by Japan Economic Newswire

Highly toxic insecticides that are banned in Japan and have never been used in the country have been detected in various parts of Japan, the Environment Ministry said Friday.

The insecticides -- mirex and toxaphene -- are believed to have come to Japan in the atmosphere or via sea from abroad, the ministry said.

"The amounts of the insecticides that have been detected do not pose an immediate threat to human health, but we need to tighten control on international management of chemicals and insecticides," a ministry official said.

According to the results of a ministry survey in fiscal 2004 on pollution by chemicals, mirex was detected at all the 17 atmospheric observation points nationwide and was found in fish, shellfish and birds at all the 22 wildlife observation points nationwide.

The insecticide was also found in water at 18 survey points and in mud at 55 points, the ministry said.

The highest density of mirex -- 16 picograms per cubic meter -- was detected in the atmosphere in Takamatsu, Kagawa Prefecture, it said. A picogram is a trillionth of a gram.

Toxaphene was not detected in water or mud, but was found in the atmosphere in a variety of places, according to the ministry.

Mirex and toxaphene are highly toxic and do not easily decompose naturally. All production, use, export and import of them are banned under the Stockholm Convention. The convention, which took effect in May with 151 signatory countries, is a global treaty to protect human health and the environment from persistent organic pollutants, which are chemicals that remain intact in the environment for long periods.

The insecticides had been used by some countries before the convention took effect, and there are countries that have not joined the convention, ministry officials said.