Introduction
In 2015, the World Health Organization (WHO) reported that one-quarter of all diseases are caused by environmental pollution. Heavy metals, in particular, pose a serious danger to human health.
What are Heavy Metals?
Metals with a density above 5g/cc are termed heavy metals. These include vanadium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, nobium, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, lanthan, hafnium, tantalum, wolfram (tungsten), rhenium, osmium, iridium, platinum, gold, mercury, gallium, indium, tin, thallium, lead and bismuth, and metalloids such as arsenic. Aluminum has a density of 2.7g/cc, so it is a light metal rather than a heavy metal. However, it is still important to treat aluminum toxicity.
Heavy Metals and Trace Elements
Some heavy metals that are present in very low concentrations are nevertheless important for life. These need to be part of our nutrition as they are required for important physiological and biochemical processes in living organisms. Copper, chromium, manganese, and zinc are examples of essential trace elements. However, if large amounts of trace elements are absorbed by the body, they can be toxic, leading to health problems in humans and animals.
Environmental Problems and Uptake into the Body
Even though heavy metals are naturally occurring elements, increasing pollution as a result of industrialization leads to an increasing toxic load for organisms. Heavy metals tend to accumulate in an organism as they are not broken down by normal chemical or biological processes. They, therefore, build up in the food chains. The toxicity of heavy metals depends on the way they are absorbed, the amount absorbed, the length of exposure, and the pathway into the body.
What Happens in the Body with Heavy Metal Toxicity?
Oxidative Stress
If the concentration of oxygen and nitrogen radicals is increased in the body and if this concentration is higher than the available antioxidant reserve, this is termed oxidative stress. Oxidative stress can be caused by emotional stress, infections, excessive solar radiation, smoking and alcohol consumption. Environmental poisons such as heavy metals lead to oxidative stress as well. The free radicals lead to mitochondrial dysfunction as well as to oxidization of fat in the bloodstream.
Silent Inflammation
If the concentration of free radicals increases, an intracellular inflammatory cascade is started due to stimulation of NFxB. NFxB starts inflammatory gene transcription, and this leads to the expression of pro-inflammatory cytokines (for example TNF alpha, Interleukin 1, 6 and 8). This leads to silent inflammation in the body, which is seen as a precursor of chronic diseases and autoimmune diseases.
Disturbance of Inter-cellular Calcium Homeostasis
Calcium is important for the biological regulation of neurotransmitters and hormones. A disturbed calcium homeostasis can block calcium channels and disturb the intracellular calcium concentration. It can affect muscular contraction and the expression of genes, and reduce enzymatic reactions as well as mitochondrial function.
Reduction of the Mitochondrial Membrane Electric Potential
The presence of cadmium, mercury, and lead can cause a reduction of the electrical potential of the mitochondrial membrane. This can inhibit cellular breathing and seriously reduce energy production as well as cellular apoptosis (programmed cell death).
Binding with Sulphur Groups and Enzymatic Inhibition
Lead, mercury, and arsenic are examples of metals which have an affinity to sulphur groups in the body such as the