The Use of Pesticide - Term Paper Example

Pesticide Pollution A pesticide can be defined as any chemical, biological, antimicrobial, disinfecting substance which is used against pests. A pesticide is used to prevent, destroy and repel the pests. Pests include anything from the insect, plant pathogens, mammals to microorganisms that spread diseases. Pesticide covers a broad range of products that are used to control pests. Pesticides include insecticides, herbicides used for weeding, fungicides which kills fungi, molluscicides, a chemical used for plant growth, repellents, rodenticides etc. Pesticides are obtained naturally also, such as pyrethrum which is obtained from chrysanthemums. Pesticides are used widely for domestic purposes such as rat killers, mosquito and ant repellents etc. In agricultural sector, pesticide became a main aspect for improving yields. They are used to control insects, weeds, fungal diseases in plants. Pesticides are also used to kill rats, flies which destroy crops and to prevent food from being contaminated. The pesticide era started before 2000 B.C. Around 4500 years ago, ancient Sumerians used elemental sulphur, Compounds of Arsenic, Lead, and Mercury was applied in 15th century. The tobacco product, nicotine sulphate was used in 17th century. Natural products such as pyrethrum and rotenone are obtained from chrysanthemums and vegetables respectively. In 1890s, Lead Arsenate and compounds of di-nitro phenol were used. The 20th century saw introduction of many pesticides such as Arsenic compounds, sulphur products, cyanides and nicotine compounds. In 1932, ethylene was first used as plant growth regulator to promote flowering in pineapples. In 1939, DDT was discovered. DDT was a powerful insecticide. During 1960, herbicides based on lead and nitrogen, carboxylic acids such as di-chloro phenoxy acetic acid etc. were used. The 20th century saw the use of large amount of pesticides. The developing countries are still using increased amount of pesticides for pest control and crop yield. Every advantage has a disadvantage associated with it. Use of pesticides for crop yield and killing of pests in turn affected the environment, wild life and humans. The use of pesticide increased enormously in 20th century. It was discovered traces of DDT was found in many fish-eating birds and it hindered their reproduction. This was the finding which shocked the world because it hindered bio-diversity. Even though DDT was banned in some nations, it is still used in developing countries as an insecticide. The uses of pesticides cause problems such as DNA damage to humans and cause cancer. “The European Parliament has voted to tighten rules on pesticide use and ban at least 22 chemicals deemed harmful to human health.” (BBC News, 13 January 2009) 13 Jann 2009. The Government framed rules according to which the usage of pesticide in public places especially schools would be either banned or restricted, Aerial crop-spraying over a large area was banned. The goal of European Union was to reduce the usage of agricultural toxic pesticides by half by 2013. Application of Pesticides: Pesticides come in different packages such as bait, capsule suspensions, dustable powder, emulsifiable concentrate, emulsions, granules, suspension concentrates, water dispersible granules and tablets, ultra-low-volume liquid, wettable powders and water-dispersible powders. The pesticides are applied to the target sites through different methods. According to (WHO 2006, pg5-8), hand-operated compression sprayer is designed to apply to breeding sites and onto surfaces where the pest will come in contact. Power operated mist blowers come as portable knapsack mist blowers which are powered by a two-stroke engine. It produces high-velocity air stream. Low volume of insecticide can be blown as a fine mist. The insecticides are either used in technical grade form or diluted in oil or water and are used in aerosol generators. Cold fogging instrument is used. If the volume of pesticides sprayed per unit area is less, large areas can be covered at a faster rate. Power operated thermal foggers are used in application of pesticides in certain cases. Emergency vector control programmes involves the use of aerial spraying equipment for the application of chemicals. Dusters are used to apply dust to control insects such as lice, rodent fleas etc. Mode of action: Mode of action of pesticides refers to the way the chemical attacks the biological process of the pests. Mode of action of chemicals varies with the cells they attack. To understand how pesticides work (their mode of action), ‘..it is necessary to understand how the pests’ targeted systems normally function.’ (Brown 2006) It is necessary to understand the mode of action to prevent resistance of pesticides. Some herbicides used on weeds attack the chloroplasts. Pyrethroid and neonicotinoid attack nerve cells. Organochlorine insecticides affect the chloride channel and thus affect the nerve cells of the insects. Insecticides known as chitin Synthesis Inhibitors (CSI) block the production of chitin in insects. An insect poisoned with CSI cannot reach the adult stage and hence dies. Organophosphate and carbamates are insecticides known as cholinesterase inhibitors. When an insect is poisoned, the cholinesterase becomes unavailable and the neurotransmitter continues to send electrical charge which causes overstimulation of the nervous system and hence causes its death. Insect growth regulators (IGR) attack the endocrine system which is the hormone producer needed for