Plutonium and Caesium: Nuclear-test legacy in stratosphere bigger than thought

Plutonium cycle in the atmosphere. Credit: : J.A. Corcho Alvarado

Levels of radioactive plutonium in Earth's stratosphere from nuclear tests and accidents is higher than previously thought, but probably not dangerous to humans, scientists in Switzerland said Tuesday.

It was previously thought that plutonium radionuclides—radioactive atoms which can take decades or thousands of years to degrade—were present in the stratosphere only at negligible levels.

It was also believed that levels of these pollutants were higher in the troposphere, the layer of the atmosphere that is closest to the ground, than in the stratosphere.

Both ideas turn out to be wrong, according to the new study, whose authors also found no likelihood of a hazard to health.

Radiation levels in the stratosphere are "more than three orders of magnitude higher than previously thought," study co-author Jose Corcho of the Swiss Federal Office for Civil Protection told reporters.

The team also found that volcanic eruptions may shift those pollutants from the stratosphere into the troposphere, closer to Earth.

But Corcho said there was no evidence of danger.

"The levels of plutonium and (caesium) currently found in the stratosphere are low, and comparable to the levels measured at ground level air (troposphere) at the end of the sixties and in the seventies," he explained.

The aerosol collection devices mounted on the wings of a Tiger (F5E/F), aircraft of the Swiss Air Force. 

Credit: Swiss Federal Office of Public Health

"Although I'm not a health specialist, I would say that the current levels of plutonium found in the stratosphere do not represent a risk for the population."

The study, published in the journal Nature Communication, said the radioactive particles in the stratosphere mainly came from above-ground nuclear weapons tests in the 1950s and early 1960s.

Other sources were the burn-up of an ill-fated US navigation satellite in 1964 that spilled its plutonium fuel into the atmosphere, and nuclear power plant accidents like Chernobyl and Fukushima.

The team used aerosol samples taken by Swiss military aircraft since the 1970s as part of the country's environmental surveillance programme.

More information: Paper: dx.doi.org/10.1038/ncomms4030

Dow Chemical: Gas tragedy leaves legacy of 'Bhopal brides' 25 years on

Jyoti is one of many Indian women whose dreams of a glittering wedding were shattered after the Bhopal gas disaster killed thousands 25 years ago this week and left many more ill from exposure.

Having endured the lethal billow of methyl isocyanate gas which seeped from the Union Carbide plant on December 3, 1984, Jyoti and her contemporaries then suffered the stigma of being survivors.

"No one would marry her," said her mother Sheela. "They looked at her health and saw how sick she was, and that she was always going for treatment for her kidney and respiratory problems."

At just 39, Jyoti is practically a spinster by Indian standards, where despite increased educational and career opportunities, women are still pressured to marry young and reproduce soon after.

But the chances of a childless marriage or spending a fortune treating children with birth defects turned many Bhopal women into pariahs.

Research conducted by the state-run Indian Council of Medical Research (ICMR) until 1994 showed that 25,000 people had died from the consequences of gas exposure -- in addition to the 8,000 to 10,000 people who were killed within the first three days.

Government statistics compiled after 1994 concluded that at least 100,000 people living near the factory in central Madhya Pradesh state were chronically sick, with more than 30,000 residing in areas with contaminated water.

According to the ICMR, the number of still births and miscarriages increased immediately after the disaster, and activists say more than 350 tonnes of toxic waste strewn around the site still pollute soil and groundwater in the area, leading to hormonal and fertility disorders and other illnesses.

"My daughter has been married for more than five years and she still has no children," lamented 60-year-old Savra Bi, who lives in a crude row of shacks close to the plant, in the old part of Bhopal which was worst hit.

"After 1984, for 10 years no girl had a good marriage," agreed Champa Devi Shukla, a managing trustee with the Chingari Trust, which provides medical care to children with gas-related congenital deformities.

"Men thought they might miscarry. Even men in the new part of the city refused to marry them