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Acid rain is formed when sulfur dioxide and nitrogen oxides reach the air and are transformed into sulfate or nitrate particles. When combined with water vapor, they are converted into sulfuric or nitric acids. Acid rain can adversely affect aquatic life, erode stone buildings and marble statues, and seriously threaten trees and crops. Power plants that burn coal to generate electricity are a chief cause of acid rain. The US Congress and US Environmental Protection Agency (US EPA) have worked to reduce acid rain by restricting the amount of sulfur allowed in the coal burned by power plants and other industrial sources. In some areas, where pollution is concentrated, plants may burn only coal with 1% sulfur or less. In rural locations, a maximum sulfur content of 2% is allowed. Nitrogen oxide emissions from cars also contribute to acid rain. These emissions are being reduced by new car emissions standards that have been established by the US EPA. Acid rain monitoring stations are built to determine the long-term effects of acid deposition. The 1990 Federal Clean Air Act Amendments required power plants across the nation to reduce sulfur dioxide and nitrogen oxide emissions. These measures have significantly reduced the pollutants that contribute to acid rain formation.

Aquatic life at all levels of the food chain can be harmed by acid rain. Destruction begins at the lowest level of the food chain, when the tiny microorganisms that are food for minnows and other small organisms die. As food sources dwindle, more and larger fish die. Acid in the water may also interfere with oxygen circulation, harm fish gills and cause heart problems in fish. Even though acid rain is a complex global problem, there are things that each of us can do to help control it. Conserving energy helps by reducing electricity demands on our power plants. Carpooling also helps, by reducing emissions of nitrogen oxides. And widespread recycling will also help control acid rain. By minimizing the volume of waste we generate, we are contributing to reductions of nitrogen oxide emissions from waste incinerators. These are a few ways that, with enough individuals acting on behalf of the environment, each of us can make a difference.

This paper extends the theory of fuzzy diseases predictions in order to detect the causes of business failure. This extension is justified through the advantages of the reference model and its originality. Moreover, the fuzzy model is completed by this proposal and some parts of it have been published in isolated articles. For this purpose, the fuzzy theory is combined with the OWA operators to identify the factors that generate problems in firms. Also, a goodness index to validate its functionality and prediction capacity is introduced. The model estimates a matrix of economic- financial knowledge based on matrices of causes and symptoms. Knowing the symptoms makes it possible to estimate the causes, and managing them properly, allows monitoring and improving the company’s financial situation and forecasting its future. Also with this extension, the model can be useful to develop suitable computer systems for monitoring companies’ problems, warning of failures and facilitating decision-making.