The main pollutant had changed from simple to complex status. Before, the main form of pollutants were smoke and sewage, but now, thousands and thousands of chemical compounds release either deliberately or accidentally to our environment. This in turn, due to the hanging nature of human activities. Two major form of human activities contribute to the changing nature of pollutants, they are agricultural and industrial activities.
The traditional method of ‘slash and burn’ had been criticise and seen as a form of unsustainable farming method, but surprisingly, it’s actually a relatively sucessful way of cultivating herbaceous food plants without over stressing the forest ecosystem as a whole. This is because given plenty of land, so that the cultivation patches are always surrounded by plenty of forest, and there are plenty of time allowed for the sucession to grow back to forest, the process need not to be inefficient or laod to long term ecological changes.
However, large scale extensive use had a dramatic ecological effects result in significant nutrient loss that may require many centuries of soil maturation or a major fertilisers to put it back. If the ecological system need to be modofied extensively for massive food production, it is essential to increase management effort and also the deliberate application of fertilisers to put back the nutrient that losses in the soil before, as a consequences, the production of food per unit area has increase dramatically.
The agricultural are now more depends on urban technology to supply the fertilisers and equipment that make the intensive cultivation possible. As the quantity and quality of crops gets better, it gives a great opportunity to the insects or parasites specialising in the species to grow, it then become pest. Hence , the need for more management and the use for pesticides increase.
Toxic substances can have side-effect on wildlife, which further decrease the natural enemies of the pest ,over use of pesticides creates insect resistance, destruction of natural enemies and resurgence of pest species leading in tun to increased spraying – a syndrome known as the ‘pesticide treadmill’. Stable pesticides, such as organochlorines which do not degrade quickly, can bioaccumulate, by building up in the body fat of animals amd can also ‘travel’ over long distence e. g. They have been found in the body fat of Antartic penguins.
Atrazine, a newer generation of pesticide, has also been found in the Artic. Pesticide also contributed to soil degradation and to damaging monoculture cropping. The other form of human activities that greatly the changing patterns of pollutant is industrialisation. Stress was imposed on ecosystems as a consequence of the urbanisation and technological development of human societies, activities like energy generaion, metal melting and mutifarious aspects of manufacturing industry produce diiference sort of polluant substances. Most of then are of chemical pollutants. E. . exhaustion from vehicle contain carbon monoxide, nitrogen dioxide,hydro carbon and Nitric oxide, all have negative effects on human health and causing problems with ozone depletion.
There are a increasing concern of chemical reaction in those pollutant , which causes envionmental reaction. Therefore causing a change in the nature of environmental reaction, new chemical compound was created, and they go from primary pollutants to secondary pollutants. Most of these subatances we can smell, taste or see, but there are also some pollutants that is sensory amotality, e. g. we can’t see radiation, we can’t taste pesticide once it’s on an apple.
As pollutants are getting more complicated ( due to different kinds of chemical reaction), there is a increasing dependence on science to tell us what is out there, there is a increasing fear because we can’t tell. Compare of 25 years ago, USA air quality is much improved, although pollution is atill obvious – traffic fumes in city traffic, exauted gas that irritate the eyes and lungs or smog that obscure the view. Even when pollution is not visible and no adverse effects are noticed, air may still contains pollutants at levels that provoke concern.
Another example will be water. The water or it’s sediments may cantain synthetic chemicals, the word synthetic is deliberately used because there are always thousands of natural chemicals present. If the level of human generated chemicals is high enough in a water body to affect bird reproduction adversely or to cause tumors in fish, all would agree that the water is polluted whether or not pollution is visible. However, one thing seems to be neglected is that there is the possibility of adverse long term consequences of even very low concentrations.
If the levels of all chemical are added together, the total can cause adverse effects, the effect may be synergistic- one chemical may magnify the effect of another. There are thouands of natural chemical present in water, soil and food, many of which are similar, or identical to anthropogenic (human generated) chemicals, an animal’s body cannot tell whether a chemical comes from a natural source of from a human source. Which means it’s difficult to identify thus, prevent negative health effect that those pullutants can bring.
In the US and other western countries, many polychlorinated chemical such as DDT and PCBs have ben banned, with the result that environmental polluted level are now lower. But does all our awareness and fear for pollution due to changing nature to pollutants? Radioactive chemical radon, which is ubiquitous in the environment from natural sources, is asocited with human lung cancer. And consider the chemical arsenic, in some locales, enough arsenic is naturally present in drinking water to increase cancer risk of persons drinking it by as much as 1%.
In these case, it’s not the changing nature of pollutants causes fear, is the advance of science technology is now able to bring up potential danger that we didn’t notice before. How are the polutants substances difference now from before? And why should we fear for it? Pollutant substances are defined as substances causing damage to targets in the enviornment. Recent evidence suggests that a high proportion of cancer ( perhaps as many as 60 – 80 %) may be provoke by environmental factors rahter than result from genetic defects and biochemical instabilities.
Similarly, many cases of teratogenesis ( the production of abnormal embryos) can be linked to exposure of the mother to organic compounds like dioxins, hexachlorphene and organic solvents. There are difference pollutant categories. Organic pollutants includes PCBs, most pesticide pollutants e. g. DDT and the carbamate pesticides and oil, which becomes a pollutant when spilled be accident. There are also inorganic pollution, one of the example would be the synthetic plant nutrients found in fertilizers, e. g. Nitrate. It also includes nitrogen and sulfur acids found in acid rain and metals.
Mercury is found naturally in marine waters and some fresh waters, but it is also often the result of human activities. When electric power plants or other facilities burn coal, oil or waste that contain mercury, the volatile mercury escapes into the atmosphere and later settles onto land and water. The other type of pollutants is acid pollutant, acids are found in runoff from coal mining and metal mining sites. Hydrogen chloride, a gas emitted by incinerators, which forms hydrochloric acid after react with moisture. Physical pollutants is any solid material found in an inappropriate location.
Soil, carried in rainwater runoff from agricultural fields, city streets and constrution sites is an example of physical pollution. Biological pollutants includes dead and living micro organisms and fragments of insects and other organisms that can caontaminate air, water or food. Before the development of agricultiral sectors and industrailisation, physical pollutants and biological pollutants may be counted for the major souce of pollution, but as other human activities increase there’s a massive amount increase in the other types of pollutant substances.
There are an increasing concern for environmental issues causing by pollution, e. g. global warming, ozone depletion, pesticide and fertiliser problem such as food poisoning and urban air pollution. The increasing fear of our environment comes from two major area. What we did not know could be harmful before, and what we know we cannot tell now whether it is harmful or not. The changing nature of pollutants to a more complex chemical contents also bring the fears that we don’t know what are we eating, drinking or breathing, but if scientists can provide us with good knowledage of information, the panic seems to be less.