Human activities like the formation of the Sahara desert have negatively impacted ecosystems. The depletion of the ozone layer by chlorofluorocarbons released from refrigerants and air conditioners allows more UV radiation to reach the Earth, increasing skin cancer, eye disease, and immune system damage in humans as well as mutations in plant DNA. While ozone in the stratosphere protects life on Earth, ozone in the troposphere is a air pollutant. Images of Antarctica indicate the ozone layer is slowly recovering due to reduced CFC emissions.

2. Effect of man's activities
on the ecosystem

3. The formation of Sahara desert
is an example of the ill effect of man's activities
on the delicately balanced ecosystem.

6. Effects of Ozone Depletion

7. What is Ozone? Ozone Layer?
 Ozone (O3) is a highly-reactive form of oxygen.
 Unlike oxygen (O2), ozone has a strong scent
and is blue in color.
 Ozone exists within both the tropospheric and
stratospheric zones of the Earth’s atmosphere
 In the troposphere, ground level ozone is a major
air pollutant and primary constituent of
photochemical smog
 In the stratosphere, the ozone layer is an
essential protector of life on earth as it absorbs
harmful UV radiation before it reaches the earth.

8. CFC’s and ozone depletion
 Chlorofluorocarbons are
created and used in
refrigerators and air
conditioners. These
chlorofluorocarbons are not
harmful to humans and have
been a benefit to us. Once
released into the atmosphere,
chlorofluorocarbons are
bombarded and destroyed by
ultraviolet rays. In the process
chlorine is released to destroy
the ozone molecules

9. Harmful effects of UV rays on
people
 Skin cancer
 Cataracts and eye disorders (corneal
sunburn and blindness)
 Immune system damage

10. Plants

11. DNA & UV-B
 DNA absorbs UV-B radiation
 Changes shape in DNA
 Changes in the DNA molecule mean that
enzymes cannot “read” the DNA code
 Results in mutated cells or the cells die
 Cells have developed the ability to
repair DNA
 A special enzyme arrives at the damage
site
 removes the damaged section of DNA
 replaces it with the proper components
 This makes DNA somewhat resilient
to damage by UV-B

12. Manifestations of…
Cataracts
Cancer
Pterygium
brought on by
over exposure to
UV-B

13. Protection
 Sunglasses with 100% UV block
 Wrap around sunglasses
 Eye protection for children
 Hats

14. Images of Antarctica Taken Indicate A Slow
Recovery

15. Tools to reduce waste:
The Four Rs:
Rethink
Reduce
Reuse
Recycle
Incineration
Sewage treatment

16. RETHINK
We know that most items we purchase will be
thrown away eventually, so why not design for the
“end of life” of the product? Engineers and
product designers need to address:
• Packaging: materials comprise 65% of our
waste.
• Toxic substances: substitute with less toxic or
benign materials (i.e. lead-free solder) that can
be harmlessly disposed of or recycled.

17. REDUCE
As consumers, we make choices about the
products we purchase and how much use we get
out of them.
• Bottled water vs personal water bottles
• Single use shopping bags vs. reusable bags
• Coffee and soda “go-cups” vs. reusable
insulated cups
• Food packaged in individual servings vs.
buying in bulk (i.e. oatmeal, pasta)
• News papers vs. On-line news
• Paper bills and newsletters vs. email or on-line

19. What is REUSE?
Cleaning and using
the material over
and over again
increasing the
lifespan of the
product

20. Benefits of Recycling
Fig. 24-8 p. 541

21. Economics of Recycling
• Paper, aluminum,
steel are easy to
recycle and make
easy economic sense
• Glass and plastic
expensive to recycle
• Employs 1.1 million
people

22. Deep-well Disposal
Fig. 24-21 p. 553

24. INCINERATION
Incineration means reducing to ashes.
The burning of substances at high
temperature to form ash is called
incineration. All the organic matter
present in waste is removed as carbon
dioxide and water vapour . The ash left
behind is removed from time to time.

25. SEWAGE
TREATMENT
The dirty drain water containing
urine and faeces which is carried
from our home by underground
pipes is called sewage. Treatment
of sewage is important before it
dumped into the river.