Ingested nitrate and nitrite and bladder cancer in Northern New England

Abstract

OPS 36: Health effects of dietary exposures, Room 210, Floor 2, August 27, 2019, 4:30 PM - 5:30 PM Background/Aim: N-nitroso compounds (NOCs) are hypothesized human bladder carcinogens. Nitrate and nitrite are NOC precursors; sources include contaminated drinking water and diet. We examined nitrate and nitrite ingestion and bladder cancer risk in the New England Bladder Cancer Study, a population-based case-control study in Maine, New Hampshire, and Vermont. Methods: Using historical nitrate measurements for public water supplies, measured and modeled values for private wells and self-reported water intake, we estimated average nitrate concentrations (NO3-N mg/L) and average daily nitrate intake (mg/day) from 1970 to diagnosis/reference date for 987 cases and 1180 controls. We also estimated source-specific (animal, plant, processed meat) dietary nitrate and nitrite intakes using a food frequency questionnaire (1037 cases and 1225 controls). We used unconditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI) adjusting for age, gender, smoking, disinfection by-products, and other factors. We evaluated interactions with factors affecting NOC formation (i.e., red and processed meat, vitamin C, smoking). Results: Average drinking water nitrate concentration above the 95th percentile (>2.07 mg/L) compared with the lowest quartile (<=0.21 mg/L) was associated with bladder cancer risk (OR=1.50, CI: 0.97-2.32; p-trend=0.01); the association was similar for average drinking water nitrate intake. We observed positive associations for dietary nitrate and nitrite intakes from processed meat (highest vs. lowest quintile OR=1.42, CI: 1.01-1.98; p-trend=0.04; OR=1.48, CI: 1.04-2.09; p-trend=0.04, respectively), but no trends for other sources. Risk was highest among those with >2.07 mg/L NO3-N and >median red or processed meat intake vs <0.21 mg/L NO3-N/< median intakes (OR=2.61, CI: 1.33-5.11 and OR=3.47 CI: 1.75-6.87; p-interaction=0.05 and 0.07, respectively). We observed no interaction with vitamin C or smoking. Conclusions: Our results suggest the importance of both drinking water and dietary nitrate sources as risk factors for bladder cancer especially among those with high red or processed meat intake