its growth. Insects poisoned with IGR cannot molt or reproduce and hence die. Azadirachtin is a feeding deterrent and a growth regulator. It affects the normal feeding behavior of insects and related anthropoids. Tebufenozide affects ecdysone; the hormone needed for metamorphosis and hence affects the molting in insects. Cryolite is an inorganic insecticide and a nonspecific feeding blocker. Some insecticides stop or disrupt energy production. When the insect is poisoned, it cannot produce energy from food and eventually dies. Causes of pesticide pollution: Pesticide causes water pollution by running off. The chemicals get washed down to nearby water sources by rain. Pesticides affect the soil by producing a knock-on effect upon water retention. They kill the good insects. Soil fertility is affected as active organisms needed for fertility is destroyed by pesticides. Pesticides applied to soil affect the vegetables and fruits which are found to possess the pesticide residues. Pesticides affect the eco system by killing pollinators such as bees and hoverflies. With missing of bees, pollination will be affected and hence the production of fruits and grains. Atrazine, weed killer, is found to feminize the frogs. In humans, exposure to pesticides is found to cause Parkinson’s disease and cancer. Fate and behavior of pesticides: When a pesticide is released into the environment, not all of them reach the target. Pesticides get spread in the environment through process such as adsorption, transfer, breakdown and degradation. The fate of pesticides depends on the property of pesticide, property of soil, site conditions and management practices. The transfer processes are volatilization where the chemicals get converted into gas and move away from the target site. This process occurs readily from sandy and wet soils. Spray drift is the movement of pesticides in air. This drift increases with strong wind, small size of the drops, and greater distance from the ground. This can affect people, animals and other insects and can pollute water sources. Runoff increases with heavy rain. Runoff contaminates water sources. Figure 1: Fate of Pesticides (Gardner, 2008) Leaching occurs due to movement of pesticides in water through the soil. Leaching is influenced by the characteristics of soil and pesticide and their interaction with water. Water soluble pesticides, sandy soil, rain, less adsorption of pesticide to the soil are the factors which increases leaching. Pesticides get absorbed in the plants and gets released back when the plant or animal decays. The characteristics of pesticides such as their solubility in water, soil adsorption, their persistence in the environment determine their fate. If the pesticides have high solubility, low adsorption and long persistence they can easily runoff in water. The behavior of pesticides in the given environment is attributed to the interaction of these factors with the soil type and environmental conditions. Fate of pesticides in soil: The properties of pesticides which affect the movement of pesticides are soil texture, permeability and organic matter in the soil. Pesticides get adsorbed if the soil is high in clay or organic matter. This is because they have more surface area for adsorption. They do not get adsorbed in sandy soils. More coarse the soil, greater is the chance of groundwater pollution. Transfer of pesticides through volatilization occurs freely from sandy and wet soils. If the soil has high moisture content, or if the soil can be easily eroded, pesticides get transferred through runoff. Leaching takes place if the soil is sandy and if there is a poor adsorption of pesticides to the soil. Organic matter has good adsorption. Soils which are alkaline help in the breakdown of organophosphates. Pesticides in surface and ground water: The high the water table (ground water level), the less will be the soil which acts as a filter. Extra precautions should be taken in such areas while applying fertilisers. In regions where water table is low, there is less chance of percolation of water soluble pesticides. Ground water will also be polluted if the layers between soil and ground water are highly permeable. If the permeability of geologic layers is rapid, the ground water pollution is more. Clay, which is less permeable, has very less chance of percolation. Climate also plays a significant role in the ground water contamination. High rainfall regions have high chance of pesticide percolation. High soil permeability in those regions further escalates percolation. Surface water contamination occurs mainly by runoff. With heavy rain, the pesticides get washed away to the nearest water sources such as ponds, lakes, rivers etc. In some cases, they are sprayed in water sources to control pests. Atrazine, an herbicide has contaminated waterways and caused feminization of male frogs. Atrazine pollution is found in countries such as United States, South Africa, Germany and Denmark. Glyphosate herbicide is a reason for 70% decline in frog biodiversity and 86% decrease in total tadpoles. Practical Solutions for pesticide pollution: Several practices can be undertaken to reduce the pesticide pollution. They are Integrated pest Management (IPM) process is not solely dependent on chemicals. IPM involves monitoring crops regularly for pest levels, undertaking non-chemical controls such as sanitation, plant resistance, biological control, cultural controls, mechanical controls etc. and maximizing the benefits of these non- chemical processes. Prevention of back siphoning