Heavy Metals and Food Safety

All living organisms are made up of macro elements viz. Carbon, Nitrogen, Phosphorous etc. as body constituents and micro elements viz. Iron, Cobalt and Zink which are constituents of body metabolism. Heavy metals are micro elements and are so called because of their high density and also biological importance in trace amounts; the term heaviness is also linked to their toxicity.

Non-essential heavy metals viz. lead, cadmium, mercury, etc. are highly toxic even at very low concentrations, they are non -biodegradable and cause severe toxic effects to living organisms.

Essential Heavy metals viz. vanadium, manganese, selenium, nickel and arsenic are less toxic at low concentrations and they act as coenzyme in biological process. For example hemoglobin and Myoglobin consist of Iron, Vitamin B12 consist of cobalt.

Arsenic and their compounds cause urinary bladder, liver, and lung cancers. Hexavalent chromium causes lung cancer and nickel and its compounds cause nasal cavity and lung cancers. All these elements cause cancers to human beings by the route of exposure is through inhalation and ingestion. The toxicity of mercury depends on its chemical composition. Methyl mercury is more toxic than inorganic mercury and is a cause of concern in sea food. Due to its toxic nature and historical incidents like Minamata.

Regarding the availability of various heavy metals in the earth’s crust is about 5%, among which iron occupies nearly 95%. Heavy metals enter food chain through various environmental sources such as air, water, and soil which mostly gets polluted due to increased industrial activities in recent years.

Food Safety and Standards (Contaminants, Toxins and Residues) Regulation, 2011, has specified maximum limits of metal contaminants in different food categories based on risk assessment studies. A robust food testing ecosystem has been established by FSSAI by strengthening primary food testing labs and referral food labs. Heavy metals are commonly analysed by equipments like AAS, ICP-OES, ICP-MS, etc which have capabilities of quantitatively analysing toxic heavy metals viz. lead, cadmium, chromium and, mercury at sub ppb level with high accuracy.