Table 2.

Given weights for each criterion

Heavy Metal	W (%)	Influence on environment and health (http://www.lenntech.com/periodic/elements)
Pb	14	retained in the human organism and is carcinogenic; Lead accumulates in the bodies of water organisms and soil organisms. These will experience health effects from lead poisoning
Cd	16	accumulate in mussels, oysters, shrimps, lobsters and fish; retained in the human organism and is carcinogenic
Hg	16	Poisonous, not carcinogenic; toxic to the nervous systems; bioaccumulates in fish and shellfish
As	10	one of the most toxic elements; fish absorb arsenic; Toxic to plants
Cr	9	Damage to the nervous system, fatigue, irritability; Chromium(VI) is mainly toxic to organisms. It can alter genetic materials and cause cancer.
Mn	9	Influence on the nervous system Manganese can cause both toxicity and deficiency symptoms in plants, one out of three toxic essential trace elements
Co	5	accumulation in plants and animals may occur, possibly carcinogenic to humans(2B-IARC)
Ni	9	No accumulation in plants or animals. Evidence for carcinogenicity in humans (Group 1 and 2B by IARC)
Cu	4	it can accumulate in plants and animals. Harmful to animals and plants
Zn	9	relatively harmless. Only exposure to high doses has toxic effects, Zinc may also increase the acidity of waters., fish can accumulate zinc
Total	100