Nickel (Ni) is widely
distributed in nature and is found in animals, plants, and soil; the
concentration of Ni in soil is approximately in the range of 4–80 ppm. Large
amount of Ni is released in the atmosphere due to natural as well as
anthropogenic activities including fossil fuel consumption, the industrial
production (mining, smelting, and refining), use, and disposal of nickel
compounds and alloys, and waste incineration.
In coastal sediments of the Arabian Sea along with the urban Karachi, the
maximum concentration of 74 mg/kg Ni was found at the Lyari location at the most
downstream part of the Malir River. In another study the second highest value of
56.46 mg/kg was found at Karachi Port Trust (KPT) Boat Building Area. In
vegetables, the concentrations of Ni 30.1 mg/kg was observed in vegetables
irrigated with sewage water in the suburbs of Peshawar city, KPK.
Human exposure to Ni results from Ni contaminated food ingestion, water,
inhalation, and percutaneous absorption [98, 128]. According to International
Agency for Research on Cancer evaluation, Ni compounds are carcinogenic to
humans. Ni metal and compounds cause cancers of the lung and of the nasal cavity
and para-nasal sinuses. High nickel concentrations in surface waters can
diminish the growth rates of algae. Microorganisms can also suffer from growth
decline due to the presence of nickel.