People around the world are concerned that chlorofluoromethanes released from aerosol sprays can pose a serious threat to their health through depletion of the ozone layer. The primary concern about the ozone layer depletion is that the ultraviolet ray intensity at the surface of the Earth would increase, bringing about more skin cancer fatalities among Caucasians. According to the IMOS report, Fluorocarbons and the Environment, issued earlier this year, there is persuasive, although not absolutely conclusive, clinical and epidemiological evidence of a direct link between solar radiation and the historically observed incidence of several, generally non-fatal, types of skin cancer in humans. I certainly do not find this evidence conclusive, and believe an alternative case can be made.It is a long known fact that ultraviolet intensity at the land surface increases with altitude above sea level. In going from sea level to the altitude of Denver, Colorado (1 mile, 1.61 km.), the ultraviolet intensity at 295 nm increases by 125 percent. The residents of Colorado (mean elevation 2.1km.) have always been subjected to UV intensities several times greater than those that might result, on the average, from the hypothesized ozone layer depletion of 16 percent (33 percent increase in UV) by 2000 AD. In addition to the higher UV content of Colorado sunshine, the percentage of clear days (70 percent) is above the national average.Publications by the American Cancer Society show that Colorado has one of the lowest skin cancer fatality rates of all of the states, 1.69 deaths per 100,000 population compared with a national average of 2.40 per 100,000. The entire desert southwest has about 125 per cent greater UY intensity in sunshine, due to altitude, than does New England, yet the death rate from skin cancer in New England is 24 per cent higher than it is in the southwest.On the world basis, many factors appear to play a more important role in skin cancer fatalities than UV intensity. In the equatorial regions, UV intensity at the land surface is higher because the Sun’s rays pass through the ozone layer more perpendicularly than in more northerly or southerly latitudes. In spite of this, the lowest reported skin cancer death rates in the world come from Mauritius (0.2 per 100,000) and Nicaragua (0.2 per 100,000), even though they are located in near-equatorial regions. On the other hand, Ireland (2.64 per 100,000) has the world’s third highest rate while England and Wales (1.50 per 100, 000) is 27th. Mexico (0.65 per 100,000) is 38th.Evidence is strong that UV intensity is not the principal factor in determining the skin cancer death rate. Genetic factors, skin pigmentation, behavioral characteristics, medical facilities, broad straw hats, and suntan lotion all have some influence on skin cancer fatalities. An additional 4,000-12,000 deaths per year from skin cancer in the U.S. have been predicted for a 16 percent depletion of the ozone layer. It should be remembered that present annual deaths in the U.S. from this cause are 5,000.Some authors have recommended an immediate ban on the use of fluorocarbons without any direct evidence that they affect the ozone layer. To me the indirect evidence strongly suggests that these compounds are unlikely to have a significant effect on the Earth’s ozone layer and even if they did, an increase in skin cancer deaths would not necessarily result.1.What is one consequence for the inhabitants of Denver of the fact that the town is situated at an altitude of 1 mile above sea-level?2.From the passage, what do you know about the number of cloudy days per year in Denver?3.What is the relationship between skin cancer and UV intensity according to this passage?4.What does the author imply about the skin cancer death rate in Ireland? 5.Approximately what percentage increase in skin cancer deaths has been predicted for the U.S. with a 16 percent reduction in the ozone layer?