Prof ( Dr) R D Gupta
If one goes by the alarming levels of heavy metals like Hg, Pb, Cd, As and other toxic pesticides and chemicals found in food grains, vegetables, fruits and drinking water, an ancient epicurean slogan could well be twisted to: ” Eat, drink but do not be merry. Because tomorrow one will die”.
Now a days studies have been conducted both by the agricultural scientists and environmentalists, which have revealed that with the daily food and water intake, high amount of heavy metals, pesticides, pathogens and bacteria are ingested. And they, then pose increased risks to diseases like cancer, high blood pressure and mental impairment of children.
But unlike bacteria and pathogens, the heavy metals get accumulated in the human bodies and cannot be flushed out of the excretory system through urine and faeces. Neither these can be bombarded out with antibiotics (Anonymous, 2003).
Industrial effluents, domestic sewage, heaps of garbage dumping near water bodies and sediments brought about by the running water through streams and rivers, are the main sources of heavy metal pollution. These sources spew salts of heavy metals like Hg,Pb,Cd and As vis-vis Fe,Cu,Mn, Zn. These unwanted metals also find their way into various daily usable products viz; the batteries, lamps, thermometers (Hg), petrol additives, air, water (Pb),metal alloys, pigments for paints, cement, paper, rubber (Cr), and Ni and Cd rechargeable batteries.
Some heavy metals like Fe,Cu,MN and Zn are, however, essential both to animals, human beings and plants when are present in trace or minor amounts . But when these essential elements or metals are present in higher concentration also become toxic. These days the pollution of food and water by these heavy metals is a matter of great concern, which is described briefly here under:
a). Lead poisoning: Tests carried out by Bhaba Atomic Research Centre revealed that 50% of Mumbai’s population contained toxic level of Pb. In seven cities of India like Mumbai, Delhi, Chenna, Hyderabad, Vellore, Kolkata and Bangalore, more than 50% of the Children below 12 years of age had blood level the safe limit.
Lead to bloodlessness, convulsions liver and kidney problems and retardation in metabolic activities of the body. It also produces anaemia, abdominal pain, and hypertension. Hampers the growth of children. The red blood cells lose their hemoglobin binding capacity with oxygen.
Various lakes of Jammu and Kashmir, and Khol and Dedani nallahs in Doda , have been found to possess Pb in more concentration than the permissible limit.
b). Mercury poisoning : There are many reports about the pollution of water bodies with Hg. One such area is 20 Km stretch close to new Mumbai in Maharashtra. There are 1200 Industrial units in the Thane-Balapur Industrial area, which are polluting the sediments of the river Ulhas. It has registered high levels of Hg and As and is a potential sources disaster. Deposits of Hg in the human bodies lead to headache, pain in some parts of body, intestinal problems like diarrhea, blood malfunctioning.
c). Cadmium poisoning : High concentration of Cd poisoning is the cause of the itai-itai disease which gives severe distress to the victum. It is very toxic even in low concentration as it accumulates in the human kidney and liver. Its high level in human cells/ tissues leads to suppression of growth, bone deformation, blood lessness, rental problems, It also causes anaemia and atrophy in some part of reproductive system and liver injuries.
The concentration of Cd in sewage sludges of various basins of Dal lake has been reported beyond the permissible limits ( Goverdhan,1989).
d). Chromium poisoning: The soils in the vicinity of leather tanneries get polluted through direct disposal of Cr rich effluents to the agriculture lands. It then goes from agriculture lands to various aquatic ecosystems and finally to the animal / human bodies. The Cr is said to be carcinogenic agent and also leads to some kidney disorders.
e). Fluorine poisoning: In the world,200 million people from 25 nations have great health risks, with high fluorine in the drinking water. In India, almost 60-65 million people drink fluorine contaminated groundwater and the number affected by fluorosis is estimated at 2.5 to 3.0 millions in many states especially Andhra Pradesh, Bihar, Gujarat, Madhya Pradesh , Punjab, Rajasthan, Tamil Nadu and Uttar Pradesh ( Kumar et al 2001).
Pesticide residues on vegetables: Pesticides, though quite effective in pest control, are toxic and leave residues which become harmful for humans and animals. Excessive pesticide residue on vegetable may threaten human. It also acts as non-tariff barrier in vegetable exports as countries may ban or refuse to accept the shipments of commodities, having unacceptable levels of pesticides residue. It may also take place in other food stuffs.
Checking the heavy metal pollution and pesticidal residues:
i). Plantation: To check the inflow of the weathered sediments into the various aquatic ecosystem during soil erosion, plantation of tress is the most important control measure. This requires more attention in case of mining / quarrying degraded areas and deforested catchments. While planting the trees emphasis should be given to grow the local species.
ii). Phytoremediation: Plants belonging to Brassicaceae and Asteraceae are capable of withstanding high levels of heavy metals in their aerial parts. Amaranthus and Cannabis spp. are the best examples in this, respect. Therefore such plant species may be grown in heavy metal polluted areas.
iii). Use of Rhizobium Culture : Rhizobium culture has proved useful to deal with Mn-ore waste dumps for restoring metal free environ and soil productivity.
iv). Chemical remedies : Several chemical compounds like gypsum, lime, zinc, phosphorus have been found effective to reduce toxicity of heavy metal pollution.
Peeling: The outer leaves of vegetables often contain residues of pesticides applied during the growing season. Therefore, peeling or trimming of the vegetables or fruits must be resorted to lessen the pasticides residues.
Washing: The peeled vegetable are required to wash atleast twice with cold water and once with warm water to make the vegetable free from pesticide residues. It is also desirable that all the fruits be washed thoroughly prior to their consuming.
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