One in six couples experience fertility problems. Environmental factors may affect reproductive health; however, evidence is lacking regarding drinking water nitrates and outcomes of male and female fertility. The aim of this study was to investigate if exposure to nitrates in drinking water is associated with adverse reproductive outcomes in humans, and animals of fertile age. We conducted a systematic literature search and included case-control studies, cohort studies, and randomized control trials reporting on the association between drinking water nitrate exposure of men, women, or animals and adverse reproductive outcomes, specified as: Semen quality parameters, time to pregnancy (TTP), pregnancy rates, assisted reproductive technologies (ART), and spontaneous abortion. Findings were reported in a narrative synthesis. A total of 12 studies were included. The only human study included reported a decrease in spontaneous abortion at any detectable nitrate level. Overall, the 11 included animal studies support a potential negative effect on semen quality parameters but report equivocal results on TTP and number of offspring produced, and higher risk of spontaneous abortion. In conclusion, animal studies indicate possible effects on semen quality parameters and spontaneous abortion. However, with a few studies, including some with methodological limitations and small sample sizes, caution must be applied when interpreting these results.

Infertility is a worldwide health issue, but mechanisms of both male and female reproductive toxicity remain to be elucidated. So far, a limited focus has been on potentially harmful environmental factors such as arsenic, which is naturally occurring in groundwater. The objective of this review was to systematically investigate the association between arsenic in drinking water and adverse reproductive outcomes in men and women of fertile age. We conducted a systematic literature search and included case-control studies and cohort studies reporting on decreased semen quality characteristics, increased time to pregnancy, infertility, or spontaneous abortion. In total, 433 articles were screened and ultimately, eight studies were included. Included literature was quality assessed with the Newcastle-Ottawa Scale. Findings were reported in a narrative synthesis. Only one study investigated male fertility. An association between increasing arsenic exposure and decreasing semen quality characteristics was found, as well as an indication of arsenic accumulation in seminal plasma. These findings are, however, at high arsenic levels (>1000 µg/L). No consistent evidence was found to support the hypothesis that arsenic exposure from drinking water is a cause of longer waiting time to pregnancy or spontaneous abortion, being the only endpoints investigated in the included literature. In conclusion; the evidence is sparse and of varying quality, however, it does warrant attention, as it conflicts with existing evidence, mainly from cross-sectional or ecologic studies.