1
																2
3					4																					5
																				6
												7						8
								9
																								10
	11
	12
												13
	14
15
					16
							17							18
				19
20
									21

Across 3. difficulty in breathing 9. emitted by the digestion of food by animals, for example cattle 10. protective sunscreen that shields us from the high levels of UV radiation 11. caused by greenhouse effects 12. emitted from agricultural processes (NH3) 13. An odorless, colorless, and highly poisonous gas (CO) 15. examples are moulds and viruses, which play a part in allergies and asthma 16. causing irritations, rashes etc. 18. effects of long term exposure to pollutant chemicals 19. (CFCs). harmful to ozone layer 20. (VOCs).examples are Benzene, Formaldehyde, and Naphthalene 21. heading for dust, pollen, soot, smoke, and liquid droplets etc

Down 1. (POPs).chemical substances persisting in environment, bioaccumulate through food web 2. corrosive gas produced by the burning of fuels; an ingredient of acid rain (SO2) 4. kill aquatic life, cause damage to buildings, harmful to human's health 5. (human activity) mostly related to burning different kinds of fuel 6. another example of cleaner fuel 7. produced by nuclear explosions, war explosives 8. greenhouse gas emitted from combustion 14. result of road traffic and energy production (NO2) 17. example of cleaner fuel