo ship from the Republic of Korea posed a potential threat to the water supply of Zhenjiang, a city of 3 million people in East China's Jiangsu province.

Phenol, also known as carbolic acid, is an organic compound that can irritate eyes and skin. Soluble in water, it can damage the liver and kidneys if absorbed in large amounts.

Officials said pollution and water shortages are major bottlenecks to China's sustainable development.

In 2010, the total discharge of wastewater reached 75 billion tons; nearly 40 percent of river water failed to reach quality standards, according to the Ministry of Water Resources.

With a population of 1.3 billion people, China now consumes more than 600 billion cubic meters of water a year, or about three-quarters of its exploitable water resources, Hu said.

Per capita water use in China is 2,100 cubic meters, or about 28 percent of the world average, according to the Ministry.

About two-thirds of Chinese cities are short of water, while nearly 300 million rural residents lack access to safe drinking water, Hu said.