Nitrates in drinking water and the risk of death from rectal cancer: does hardness in drinking water matter?

Nitrate and nitrite contamination in drinking water and cancer risk: A systematic review with meta-analysis

BACKGROUND

Pollution of water sources, largely from wide-scale agricultural fertilizer use has resulted in nitrate and nitrite contamination of drinking water. The effects on human health of raised nitrate and nitrite levels in drinking water are currently unclear.

OBJECTIVES

We conducted a systematic review of peer-reviewed literature on the association of nitrate and nitrite in drinking water with human health with a specific focus on cancer.

METHODS

We searched eight databases from 1 January 1990 until 28 February 2021. Meta-analyses were conducted when studies had the same exposure metric and outcome.

RESULTS

Of 9835 studies identified in the literature search, we found 111 studies reporting health outcomes, 60 of which reported cancer outcomes (38 case-control studies; 12 cohort studies; 10 other study designs). Most studies were set in the USA (24), Europe (20) and Taiwan (14), with only 3 studies from low and middle-income countries. Nitrate exposure in water (59 studies) was more commonly investigated than nitrite exposure (4 studies). Colorectal (15 studies) and gastric (13 studies) cancers were the most reported. In meta-analyses (4 studies) we identified a positive association of nitrate exposure with gastric cancer, OR = 1.91 (95%CI = 1.09-3.33) per 10 mg/L increment in nitrate ion. We found no association of nitrate exposure with colorectal cancer (10 studies; OR = 1.02 [95%CI = 0.96-1.08]) or cancers at any other site.

CONCLUSIONS

We identified an association of nitrate in drinking water with gastric cancer but with no other cancer site. There is currently a paucity of robust studies from settings with high levels nitrate pollution in drinking water. Research into this area will be valuable to ascertain the true health burden of nitrate contamination of water and the need for public policies to protect human health.

Exposure-based assessment and economic valuation of adverse birth outcomes and cancer risk due to nitrate in United States drinking water

BACKGROUND

Nitrate ingestion from drinking water has been associated with an increased risk of adverse birth outcomes as well as elevated risk of colorectal cancer and several other cancers. Yet, to date, no studies have attempted to quantify the health and economic impacts due to nitrate in drinking water in the United States.

METHODS

This study presents a first-of-its-kind comprehensive assessment of nitrate exposure from drinking water for the entire United States population. This exposure assessment serves as the basis for our analysis of the annual nitrate-attributable disease cases in the United States and the associated economic losses due to medical costs and lost productivity. Additionally, through a meta-analysis of studies on drinking water nitrate and colorectal cancer, we examine the exposure-response relationship for nitrate and cancer risk.

RESULTS

On the basis of national nitrate occurrence data and relative risk ratios reported in the epidemiology literature, we calculated that annually, 2939 cases of very low birth weight, 1725 cases of very preterm birth, and 41 cases of neural tube defects could be related to nitrate exposure from drinking water. For cancer risk, combining nitrate-specific risk estimates for colorectal, ovarian, thyroid, kidney, and bladder cancers results in a range of 2300 to 12,594 annual nitrate-attributable cancer cases (mean: 6537 estimated cases). For medical expenditures alone, this burden of cancer corresponds to an annual economic cost of 250 million to 1.5 billion U.S. dollars, together with a potential 1.3 to 6.5 billion dollar impact due to lost productivity. With the meta-analysis of eight studies of drinking water nitrate and colorectal cancer, we observed a statistically significant positive association for nitrate exposure and colorectal cancer risk and calculated a one-in-one million cancer risk level of 0.14 mg/L nitrate in drinking water.

CONCLUSION

Health and economic analyses presented here suggest that lowering exposure to nitrate in drinking water could bring economic benefits by alleviating the impacts of nitrate-associated diseases.

Origin and distribution of nitrate in water well of settlement areas in Yogyakarta, Indonesia

Pollution of nitrate in water wells in Yogyakarta City was reported to increase for two decades. This study aimed to describe nitrate contamination in the water wells of colorectal cancer (CRC) and inflammatory bowel disease (IBD) patients, previously described elsewhere. Nitrate and chloride content of 150 water samples from the wells of patients with CRC and IBD who were residing in Yogyakarta, Sleman, or Bantul districts were examined. Description of nitrate contamination was presented in the form of box plot charts and map. Kruskal-Wallis analysis was used to measure the difference of nitrate concentration in three areas of study. Comparisons of nitrate and chloride concentrations were used to determine the source of nitrate contamination in water well. Fisher's exact test was used to describe the relationship of well distance with the septic tank to nitrate concentration in water well. The wells in Yogyakarta City had the highest median nitrate content compared to Sleman and Bantul (P = 0.001) with the median of 56.6, 13.1, and 7.7 for Yogyakarta, Sleman, and Bantul, respectively, and most tested samples exceed WHO safe drinking water standards. The spread of nitrate contamination has occurred in areas adjacent to Yogyakarta City compared to the previous report. The ratio of nitrate to chloride (1-8:1) suggested that the source of nitrate contamination in water wells in the study area came from feces due to inadequate on-site sanitation. The mapping showed nitrate contamination in water wells in Yogyakarta City, Sleman, and Bantul districts had spread according to urban development.

