Cancer-related deaths have more than doubled in some areas along the basins of the heavily polluted Huai River in the past three decades, according to the first official study by mainland medical experts confirming a link between rising cancer rates and heavy pollution.
In Shenqiu county, Henan, the mortality rate from liver cancer increased more than fivefold between 1973 and 2006, according to the joint study by the Chinese Centre for Disease Control and Prevention, the Chinese Academy of Sciences, and the Chinese Academy of Medical Sciences.
The study monitored 14 counties in four provinces - Anhui, Shandong, Jiangsu and Henan - along the Huai and its tributaries since 1973, when the cancer mortality rate in most of those places was less than the national average.
But three decades of unbridled economic growth have not only turned the Huai into one of the most polluted rivers in the country, they have also created "cancer villages" with cancer death rates above the national average, according to data compiled by the study.
"In most of the monitored counties, the death rate from cancer has increased by more than 20 per cent - the average national growth over the period. Several counties recorded an alarming surge of more than 100 per cent," the study says.
Malignant tumours of the stomach, liver and oesophagus were the most common types of deadly cancer reported, according to the findings.
Between 1973 and 2006, the death rate from liver cancer in Mengcheng county, Anhui, increased 3.7 times. Deaths from the same type of malignancy rose 2.7 times in Wenshang county, Shandong, and 2.4 times in Lingbi county, Anhui. Death from stomach cancer multiplied 2.6 times in Shenqiu county.
Mainland authorities have been reluctant to acknowledge the impact of pollution on health, despite mounting public complaints. In February, the Ministry of Environmental Protection for the first time admitted the existence of "cancer villages" due to toxic chemical pollution.
The findings from the recently released study, commissioned by the State Council, offer the first comprehensive statistical proof of a link between cancer and pollution on the mainland, as the collection of data about deaths at the local level has been extremely difficult without local governments' permission.
"The data confirms a geographical overlap in the increased cancer death rate and water pollution in the Huai river basin, and a temporal lag - a high occurrence of cancer following a surge in pollution - for about a decade," said Professor Yang Gonghuan, a former deputy director of the Chinese Centre for Disease Control and Prevention.
Medical experts ruled out other known risk factors for cancer, such as rates of smoking and eating and the prevalence of hepatitis B, which were about on par with the national average.
Pollution data compiled by the study shows that water quality in the Huai river basin - including in its tributaries and lakes - deteriorated significantly between 1982 and 2005, particularly in the later years. In some years the water quality in more than 60 per cent of the 1,000-kilometre-long river was rated "severely polluted".
The startling figures were attributed to breakneck industrial growth in the region. For instance, Shenqiu county has been one of the country's major paper-making bases, where over the past decade, waterways once renowned for their beauty in "a fertile land of fish and rice" have turned black, Yang said.
The study fails to note, however, that the period with the worst pollution record - the years of 1996, 1997, 2001, 2002, 2004 and 2005 - corresponded with a massive decade-long environmental campaign to resurrect the Huai that was mostly a failure.
In 1994, the central government allocated 60 billion yuan (HK$75 billion) to close 4,000 polluting factories and build 250 wastewater-treatment facilities in the basin's four provinces, vowing that the Huai would be clean by the end of 2000.
But a decade later, the then State Environmental Protection Agency admitted that pollution in the basin was as serious as ever, and the clean-up deadline was pushed back six years to 2010.
In the absence of scientific evidence, local governments turned a deaf ear to villagers' complaints about rising cancer rates and demands for clean water. Only last month, The Beijing News quoted a health official in Yingshang county, Anhui, who refused to admit that pollution could cause cancer.
"It's like eating from the same plate of food - some people might get ill while others turn out to be all right. Nobody can tell exactly why," the official was quoted as saying.
Yang said local authorities might also be worried that linking major health problems to pollution would deter investors and embolden victims to seek compensation.
Yang said the purpose of the study was not to hold anyone accountable: "Rather, we want to sound an alarm that the country's economic development should no longer come at the expense of public health."
Even though the Huai has shown signs of recovery since 2005, the study warned that the high occurrence of cancer in areas around the river was likely to continue for at least 10 years as symptoms of cancer often took years to emerge following exposure to pollution.