Heavy Metals

Heavy metals are found everywhere in nature, and cannot be degraded or destroyed. While some metals like selenium, copper and zinc are essential to our diet at trace levels, any metal in our food is toxic at high levels. The most notorious heavy metal contaminants are mercury, lead, and cadmium. They tend to be dangerous because they bioaccumulate in animal tissues over time. Heavy metal contamination usually originates from polluted water supplies. Fish are most susceptible to heavy metal contamination. The most widely used analytical methods for determination of heavy metals in food are graphite furnace atomic absorption spectrometry (GFAAS) and Inductively Coupled Plasma (ICP).

Mercury enters our food supply through several sources; the first is from contaminated water supply inhabited by fish that are later consumed by humans. Mercury concentrations in fish significantly exceed the concentrations in the water. Meat can also contain mercury, after environmental pollution of fields that livestock use for grazing. Mercury is not commonly found in plant products, but it can enter human bodies through vegetables and other crops when sprays that contain mercury are applied in agriculture. Mercury exposure affects the central nervous system, brain functions, causes DNA and chromosomal damage, and causes reproductive problems. The most common route of human exposure to mercury is through environmental contamination of our food source.

Lead is one of four metals that have the most damaging effects on human health. It has a variety of applications - from use in pipes and paints, to its use in pesticides and a number of other applications. It can enter the human body through uptake of food (65%), water (20%) and air (15%). Many foodstuffs, including fruit, vegetables, meat, grains, seafood, soft drinks, and wine, contain lead. Cigarette smoke also contains small amounts of lead. Lead can enter (drinking) water through corrosion of pipes; this is more likely to happen when the water is slightly acidic - that is why public water treatment systems are now required to carry out pH-adjustments of drinking water. Lead causes many problems in the human body upon bioaccumulation such as disruption of blood synthesis, kidney damage, high blood pressure, miscarriage, low sperm count, etc.

Unlike mercury and lead, human exposure to Cadmium is most always through food. It often shows up paired with zinc, and is a by-product of zinc, lead and copper extraction methods. Cadmium exposure is compounded in the body by consuming foods rich with this element, such as mushrooms and shellfish. Additionally, Cadmium is present in cigarette smoke, which acts as a blood transport mechanism for cadmium into the lungs. It can also travel via the blood into the liver and then into the kidneys.