Long-Term Exposure to Nitrate and Trihalomethanes in Drinking Water and Prostate Cancer: A Multicase-Control Study in Spain (MCC-Spain)

Long-term cancer and overall mortality associated with drinking water nitrate in the United States

OBJECTIVES

Nitrate is a probable carcinogen regulated in drinking water by the US Environmental Protection Agency (EPA) to a maximum contaminant level (MCL) of 10 mg/L nitrate-nitrogen (NO3-N; equivalent to 44.3 mg/L NO3). We aimed to determine the association of US drinking water nitrate levels with overall as well as cardiovascular, cancer, and other cause mortality.

STUDY DESIGN

This study used a population-based retrospective cohort design.

METHODS

We analyzed data from 2029 participants of the 2005-2006 National Health and Nutrition Examination Survey followed for mortality until 2019 for a median of 13.9 years. We used Cox proportional hazards regression to estimate the hazard ratio (HR) and 95% confidence interval (CI) for mortality associated with drinking water nitrate, adjusting for covariates that included socio-economic factors and pack-years of cigarette smoking.

RESULTS

Drinking water nitrate was detected in 50.8 % of the samples, had a median concentration of 0.77 mg/L NO3, and was above US EPA MCL in 0.4 % of participants. In adjusted analysis, drinking water nitrate detection was associated with 73 % higher cancer mortality (HR: 1.73, 95% CI: 1.19-2.51), whereas a 10-fold increase in drinking water nitrate levels was associated with 69 % higher cancer mortality (HR: 1.69, 95% CI: 1.24-2.31) and 21 % higher overall mortality (HR: 1.21, 95% CI: 1.00-1.46). Drinking water nitrate below EPA MCL was still associated with higher cancer mortality (HR: 1.61, 95% CI: 1.07-2.43 per 10-fold increase and HR: 1.61, 95% CI: 1.08-2.42 for detection).

CONCLUSIONS

Levels of drinking water nitrate may be an overlooked contributor to cancer mortality in the United States.

Ingested nitrate and nitrite and end-stage renal disease in licensed pesticide applicators and spouses in the Agricultural Health Study

BACKGROUND

Nitrate and nitrite ingestion has been linked to kidney cancer, possibly via the endogenous formation of carcinogenic N-nitroso compounds. These exposures might also contribute to end-stage renal disease (ESRD).

OBJECTIVES

We investigated associations of drinking water nitrate and dietary nitrate and nitrite intakes (total and by food type) with incident ESRD in the Agricultural Health Study. We also explored modifying effects of vitamin C and heme iron intake, which may affect endogenous nitrosation.

METHODS

We performed complete case analyses among private pesticide applicators and their spouses. We obtained water nitrate estimates for participants whose primary drinking water source at enrollment (1993-1997) was public water supplies (PWS) or private wells (N = 59,632). Average nitrate concentrations were computed from historical data for PWS users and predicted from random forest models for private well users. Analysis of dietary nitrate and nitrite was restricted to the 30,177 participants who completed the NCI Dietary History Questionnaire during follow-up (1999-2003). Incident ESRD through 2018 was ascertained through linkage with the U.S. Renal Data System. We estimated adjusted hazard ratios (HRs) and 95%CI for associations of tertiles (T) of exposure with ESRD overall and explored effects in strata of vitamin C and heme iron intake.

RESULTS

We identified 469 incident ESRD cases (206 for dietary analysis). Water nitrate and total dietary nitrate/nitrite were not associated with ESRD, but increased ESRD was associated with nitrate and nitrite from processed meats. We found apparent associations between nitrite and ESRD only among participants with vitamin C

SIGNIFICANCE

ESRD incidence was associated with dietary nitrate/nitrite from processed meat among all study participants and with total dietary nitrite among participants with lower vitamin C or higher heme iron intake.

IMPACT STATEMENT

There are few well-established environmental risk factors for end-stage renal disease (ESRD), a worldwide public health challenge. Ingestion of nitrate and nitrite, which may lead to endogenous formation of carcinogenic N-nitroso compounds, has been linked to some cancers and chronic diseases. We investigated these exposures in relation to ESRD in an agricultural cohort. ESRD incidence was associated with dietary nitrate/nitrite from processed meat and with total dietary nitrite among subgroups with lower vitamin C or higher heme iron intake. This study provides preliminary evidence that points to dietary nitrite and possibly dietary nitrate intake as a potential contributor to ESRD.

