Ingested Nitrates and Health Consequences. Jean Bokelmann M.D.

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1 Ingested Nitrates and Health Consequences Jean Bokelmann M.D.

2 Sources of Ingested Nitrates Drinking water Vegetables Especially synthetically fertilized vegetables Much less with organic vegetables

3 EPA Drinking Water Limits Based primarily on a study of 139 cases in Minnesota in 1950 (7) and a survey in 1951 of state health officials regarding methemoglobinemia cases. The EPA set the drinking water nitrate limit at 10mg/liter to protect infants from developing methemogloginemia (Blue Baby Syndrome).

4 Consequences of Ingested Nitrates Methemoglobinemia Miscarriages? Neural tube defects? Various Cancers?

5 Mechanism for Methemoglobinemia Nitrates in the stomach become Nitrites Nitrites interact with the iron in hemoglobin to make the hemoglobin unreceptive to oxygen. Thus the red blood cells are unable to pick up oxygen in the lungs and carry it to the body s tissues.

6 Methemoglobinemia Infants less than one year of age are particularly susceptible to this problem, which also seems to be compounded by exposure to coliform bacteria that might also be present in the drinking water. Potential fatality from methemoglobinemia is about 7%.

7 Methemoglobinemia Methemoglobin levels have been shown to be elevated in infants consuming water within the EPA range, but not high enough to cause methemoglobinemia. What might be the effect on brain and organ development with elevated subclinical methemoglobin levels?

8 Pregnancy and Nitrates Some reports have suggested an association between exposure to nitrates in drinking water and spontaneous abortions, intrauterine growth restriction, and various birth defects. However, the current literature does not provide sufficient evidence of a causal relationship between exposure to nitrates in drinking water and adverse reproductive effects Neural tube defects found to be more common with nitrate ingestion in presence of nitrosation precursors (red meat, certain drugs)

9 Nitrosation: Mechanism for Cancer Nitrates become nitrates and combine with other ingested organic substances in stomach becoming N-Nitrosocompounds. N-Nitroso-compounds have been shown to be strongly carcinogenic in animals. The question is whether long-term daily exposure to lower levels of nitrates in water can cause cancer

10 Nitrosation Vitamin C reduces nitrosation Vitamin E reduces nitrosation Turmeric reduces nitrosation Smoking increased nitrosation Red meat increases nitrosation Bowel inflammation increases nitrosation

11 Nitrates and Cancer Iowa Women s Health Study Compared women drinking water with nitrate concentration of <0.36 mg/liter >0.36 &< 1 mg/liter >1 &< 2.6 mg/liter >2.6mg/liter

12 Nitrates and Cancer Compared to women in the <0.36 group, women in the > 2.6mg/l were nearly 3 times as likely to develop bladder cancer, and nearly twice as likely to develop ovarian cancer On the flip side, they were about half as likely to get uterine and rectal cancer.

13 Nitrates and Kidney Cancer Another study showed no association between nitrate levels and renal cell cancer UNLESS the red meat consumption was factored in: Those who ate more red meat and ingested more nitrates (nearly two-fold increased risk for kidney cancer) Those who had low Vitamin C intake and ingested more nitrates (nearly two-fold increased risk for kidney cancer)

14 Colon Cancer Increased nitrate ingestion below the EPA limit in conjunction with nitrosation precursors (red meat, certain drugs) has been shown to increase colon cancer risk.

15 Summary Known risk: Methemoglobinemia at levels >10mg/liter Probable risks at lower levels: Bladder cancer, ovarian cancer Possible risks at lower levels: Impaired brain and organ development in infants Miscarriages, congenital malformations, growth restriction Kidney cancer, colon cancer, neural tube defects (in conjunction with other dietary factors (nitrosation precursors, etc):

Nitrate in drinking water and cancer risk

Nitrate in drinking water and cancer risk Mary H. Ward, M.S., Ph.D. Occupational and Environmental Epidemiology Branch Division of Cancer Epidemiology & Genetics NCI, NIH Challenges to Providing Safe Drinking