Nitrogen-nitrate exposure from drinking water and colorectal cancer risk for rural women in Wisconsin, USA

Abstract

One unintentional result of widespread adoption of nitrogen application to croplands over the past 50 years has been nitrate contamination of drinking water with few studies evaluating the risk of colorectal cancer. In our population-based case-control study of 475 women age 20-74 years with colorectal cancer and 1447 community controls living in rural Wisconsin, drinking water nitrate exposure were interpolated to subjects residences based on measurements which had been taken as part of a separate water quality survey in 1994. Individual level risk factor data was gathered in 1990-1992 and 1999-2001. Logistic regression models estimated the risk of colorectal cancer for the study period, separately and pooled. In the pooled analyses, an overall colorectal cancer risk was not observed for exposure to nitrate-nitrogen in the highest category ($10 ppm) compared to the lowest category (,0.5 ppm). However, a 2.9 fold increase risk was observed for proximal colon cancer cases in the highest compared to the lowest category.Statistically significant increased distal colon or rectal cancer risk was not observed. These results suggest that if an association exists with nitrate-nitrogen exposure from residential drinking water consumption, it may be limited to proximal colon cancer.

Nitrates in Drinking Water and the Risk of Death from Rectal Cancer: Does Hardness in Drinking Water Matter?

“…However, our observations are in contrast to results reported in previous epidemiologic studies (Geleperin et al, 1976;Jensen, 1982;Morales Suarez-Varela et al, 1995;Weyer et al, 2001;De Roos et al, 2003;McElroy et al, 2008). The reason for these inconsistencies is not known.…”

“…No marked association between rectal cancer risk and measures of nitrate in public water supplies, including average nitrate and the number of years with elevated average nitrate levels, was observed. From a case-control study conducted in Wisconsin women, McElroy et al (2008) reported that nitrate exposure from drinking water was not significantly associated with increased risk of rectal cancer.…”

Colorectal cancer risk and nitrate exposure through drinking water and diet

“…Our results are comparable to previous case–control studies from the United States, although those studies evaluated residential, but not ingested nitrate, at higher levels than those observed in our study. A 2.9‐fold increased risk of proximal colon cancer for NO 3 ‐N residential levels ≥10 mg/L (44 mg/L of ) versus <0.5 mg/L has been reported . Increased risk of colon cancer was found among subjects with residential NO 3 ‐N levels >5 mg/L for >10 years and low vitamin C intake or high meat intake .…”

Nitrate-nitrogen levels in rural drinking water: Is there an association with age-related macular degeneration?

“…[10] In a female colorectal case-control study, nitrate-nitrogen exposure from rural private drinking water was associated with increased colon cancer risk. [11] AMD pathogenesis is largely unknown, [12] although neuroinflammatory response including immune cells reacting to persistent stressful stimuli generating low-grade chronic inflammation or compromised autoimmunity related to oxidative stress may provide insight into the mechanism leading to AMD. [13] Similarly, mechanisms associated with nitrate exposure and inflammatory response in humans has not been well described but a few recent studies are suggestive of an association.…”