Автор работы: Пользователь скрыл имя, 18 Ноября 2011 в 19:48, реферат
People have always polluted their surroundings. But until now pollution was not such a serious problem. People lived in uncrowned rural areas and did not have pollution — causing machines. With the development of crowded industrial cities which put huge amounts of pollutants into small areas, the problem has become more important.