Nitrate in drinking water and risk of colorectal cancer in Yogyakarta, Indonesia

Nitrate concentration in well water in Yogyakarta, Indonesia, and its surroundings tended to increase rapidly from time to time, and it may be associated with an elevated risk for several types of cancer. The purpose of this study was to examine the association between nitrate in drinking water and colorectal cancer (CRC) risk occurrence. A case-control study was conducted in Yogyakarta Special Province. Pathologically confirmed 75 CRC patients and 75 controls were consulted and their individual well water was sampled and examined for nitrate concentrations. Logistic regression analysis was conducted to establish the association between nitrate and CRC risk development. There was a significant correlation between nitrate in drinking water and CRC occurrence, and this value was relatively stable after being adjusted for protein intake, smoking history, age, and family history of cancer. These findings demonstrated that the risk of CRC development was fourfold among those with >10 years of nitrate exposure from well water compared with those with ≤10 years of nitrate exposure. Consequently, a significant association between nitrate in drinking water and occurrence of CRC in Yogyakarta was established.

Does drinking water influence hospital-admitted sialolithiasis on an epidemiological level in Denmark?

OBJECTIVES

Sialolithiasis, or salivary stones, is not a rare disease of the major salivary glands. However, the aetiology and incidence remain largely unknown. Since sialoliths are comprised mainly of calcium phosphate salts, we hypothesise that drinking water calcium levels and other elements in drinking water could play a role in sialolithiasis. Owing to substantial intermunicipality differences in drinking water composition, Denmark constitutes a unique environment for testing such relations.

DESIGN

An epidemiological study based on patient data extracted from the National Patient Registry and drinking water data from the Geological Survey of Denmark and Greenland retrieved as weighted data on all major drinking water constituents for each of the 3364 waterworks in Denmark. All patient cases with International Statistical Classification of Diseases 10th Revision (ICD-10) codes for sialolithiasis registered between the years 2000 and 2010 were included in the study (n=3014) and related to the drinking water composition on a municipality level (n=98).

PRIMARY AND SECONDARY OUTCOME MEASURES

Multiple regression analysis using iterative search and testing among all demographic and drinking water variables with sialolithiasis incidence as the outcome in search of possible relations among the variables tested.

RESULTS

The nationwide incidence of hospital-admitted sialolithiasis was 5.5 cases per 100,000 citizens per year in Denmark. Strong relations were found between the incidence of sialolithiasis and the drinking water concentration of calcium, magnesium and hydrogen carbonate, however, in separate models (p<0.001). Analyses also confirmed correlations between drinking water calcium and magnesium and their concentration in saliva whereas this was not the case for hydrogen carbonate.

CONCLUSIONS

Differences in drinking water calcium and magnesium may play a role in the incidence of sialolithiasis. These findings are of interest because many countries have started large-scale desalination programmes of drinking water.

Multiple imputation for assessment of exposures to drinking water contaminants: evaluation with the Atrazine Monitoring Program

BACKGROUND

Drinking water may contain pollutants that harm human health. The frequency of pollutant monitoring may occur quarterly, annually, or less frequently, depending upon the pollutant, the pollutant concentration, and community water system. However, birth and other health outcomes are associated with narrow time-windows of exposure. Infrequent monitoring impedes linkage between water quality and health outcomes for epidemiological analyses.

OBJECTIVES

To evaluate the performance of multiple imputation to fill in water quality values between measurements in community water systems (CWSs).

METHODS

The multiple imputation method was implemented in a simulated setting using data from the Atrazine Monitoring Program (AMP, 2006-2009 in five Midwestern states). Values were deleted from the AMP data to leave one measurement per month. Four patterns reflecting drinking water monitoring regulations were used to delete months of data in each CWS: three patterns were missing at random and one pattern was missing not at random. Synthetic health outcome data were created using a linear and a Poisson exposure-response relationship with five levels of hypothesized association, respectively. The multiple imputation method was evaluated by comparing the exposure-response relationships estimated based on multiply imputed data with the hypothesized association.

RESULTS

The four patterns deleted 65-92% months of atrazine observations in AMP data. Even with these high rates of missing information, our procedure was able to recover most of the missing information when the synthetic health outcome was included for missing at random patterns and for missing not at random patterns with low-to-moderate exposure-response relationships.

