The whole industrial process which makes many of the goods and machines we need and use in our daily lives, is bound to create a number of waste products which upset the environmental balance or the ecological(生态的)balance as it is known. Many of these waste products can be prevented or disposed(处理) of sensibly, but clearly while more and more new goods are produced and made complex, there will be new, dangerous wastes to be disposed of, for example, the waste products from nuclear power stations. Many people therefore see pollution as only part of a larger and more complex problem, that is, the whole process of industrial production and consumption of goods. Others see the problem mainly in connection with agriculture, where new methods are helping farmers grow more and more on their land to feed our ever-increasing population. However, the land itself is gradually becoming worn out as it is being used, in some cases, too heavily, and artificial fertilizers(人造肥料) cannot bring back the balance. Whatever is underlying(潜在的)reasons, there is no doubt that much of the pollution caused could be controlled if only companies, individuals and governments would make more efforts. In the home there is an obvious need to control litter(杂乱的废物)and waste. Food is wrapped up three or four times in packages that all have to be disposed of drinks are increasingly sold in bottles or tins which cannot be reused. This not only causes a litter problem, but also is a great waste of resources, in terms of glass, metals and paper. Advertising has helped this process by persuading many of us to buy things we don't want to buy. Pollution and waste continue to be a problem everyone can help to solve by cutting out unnecessary buying, excess consumption and careless disposal of the products we use in our daily lives. The main cause of pollution is______.