US businesses in China are increasingly concerned about Internet censorship, data security and air pollution in the world's second-largest economy, according to a survey. A total of 56 percent of respondents to the survey by the American Chamber of Commerce in the People's Republic of China (AmCham China) said that Internet censorship was an impediment to their business. The results were included in the organisation’s China Business Climate Survey Report, released Wednesday. Two-thirds of respondents said that "the blocking of search engines negatively or somewhat negatively impacts their ability to conduct business". A total of 47 percent said their greatest concern in using cloud computing in China was data security, up slightly from 46 percent the year before. "As well as finding it difficult to access credible data, companies are also concerned about protecting their own data," the report said. Chinese authorities maintain a huge surveillance network, including online, where the so-called Great Firewall of China blocks access to sites deemed sensitive and a vast censorship machine deletes content considered objectionable. In a report released in February last year, security firm Mandiant said China was devoting thousands of people to a military-linked unit that has pilfered intellectual property and government secrets. China has countered that leaks by former American intelligence contractor Edward Snowden -- revealing mass US electronic surveillance programmes -- are evidence that the United States is guilty of double standards when it comes to online espionage. A total of 365 AmCham members responded to the survey, the 16th by the organisation. China's air quality was having a negative impact on executive recruitment and retention, 48 percent said, a jump from 34 percent in last year's poll. "As labour costs rise and companies continue to face difficulty recruiting managers, air quality concerns may be an increasingly important factor," the report said. China's pollution problems -- blamed on decades of no-holds-barred economic development -- have led to public anger and official concern. In January 2013 an "airpocalypse" shrouded the capital Beijing in thick smog, with particulate matter shooting 40 times past UN standards. Premier Li Keqiang vowed to "declare war" on pollution at the country's annual legislative gathering this month, and announced new measures to add to a raft of others issued over the past year.