PESTICIDES AND THEIR EFFECTS
Strict vigil under expert guidance needed while using pesticides
By Dr.S.M.Alam and M.A. Khan
Mar 01 - 07, 1999
The pesticides have been used to protect food stuffs, livestock and health of mankind. The development of resistance in insects population against pesticides poses a severe threat to agricultural productivity of the country. The tremendous advancements in scientific chemistry and other biochemical fields have led to the manufacture of various pesticides with quite different mode of actions and properties. Men and animals are exposed to the uptake of pesticides from air and water and through other sources. Pesticides include insecticides, which deal with the extermination of insects, herbicides which is used for extermination of weeds, and fungicides for the control of fungi. It is a general accepted view that pesticides fall under four chemical groups. These are: (i) organochlorines (ii) organophosphates (iii) carbonates and (iv) pyrothroides.
In Pakistan, nearly 50 per cent of the pesticides used are either extremely hazardous or highly hazardous. Pesticides residue cause dermal and nervous systems toxicity. Waters containing pesticides, when used for drinking purposes, can lead to harmful effects, ranging from mild headache and skin allergy to cancer of internal organ. The adverse health effects depend upon the degree of toxicity of the pesticide, amount of water intake each day and the individual health. Adverse effects on human health can also be caused by impurities in the pesticides.
The threat of pesticide resistance to agricultural productivity is accelerating as the commercial development of new pesticides has been slowed down. It is estimated that for developing a pesticide, over 15,000 chemicals are screened and about 8 to 10 years of research and development are taken. During 1994, total pesticides sale in the world was worth $27,285 million. At present in Pakistan, the major pest control strategy is the use of chemicals, some of which belong to WHO category A and B, extremely hazardous. Since 1980, there is almost a linear increase in the use of pesticides. At present nearly, 86 pesticide companies are registered with the agriculture ministry. During 1994, the pesticides consumption was 23,212 metric tons. Widespread use of pesticides has resulted in their presence and persistence in various crops and their occurrence in food and products. About 30 per cent of potential crop production in the world is lost every year due to bad weather, pests and diseases. The losses may increase further if, the case of pesticides is abandoned.
The use of pesticides has been increased manifold in recent years. A variety of pesticide chemicals are available in the market for the control of insect pests, attacking vegetable and other crops in Pakistan. As each crop is susceptible to attack by more than one pest. It is usually treated with several pesticides before harvest. It is estimated that 80% of the total pesticides consumed in Pakistan are used for the protection of cotton crop, from July to October of the growing period.
The historical analysis of pest occurrence in Pakistan indicates that the current system of pest management, which relies mainly on the use of pesticides (over 6 spray/season) is responsible for the change in cotton pest complex and thus can be concluded that it is a never ending practice.
The pests, diseases and weeds cause heavy losses to crops. Some experts estimate such losses to be as high as 20 per cent and even more. The indiscriminate use of pesticides has to be discouraged and sale of adulterated ones be strictly banned. Quality control of chemicals, being used against pests and diseases, needs to be strictly enforced so that their effectiveness is not impaired.
Furthermore, instead of importing chemicals, indigenous production (such as use of neem leaves etc) be encouraged by providing facility, so that they are easily available to farmers at lower prices. It is also the duty of every citizen and concerned agency of pesticides to ensure distribution and sale of their products honestly to the users for agricultural crops.