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?
The review article provides a comprehensive synthesis of the sources, environmental cycling, uptake, and biological impacts of heavy metals, with a particular focus on their effects on plants and human health. The article systematically discusses the geochemical, agricultural, and industrial origins of heavy metals such as cadmium (Cd), lead (Pb), copper (Cu), chromium (Cr), nickel (Ni), arsenic (As), zinc (Zn), iron (Fe), manganese (Mn), mercury (Hg), and cobalt (Co). It details how these metals, either as essential micronutrients or as non-essential toxicants, persist and accumulate in the environment. Special attention is given to the mechanisms of heavy metal uptake by plants, their physiological and biochemical responses, and the consequences for crop productivity and food safety. The review also outlines the toxicology of these metals in humans, including exposure pathways, accumulation patterns, and associated health risks, referencing both global and Indian safety standards.
Who was reviewed?
The review synthesizes findings from a wide array of primary research studies, global datasets, and governmental reports relevant to heavy metal contamination and toxicity. It covers experimental research on crop plants (such as rice, wheat, barley, maize, potato, and various vegetables), studies on environmental samples (soil, water, and sediments), and epidemiological data concerning human populations exposed to heavy metals. The referenced literature encompasses international research, including case studies from Japan, Indonesia, China, Greece, Albania, and Australia, as well as data from Indian regulatory agencies. The human health analysis draws from occupational, environmental, and dietary exposure assessments, integrating findings across disciplines of plant physiology, environmental toxicology, and public health.
Most important findings
| Critical Points | Details |
|---|---|
| Persistence and Sources of Heavy Metals | Heavy metals are persistent environmental pollutants, originating from both natural (rock weathering, volcanic activity) and anthropogenic sources (mining, smelting, agriculture, fossil fuel combustion, waste incineration, traffic). Industrial activities and the use of contaminated fertilizers and pesticides have led to dangerous localized accumulations in soils and crops in several regions worldwide. |
| Uptake and Accumulation in Plants | Plants absorb heavy metals primarily through their roots, with accumulation patterns determined by species, metal type, soil pH, and organic matter. While essential metals such as Cu, Zn, Fe, Mn, Mo, Ni, and Co are required in trace amounts, they become toxic at elevated levels. In contrast, non-essential metals like Cd, Pb, As, and Hg are harmful even at low concentrations. Although roots usually contain the highest metal levels, edible tissues (leaves, fruits, grains) also accumulate metals, posing significant food safety risks. |
| Effects on Plant Physiology and Yield | Excess heavy metals impair photosynthesis, nutrient uptake, enzyme activity, water balance, and membrane stability in plants. They trigger oxidative stress, disrupt antioxidant defenses, inhibit growth, and reduce biomass and yield. Metals such as Cd, Ni, and Cu hinder chlorophyll synthesis and photosynthetic efficiency, while Pb, Cd, Zn, Cr, and Ni induce Fe deficiency and water stress, collectively diminishing food quality and agricultural productivity. |
| Human Exposure and Toxicology | Excess heavy metals impair photosynthesis, nutrient uptake, enzyme activity, water balance, and membrane stability in plants. They trigger oxidative stress, disrupt antioxidant defenses, inhibit growth, and reduce biomass and yield. Metals such as Cd, Ni, and Cu hinder chlorophyll synthesis and photosynthetic efficiency, while Pb, Cd, Zn, Cr, and Ni induce Fe deficiency and water stress, collectively diminishing food quality and agricultural productivity. |
| Relevance to Heavy Metal Certification Programs | The article underscores the necessity of regular monitoring of heavy metal levels in soils, crops, and water, alongside establishing enforceable safety limits. It emphasizes understanding plant-specific accumulation patterns for accurate food chain risk assessment and provides reference ranges for uncontaminated soils and crops, human toxic limits, and Indian regulatory standards to support certification and compliance. |
Key implications
This review underscores the critical need for comprehensive monitoring and regulation of heavy metals in agriculture, food, and water. For certification programs like HTMC, it highlights the necessity of plant-specific risk assessments, adherence to national and international safety thresholds, and routine testing to ensure food safety and public health protection.
Citation
Sharma RK, Agrawal M. Biological effects of heavy metals: An overview. J Environ Biol. 2005;26(2 Suppl):301-313.
Heavy metals are high-density elements that accumulate in the body and environment, disrupting biological processes. Lead, cadmium, arsenic, mercury, nickel, tin, aluminum, and chromium are of greatest concern due to persistence, bioaccumulation, and health risks, making them central to the HMTC program’s safety standards.
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.
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.
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.
