NASA confirms the Earth's atmosphere still contains ozone depleting compound from a substance banned decades ago.

This compound, Carbon Tetrachloride (CCl4), was once used as a dry cleaning and fire-extinguishing agent. Carbon tetrachloride is both ozone-depleting and a greenhouse gas. CCl4 has an atmospheric lifetime of 85 years.

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Exposure to high concentrations of carbon tetrachloride (including vapor) can affect the central nervous system and damage the liver and kidneys. It could result in coma and even death after prolonged exposure.

Chronic exposure to CCI4 can cause liver and kidney damage and could result in cancer. 

After the 1987 Montreal Protocol regulated this compound, there were no reported new CCl4 emissions from 2007 to 2012.

New NASA research suggest otherwise. NASA found there were CCl4 emissions equivalent to 39 kilotons, or some 30 percent more emissions since the treaty took effect.

Qing Liang of NASA said they aren't supposed to be seeing this it all. The data does show there are unidentified industrial leakages from contaminated sites or unknown CCl4 sources.

Researchers explain that since 2008, CCl4 accounted for 11 percent of chlorine available for ozone depletion. They believe this percentage isn't enough to alter the decreasing trend of ozone-depleting substances.

Despite this, researchers and lawmakers still want to find out the source of the unexplained emissions.

Researchers surmise there's a CCl4 loss process they can't understand or there are unreported CCl4 emissions not yet identified.

They're also wondering why emission declined slower than expected.

With zero emissions reported for five years, atmospheric concentration of the compound should have fallen four percent per year but upon observation, researchers found that it's only fallen one percent per year.

Paul Newman, one of the researchers, said people believe the emissions of ozone depleting substances have stopped because of the Montreal Protocol.

"Unfortunately, there is still a major source of CCl4 out in the world," he added.