Exercise 16. Change the following sentences, active to passive, passive to active

1. The ozone layer is being damaged by chemicals. 2. Environmentalists say we should avoid spray cans. 3. People cut down trees. 4. This is known as global warming. 5. We cannot escape the Earth's heat.

Exercise 17. Put the verbs in brackets in the correct form (active or passive).

Forms of Environmental Disease

Environmental diseases can affect any organ system of the body. How the diseases (to express) depends on how the particular environmental agent (to enter) the body, how it (to metabolize), and by what route it (to excrete). The skin, lungs, liver, kidneys, and nervous system commonly are affected by different agents in different settings. Of particular concern (to be) the capacity of many environmental agents to cause various cancers, birth defects or spontaneous abortions (through fatal exposure), and mutations in germ cells, the last-named raising possibilities of environmentally caused genetic diseases in later generations.

Exercise 18. Read the text. Fill in the gaps with one of the words

From the box.

Cancers, chronic, clear-cut, doses, epidemiological, exposure, illnesses, nonspecific, otherwise, periods, toxic

Environmental__ can be mild or severe and can range from

Transient to___, depending on the__ of toxin received. Some

Diseases occur abruptly after a toxic, whereas the time of onset of