AMMAN (J.T.) — High levels of an ozone-destroying chemical found in the atmosphere around the Dead Sea cannot be blamed on local chemical works, a team of researchers from Israel and Germany has discovered.

The factories, which produce bromine compounds and other chemicals from Dead Sea salt, have been linked with high levels of bromine oxide (BrO), a potent ozone-depleter. But the scientists say that the chemical is produced in a natural reaction in the salt pans around the edge of the landlocked sea.

Jordanian and Israeli chemical firms will welcome the conclusion, but the research does not completely absolve humans: the salt pans are growing ever larger as more freshwater is removed from the River Jordan before it reaches the Dead Sea.

The researchers made their discovery in a mobile laboratory parked on a dam between the northern and southern sections of the sea, with open water to the north and salt pans to the south. Levels of BrO were at their highest — and ozone levels were lowest — when the wind was blowing from the south.

Although there are chemical works south of the dam, the researchers rule them out as the source of the BrO. Fluctuations in BrO levels do not correspond with levels of other industrial pollutants from the factories, they point out. The distribution of the BrO also suggests that it originates over a wide area rather than at localised points.

BrO is probably produced by oxidation of salts on the surface of the pans, the researchers say, but the exact mechanism remains a mystery. Geochemists know that the chemical is also released from the surface of freezing seawater in the Arctic. "Whether the same bromine release processes as in the Arctic occur at the Dead Sea is not clear," the team writes.