Pesticide Residues in Fish - Pesticides: Evaluation of Environmental Pollution - page 363

TABLE 13.2
Some Important Pesticides and the Nature of Impact

Pesticide Food Contaminated Impact

Organochlorines
Aldrin

Fish, milk, and fat Accumulation in human tissues

DDT Fish, milk, fat, and meat Accumulation in human tissues, low

toxicity, induction of liver enzymes

Lindane Fruits, vegetables, cereals,

milk, and fat

Accumulation in human tissues, toxic to
bone marrow, probably carcinogenic

Heptachlor Fish, milk, and fat Accumulation in human tissues, toxic to

bone marrow, probably carcinogenic

Organophosphorus
Malathion

Fruits Acute toxicity, neurotoxicity

Parathion Fruits and vegetables Acute toxicity, neurotoxicity

The excessive toxic residues of pesticides may accumulate in living organisms and cause
acute or chronic toxicity. These residues may affect the soil fertility and lower the drought
tolerance of the crops. The nature of pesticide impact through the toxic residues is indi-
cated in Table 13.2.
Generally, the type of pesticide used varies with geographical area. For example, humid
countries such as mid-European and the Scandinavian countries use mainly herbicides for
weed control problems, while Mediterranean countries use pesticides for agricultural fun-
gus control. Hence, different countries are facing different environmental problems. Overall,
during pesticide application, less than 5% of the pesticide applied can reach its intended
target because of losses from volatilization or washout, which further reinforces the need for
assessing the environmental impact of these compounds. To do this, it is important to know
their chemical properties, environmental fate, and impact on nontarget species in order to
protect wildlife and humans from pesticide risks.

13.2 Movement of Pesticides in Water
Pesticides enter the water from various sources such as runoff from agricultural lands, direct
deposition from spray operations, industrial effluents, spraying of cattle, dust, and rainfall.
In water, the residues and their degradation products are distributed between the truly dis-
solved form and those incorporated into sediments, benthic invertebrates, aquatic plants,
plankton, aquatic invertebrates, suspended detritus, and fish. Pesticides can leave aquatic
systems by volatilization or codistillation, as residues in fish, which are eaten by humans,
birds, and animals, or by degradation, burial in sediments, or overflow. Some of the pesti-
cides also end up in groundwater systems by leaching down through the soil. They easily
find their way from the soil surface to the atmosphere, due to their high vapor pressures, and
migrate with the air currents to distant areas and then later fall back to land as precipitation,
into streams, lakes, and even drinking water. That is why pollution by pesticides occurs
even in remote areas, where they have not been used for decades (Wania and Mackay 1996).
Figure 13.1 shows the dynamic movement of pesticides in the aquatic environment.
Investigation of the atmosphere over Europe indicated that the highest concentrations
of OCPs are observed over the region where OCPs were produced and used in high doses
and over urban areas. A higher concentration of lindane was found over the southern and