Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was reviewed?
This systematic review synthesized evidence on mercury hematological effects in humans across six databases and repositories (1950–Feb 2018), following PRISMA and registered in PROSPERO. It screened 1,297 records and included 80 observational studies encompassing 9,284 individuals, with exposure via seafood, dental amalgam, artisanal and small-scale gold mining (ASGM), consumer products, medicines, and environmental sources. Quality was appraised with the EPHPP tool. The review’s core aim was to determine whether mercury exposure is associated with clinically relevant changes in blood cell indices pertinent to HTMC.
Who was reviewed?
The pooled population included 6,601 non-occupationally exposed individuals and 2,605 occupationally exposed workers across 34 countries. Children and teenagers predominated in non-occupational exposure (≈75%), largely through diet, whereas adult men predominated in occupational settings (e.g., agriculture, chlor-alkali, lamp factories, dentistry, and ASGM). Chronic exposure was common in both groups. Overall, blood counts were normal in most exposed persons (6,012), yet 1,914 cases with hematologic effects were cataloged, including severe events and 29 deaths, chiefly linked to medicinal mercury. These demographics define where mercury hematological effects are most likely to be detected in practice.
Most important findings
| Critical point | Details |
|---|---|
| Spectrum and frequency of effects | Across 69 studies, 2,376 hematologic findings were recorded in 1,914 people; anemia (n=875) was most frequent, followed by lymphocytosis (n=361) and lymphopenia (n=306). All marrow lineages were affected (erythroid, myeloid, lymphoid, platelets). |
| Severity and fatalities | Severe outcomes included thrombocytopenia with bleeding, aplastic anemia, neutropenia with sepsis, and multiple organ dysfunction; 29 deaths were reported, 19 directly hematologic (mostly hemorrhage). |
| Statistical associations relevant to standards | Three studies reported adjusted associations: inverse associations for anemia (β≈−0.14 g/dL hemoglobin), lymphopenia (β≈−0.23 to −1.26), and positive associations for neutrophilia and basophilia (β≈1.38). Although causality cannot be inferred from observational data, these signals are robust directionally for risk assessment. |
| Exposure pathways shaping risk | Non-occupational: seafood (especially top-trophic fish), proximity to ASGM, dental amalgam, traditional medicines/cosmetics. Occupational: agriculture (organomercury fungicides), chlor-alkali, lamp factories, dentistry, and mining. Chronic exposure predominated; ASGM remains the largest anthropogenic source. |
| Age/sex patterns | Children/teens were the majority among non-occupational exposures and showed anemia and leukocyte shifts; adults in workplaces showed lymphocyte perturbations (both lymphocytosis and lymphopenia) and occasional polycythemia. |
| Mechanistic hypotheses | Proposed mechanisms include direct marrow toxicity, apoptosis of hematopoietic/immune cells, immunologic hypersensitivity, hemolysis, inflammatory pneumonitis (driving neutrophilia), and altered erythropoietin levels (polycythemia). |
| Normal counts despite exposure | Despite many effects, 6,012 exposed persons had normal blood counts, underscoring interindividual variability and the need for exposure-contextualized interpretation rather than a single universal biomarker threshold. |
| Study quality | Most studies were rated “weak” by EPHPP due to design and confounding limitations, arguing for cautious interpretation and the need for better-designed cohorts for regulatory calibration. |
Key Implications
For HTMC, primary regulatory impacts include recognition that mercury hematological effects span anemia, leukocyte dyscrasias, and thrombocytopenia with occasional severity; certification requirements should mandate exposure history plus CBC and differential for at-risk groups and products; industry applications involve seafood sourcing controls and ASGM-adjacent supply chain vetting; research gaps include causal dose–response in children and women of childbearing age; practical recommendations are to align product limits with hematologic risks, set action levels linked to hemoglobin and leukocyte changes, and require periodic CBC monitoring when exposure biomarkers approach intervention thresholds.
Citation
Vianna AS, de Matos EP, de Jesus IM, Asmus CIRF, Câmara VM. Human exposure to mercury and its hematological effects: a systematic review. Cad Saude Publica. 2019;35(2):e00091618. doi:10.1590/0102-311X00091618.
Mercury (Hg) is a neurotoxic heavy metal found in various consumer products and environmental sources, making it a major public health concern. Its regulation is critical to protect vulnerable populations from long-term health effects, such as neurological impairment and cardiovascular disease. The HMTC program ensures that products meet the highest standards for mercury safety.
