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New findings published in the American Journal of Epidemology show that long-term exposure to nitrates in drinking water does not raise the likelihood of developing pancreatic cancer.
However, the risk may be increased with the consumption of dietary nitrite from animal products.
"N-Nitroso compounds, known animal carcinogens, are formed (internally) from drinking water and dietary sources of nitrate and nitrite," Dr. Mary H. Ward, of the National Cancer Institute, Bethesda, Maryland, and colleagues explain in the April 1st issue of the Journal.
This prompted the researchers to look at whether increased intake of nitrate and nitrite from water and diet was associated with pancreatic cancer risk.
Ward's group linked detailed water source histories with nitrate measurements from Iowa community water supplies. They then compared 189 people from the area who had pancreatic cancer with 1244 "control" subjects without cancer.
The risk of pancreatic cancer did not rise with increasing nitrate consumption from drinking water. In fact, increased intake was associated with a decreased risk in women, but not in men.
Conversely, higher levels of dietary nitrite from animal sources was linked with an elevated risk of pancreatic cancer.
Overall, the researchers conclude: "The average nitrate level in community water supplies over an approximately 25-year period was not associated with pancreatic cancer risk in this study population."
However, the findings do "suggest a role for nitrate derived from animal sources as a pancreatic risk factor."