Considering of weather and irrigation plans: Knowledge of weather conditions would avoid pesticide movement through runoff and leaching. Proper pesticide use and storage: Proper care taken before the application of pesticides and during their storage and during their application will reduce pesticide pollution. Care taken to avoid mixing of pesticides near wells would protect water sources. Safe disposal of chemical and pesticide waste helps in clean-up of the environment and would reduce pollution. Leaving buffer zones around sensitive areas such as buildings, public places, wetlands, wild life habitats etc. would ensure safety. Application of pesticides can be avoided when wind favours drift of fertilisers. Proper maintenance of application equipment such as cleaning and calibrating would avoid proper use of pesticides without wastage or spillage. Impact of agricultural farming in surface and ground water in UK Agricultural farming is one of the main causes for water pollution. The pollutants pollute the surface water sources by runoff and groundwater through leaching. Water pollution caused by pollutants over a large area is called diffuse water pollution. In farming, diffuse water pollution occurs due to fertilisers, manure and live stocks. The nutrients from fertilisers and faeces from livestock contaminate the water. Back flow of pesticides to the water source and soil erosion pollutes the water source. Improper handling and application of pesticides can cause wastage and spillage which in turn pollutes water. The approximate percentage of harmful chemicals in a particular catchment in UK is found to be consisting of 60% nitrates, 25% phosphorus. (Business Link) . The percentage differs from catchment to catchment. Water pollution affects the bio-diversity of species and makes water not fit for drinking, recreation and shellfishery harvesting. Water pollution arising from high level of nitrates and phosphates causes eutrophication. Eutrophication leads to enrichment of nutrients in water, which further leads to quicker growth of algae which in turn causes imbalance in organisms present in water. This growth of algae removes oxygen from water, which causes death of water bodies. Excess nitrates should be removed from both ground and surface water to make it safe. 70% of England comes under the Nitrate Vulnerable Zone (NYZ) regulations which intend to reduce the nitrate pollution. Pollution of ground water from chemicals include deterioration in the quality of ground water, impacts on groundwater-dependent surface water quality and ecology, impacts on groundwater-dependent terrestrial ecosystems (GWDTE), direct effect of specific ground water abstraction and associated treatment requirements. (Pesticides 2009) The surface water pollution on a catchment scale may be influenced by its hydrogeological setting and its proximity to the pesticide use. The Environment Agency (EA) detected 100 pesticides in fresh water in England and Wales during 1995-2004. The majority of the pollutants were found to be in small quantities and below relevant Environmental quality standards (EQS). Isoproturon and mecoprop are the agricultural pesticides found in surface waters. The control measure banned herbicides simazine and atrazine for non-agricultural use. Diuron is the alternative for atrazine. Bentazone was found to be above the prescribed concentration in both surface and ground water. In 2005, it was found that bentazone was second to atrazine to be detected in ground water. (DEFRA 2006) Proper management practices ensure the effective use of pesticides without affecting the environment. The Stockholm convention provides tools for managing pesticides and other chemicals. The Food and Agriculture Organization (FAO) started a programme in 1994 for prevention and elimination of obsolete pesticide and supports the countries for proper disposal. FAO works in IPM, controls highly hazardous pesticides, guides in developing good pesticide legislation, register and import controls, regulates pesticide residues etc. The European Union made rules under which use of pesticides near schools or any public places, wholesale aerial crop-spraying, would be banned. Buffer zones required in protecting water sources. The EU also aims at reducing the use of pesticides by 2013. The restriction in the use of pesticides is welcomed by organic farmers for it helps in the growth of organic farming. References BBC News 2009, ‘Euro MPs back Pesticide control’, 13 January 2009, available at [viewed on 20 November 2010]. Brown E. Amy 2006, ‘Mode of action of Insecticides and Related Pest Control Chemicals for Production Agriculture, Ornamentals, and Turf’ Maryland Cooperative Extension, University of Maryland, Available at [viewed on 20 November 2010.] Business Link, n.d., Catchment Sensitive Farming, Environment Agency, viewed 20 November 2010, http://www.businesslink.gov.uk/bdotg/action/detail?itemId=1083648100&type=RESOURCES Department for Environment, Food and Rural Affairs (DEFRA) 2006, DEFRA, viewed 20 November 2010, Gardener D. Ronald 2008, Understanding the fate of pesticides after application, Cornell University Cooperative extension, viewed 20 November 2010. Pesticides 2009, River Basin Management Plans – Groundwater classification, Northern Ireland environment agency, viewed 20 November 2010, World Health Organisation, 2006, ‘Pesticides and their application’ [pdf], World Health Organisation. Available at http://whqlibdoc.who.int/hq/2006/WHO_CDS_NTD_WHOPES_GCDPP_2006.1_eng.pdf [accessed date 20 November 2010] Read More