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

Roberto Picetti, Megan Deeney, Silvia Pastorino, Mark R. Miller, Anoop Shah, David A. Leon, Alan D. Dangour, Rosemary Green

Research output: Contribution to journalReview articlepeer-review

Abstract

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 con-
ducted 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.
Original languageEnglish
Pages (from-to)112988
JournalEnvironmental Research
Volume210
DOIs
Publication statusPublished - 22 Feb 2022

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