China produces more than half of the world's cement. According to the National Bureau of Statistics, the country's cement output from January to May reached more than 866 million metric tons, up by 8.9 percent from the same period last year.

The cement industry is among the six most heavily polluting industries that were required by the Environmental Protection Ministry to meet international emission limits from March this year. Dust emissions from the cement industry accounted for about 30 percent of total industrial emissions in 2009.

"We found that this industry has shocking problems with dust and waste gas emissions. The cement industry's violations have deeply harmed the living environment and health of those who live near the factories," said Fang Yingjun from environmental NGO Green Jiangnan.

Subcompanies from four large cement companies that are members of the Cement Sustainability Initiative, which is described on its website as being "a global effort by 24 cement producers that believe there is a strong business case for the pursuit of sustainable development", appear in the report.

The environmental NGOs said they have contacted the 17 listed companies to inform them of the aforementioned pollution problems, but most of the offenders took an evasive stance.

Questions:

1. According to the story, how many cement companies were found to have violated environmental protection laws?

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