PESTICIDES USES AND ABUSES
A pesticide is a poison used to kill an insect, an animal, or a plant, which is considered as a pest.
A. Desirable characteristics in a pesticide:
• Only a small amount is needed to kill targeted pests( specific),
• Has low toxicity to non-target species,
• Has a lifetime long enough to kill target Pests( does not persist in the environment),
• Degrade into benign products,
• Does not bio-accumulate,
• Does not run off with water from application site,
•Pests are slow to develop resistance to it.
B. Benefits of pesticides:
1. Improving productivity
2. Protection of crop losses/ yield reduction
3. Vector disesese control
4. Quality of food: In countries of the first world, it has been observed that a diet containing fresh fruit and vegetables far outweigh potential risks from eating very low residues of pesticides in crops
5. Other areas – transport, sport complex, building: The transport sector makes extensive use of pesticides, particularly herbicides. Herbicides and insecticides are used to maintain the turf on sports pitches, cricket grounds and golf courses. Insecticides protect buildings and other wooden structures from damage by termites and wood boring insects .
C. Hazards of pesticides:
1. Direct impact on human: Certain environmental chemicals, including pesticides termed as endocrine disruptors, are known to elicit their adverse effects by mimicking or antagonizing natural hormones in the body and it has been postulated that their long-term, low-dose exposure is increasingly linked to human health effects such as immune suppression, hormone disruption, diminished intelligence, reproductive abnormalities and cancer.
2. Impact through food commodities: cucumbers, apples, tomatoes, lettuce, strawberries, mandarins, pears, bananas,beans, and potatoes are many of the food commodities with extensive pesticides use such as acephate, carbendazin, chlorothalonil, chlopyriphos, DDT, diazinon, endosulfan, methamidophos, iprodione, metalaxyl, methidathion, thiabendazole, triazophos.
3. Impact on environment: Pesticides can contaminate soil, water, turf, and other vegetation. In addition to killing insects or weeds, pesticides can be toxic to a host of other organisms including birds, fish, beneficial insects, and non-target plants.
Insecticides are generally the most acutely toxic class of pesticides, but herbicides can also pose risks to non-target organisms.
4. Surface water contamination: Pesticides can reach surface water through runoff from treated plants and soil. Contamination of water by pesticides is widespread.
5. Ground water contamination: Groundwater pollution due to pesticides is a worldwide problem. According to the USGS, at least 143 different pesticides and 21 transformation products have been found in ground water, including pesticides from every major chemical class. Once ground water is polluted with toxic chemicals, it may take many years for the contamination to dissipate or be cleaned up. Cleanup may also be very costly and complex, if not impossible.
6. Soil Contamination: Uncontrolled application of pesticides can contaminate soil and may kill other non-target organisms. Pesticides can damage soil biomass and microorganism such as bacteria, fungi, and earthworms. Microbial biomass is a labile component of soil organic matter and has an important role in soil nutrient element cycle.
7.Contamination of air, soil, and non-target vegetation: Pesticide sprays can directly hit non-target vegetation, or can drift or volatilize from the treated area and contaminate air, soil, and non-target plants.
8. Non-target organisms: Pesticides are found as common contaminants in soil, air, water and on non-target organisms in our urban landscapes. Once there, they can harm plants and animals ranging from beneficial soil microorganisms and insects, non-target plants, fish, birds, and other wildlife. Eg: Exposure of eggs to 2,4-D reduced successful hatching of chicken eggs (Duffard et al., 1981) and caused feminisation or sterility in pheasant chicks (Lutz et al., 1972).