Black Rain: Radioactive fallout from atmospheric nuclear detonations

SINCE the end of World War II, nuclear weapons were developed and indiscriminately tested in the atmosphere, underwater, and in outer space by the five nuclear powers -- China, France, UK, USA, and the former USSR. To date, total number of nuclear tests carried out by these countries exceeds 2,000. More than 500 of these were "atmospheric tests" conducted above ground mostly in the '50s, '60s, and '70s.

After a nuclear explosion, residual radioactive nuclei attach themselves to atmospheric dust particles that eventually fall to earth as radioactive fallout, also known as "Black Rain." Since 1945, these five countries have released into the atmosphere umpteen tons of radioisotopes. They are now widely dispersed and deposited all over the world.

An isotope is a nucleus containing different number of neutrons, but otherwise identical to the regular nucleus. An isotope that disintegrates spontaneously giving off radiation is called a radioisotope. Longevity of radioisotopes is measured in terms of half-life -- the length of time it takes for half of their radiation to dissipate. After one half-life, one half of the radiation will be left; after two half-lives, one half of one half or one fourth of the radiation will be left, and so on. As a rule of thumb, a radioisotope becomes harmless after ten half-lives.

Two of the radioisotopes in the fallout that are of most concern to us are strontium-90 and cesium-137, each with a half-life of approximately 30 years. They are also produced as radioactive waste in a nuclear power plant and are considered extremely hot in the radioactive sense. They are the most troublesome waste to dispose of.

Strontium-90 mimics calcium and cesium-137 mimics potassium. The former is transmitted to humans via plants, cow's milk, and various cereals including rice. Mistaking it for calcium, it is taken up by plants, especially in soils with low calcium content.

When we breathe or eat strontium-90, it will do what calcium does to our body, namely, migrate to our bone marrow. Since marrow is the principal site of blood cell production, white and red blood cells will be irradiated by the radioactive strontium-90, adversely affecting their reproduction. Internal exposure to strontium-90 is linked to bone cancer, cancer of the soft tissue near the bone, and leukemia. Asians who have abundant rice in their diet have a strontium-90 uptake six times that of people in western countries.

Cesium-137 is immobilised by the clay found in most soils but when as fallout it settles on the leaves of plants. It can be absorbed and translocated to the rest of the plant and even concentrated in some tissues such as those in potato tubers.

Since cesium-137 mimics potassium which is involved with the process of muscle contraction, after entering the human body most of it gets more or less uniformly distributed with higher concentration in muscle tissues. It affects the chromosomes within tissue cells, but the injury to the body is caused primarily by interfering with cell biology. Like most radioisotopes, exposure to radiation from cesium-137 results in increased risk of cancer. If exposed to very high level of cesium-137, serious burns, and even death, can result.

In the 1950s, adverse effects of strontium-90 on mother's milk and babies teeth made us aware of the danger to which we were subjected. This led to the signing of the Partial Test Ban Treaty in 1963. Showing total disregard toward human life, France and China did not sign the treaty and continued with atmospheric tests until 1974 and 1980, respectively.

All of us born in the first half 1950, irrespective of geographic location, have received a "healthy" dose of radiation from the fallout. Those of us who live near or work in nuclear facilities may have increased exposure from routine emissions. The accident at the Chernobyl nuclear power plant in 1986 aggravated the problem by introducing a large amount of strontium-90 and cesium-137 into the environment.

We do not know for sure the number of fatalities that could be attributed to radiation exposure from the tests. It is, however, believed that hundreds of thousands of people born in the '50's and '60s may have died of cancer caused by fallout radiation. In a 1991 study, International Physicians for the Prevention of Nuclear War predicted that about 2.4 million people will "eventually die from cancer as a result of atmospheric testing."

The short half-life of strontium-90 and cesium-137 does not mean that they become harmless after 30 years. As mentioned above, it merely means that after 30 years they remain half as radioactive. Produced almost two half-lives ago, both the isotopes will remain dangerously radioactive in the atmosphere for at least another 100 years. So, the figure of 2.4 million fatalities seems attainable!

Here is a Catch-22 situation. Caribou and reindeer in the arctic tundra feed extensively on lichens in the winter. Lichens accumulate cesium-137 to a level well above that of other plants. When these radioactive lichens are eaten by caribou or reindeer, the cesium-137 makes its way into the meat of these animals. Consequently, in the winter, caribous have only lichens to eat and the Eskimos have only caribous to eat!

Pro-nukes argue that harnessing of nuclear power is a quintessential demonstration of the brilliance of the human mind. Environmentalists and anti-nukes on the other hand contend that this brilliance lacks wisdom, and that these minds are personification of Stanley Kubrick's Doctor Strangelove.

Atmospheric nuclear tests may have stopped decades earlier, but we are still living under the Damoclean sword of radioactive fallout. It is impossible to avoid the leftover radioactivity from atmospheric testing that is present in the environment. Hence it is not only our generation, but many more generations to come that will continue to live under this sword because of the malevolence shown and sins committed by the "high priests" of the atomic cult.

The writer is a Professor in the Department of Physics and Engineering Physics, Fordham University, New York.