There are many sources of pollution

There are many sources of pollution in our modern world. At present, the most
serious sources are acid rain, car exhaust fumes and oil spills. Factory chimneys give
out smoke that contains sulphuric dioxide and nitrogen oxide. These gases combine
with moisture in the atmosphere to form sulphuric acid and nitric acid. When it rains,
these acids dissolve in the rain and make it acidic. Acid rain is believed to be the
worst pollution of all. It has harmed aquatic life by turning many lakes into lifeless
bodies of water. Car exhaust fumes contain carbon monoxide and lead which are
highly poisonous. In big cities, the exhaust fumes build up and pose a health hazard to
human beings. Pollution of the sea by oil threatens marine life. Much of the oil
comes from ships that clean their fuel tanks while at sea. Offshore oil wells also
discharge vast amounts of oil into the sea. Pollution of the sea can also be caused by
oil spills.