OVER the last month, China has reported two cases of large-scale lead poisoning among children living close to heavily polluting factories. Here are some questions and answers about pollution problems in China, the world's most populous nation: How bad is pollution in China? For decades, there were few fetters on the waste that factories, plants and power stations in China pumped into the air and water. Parts of the countryside have been blighted by pollution, which has become widespread following the rapid growth that has made China the world's third-largest economy. Over the past decade, Beijing has strengthened efforts to limit pollution, punishing and shutting down some offenders. But growth is still a priority, especially for local governments, and environmental protection officials have relatively little sway. In 2008, 45 percent of key river and waterway sections monitored by the Ministry of Environmental Protection were classified as polluted to such an extent they were unsuitable for human contact and in some cases even for irrigation. Of 113 key cities under air quality monitoring, 58 percent reported an average of good or excellent air quality in 2008, an improvement of 13 percentage points compared to previous years. But some experts have said those numbers reflect official manipulation and do not reflect the real level of air pollution. The World Bank has previously estimated that of the world's 30 most polluted cities, 20 are in China. What are the consequences? The most immediate consequence is health problems. Areas badly hit by pollution often report higher-than-normal levels of cancers, respiratory diseases, diarrhoea and other illnesses. Two years ago, the World Bank estimated that 460,000 Chinese died prematurely every year from breathing polluted air and drinking or washing in dirty water. Pollution also restricts the country's scare supplies of water suitable for drinking, and it can dent crop yields. All of this adds up to economic costs that at least partly offset gains from fast growth. The World Bank estimated in 2007 that the health and other consequences of outdoor air and water pollution cost China's economy around $100 billion a year, equal to about 5.8 percent of the nation's GDP. What does the public think? Many Chinese long saw pollution as an unavoidable cost of economic growth. But in recent years, growing public awareness, accompanied by greater official and media attention to the problem, has stoked rising complaints about toxic air and water. Officials say protests over the problem have been growing, especially in the countryside, where farmers' crops and water supplies can be spoiled by filthy waste from industry. Pan Yue, the deputy chief of the national environment watchdog, has said that in 2005 alone there was a 29 percent rise in the number of “mass incidents” – an official term for protests – over pollution and other environmental problems. In cities, residents have also become more vocal about pollution worries, sometimes launching protests and petitions against proposed industrial developments. In 2007, residents of Xiamen, a coastal city in Fujian province, held large demonstrations against a proposed chemical plan. The Xiamen city government later dropped the project, and there have been similar citizen mobilizations in other cities. What is the government doing? The government says it is committed to greener growth. The current five-year development plan, which runs through 2010, has set a goal of cutting sulphur dioxide emissions and a key water pollution indicator, COD, by 10 percent compared to 2005 levels. China's environmental protection watchdog was raised to ministry-level last year, giving it more power. But officials are still under government and public pressure to keep up economic growth and job creation, and so local governments can turn a blind eye to polluters. What could happen next? Contention over environmental issues is likely to flare from time to time. The government is trying to clean up growth, but public expectations are also rising. That could stoke greater public opposition to industrial plants, nuclear power stations and other proposed developments. But those rising public expectations must compete with a belief that economic growth and jobs remain paramount – and the government is most unlikely to sacrifice that priority.