We measure heavy metals in each and every thing and compared it with standard Guidelines. If the total concentration in water, soil or crop is high, straight away we declared that as hazardous and recommend treatment. For example Chromium is present in the environment in several forms. Chromium III (Cr III) and Chromium VI (Cr VI) are common forms. Cr III is comparatvely safe, while Cr VI is hazardous. We discuss this irrespectively of it's oxidation state. The same is the case with other heavy metals also. If look into the present status of research, every thing is hazardous.
Well,
If it is possible to extract any chemical element(metals) from the process of treatment, here the process will be profitable in two ways the first is productivity of metals and the second treating water. If the extraction process is not economically feasible, in this case your recommendation is in its place.
Regards
As the different forms of metals eg anorganic forms of Hg and organic ones, can be converted into each other, it is not so easy to have different limits for different forms.
In principle it can be done. But also remember, all elements are dangerous, just the dose determines whether there might be a potential health problem.
Sometimes in aquatic deposits a giant amounts of organic forms of metals are stored (like in large reservoirs or lakes). Actually no any reason or just a possibility to move them as they are immobilized. But it appear danger if environment change into acidic pH. As well we know that the most toxic are Hg and Cd. As well eg Fe presence can decrease a bad influence of previous two. So, the question isn't so simple!
WHO recommendations are presented for every parameters and conditions of water. We should follow it for treatment of water.
Yes I agree, coz of financial ego of our work or promoting some new products often on experiment
The problem is that heavy metals have cumulative effects in our body and have a long half life eg. Lead can be stored in bones for 20 years or more and released into blood affected by calcium intake. Also cadmium is classified as a carcinogen because it has a high affinity to accumulate in fatty tissue so it has a relation to cancer breast. So measurment of heavy metals in water, crops, air is very important to avoid health hazards
Most of the heavy metals are casinogenic, while others are ant-nutrients , treatment has to be done to prevent worsening of condition when it comes to human metabolism. This has to be based on experimental successful evidence.
These cannot be removed (I mean Heavy metals) and its carried out unnecessarily - However Bioremediation may be a process
Mercury in marine biota and human health
The toxicity of mercury has been known for centuries. Mad hatters in Victorian England got their names from the convulsions and loss of neuromuscular coordination symptomatic of chronic poisoning from the mercury used in the treatment of felt in hat manufacture. Inorganic mercury can be readily excreted and, while it is dangerous to those exposed to it occupationally. Organic mercury (methyl mercury) cannot be excreted easily and so may accumulate to toxic concentrations as a result of intermitted exposure over several years. It is a cumulative poison and since it can cross the barrier from blood vessels in the brain into the nervous tissue, it causes progressive and irreversible brain damage.
Human exposure to methyl mercury occurs only through the consumption of contaminated fish and seafood. This was brought to light by an outbreak of methyl mercury poisoning in the small Japanese coastal town of Minamata (Minamata disease). The only industry there was a factory that began producing vinyl chloride and acetaldehyde in 1952, both processes involving the use of mercury catalysts, large quantities of which were lost in washing the product and were discharged into the bay. The illness first appeared in 1953, and affected only fishermen and their family, but it was not diagnosed as metal poisoning derived from fish and seafood taken from Minamata Bay until 1956. In all 2000 cases were recognised; of these 43 died during the epidemic and over 700 of the survivors were left with severe permanent disabilities.
Cadmium and public health
Cadmium was claimed to be responsible for an outbreak of itai itai disease in a Japanese village on the Jintsu river. The painfull disease affected the bones and joints of old women, and resulted in a number of deaths. At the time, it was attributed to contamination of rice by cadmium in the effluent from a zinc smelter, but now it appears more likely to have been associated with malnutrition and vitamin deficiency.
In fact, there are no well-authenticated reports of cadmium contamination of sea food causing damage. High concentrations of cadmium (173 ppm) and zinc (57600 ppm) in oyster from the Derwent estuary in Tasmania caused nausea and vomiting in people who consumed them, but there were no further effects.
Copper in marine biota and public health
Bivalves growing in contaminated water have the capacity to accumulate copper. The concentration factor for oyster may be as high as 7500 and they may accumulate so much copper in their tissue systems that the flesh becomes green. This commonly happens to oysters in the River Fal and they have to be relaid in uncontaminated water for a year before they can be marketed.
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