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A Pesticide is any substance or mixture of substance used to kill, repel, or control certain forms of plant or animal life that are considered to be pests. Though often misunderstood or referred to as insecticide,pesticides cover a wide range of substances including:
1. Herbicide for controlling weed or unwanted vegetation
2. Insecticides for controlling a wide variety on of insects
3. Fungicides used to prevents the growth of molds and fungi
4. Disinfectants used for preventing the spread of bacteria
5. Rodenticides used for controlling mice and rat
What are Pests?
Pests are living organisms which are present where they are not desired or that cause damage to crops or humans or other animals. Example include: insects, unwanted plants (weeds), fungi, bacteria, mice and other animals.
HISTORY OF PESTICIDE USE
The pest outbreaks in agriculture have caused severe economic and human losses over time. Potato blight epidemic in Ireland during 1845 and 1846 caused the death of more than a million people. ‘Downey’ and ‘Powdery’ mildew in 1872 devastated the French wine industry.
Despite the advancement in agricultural sciences, insect pests, diseases, weeds and birds cause specific crop losses varying between 10 and 90% and on average 35 – 40% of all potential food and fiber crops are lost to pests.
The discovery of Bordeaux mixture in 1882 and Paris Green in 1870,proved successful against grape disease and potato beetle, respectively and heralded the first documented use of pesticides. Sulphuric acid was used as a selective herbicide in cereals in France in 1931 and in the United Kingdom the same practice was adopted in 1932.
Developments in the use of pesticides
Tobacco juice (nicotine) was one of the first insecticides of the modern era, while the use of arsenic and sulphur can be traced back to Antiquity. However, chemical control only developed in the 19th century, with the use of products of vegetable origin (rotenone and pyrethrum) or mineral origin (copper and arsenic). In 1939, P. Muller discovered the properties of DDT (dichlorodiphenyltrichloroethane), which was marketed in 1943, started the era of synthetic pesticides.
In Europe and in North America, herbicides represent 70 to 80% of the products used (in particular because of the strong increase in maize crops) whereas in the tropics, 50% of products applied are insecticides. Crop diversification, bringing about improved standards of living in some countries, also changes this balance, and China has also converted the equivalent of the surface of England from paddy fields to market garden crops, resulting in the diversification of products used.
Global pesticide use (source: www.epa.gov)
Though pesticides are not yield-enhancing chemicals like fertilizers, they reduce the damage caused by insect pests, diseases and weeds. It is estimated that each dollar invested in pesticide control gives a benefit of approximately $4 in crop saved, and overall losses to pest would increase by 10% if no pesticides were used at all and specific crop losses would range from zero to nearly 100%
Effect of Pesticide usage
The success of pesticides in reducing damage on crops has become a major source of problems associated with pesticide use. Growers have been so impressed by the spectacular initial reduction of damage on crops and the gain in production per hectare that, they have tried to use increasing amounts of product, thus wasting their resources while contaminating the underground water and the soil. Other problems include spraying apparatus which is often badly maintained, presence of chemical substances damaging to health, safety advice which can be difficult for farmers to understand or are simply ignored. This has resulted in the following consequences;
· Environmental pollution from the soil and water.
· Serious health issues for both farmers and consumers because of incorrect use;
Environmental effects of pesticide usage
Pesticides are toxic chemicals designed to be deliberately released into the environment. Although each pesticide is meant to kill a certain pest, a very large percentage of pesticides reach a destination other than their target. They enter the air, water, sediments, and even end up in our food. Pesticides easily contaminate the air, soil and water.
Soil contamination: Many of the chemicals used in pesticides are persistent soil contaminants, whose impact may endure for decades and adversely affect soil conservation. Pesticides do not necessarily distinguish between “pests” and other living things. The use of pesticides decreases the general biodiversity in the soil. Pesticides can kill beneficial soil bacteria, earthworms, snails, frogs, birds, and other valuable species. Soil microorganisms play a key role in maintenance of soil structure, transformation and mineralization of organic matter, making nutrients available for plants.The application of pesticides (especially long-term) can cause significant irreversible changes in their population. Inhibition of species, which provide key process, can have a significant impact on function of whole terrestrial ecosystem.
Water contamination: Pesticides can get into water via drift during pesticide spraying, by runoff from treated area, leaching through the soil. In some cases pesticides can be applied directly onto water surface e.g. for control of mosquitoes. Water contamination depends mainly on nature of pesticides, soil properties, weather conditions, landscape and also on the distance from an application site to a water source. Rapid transport to groundwater may be caused by heavy rainfall shortly after application of the pesticide to wet soils.
Fish and other aquatic life may be harmed by pesticide-contaminated water. Application of herbicides to bodies of water can cause plants to die, diminishing the water's oxygen and suffocating the fish. This can lead to reduced populations, decreased immunity to disease, etc.
Air contamination: During and after the application of a pesticide either in powdery form or liquid form, a substantial fraction of the dosage applied may enter the atmosphere in the gas phase and as small droplets and may be transported over shorter and longer distances
Residues arising from these deposition following volatilization, spray drift, air movement can lead to environmental contaminant.
Hazardous effects of pesticide and protective measures
Although using pesticides results in better food supply for the consumer, the inappropriate and/or excessive use of pesticides does however lead to various undesirable side effects, particularly on the environment and human health.
The contamination of the environment and the absorption of residues of pesticides contained in the food and drinking water clearly have harmful repercussions on health. These undesirable effects have led several international organisations, such as the FAO (Food and Agricultural Organisation) (International Code of Conduct FAO, Rome 1985), the OECD (Organisation for Economic Co-operation & Development), the UNEP (United Nations Environment Program) or the EU to take action with governments to ensure that they review their regulations on production, purchasing, marketing and the use of pesticides.
