Hunt for source of toxin

2012-09-10 00:00

A JAPANESE scientist who collects tiny plastic pellets to monitor global oceanic pollution hopes to uncover the source of a toxic pesticide found at high levels in Durban.

What Professor Shige Takade from the Tokyo University of Agriculture and Technology wants to establish is whether the detection of the chemical HCH from two sites south of Durban is the result of new or historical use.

HCH, or hexachlorocyclohexane, was a popular ingredient in pesticides until it was outlawed by the Stockholm Convention, an environmental treaty signed in 2001 that seeks to eradicate or regulate the use of organic pollutants that linger in the environment for years.

Takade, who runs International Pellet Watch, found high levels of the chemical in pellet samples he analysed in November last year.

He has spent the last week collaborating with the Council for Scientific and Industrial Research at the University of KwaZulu-Natal and on Friday presented some findings.

He also took sediment samples from Isipingo estuary, which he will take back to Japan with him tomorrow to help answer the question of where the HCH is coming from.

“Our concern is the HCH in the area, and whether it was derived from legacy pollution or current emissions.”

Legacy pollution is the term used to describe pollutants that have remained in the environment for years, and even decades.

HCH, unlike like DDT, which is also banned, is unstable and breaks down relatively quickly.

Not being a toxicologist, Takade was unable to say what the potential harm would be to human life, if any, at the levels he discovered.

His readings put a site in South Durban at 34 nanograms per gram (ng/g) and 61 ng/g further south at Isipingo.

Globally, it puts Durban at the top end of the scale, while readings of DDT were comparatively low when benchmarked with hotspots in the U.S., Japan and Western Europe.

Takade monitors pollutants by analysing small plastic pellets gathered by volunteers around the world.

Since starting his programme in 2005, he has mapped 200 locations in 40 countries.

The pellets, which are basically petroleum products used to manufacture plastic, get washed up on beaches, having undergone a journey that usually begins with spillage in transport.

The pellets absorb various pollutants, making them accurate indicators — as accurate as mussels, a more conventional form of monitoring — of the state of the marine environment.

Three other sites in the Western Cape monitored since 1989 have shown a steady decrease in the presence of these chemicals, suggesting global regulation is working.

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