One can deduce so far that heavy metals are commonly found in our environment yet are found in concentrations to small to cause adverse effects to public health. That is until commercialisation of resources of the local environment takes place. In the case of Mercury, mercury poisoning was a little occurring problem until fish become exposed to the toxic substance through industrial waste. The USA has large problems with mercury causing neurological damage and infertility, it was only decades after the Minimata disaster that many authorities woke to the grave realisation that mercury had dire health, and ultimately economic, consequences.
On a similar scale to Minimata, Bangladesh, predominantly the Ganges delta, has suffered mass arsenic poisoning with many people becoming critically ill and unable to support families. Both arsenic and mercury are responsible for mass poisoning from natural sources. Arsenic was the result of years of deposition in the Ganges aquifer during the last glaciation and was not correctly checked before being cleared for domestic water use. Mercury, on the other hand, was responsible for an early mass extinction of early species during the evolution of our current atmosphere causing the evolution of toxic metal defences in the biology of modern day animals.
The next metal that will be discussed is Cadmium, a naturally occurring heavy metal that is commonly found. Levels of dangerous cadmium have started to appear in the environment, like mercury, since industrialisation and its main sources are sewage, fertilisers and other agricultural products. Similar to mercury, cadmium's most effective poisoning method is via the food chain, this is because plants generally have a much higher cadmium tolerance level than animals and as such create cadmium reserves. The next post will discuss the work by Satarug et al. (2002) where cadmium was studied in the non-occupationally exposed population.
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