Pesticides use has expanded dramatically since the discovery of DDT in 1939 and are designed to kill specific pests and also has shown tremendous effects on humans.The World Health Organization estimates that there are 3 million cases of pesticide poisoning each year and up to 220,000 deaths, primarily in developing countries. The application of pesticides is often not very precise, and unintended exposures usually results. Humans are also vulnerable to the harmful effects of these pesticides exposure. Even very low levels of exposure during development may have adverse health effects in children.
Human poisonings and their related illnesses are clearly the highest price paid for pesticide use. Pesticide exposure can cause a wide range of acute and chronic health effects.
· Contact with some pesticides will harm your skin. These pesticides may cause your skin to itch, blister, crack, or change color.
· Your entire respiratory system can be burned by some pesticides, making it difficult to breathe.
· Some pesticides that get into your eyes can cause temporary or permanent blindness or severe irritation
Chronic effects: These are illnesses or injuries that appear a long time, usually several years, after exposure to a pesticide. Some delayed effects that are suspected to result from pesticides' chronic toxicity include:
▪ Production of tumors (oncogenic effect),
▪ Production of malignancy or cancer (carcinogenic effect), or
▪ Changes in the genes or chromosomes (mutagenic effect)
Some people are sensitive to certain pesticides. These allergic effects include:
· Systemic effects, such as asthma or even life-threatening shock,
· Skin irritation, such as rash, blisters,
· Open sores and eye nose irritation, such as itchy, watery eyes
Other possible health effects include hypersensitivity; pesticide exposure also leads to hormone disruption, and problems with reproduction and fetal development.
Children are at greater risk from exposure to pesticides because of their small size: relative to their size, children eat, drink, and breathe more than adults. Their bodies and organs are growing rapidly, which also makes them more susceptible; in fact, children may be exposed to pesticides even while in the womb.
The development of threshold treatments for better respect of the environment and for better health security aim at reduction of the use of pesticides and risks associated with.
Maximum Residue Limit (MRL)
The realization that pesticides while useful for efficient food production can be extremely dangerous has resulted in the setting up of worldwide standards specifying the maximum levels of residue to be found on crops prior to harvest and sale.
Maximum Residue Levels (MRLs) as they are popularly called are part of Good Agricultural Practices(G.A.P) and are meant to reflect the highest amount of pesticide residue allowed in food substance treated with correctly applied pesticides. MRLs are primarily trading standards, which are applied to help ensure that residue levels do not pose unacceptable risks for consumers of such food.
National authorities such as Standards Organisation of Nigeria (SON) and NAFDAC are responsible for setting the standard, controls and enforcement of MRLs for each country. These standards are harmonized into the Codex Alimentarius (Codex Alimentarius Commission) which was established by FAO and WHO in 1963. The commission ensures coordination of all food standards work undertaken by international governmental and non-governmental organizations.
Farmers, importers, distributors and retailers are responsible for ensuring marketed food complies with all statutory MRLs set.
How to avoid pesticide contamination
Pesticide use in general can be made safer for the environment and human health risks minimized by:
1. Training users and advisers to high standards, backed-up by certification in Pesticide use.
2. Using the right Pesticide Protective Equipment (PPE) such as nose mask, chemical resistant glove, protective suits, boots, safety goggles during mixing and field applications.
3. Using alternative methods of pest control (although these too can involve environmental risks), or combining these with chemical methods.
4. Where two or more pesticides may be equally effective, selecting the one that is likely to involve least environmental risk.
5. Working to a crop management plan based on proper risk assessments and cautious decisions.
6. Using the most appropriate application technique and regularly checking and calibrating equipment.
7. Disposing of containers and unused products correctly.
There are arguments for the use of pesticides and also for not using them. The fact still remains that pesticides are cheaper and faster in dealing with potentially destructive pests. We advocate that if you must use them ensure that you use them properly and in accordance with the rules and specifications. In fact there are various standards that have been set to ensure that farmers, consumers and the environment are adequately protected. One of such is a list of approved pesticides developed by NAFDAC.
As part of our objective to ensure that Nigerian farmers have the right information at their disposal, SENCE Agric in partnership with COLEACP (Europe-Africa-Caribbean-Pacific Liaison Committee) – A European based Organization promoting Food Safety and Good Agricultural practices (GAP) in Africa, Caribbean and pacific ACP countries – provides extensive training services on the following:
1. Safe use of pesticides (Spraying technique, how to avoid environmental pollution etc.)
2. Pesticide application in compliance with Maximum residue limit (MRL) in food.
3. Control of hazard associated with the use of pesticides.
4. Appropriate use of pesticides and alternatives available.
5. Good Agricultural Practices (G.A.P)
6. Maintaining good hygiene principles on the farm and pack house
7. Certification process in compliance with Export standards acceptable globally
For more information,
Contact SENCE Agric on
Anonymous. A practical Guide to Sulphoric Acid Spraying in Agriculture; National Sulphuric Acid Association Ltd U.K. undated
 Courtesy: http://pip.coleacp.org
Pimentel, D.; Acquay.H.; Biltonen, M.; Rice.P Silva.M et.al.Environment and Economic costs of pesticide use.BioSccience 1992, 42 (10), 750 -760.
 U.S. Environmental Protection Agency (2007), Sources of common contaminants and their health effects. Epa.gov. Retrieved on 2007-10-10.
 Gath, B., Jaeschke, W., Kubiak, R., Ricker, R., Schmider, F. and Zietz, E.(1993). Depositionsmonitoring von Pflanzenschutzmitteln: Teil 2 SüddeutscherRaum. Nachrichtenbl.DeutscherPflschtzd., 45, 134-143.
 Courtesy: Canadian Centre for Occupational Health and Safety