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Key Words

• Chronic kidney disease
• End-stage renal disease
• Nitrate
• Nitrite
• Processed meat
• Water pollution

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MESH Headings

• Humans
• Nitrates/analysis
• Kidney Failure, Chronic/epidemiology
• Kidney Failure, Chronic/chemically induced
• Male
• Nitrites/analysis
• Nitrites/adverse effects
• Female
• Middle Aged
• Spouses/statistics & numerical data
• Adult
• Pesticides
• Occupational Exposure/adverse effects
• Occupational Exposure/analysis
• Aged
• Drinking Water/chemistry
• Drinking Water/analysis
• Incidence
• Agriculture
• Diet/statistics & numerical data
• Farmers/statistics & numerical data
• Ascorbic Acid

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Affiliation(s)

Dazhe Chen Epidemiology Branch, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, USA
Christine G Parks Epidemiology Branch, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, USA
Laura E Beane Freeman Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Rockville, MD, USA
Jonathan N Hofmann Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Rockville, MD, USA
Rashmi Sinha Metabolic Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Rockville, MD, USA
Jessica M Madrigal Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Rockville, MD, USA
Mary H Ward Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Rockville, MD, USA
Dale P Sandler Epidemiology Branch, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, USA.

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Surface-Water Nitrate Exposure to World Populations Has Expanded and Intensified during 1970-2010

Excessive nitrate in surface waters deteriorates the water quality and threatens human health. Human activities have caused increased nitrate concentrations in global surface waters over the past 50 years. An assessment of the long-term trajectory of surface-water nitrate exposure to world populations and the associated potential health risks is imperative but lacking. Here, we used global spatially explicit data on surface-water nitrate concentrations and population density, in combination with thresholds for health risks from epidemiological studies, to quantify the long-term changes in surface-water nitrate exposure to world populations at multiple spatial scales. During 1970-2010, global populations potentially affected by acute health risks associated with surface-water nitrate exposure increased from 6 to 60 million persons per year, while populations at potential chronic health risks increased from 169 to 1361 million persons per year. Potential acute risks have increasingly affected Asian countries. Populations potentially affected by chronic risks shifted from dominance by high-income countries (in Europe and North America) to middle-income countries (in Asia and Africa). To mitigate adverse health effects associated with surface-water nitrate exposure, anthropogenic nitrogen inputs to natural environments should be drastically reduced. International and national standards of maximum nitrate contamination may need to be lowered.

Research Recommendations for Selected IARC-Classified Agents: Impact and Lessons Learned

BACKGROUND

The International Agency for Research on Cancer (IARC) Monographs program assembles expert working groups who publish a critical review and evaluation of data on agents of interest. These comprehensive reviews provide a unique opportunity to identify research needs to address classification uncertainties. A multidisciplinary expert review and workshop held in 2009 identified research gaps and needs for 20 priority occupational chemicals, metals, dusts, and physical agents, with the goal of stimulating advances in epidemiological studies of cancer and carcinogen mechanisms. Overarching issues were also described.

OBJECTIVES

In this commentary we review the current status of the evidence for the 20 priority agents identified in 2009. We examine whether identified Research Recommendations for each agent were addressed and their potential impact on resolving classification uncertainties.

METHODS

We reviewed the IARC classifications of each of the 20 priority agents and identified major new epidemiological and human mechanistic studies published since the last evaluation. Information sources were either the published Monograph for agents that have been reevaluated or, for agents not yet reevaluated, Advisory Group reports and literature searches. Findings are described in view of recent methodological developments in Monographs evidence evaluation processes.

DISCUSSION

The majority of the 20 priority agents were reevaluated by IARC since 2009. The overall carcinogen classifications of 9 agents advanced, and new cancer sites with either "sufficient" or "limited" evidence of carcinogenicity were also identified for 9 agents. Examination of published findings revealed whether evidence gaps and Research Recommendations have been addressed and highlighted remaining uncertainties. During the past decade, new research addressed a range of the 2009 recommendations and supported updated classifications for priority agents. This supports future efforts to systematically apply findings of Monograph reviews to identify research gaps and priorities relevant to evaluation criteria established in the updated IARC Monograph Preamble. https://doi.org/10.1289/EHP12547.