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. 
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 critically evaluated the preventive and carcinogenic effects of metals on cancer incidence, directly addressing the focus keyphrase “preventive and carcinogenic effects of metals on cancer.” Conducted according to PRISMA guidelines, it synthesized findings from 66 original studies published globally through May 2024. The review systematically collected and analyzed data on concentrations of both toxic (e.g., lead, arsenic, cadmium, chromium, nickel) and essential (e.g., selenium, zinc, iron, manganese) metals in environmental and biological samples of individuals with and without cancer. It assessed the relationship between varying metal exposure levels, cancer occurrence, and the protective or harmful roles these metals can play, depending on their concentration and biological context.
Who was reviewed?
The review encompassed 66 original peer-reviewed human studies, including case–control, cohort, and cross-sectional designs conducted worldwide. Over 1.3 million participants were represented, spanning diverse ages, genders, and populations from North America, Europe, Asia, Africa, and Oceania. The studies examined both environmental and occupational exposures, and measured metal concentrations in a range of biological samples—blood, urine, hair, serum, tissue, and nails—from cancer patients and control groups. A broad spectrum of cancer types was covered: lung, breast, prostate, stomach, colorectal, bladder, thyroid, brain, and hematological malignancies, among others. The review excluded animal studies, non-original research, and studies lacking quantitative meta-data, ensuring a direct focus on human data relevant for regulatory and certification purposes.
Most important findings
| Critical Points | Details |
|---|---|
| Toxic metals—lead, cadmium, arsenic, chromium (VI), nickel—consistently higher in cancer patients | The majority of studies reported that cancer patients exhibited significantly elevated concentrations of these toxic metals in biological samples compared to controls. This held across multiple cancer types (lung, breast, prostate, stomach, bladder, thyroid, brain) and geographies. Carcinogenic mechanisms included oxidative stress, DNA damage, epigenetic modification, and interference with essential metal-dependent proteins and enzymes. Environmental and occupational exposures (industrial emissions, contaminated water, e-waste, fertilizers) are primary sources. Epidemiological evidence indicated that even low-level chronic exposure increases cancer risk. For instance, a 1 μg/L increase in urinary cadmium was associated with a 1.25-fold increase in lung cancer risk. |
| Essential metals (selenium, zinc, iron, manganese) show U-shaped dose–response | Essential metals at low, physiological concentrations exhibited protective, anti-cancer effects—acting as antioxidants, DNA repair cofactors, and supporting normal cellular function. Lower levels of these elements were more frequently observed in cancer patients than controls, indicating a possible preventive role. However, at high concentrations, these same elements can become toxic and contribute to cancer risk, underscoring the necessity for tight homeostatic regulation and careful monitoring. |
| Mechanistic insights into carcinogenicity and prevention | Toxic metals induce carcinogenesis via ROS generation, DNA adduct formation, disruption of methylation patterns, and endocrine disruption. Essential metals counteract some of these mechanisms by supporting antioxidant defenses and genomic stability. Substitution of essential metals by toxic ones (e.g., cadmium replacing zinc in enzymes) impairs cellular protective mechanisms. |
| Implications for monitoring, regulation, and certification | The findings support regular biological monitoring of both toxic and essential metals for populations at risk, and recommend stricter regulatory controls on environmental and occupational metal emissions. Certification programs must account for both acute and chronic exposures, and should recognize the dual nature of essential metals in their standards. |
| Gaps and recommendations | Most studies measured metals in only one biological matrix, potentially underrepresenting total body burden. Prospective cohort studies and multi-matrix biomonitoring are needed. There are gaps regarding less-studied metals and mechanisms. |
Key implications
This systematic review strongly supports integrating regular biomonitoring of both toxic and essential metals into heavy metal certification programs and public health policies. Regulatory frameworks should emphasize not just limiting toxic metal exposures but also maintaining essential metals within optimal ranges, as both deficiency and excess can influence cancer risk. Certification standards must incorporate multi-matrix testing and recognize the dual (dose-dependent) roles of essential elements. These approaches will promote early detection of hazardous exposures, support preventive interventions, and ultimately reduce the burden of metal-associated cancers.
Citation
Khoshakhlagh AH, Mohammadzadeh M, Gruszecka-Kosowska A. The preventive and carcinogenic effect of metals on cancer: a systematic review. BMC Public Health. 2024;24:2079. doi:10.1186/s12889-024-19585-5
Lead is a neurotoxic heavy metal with no safe exposure level. It contaminates food, consumer goods and drinking water, causing cognitive deficits, birth defects and cardiovascular disease. HMTC’s rigorous lead testing applies ALARA principles to protect infants and consumers and to prepare brands for tightening regulations.
Arsenic is a naturally occurring metalloid that ranks first on the ATSDR toxic substances list. Inorganic arsenic contaminates water, rice and consumer products, and exposure is linked to cardiovascular disease, cognitive deficits, low birth weight and cancer. HMTC’s stringent certification applies ALARA principles to protect vulnerable populations.
Cadmium is a persistent heavy metal that accumulates in kidneys and bones. Dietary sources include cereals, cocoa, shellfish and vegetables, while smokers and industrial workers receive higher exposures. Studies link cadmium to kidney dysfunction, bone fractures and cancer.
Nickel is a widely used transition metal found in alloys, batteries, and consumer products that also contaminates food and water. High exposure is linked to allergic contact dermatitis, organ toxicity, and developmental effects, with children often exceeding EFSA’s tolerable daily intake of 3 μg/kg bw. Emerging evidence shows nickel crosses the placenta, elevating risks of preterm birth and congenital heart defects, underscoring HMTC’s stricter limits to safeguard vulnerable populations.
