An ecologic study of nitrate in municipal drinking water and cancer incidence in Trnava District, Slovakia.Environ Res. 2002 Mar; 88(3):182-7.ER
Contamination of drinking water by nitrate is an evolving public health concern since nitrate can undergo endogenous reduction to nitrite, and nitrosation of nitrites can form N-nitroso compounds, which are potent carcinogens. We conducted an ecologic study to determine whether nitrate levels in drinking water were correlated with non-Hodgkin lymphoma and cancers of the digestive and urinary tracts in an agricultural district (Trnava District; population 237,000) of the Slovak Republic. Routinely collected nitrate data (1975-1995) for villages using public water supplies were computerized, and each village was categorized into low (0-10 mg/L), medium (10.1-20 mg/L), or high (20.1-50 mg/L) average levels of total nitrate in drinking water. Observed cases of cancer in each of these villages were ascertained through the district cancer registry for the time period 1986-1995. Standardized incidence ratios (SIRs) and 95% confidence intervals (CI) for all cancer and selected cancer sites were calculated by indirect standardization using age- and sex-specific incidence rates from the entire district. For all cancer in women, SIRs increased from villages with low (SIR=0.87; 95% CI 0.72-0.95) to medium (SIR=1.07; 95% CI 1.00-1.13) to high (SIR=1.14; 1.06-1.22) levels of nitrate (P for trend <0.001); there was a similar trend for all cancer in men from low (SIR=0.90; 95% CI 0.81-0.99) to medium (SIR=1.08, 95% CI 1.02-1.16), but not for high (SIR=0.94; 0.88-1.02), nitrate levels (P for trend <0.001). This pattern in the SIRs (from low to high nitrate level) was also seen for stomach cancer in women (0.81, 0.94, 1.24; P for trend=0.10), colorectal cancer in women (0.64, 1.11, 1.29; P for trend <0.001) and men (0.77, 0.99, 1.07; P for trend=0.051), and non-Hodgkin lymphoma in women (0.45, 0.90, 1.35; P for trend=0.13) and men (0.25, 1.66, and 1.09; P for trend=0.017). There were no associations for kidney or bladder cancer. These ecologic data support the hypothesis that there is a positive association between nitrate in drinking water and non-Hodgkin lymphoma and colorectal cancer.