Metals are actually the natural component of the earth’s crust. Generally metals exist in their pure form e.g. lead or tin, or by proportional combination of metallic element with non-metallic element; e.g. sodium with oxygen forms sodium oxide. Metals (iron, sodium, potassium, selenium, magnesium, copper, calcium and zinc) are also required by the human body for the proper functioning and growth of the cellular processes. But these metals are required only in trace amounts by the human body; the excess quantities can contaminate the food, hence they are also known as metal contaminants.
The metals that are concerned with the harmful health effects are- lead (Pb), mercury (Hg), cadmium (Cd), arsenic (As) and tin (Sn). Lead and mercury are also referred to as heavy metals because of their high atomic weight. Moreover, individuals are also being exposed to metals at the workplace such as beryllium and nickel that causes lung injury. These metals become contaminants if present in food or drinking water at higher concentrations. Chromium and uranium are present as contaminants in food or water.
These metal contaminants enter into food due to industrial emissions, agricultural processes and environmental pollution; for example, the source of mercury, cadmium and lead is the burning of fossil fuels and industrial emissions. When these toxic metals make their presence in air, water and soil, these are taken up by plants and animals and in turn enter into the food chain for humans.
Some major metal contaminants in food:
Beverages and rice is the major source of inorganic arsenic, whereas organic arsenic is mainly found in seafood. Apple juice is the main concern now a day for highly metallic contamination.
Mercury mainly comes from marine animals such as fishes. Methyl mercury is found in fishes which is easily absorbed by the human intestinal system and enters the brain.
Cereals, grains and leafy vegetables are the source of cadmium. These sources do not provide much cadmium as is absorbed from fumes, dust and cigarettes.
Lead is used in almost every substance as pollutant and thus, is present in every food product.
Health risks due to metallic contaminants:
Excessive exposure to mercury leads to the damage of central nervous system and kidney. It mainly affects developing foetus and young children.
Exposure to lead for a short duration but higher concentration can cause paralysis, brain damage, anaemia and gastrointestinal problems; whereas the long-term exposure may cause reproductive damage and weak immune systems.
Exposure to excess cadmium results in the kidney damage, lung damage and skeletal changes.
Arsenic has been classified as the most toxic metal contaminants. It has been reported that arsenic has cancer-causing properties. It also causes nervous system disorders.
Tin is comparatively less toxic than the other metal contaminants. Tin is mainly found in canned food products. It leaches out into the food due to improper canning. It results in slight gastrointestinal irritation.
These metal contaminants have become a threat for healthy life. To reduce the adverse effects of these contaminants several regulatory agencies have prescribed the standards, such as-
European Commission Regulation (EC) No. 1881/20067 has established maximum levels of lead, cadmium, tin and mercury in various food products.
Australian New Zealand Food Standards Code-Standard 1.4.1 has established maximum levels of tolerance for cadmium, arsenic, mercury, tin and lead in various food items.
Food Business Operators (FBOs) need to comply the norms as discussed under FSS (Contaminants, Toxins & Residues) Regulations, 2011.