Association between mercury levels and colorectal cancer: a systematic review, meta-analysis

This study examines how mercury (Hg) levels may be linked to colorectal cancer (CRC) by reviewing and analyzing existing research. It is important to understand this connection because mercury may cause cancer.

We searched PubMed, Scopus, and Web of Science for studies published up to January 2026. We included observational studies evaluating mercury levels in patients with CRC compared with healthy controls or non-cancerous colorectal tissue, as well as studies assessing the association between mercury exposure and colorectal cancer. We analyzed the data using a random-effects model. Mercury levels were measured in subgroups within both the case and control groups to address differences in measurement methods. We assessed the quality of the included studies using the Newcastle-Ottawa Scale. All data were analyzed with STATA version 17.

This meta-analysis reviewed 8 studies selected from 1,099 database records. Four studies with 773 participants (355 cases and 418 controls) found no significant difference in mercury levels between people with colorectal cancer and healthy controls (SMD: 0.16 [-0.22, 0.54]; p = 0.42; I²: 82.25%). Subgroup analysis showed differences depending on study design, average age, percentage of male participants, and risk of bias score. Meta-regression found that participant age affected the results, while other factors did not. In two studies with 71 participants, there was also no significant difference in mercury levels between colorectal and healthy tissues in patients with colorectal cancer (SMD: -0.24 [-1.11, 0.64]; p = 0.60; I²: 76.68%), despite high variability across studies.

Our review found no significant link between mercury levels and CRC risk, underscoring the complexity of environmental toxins in cancer etiology and the need for further research on influencing factors.