Association between gastric cancer mortality and nitrate content of drinking water: ecological study on small area inequalities.
The carcinogenic feature of N-nitroso compounds has been well established. Similarly, the transformation of ingested nitrate to N-nitroso compounds in the stomach has been thoroughly documented, nevertheless nitrates' carcinogenic effect has not been proved convincingly in human. The present study was aimed to investigate a population of small villages provided by drinking water with high and widely variable nitrate content (72 mg/l median, 290.7 mg/l 95-percentile concentration). Empirical Bayes estimates for settlement-specific age-, sex-, and year-standardised mortality ratios of gastric cancer (GC) were related to the settlement level average nitrate concentrations in drinking water controlling for confounding effects of smoking, ethnicity and education. The log-transformed average nitrate concentration showed significant positive association with stomach cancer mortality in linear regression analysis (p = 0.014). The settlements were aggregated according to the nitrate concentration into 10-percentile groups and the standardised mortality ratios (SMRs) were calculated. Those groups with higher than 88 mg/l average nitrate concentration showed substantial risk elevation and the log-transformed exposure variables proved to be significant predictors of mortality (p = 0.032) at this level of aggregation also. The association seemed to be fairly strong (r2 = 0.46). Although this investigation constituting an ecological study has certain limitations, it supports the hypothesis that the high level of nitrate in drinking water is involved in the development of GC.
Sandor
J
J
Department of Public Health, University of Pecs, Hungary. janos@pubhealth.pote.hu
Kiss
I
I
Farkas
O
O
Ember
I
I
D001499:Bayes Theorem; D005260:Female; D005618:Fresh Water / Q000737:chemistry*; D006801:Humans; D006814:Hungary / Q000453:epidemiology; D016014:Linear Models; D008297:Male; D009566:Nitrates / Q000009:adverse effects*; D012307:Risk Factors; D012424:Rural Population; D017062:Small-Area Analysis; D013274:Stomach Neoplasms / Q000139:chemically induced / Q000401:mortality*
D009566:Nitrates