CONCLUSIONS

Multiple imputation appears to be an effective method for filling in water quality values between measurements.

Effect modification by drinking water hardness of the association between nitrate levels and gastric cancer: evidence from an ecological study

The objectives of this study were to (1) examine the relationship between nitrate levels in public water supplies and risk of death from gastric cancer and (2) determine whether calcium (Ca) and magnesium (Mg) levels in drinking water might modify the effects of nitrate on the risk of gastric cancer development. A matched cancer case-control study was used to investigate the relationship between the risk of death attributed to gastric cancer and exposure to nitrate in drinking water in Taiwan. All deaths due to gastric cancer in Taiwan residents from 2006 through 2010 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Deaths from other causes served as controls and were pair-matched to cancer cases by gender, year of birth, and year of death. Information on the levels of nitrate-nitrogen (NO(3)-N), Ca, and Mg in drinking water were collected from Taiwan Water Supply Corporation (TWSC). The municipality of residence for cancer cases and controls was presumed to be the source of the subject's NO(3)-N, Ca, and Mg exposure via drinking water. Relative to individuals whose NO(3)-N exposure levels were <0.38 ppm, the adjusted odds ratio (OR) and 95% confidence interval (CI) for gastric cancer occurrence was 1.16 (1.05-1.29) for individuals who resided in municipalities served by drinking water with a NO(3)-N exposure ≥ 0.38 ppm. There was apparent evidence of an interaction between drinking water NO(3)-N levels and low Ca and Mg intake via drinking water. Our findings showed that the correlation between NO(3)-N exposure and risk of gastric cancer development was influenced by Ca and Mg levels in drinking water. This is the first study to report effects modification by Ca and Mg intake from drinking water on the relationship between NO(3)-N exposure and risk of gastric cancer occurrence. Increased knowledge of the mechanistic interactions between Ca, Mg, and NO(3)-N in reducing risk of gastric cancer development will aid in public policy decisions and setting threshold standards.

Nitrates in drinking water and the risk of death from childhood brain tumors in Taiwan

The objective of this study was to (1) examine the relationship between nitrate (NO₃-N) levels in public water supplies and risk of death from childhood brain tumors (CBT) and (2) determine whether calcium (Ca) and magnesium (Mg) levels in drinking water might modify the effects of NO₃-N on development of CBT. A matched cancer case-control study was used to investigate the relationship between the risk of death attributed to CBT and exposure to NO₃-N in drinking water in Taiwan. All CBT deaths of Taiwan residents from 1999 through 2008 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair-matched to the cases by gender, year of birth, and year of death. Information on the levels of nitrate-nitrogen NO₃-N, Ca, and Mg in drinking water were collected from Taiwan Water Supply Corporation. The municipality of residence for CBT cases and controls was presumed to be the source of the subject's NO₃-N, Ca, and Mg exposure via drinking water. Relative to individuals whose NO₃-N exposure level was ≤ 0.31 ppm, and the adjusted odds ration (OR) (95% confidence interval [CI]) for CBT occurrence was 1.4 (1.07-1.84) for individuals who resided in municipalities served by drinking water with a NO₃-N exposure > 0.31 ppm. No significant effect modification was observed by Ca and Mg intake via drinking water. Data suggest that exposure to NO₃-N in drinking water is associated with a higher risk of CBT development in Taiwan.

Nitrates in drinking water and the risk of death from brain cancer: does hardness in drinking water matter?

The objectives of this study were to (1) examine the relationship between nitrate levels in public water supplies and risk of death from brain cancer and (2) determine whether calcium (Ca) and magnesium (Mg) levels in drinking water might modify the influence of nitrates on development of brain cancer. A matched cancer case-control study was used to investigate the relationship between the risk of death from brain cancer and exposure to nitrates in drinking water in Taiwan. All brain cancer deaths of Taiwan residents from 2003 through 2008 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair-matched to cancer cases by gender, year of birth, and year of death. Information on the levels of nitrate-nitrogen (NO₃-N), Ca, and Mg in drinking water was obtained from Taiwan Water Supply Corporation (TWSC). The municipality of residence for cancer cases and controls was presumed to be the source of the subject's NO₃-N, Ca, and Mg exposure via drinking water. Relative to individuals whose NO₃-N exposure level was <0.38 ppm, the adjusted OR (95% CI) for brain cancer occurrence was 1.04 (0.85-1.27) for individuals who resided in municipalities served by drinking water with a NO₃-N exposure ≥ 0.38 ppm. No marked effect modification was observed due to Ca and Mg intake via drinking water on brain cancer occurrence.