Des pesticides qui persistent

Photo: FermeCarignan.blogspot.com

Une étude faite par des chercheurs scientifiques en Australie a démontré comment les pesticides organochlorés portent bien leur classement parmis les polluants organiques persistants. Les pesticides organochlorés comme le DDT et le dieldrin ont été bannis et ne sont pas utilisés en Amérique du Nord, mais certains pays continuent de les utiliser, surtout pour contrôler les moustiques qui propagent la malaria.

Mais en Australie, qui ne les utilisent plus depuis les années 1990, le DDT continue d'être détecté dans les boues municipales. Ce qui est plus inquiétant encore, certains pays recyclent les boues municipales, ce qui reste de solides après que les égouts soient traités, et épandent le produit sur des terres agricoles, laissant planer le doute que le DDT est encore présent dans des régions agricoles de l'Australie.

D'où l'importance d'analyser avec viqueur les boues que l'on planifie d'épandre sur les terres agricoles, mêmes les boues municipales que l'on prévoit composter, comme pour le projet dans la ville de Carignan. Par mesure de précaution, la municipalité de Carignan a passé un règlement qui bannit l'épandage de boues municipales dans son territoire: http://monteregieweb.com/main+fr+01_300+Carignan_bannit_les_boues_d_epuration_de_son_territoire.html?ArticleID=630235&JournalID=25

Le gouvernement de l'Uganda va recommencer à épandre du DDT pour contrer la malaria au début de juin 2010: http://www.newvision.co.ug/D/8/13/721582 . Quand on sait que le DDT comme les autres pesticides organochlorés persistants migrent dans les écosystèmes pour se concentrer dans les pôles du gloge, on se dit qu'on n'est pas sorti du bois!
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"Organochlorine pesticides are called 'persistent' for a reason.

For the first time, Australian researchers find that organochlorine pesticides remain in sewage sludge for more than 10 years. Despite having phased out the use of organochlorine pesticides in the 1990s, the chemicals continue to be detected in sewage sludge in Australia, according to a study that is the first to examine this issue on that continent.

The findings are important because they show that the chemicals can linger long after they have been banned. As in many countries, the sewage sludge – the solid part of processed sewage – is often recycled and used to fertilize crops. This suggests the pesticides are still present in agricultural areas of Australia. The low levels now found in the sludge are in most cases below government regulatory standards and international policy agreements.

Organochlorine pesticides are a class of chemicals that were used to control insect pests since the 1940s. They were mostly phased out of use in the last part of last century due to their longevity, a trait that made them effective for long term pest control, but also increased concerns of potential health outcomes such as cancer in humans and ecosystem disruption. The chemicals are still detected in people even though have been phased out in many parts of the world. Some countries still use them – mainly DDT – to control mosquitoes that carry malaria.

Researchers first detected the suite of chemicals in sludge in the 1980s and have monitored them since. In some cases, it has taken as long as 15 years after the chemicals were phased out for levels to drop below detection. Of the organochlorine pesticides monitored, DDE – the breakdown metabolite of the insecticide DDT – and dieldrin are still found at detectable levels in some countries, suggesting it takes even longer for these two compounds to break apart. In Australia, low concentrations of dieldrin and chlordane were detected in sewage sludge for up to 10 years after the pesticides were no longer being used.

These are important finding for countries continuing to use, or that have only recently discontinued use, of organochlorine pesticides. The authors indicate that sewage sludge may not be the only recyclable media that may still contain these persistent pesticides. While the chronic health effects from low level and long term exposure are poorly characterized, the presence of these persistent chemicals in sewage-based fertilizers will be an environmental factor to consider in future research on the health of people who live in agricultural communities."

Excerpts of synopsys written by Synopsis by Giffe Johnson published here: http://www.environmentalhealthnews.org/ehs/newscience/organochlorine-pesticides-persistent-in-australia-world/

Unfortunately, beginning of June 2010, the government of Uganda announced it would start spraying DDT again to fight malaria: http://www.newvision.co.ug/D/8/13/721582 Knowing that this persistent organochloride pesticide migrates through the food chain to end up concentrating somehow on our planet's poles, we are not about to get rid of this curse.