The Coastal Post - September, 1996

Ultraviolet Radiation... Good or Bad ?


Since the sudden appearance of the Antarctic Ozone Hole in the mid 1980s, the danger of elevated levels of ultraviolet radiation has been brought to public attention. This has resulted in unprecedented international agreements to limit the production of ozone depleting chemicals.

Invariably, the stratospheric ozone layer is described as "a shield, protecting living things from dangerous ultraviolet radiation which causes skin cancers, cataracts and lessening of the immune system".

This static, one dimensional view of a complex process has been questioned by Forrest Mims, an independent scientific researcher, who works mostly out of his back yard. Mims sent a special, pre publication copy of his latest paper to the Coastal Post.

Writing in the September 1996 issue of Bioscience, Mims, whose specialty is measuring ozone, ultraviolet and haze, reflecting on studies which showed that frog embryos were sensitive to increased amounts of UV, asked what effect increased or decreased ultraviolet radiation might have on mosquitoes.

Working once again out of his back yard, he placed wild house mosquitoes (Culex Pipiens) in a tank ( wading pool), and covered half with a UV absorbing film and the other half with film that transmitted UV.

If there were more UV, would that reduce the population of mosquito larvae and thereby increase the algae and bacteria they fed on? Or, if there were less UV, say, caused by severe air pollution, would the mosquito population be enhanced?

Since ultraviolet radiation kills germs and virus, Mims asks if the reduction of UV in areas where it is normally high, results in an increase in disease causing organisms on exposed surfaces, in air, or in water?

In 1995, working under a small NASA contract, Mims found that during the dry season, when large areas of grasslands and rain forest are burned in Brazil, normal sunlight was reduced by 40 percent and ultraviolet B radiation was reduced by as much as 80 percent.

Despite a steadily declining stratospheric ozone layer, there has been no clear trend found in ultraviolet radiation on the earth's surface. The only detailed study done so far (Scotto, Science 239, Sept 1988) measured UV from 1974 to 1985 and found no trend. There were obvious problems with this first survey, but despite its importance, it was never repeated or expanded. The blotches of sulfate smog covering large areas of industrial countries in the northern hemisphere were not taken into consideration.

Recently, a decade of satellite data was processed by NASA scientists, showing an increasing trend in ultraviolet of just under 5 percent in the Northern Hemisphere and almost 10 in the Southern! (Geophysical Research Letters, Jay Herman et. al., August 1, 1996.)

It would appear that levels of ultraviolet radiation may be fluctuating up and down, wildly all over the surface of the earth from a variety of different forms of air pollution.

What may be bad for frog embryos, may be good for mosquito larvae and with so many things happening at once, in sequence, it may be impossible to get more than a glimpse of the "big picture" of what is happening to the eco systems involved.

Be that as it may, if Mims has done nothing more than place a dent in the idiocy of "protective shield of ozone" metaphor, he will have contributed greatly to public understanding of the complex interplay between the webs of living relationships which constitute the study of ecology.


Forrest Mims II edited his own science magazine for a while and won the 1993 Rolex Award. He has written popular books explaining electronics, many of which are available at Radio Shack. He has published in Science, Nature, Photo Biology, Geophysical Research Letters and New Scientist. Working in his backyard, using an instrument he developed, he helped NASA more accurately determine the levels of ozone over West Texas.

He was consulted on the remains of an electronic circuit board found at the crash site of the Boeing 747 blown up over Lockerbie Scotland a few years ago. The controversy over this work resulted in the publication of a letter in the New Yorker MagazineÑa very rare occurrence indeed!

Mims loaned a prototype of his Total Ozone Portable Spectrometer (TOPS) to the Coastal Post last year for Jim Scanlon's trip to the Straight of Magellan when the Ozone Hole passed over it. This year, Mims sent a Super TOPS for Jim's trip to the Western Amazon basin and the Peruvian Andes. The first production model, made by the Solar Light Company of Philadelphia, was sent to NASA, the second went to Mims, and the third went to the Coastal Post.