Chinese manufacturers have seen their costs for environmental protection rise, in many ways, since the government raised the standards over the past year.

Companies that were identified as violating environmental laws were barred from the Canton Fair, or the China Import and Export Fair, during a penalty period, said fair spokesman Xu Bing.

One such company was Jilin Fudun Timber Co., Ltd., a timber company, which was placed on a blacklist by environmental regulators last year.

The Canton Fair is the most important channel for Chinese exporters to expand overseas, so a ban means big losses.

China has conducted special campaigns against polluting companies since last year. And violators have lost more than just export opportunities: blacklisted firms find it difficult to get loans. The State Environmental Protection Administration, now the Ministry of Environmental Protection, along with the central bank and the Banking Regulatory Commission, jointly issued a "green loan" policy in July that banned loans to blacklisted companies.

In addition, the government stated that the worst violators would face shutdowns of up to three years.

A senior official with the National Development and Reform Commission, the country's top economic planner, said that "all these measures made it clear that companies must establish pollution-treatment facilities. Only paying fines for degrading the environment is definitely not enough."

As supervision strengthened, some companies had to shut down.

Fuan Textile Mill, a Hong Kong-listed company, shut down last March as it was found to be discharging wastewater directly into underground pipes. The company was fined 11.55 million yuan (1.65 million U.S. dollars).

During the spring session of this year's Canton Fair, which concluded on Wednesday, Minister of Commerce Chen Deming said China would maintain strict controls on polluting and energy-wasting companies, despite a tougher export situation.