Interview HEAVY METAL POLLUTION IN AQUATIC
ENVIRONMENT Dr. S.K. Kulshrestha Dr. S.K Kulshrestha taught Zoology to undergraduate and
postgraduate students for 32 years. He retired as the Additional Director,
Higher Education with the Government of Madhya Pradesh. Dr. Kulshrestha has to
his credit over 60 research articles in established international journals. He
has supervised three research projects on environmental and fresh water ecology. Q. How does heavy metal pollution in water affect the
environment we live in? Continuous discharge of industrial, domestic and
agricultural wastes in rivers and lakes causes deposit of pollutants in
sediments. Such pollutants include heavy metals, which endanger public health
after being incorporated in food chain. Heavy metals cannot be destroyed through
biological degradation, as is the case with most organic pollutants. Incidence
of heavy metal accumulation in fish, oysters, mussels, sediments and other
components of aquatic ecosystems have been reported from all over the world. The
incidence of mercury poisoning through fish from Minimata Bay in Japan is
glaring example. Q.
What are the other ways apart from the waterways, in which heavy metal pollution
penetrates our environment? Metallic elements are an intrinsic component of the
environment. Their presence is considered unique in the sense that it is
difficult to remove them completely from the environment once they enter into
it. Toxic metals, to a large extent are dispersed in the environment through
industrial effluents; organic wastes refuse burning, transport and power
generation. They can be carried to places many miles away from the source by the
winds depending on their physical state such as in gaseous form or particulates.
Metallic pollutants are ultimately washed out of the air by rain onto land or
the surface of the waterways. Thus, air is also a route for the contamination of
the environment. The route of contamination is from Industry, transport, power
generation, refuse burning-metal emission, industrial effluents and municipal
waste to sea food, sediments, fish, and crops. There is no satisfactory way available at present, of
assessing the environmental hazards of metallic elements commonly discharged
into the water ways or directly into the sea for the lack of reliable figures on
the amount of each metal discharged on a global basis. In polluted coastal
waters there is possibility of concentration of toxic elements within the food
chain. This may seriously affect birds and mammals dependent on sea for their
food. Q. What is the Indian situation in Heavy Metal
Pollution? A preliminary survey of mercury in fish from the Bombay
and Thana environments revealed the presence of this highly toxic metal in
muscles, brain and bones in thirty species of fish from seven different sources.
In Kalu river sediments, soils and plants on the river bank showed fairly high
contents of mercury, lead, cadmium and copper. Milk of buffalos and cows of
villages near the river had high concentration of mercury. Several studies from water bodis near coastal Bombay,
Baroda, Chandigarh, Lucknow, Madras, Khetri complex, Raipur, Kanpur and River
Cauveri have shown incidence of heavy metal accumulation in living matter.
Recent studies on Gandhisagar reservoir, Chambal river near Nagda and Kota, Khan
river near Indore, Kshipra river near Ujjain and Lower lake of Bhopal have shown
accumulation of - metals such as zinc, manganese, copper, nickel, mercury and
lead in water, sediments and fishes. Excessive amounts of some heavy metals can be toxic
through direct action of the metal or through their inorganic salts or via
organic compounds from which the metal can become easily detached or introduced
into the cell. Exposure to different metals may occur in common circumstances,
particularly in industrial setting. Accidents in some environments can result in
acute, high level exposure. Some of the heavy metals are toxic to aquatic
organisms even at low concentration. The problem of heavy metal pollution in
water and aquatic organisms including fish needs continuous monitoring and
surveillance as these elements do not degrade and tend to biomagnify in man
through food chain. Q. How does heavy metal pollution affect our health? Generally health related adverse effects are observed
after chronic exposure to low doses. Some of the health effects due to heavy
metal toxicity may be like this: Arsenic causes Periferal
neuropathy,dermatitis,digestive disturbances; while Cadmium could cause
Respiratory disorders, kidney damage, anaemia and hypertension. Lead has been
known to cause Abdominal colic, anaemia, neuropathy and Manganese-Encephalopathy.
Chromium may cause Dermatitis, ulceration and gastrointestinal symptoms. Mercury
could lead to Kidney damage and neuropathy. Q. How much quantity of heavy metals in water is safe
for consumption? World Health Organization has developed guideline
values to define the quality of water that can be safely consumed by everyone
throughout their life times. According to these, 0.05 mg/litre of Arsenic, 0.005
mg/litre of Cadmium, 0.05 mg/litre Chromium, 0.05 mg/litre Lead, 0.001 mg/litre
Mercury, 0.01 mg/litre Selanium, 0.3 mg/litre Iron and 0.1 mg/litre Manganese The present status of the techniques
and programme for monitoring of heavy metal pollution in aquatic environment in
India may provide a baseline data on actual heavy metal pollution levels in many
Indian water bodies. This may form support to develop policies and measures to
improve our aquatic environment.