Wednesday, November 9, 2011

Sources of Hazardous Metals and Minerals


Environmental pollution from hazardous metals and minerals can arise from natural as well as anthropogenic sources. Natural sources are: seepage from rocks into water, volcanic activity, forest fires etc. Pollution also arises from partitioning of polluting elements (which are concentrated in clay minerals with high absorption capacities), between sedimentary rocks and their precursor sediments and water. (Sisir Sen, personal communication). With rapid industrialization and consumerist life style, anthropogenic sources of environmental pollution have increased. The pollution occurs both at the level of industrial production as well as end use of the products and run-off. These toxic elements enter the human body mostly through food and water and to a lesser extent through inhalation of polluted air, use of cosmetics, drugs, poor quality herbal formulations particularly ‘Ayurvedic/Sidha bhasamas’, (herbo-mineral preparations) and `Unani’ formulations, and even items like toys which have paints containing lead.

Heavy Metals and Aluminium

The industrial sources of heavy metals are in various fields. Chromium (Cr) is found in Mining, industrial coolants, chromium salts manufacturing and leather tanning. Lead (Pb) is released in industries like lead acid batteries, paints, E-waste, Smelting operations, coal- based thermal power plants, ceramics, bangle industry where as Mercury (Hg) is released from Chlor-alkali plants, thermal power plants, fluorescent lamps, hospital waste (damaged thermometers, barometers, sphygmomanometers), electrical appliances etc. Arsenic (As) is found in Geogenic or natural processes, smelting operations, thermal power plants, fuel burning. Copper (Cu) from

Mining, electroplating, smelting operations, Vanadium (Va) from Spent catalyst, sulphuric acid plant and Nickel (Ni) is found in Smelting operations, thermal power plants, battery industry.Cadmium (Cd) is released in Zinc smelting, waste batteries, e-waste, paint sludge, incinerations & fuel combustion, Molybdenum (Mo) in Spent catalyst and Zinc (ZN) is released in Smelting, electroplating.

Besides the industrial sources of lead, listed above, lead exposure also occurs through gasoline additives, food can solder, ceramic glazes, drinking water system, cosmetics, folk remedies, and battery/plastic recycling industry1. According to some work done at the DPSAR university, New Delhi many brands of cosmetics like talcum powder, lipsticks, shampoos, ‘kajal’ and hair colours contain heavy metals.

Ash dumps from thermal power plants, contain many polluting metals and complexes, which are carried to nearby water bodies and ground water. Volatile complexes such as those from Uranium, enter the atmosphere via chimney emissions. The U content of coal may be as low as 0.2 ppm, but considering the millions of tons of coal that is burnt it is an important pollutant. (Sisir Sen, personal communication).

In recent years the use of energy-saving CFL bulbs has gone up enormously. Thus, according to a recent report the production of CFL bulbs has increased from 19 million in 2002 to 500 million in 2010. Each bulb contains 3-12 mg of mercury. With no system to recover these bulbs and safe disposal, these can prove to be a major health hazard.

The major heavy metal contaminated sites in India, are Ranipet in Tamil Nadu, Kanpur, Uttar Pradesh, Talcher in Orissa and Vadodara in Gujarat for Chromium. Ratlam in Madhya Pradesh, Bandalamottu Mines in Andhra Pradesh, Vadodara in Gujarat and Korba in Chattisgarh are grossly polluted with Lead.

Kodaikanal, Tamil Nadu, Ganjam, Orissa and Singrauli, Madhya Pradesh are heavily polluted with Mercury. Tuticorin in Tamil Nadu, West Bengal and Ballia and other districts oh Uttar Pradesh is known for Arsenic pollution. Tuticorin, Tamil Nadu, Singbhum Mines of Jharkhand and Malanjkahnd, Madhya Pradesh have copper pollution. Data of CPCB show that Gujarat, Maharashtra and Andhra Pradesh contribute to 80% of hazardous waste (including heavy metals) in India.

Apart from industries, roadways and automobiles contribute substantially to the environmental burden of heavy metals since particulate matter in traffic emissions include heavy metals like lead, cadmium and arsenic. Exposure to traffic emissions, especially diesel exhaust may enhance asthma, allergen responsiveness and inflammation, leading to atherosclerotic vascular disease. Role of metal per se in this pathology is however not clear.2, 3. With the use of unleaded petrol, the burden of lead has decreased.

Aluminium pollution is associated with bauxite mining. With steady increase in demand for aluminium in India, its anthropogenic pressure is increasing. India ranks sixth in bauxite mining and 8th in aluminium production. The state of Orissa is worst affected.

Significant concentration of total and hexavalent chromium is observed in many wells located in the close vicinity of some of the industries in the industrial area of Ranipet, in Tamil Nadu. The sources are clusters of tanneries and other industries located in the area. The concentration of total chromium in these wells varies between 3.1 to 246 mg/L whereas the concentration of hexavalent chromium varies between 2.1 to 214 mg/L which far exceed the concentration of 0.05 mg/L prescribed under Indian Standards Specification for Drinking water quality. The ground water in these areas is therefore, severely contaminated with hexavalent chromium. Based on the detailed laboratory scale studies and techno-economic evaluation, an in-situ bioremediation (biotransformation) option was recommended by NEERI for implementation of bio-remediation of contaminated ground water in the critically polluted area’ [Ref. Tamil Nadu Pollution Control Board: ‘Revised

Village Khanpur in Rania area of Kanpur Dehat also revealed high levels of hexavalent chromium in groundwater ranging from 1.05 to 35.34 ppm.

Fluoride

Natural sources contribute to the bulk of environmental load of fluoride and arsenic. In India, 19 out of 35 states and Union territories have ground water highly contaminated with fluoride, with levels exceeding 1.0 mg/L and going up to 48mg/L4,5.

In states like Andhra Pradesh, Gujarat and Rajasthan, 70-100% districts contain high fluoride levels in food and water. Black rock salt (CaF2) commonly used as flavouring agent in road side, as well as processed and home-cooked foods contributes significantly to the ingestion of fluoride. It contains 157 ppm F--. Public awareness in this regard is needed. Dental products, anti-depressant and anti - cholesterol drugs used for long term treatment are important sources of fluoride. Industries using fluoride salts/hydrofluoric acid pollute the work environment and are a source for high ingestion/inhalation of fluoride dust and fumes by the Industrial workers.

Arsenic

Pockets in West Bengal, Bihar, UP, Assam and Chhatisgarh are the major states affected by arsenic contamination of water, West Bengal being by far the worst affected. Ground water of 9 out of 16 districts of West Bengal is heavily contaminated with arsenic, affecting 26 million people6. In a U.P. Jal Nigam/IITR survey of 66671 samples of water from hand pumps in 20 districts of U.P., 42% were found to contain > 10 ppb arsenic of which 2610 (4%) had > 50 ppb arsenic. Children ingest arsenic through pica behaviour.

While the high burden of environmental pollution in developed countries like India is due to high level of resource consumption, in developing countries like India it is due to outdated technologies, over exploitation of natural resources and weak environment regulations and enforcement.

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