Read the text and decide which of the phrases in bold

Read the text and decide which of the phrases in bold express cause and which express effect according to the context? Every year the worlds industries pollute the atmosphere with about 1,000 million tons of dust and other substances. The waste from factories and industrial plants, electric and atomic power stations gets into lakes, rivers and seas; it poisons the air, it destroys plants and animals. Pollution of the environment threatens human health. It can lead to different diseases of the central nervous system and so on. Ignorance about ecology leads to further destruction of nature and worsens living conditions for all living beings. A lot of forests are being cut down, marshes and lakes are drying up. This breaks the ecological balance and deprives lots of animals of places to live. People have destroyed nature by building huge cities, cutting down trees, excavating mountains and digging mines. In pursuit of new inventions and discoveries, as well as higher and higher profits man has forgotten about nature and it has led him to the edge of ecological catastrophe.