Emissions from new coal-fired power stations planned in Guangdong could cause as many as 16,000 deaths in the next 40 years, research by an air-pollution specialist indicates.
The "shocking" findings have brought a call for the province to wind back plans for the 22 additional stations and return to a 2009 policy of no new coal-fired plants in the Pearl River Delta.
The estimates were made by Dr Andrew Gray, an American private air quality consultant commissioned by Greenpeace to study the health impact of the new plants' emissions of fine particles measuring less than 2.5 micrometres. The extra deaths would add to an already heavy health toll - put at 3,600 deaths and 4,000 cases of child asthma in 2011 alone - from the 96 coal-fired plants already in operation in the province and Hong Kong.
Greenpeace climate and energy campaigner Zhou Rong said: "The cumulative impact of these new plants on human health is simply shocking.
"The Pearl River Delta [PRD] region should strictly enforce the policy of no more new coal-fired power plants in the PRD published in 2009. Guangdong has ignored its earlier pledge to ban new coal-fired power plants in order to feed its hunger for energy."
Some online comments on the mainland described Greenpeace's proposal to scale back the plants as partial and unrealistic.
"So shall Guangdong build more large-scale nuke plants or shall it transport more electricity from the country's southwest?" Yu Yang , a student at Stanford University who researches on environment policy, wrote on his microblog.
For his study, Gray used the CALPUFF computer model, endorsed by the United States Environmental Protection Agency for trans-boundary air pollution, as well as emission data from the Ministry of Environmental Protection and power companies.
The health impact estimates were also based on a model developed by the World Health Organisation on mortality risks from human exposure to fine particles.
Half of the additional power stations, with a total capacity of 26,000 megawatts, are under construction and the rest are in the planning stage.
Of the predicted 16,000 premature deaths in the next four decades, two-thirds would be related to strokes, the report said. The rest would be from lung cancer and heart disease.
It said the pollution would also lead to 15,000 new cases of child asthma and 19,000 of chronic bronchitis.
Most new deaths and child asthma cases would be in the delta region, with 1,700 and 1,300 respectively in Hong Kong.
Zhou said Guangdong, as the most economically powerful province, could have made a bold decision to cap coal use, and harness more renewable energy.
The projection was released weeks after reports that Shenzhen had suspended a planned coal-fired power plant after public opposition, she said.
The Environmental Protection Department said Hong Kong had banned new coal-fired plants since 1997 and imposed emission caps on power plants. A spokesman said the city had also agreed with Guangdong on goals to reduce emissions for 2015 and 2020.
Simon Ng Ka-wing , an energy researcher with think tank Civic Exchange, said the method adopted by Gray was in common use but called for him to disclose more of the assumptions behind the study.
Ng also said the choice of fuel mix was a complicated balance to strike. "Ideally, coal use should be capped given its footprint on air quality … but whether it could be enforced is a challenge," he said.
Instead of coal, more expensive gas could be harnessed, but its supplies were more limited. Another option was nuclear, but this carried safety concerns.
Greenpeace has been campaigning worldwide to eliminate nuclear power, citing environmental and safety concerns.
Yu Yang added that hydroelectricity from China's southwest could be more polluting or damaging to local ecology. "When targeting a polluting industry, an environmental organisation should also consider the alternative solution and its corresponding environmental price,'' he wrote.