The Toxic Effects of Heavy Metals
Heavy metals are commonly defined as those having a specific density of more than 5 g/cm3 such as lead, mercury, aluminum, arsenic, cadmium, nickel.
They are widely distributed in the earth’s crust, but present at very low concentrations in the body. Their presence in the atmosphere, soil, and water, even in traces, can cause serious problems to all organisms. Their main impact on human health is principally through occupational exposure, environmental contamination, and accumulation in food, mainly in vegetables grown on contaminated soil. Arsenic and cadmium, in addition to mercury and lead, have been identified as the most probable causes of heavy metal-related disease observed in primary care medicine . Exposure to one heavy metal contaminant is often accompanied by exposure to others.Request More Information
Heavy metals are toxic because they may have cumulative deleterious effects that can cause chronic degenerative changes, especially to the nervous system, liver, and kidneys.
It is, therefore, expected that joint interactions may occur in populations exposed to mixtures of metals.
Heavy metals are toxic because they may have cumulative deleterious effects that can cause chronic degenerative changes , especially to the nervous system, liver, and kidneys, and, in some cases, they also have teratogenic and carcinogenic effects . The mechanism of toxicity of some heavy metals still remains unknown, although enzymatic inhibition, impaired antioxidants metabolism, and oxidative stress may play a role. Heavy metals generate many of their adverse health effects through the formation of free radicals, resulting in DNA damage, lipid peroxidation, and depletion of protein sulfhydryls (e.g., glutathione).
Living in a Toxic World
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The importance of these metals as environmental health hazards is readily evident from the fact that they ranked in the top 10 on the current Agency for Toxic Substances and Disease Registry Priority List of Hazardous Substances . This listing is based on the toxicity of the substance and the potential for exposure from air, water, or soil contamination. As a result of the extensive use of these metals and their compounds in industry and consumer products, these agents have been widely disseminated in the environment. Because metals are not biodegradable, they can persist in the environment and produce a variety of adverse effects. Maximum levels for heavy metals in food have been set in consideration for possible chemical contaminants. Although contaminated food may contain environmental toxins, they are also a very important source of nutrients, for example omega 3 fatty acids, which may prevent chronic diseases like CVD. Thus, an attempt has been made to allow people to obtain the beneficial health effects of natural food without excessive exposure to possible contaminants. Evaluations of heavy metals toxicity have been made by several international bodies, like the Center of Disease Control (CDC), World Health Organization (WHO), Occupational Safety and Health Administration (WHO-OSHA), International Programme on Chemical Safety (WHO-IPCS), Joint FAO/WHO Expert Committee on Food Additives (JECFA), and International Agency for Research on Cancer (IARC) (Table 2). Some of them have been classified as carcinogens of category 1 (cadmium). Currently, there are insufficient data to set a threshold value above which heavy metals would exert their negative effects. Defining this threshold might be fraught with difficulties since it might well be population-dependent due to differences in the population intake of dietary antioxidants or differences in their genetic-based defenses.