7.6 million square miles Reduction in depletion of 2.4 million square miles from 2006 to 2013. Success of Montreal Protocol and subsequent protocols. Australian researchers predict that the ozone hole will be completely healed by 2050 AD, because of the complete ban on the production and sale of CFCs.
Why is ozone depletion of concern to mid-latitude residents, like the people of New England? When the Arctic ozone hole breaks up, parcels of ozone- depleted air move southward over North America, Europe, and Asia. In the spring and early summer we are exposed to excess levels of UV radiation as blobs of ozone depleted air move over our area . Ozone levels that are 22% below normal have been recorded around Portland ME in southern Maine, a city which is not that far north of Worcester. The ozone hole usually fills in by June in the Arctic as ozone enriched air circulates towards the Arctic from the tropics. The ozone hole usually fills in by December in the Antarctic.
The Montreal Protocol (1987) • An international agreement • Slow phase-in • New refrigerants were developed. • Exceptions for medical uses, that have now been phased out. • One of the most successful international environmental agreements ever. • By 2013, 190 nations had signed the Montreal Protocol and the protocols that strengthened it.
Effects of Ozone Depletion Each 1% decrease in the concentration of stratospheric ozone increases the amount of UV radiation that reaches the Earth’s surface by about 2%. By 2000 AD peak sun burning levels in New Zealand were about 12% higher than 10 years earlier. UVC (200 – 290 nanometers) This type of ultraviolet radiation is harmful to all living things: a) chromosome mutations b) kills single cell organisms c) severely damages the cornea of the eye All UVC is absorbed in the ionosphere and by the stratospheric ozone layer .
When stratospheric ozone is depleted, two major types of UV radiation are allowed through to Earth’s surface: UVA (320 – 400 nanometers; .320 - .400 micrometers) UVA radiation penetrates deep into the base layer of the skin or dermis. UVA damages the DNA (genetic code) of the skin. Although this damage is serious, it is less damaging than the damage caused by UVB. UVA causes long term skin damage that shows up years later as accelerated aging and skin wrinkling.
UVB (290 – 320 nanometers; .290 - .320 micrometers) UVB radiation penetrates less deeply into the skin than UVA radiation. UVB radiation is more damaging than UVA, because it suppresses the skin’s immune system. This means that the skin’s repair and defense mechanism is held in check, leaving damage unrepaired, and opens the door for cancers.
How exactly does UVB radiation suppress the body’s immune system? 1) UVB damages the immune cells (the Langerhans Cells) found in the skin. 2) This damage leads to the activation of immune suppressor lymphocytes in the body, instead of the appropriate immune system response. 3) Although the initial damage is localized to the area of the skin exposed to the UV radiation, the resulting immunosuppression is systematic, because the suppressor cells circulate throughout the body .
- Fall '16
- Mark Smith
- Ozone depletion, Ozone Hole
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