I need you to read the syllabus first and you choose any topic Essay

I need you to read the syllabus first and you choose any topic - Essay Example Both agricultural and non-agricultural toxic compounds causing bad effects on ecological and human health; however, it is difficult to separate these effects caused from those compounds which are intentionally released by the industries as by-products or waste materials. Nevertheless, there is wide evidence that agricultural use of pesticides has a major impact on water quality and leads to serious environmental and human health problems. Factors affecting toxicity of pesticide in water Many factors of pesticides affect the quality of water causing it more toxic, degrading and lethal 1. Toxicity Concentration of the pesticide which is enough to kill half of the test organisms in a specific test period is termed as lethal dosage (â€Å"Pesticides as Water Pollutants†). The lethal dose is inversely proportional to toxicity. Thus, the lower the lethal dosage is, the higher is the toxicity. Values ranging from 0-10 are considered as extremely toxic. Toxic response can be life thre atening or chronic, causing severe health problems, for instance, cancer, infertility, hormonal imbalance, digestive problem, etc. 2. Persistence Persistence is measured by the half-life of a pesticide. It is very important to find out about the persistency of a pesticide since it gives an idea about how poisonous a pesticide can be. Persistency is inversely proportional to lethality of a pesticide, that is, the more the persistency is, the lesser is the pesticide lethal (â€Å"Pesticides as Water Pollutants†). 3. Degradation The eroding of pesticides into other products can lead to many other problems. The newly formed by-products can have different persistency, and lethality that can totally change the surrounding in which they are present. One of the examples is DDT. When it is degraded, it forms other substance (DDD and DDE) which have totally different persistency and risks. Chronology of pesticide development The impact on water pollution is related mainly to the active ingredient present in the pesticide formulation. However, additives that are used to prepare the final formulation that include wetting agents, diluents, solvents, buffers, emulsifiers, preservatives and adhesives can be the cause of water contamination. Other than the agents used for the preparation of pesticides, degrades and the by-products formed during its usage can also contaminate water and lead to water pollution. Below are the details in chronological order of various pesticides, their sources and characteristics that have been used for many years and led to water pollutions. From 1800 to 1920 In the early period, the most useful pesticides were petroleum oils, nitro-phenols, naphthalene, chlorophenols, and creosote. These products were non-specific in nature, thus causing toxicity in targeted as well as non-targeted organisms. The source of these compounds was either laboratory preparation or by-products of coal gas productions. From 1945 to 1970 Many products that were u sed during this period were organically synthesized. Pesticides like chlorinated organic, chlorinated cyclodienes, HCCH, and DDT were persistent in nature and had a wide range of selectivity among different organisms whereas pesticides like organophosphorus compounds, carbamates, and cholinesterase inhibitors had lower resistance and caused not only user toxicity but serious water contaminatio