Environment, Pollution and Recycling

3. A person or thing that is regarded as dangerous or likely to inflict pain or misery
6. Water falling from the sky that contains a high concentration of pollutants
7. Dense forest found in tropical areas of heavy rainfall
11. The process by which land changes into desert
14. A mixture of smoke, fog, and chemical fumes
15. To keep something from decay, dissolution or danger
16. Liquid discharged as waste, as from an industrial plant or sewage works

1. Chemical that is sprayed on crops to prevent insects from destroying them
2. A system involving the interactions between a community of living organisms
4. The spontaneous emission of radiation from atomic nuclei
5. Rain, snow, sleet, dew, etc, formed by condensation of water vapour in the atmosphere
8. Able to decay naturally and harmlessly
9. A mixture of decaying organic matter such as leaves, wood and manure
10. Part of the earth's atmosphere and surface in which animals and plants can live
12. Something that has a benefitial effect on environment
13. A substance that has been linked to causing one or more types of cancer