In 1984 by the Environmental Protection Agency of the Unite States made a momentous declaration that nitrite in drinking water is not carcinogenic. The current WHO Guideline for drinking-water-quality recommends thus a 1.000 mg/L.nitrite-nitrogen in drinking water. The Guideline simply states that "the weight of evidence is strongly against there being an association between nitrite and nitrate exposure in humans and the risk of cancer", with no discussion. The weight of evidence consists of studies in rats and mice, but the evidence is now called to question by the latest studies at the Center for Environment and Health Engineering at the Henan University, China.
There have been alarming cancer epidemics in China since the start of rapid industrial development in 1980. The statistics linking cancer to nitrite in drinking water alarmed the Government. The Ministry of Health's Guideline for the PMCL of nitrite in "purified drinking water" is 0.002 mg/L nitrite-nitrogen. The Chinese National Bureau of Environmental Protection recommended that the MPCL for water recharged underground (via wells) should be 0.010 mg/L nitrite-nitrogen. Since surface waters everywhere have higher values, Chinese programs of groundwater-recharge are all but ceased, leading to severe watger-shortages everywhere.
The Life Council of the United States recommended in 1981 "epidemiological studies to correlate the incidence of cancer with actual exposure to nitrate, nitrite, and nitroso compounds". Now those studies have been carried out in China and the results indicate that reduced exposure to nitrate has indeed led to a directly proportional reduction in the cancer risk.
. China won battles in their War Against Cancer, where they switched the source of drinking water. The program at the high cancer-incidence area of Linzhou County, Henan. has saved about 100,000 lives! Now the Government has budgeted 1.5 billion yuan to switch the source of drinking water for the 3.84 million people of Zhoukou County, Henan.
There is little evidence that nitrite has induced genetic changes that cause cancer. The statistical correlation suggests the possibility that nitrite in drinking water is the nutrient needed to sustain the growth of cancer. To use milk as an analogy: no amount of milk in a diet would cause a woman pregnant, but babies will die of hunger if milk is not fed to sustain their growth.
To recognize the link between cancer and nitrite pollution points to the need of a green revolution. The source of drinking water is to be switched, but the polluted surface water will have to be denitritized for groundwater-recharge to achieve hydrologic balance. New methodology for sewage-treatment works is needed to minimize nitrite pollution. The use of industrially produced CO2 to de-nitritize polluted lakes and streams will reduce greenhouse emission to alleviate global warming.