Squeeze Rhubarb, Freon, Get Toothpaste -- Scientists Find Way To Neutralize Ozone-Killing Chemicals

NEW HAVEN, Conn. - Yale University scientists have discovered a way to convert stockpiles of the banned chemical that eats away at the Earth's ozone layer into salt and an ingredient used in toothpaste.

In today's issue of the journal Science, Professor Robert Crabtree and graduate student Juan Burdeniuc describe how they used a compound found in rhubarb leaves to harmlessly break down Freon and other chlorofluorocarbons.

"We're very happy that it might make a contribution to the quality of life in the next century," Crabtree said during a news conference.

Freon is widely used in automobile air conditioners. Other CFCs include refrigerants, solvents and cleaning agents. CFCs have been linked to the shrinking of the ozone layer, which shields the Earth from the sun's ultraviolet radiation.

Scientists generally believe thinning ozone can lead to increased risk for skin cancer and cataracts. More seriously, thinned ozone could destroy plant life and lead to global warming.

Lots of Freon remains

As much as 100 million pounds of Freon, which is becoming a popular black-market item, may be stockpiled in the United States alone, according to automobile-industry estimates.

Massachusetts Institute of Technology Professor Mario Molina, who won the Nobel Prize in chemistry last year with two colleagues for demonstrating that CFCs destroy ozone, said the new process would be helpful in eliminating stockpiles but could not remove the

CFCs already in the air.

The researchers, whose work was published today, have applied for a provisional patent of their method, which uses sodium oxalate, a compound found in rhubarb leaves. The compound, when heated at about the temperature for baking bread, breaks down the CFCs into salt and sodium flouride, which is found in toothpaste.

Previously proposed methods for breaking down CFCs could cause an explosion or fire producing corrosive acid gases, Crabtree said.

"No one thought that CFCs would react with such a mild and unassuming material as sodium oxalate," Crabtree said. "It's the equivalent of watching a popgun punch holes in steel."

Most CFC production banned

Under a 1992 international agreement, 139 countries banned production of CFCs as of Jan. 1. But stockpiles can continue to be used, and developing countries such as China and India have until 2010 to comply.

In the United States, other refrigerants are now required in new cars and air conditioners, but Freon can still be used in older vehicles.

Besides being safe to use, sodium oxalate is relatively inexpensive - about $40 a pound - and readily available, Burdeniuc said.