Canards morts à cause des surfactifs?

Photo: Oiseaux du Haut-Richelieu

Qui se souvient des milliers de canards trouvés morts au Colorado durant les hivers de 2007 et 2008? Une étude vient de tentativement expliquer pourquoi ces canards sont morts dans les eaux chaudes qui sortent des usines de traitement d'eaux usées. Ces hivers étaient particulièrement sévères et les canards avaient dû venir se nourrir dans les seuls plans d'eau de la région qui n'étaient pas recouverts de glace. Mais on n'avait pas pu alors expliquer la cause de leur décès.

La plupart des victimes étaient des Canards souchet, et on a découvert que leurs plumes étaient couvertes de surfactifs qui ont la propriété de neutraliser la tension superficielle de l'eau et semblaient avoir enlevé l'imperméabilité de leurs plumes.

Les surfactifs sont ajoutés à plusieurs produits de tous les jours, comme les nettoyants, les détergents et les assouplisseurs de tissus. Le type de surfactif trouvé sur les plumes des oiseaux était du polyéthylène glycol (PEG pour les intimes), un composé chimique qui inquiète de plus en plus les autorités et les scientifiques.

La plupart des usines de traitement d'eaux usées peuvent enlever environ 92% des PEG, pourtant. et le PEG avait été détecté sur des plumes d'autres volatiles qui n'avaient pas perdu leur imperméabilité. Il faut dire que les Canards souchet ne se nourissent pas comme les autres canards et restent dans l'eau plus longtemps.

Les chercheurs avouent vouloir en savoir plus sur la recombinaison de composés chimiques qui se trouvent dans les systèmes de traitement d'eaux usées.

Les surfactifs ont des effets pervers sur la vie aquatique également. On pense que l'ingrédient qui fait le plus de tort aux amphibiens dans le pesticide Roundup serait le surfactif dans sa recette qui lui permet de pénétrer dans les tissus végétaux, mais qui tue aussi les amphibiens!
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"Large metro duck die-off blamed on chemicals

Chemicals prevalent in everyday products may be partly to blame for the deaths of more than 1,000 ducks during the winters of 2007 and 2008, according to a study released Tuesday by federal wildlife officials. The study, led by the U.S. Geological Survey and prompted by the U.S. Fish and Wildlife Service, began in fall 2008, after abnormally high numbers of birds were dying at various wastewater-treatment plants along the Front Range.

The ducks, mostly northern shovelers, were exposed to a class of chemicals known as surfactants that break down surface tension in water, the study concluded. The compound was found on their feathers and apparently compromised their ability to shed water.

Surfactants are added to many products, including cleaners, detergents and fabric softeners, according to the U.S. Department of Health and Human Services. The chemical also is used as a defoaming agent in food and is in soda pop as well, Wegrzyn said. The specific type of surfactant discovered on the birds' feathers was polyethylene glycol. PEG is considered to be a compound of "emerging concern" by some regulators, scientists and others.

About 92 percent of PEG is removed by Metro's sewage-treatment system, the district's chief chemist said.

Although the study did not blame PEG alone for the bird deaths, many of the ducks died from hypothermia or drowning because of a change in the physical makeup of their feathers. The barbules on their feathers were no longer interlocking to repel water, so it soaked their skin and feathers, Wegrzyn said.

But PEG also was found on the feathers of some birds that did not lose their ability to repel water.

Northern shovelers have unique feeding patterns compared with other ducks, Wegrzyn said. They feed mostly on microorganisms, such as algae, in water, while other ducks feed on a variety of food sources such as vegetation and insects. In addition, northern shovelers stay in the water longer to feed.

During the heavy snows and extended periods of cold weather during the winters of 2007 and 2008, much of the duck habitat in the region was covered with ice. This sent birds looking for open water at wastewater-treatment plants. There, they fed on microorganisms in the secondary clarifier and the chlorine-contact chambers.

Researchers still would like to do more work to determine what combination of chemicals present in wastewater-treatment systems affects the "waterproofing" of ducks."

Excerpts from article written by Sarah Horn published in The Denver Post here: http://www.denverpost.com/ci_15618069

Surfactants have unsuspected effects on wildlife. For example, the one used in the pesticide Roundup was found to be deadly to amphibians, especially those in their tadpole stages: http://www.medicalnewstoday.com/articles/22159.php It is the surfactant in Roundup that lets it penetrate the tissues of plants to kill them. It also contributes to the decline of our amphibian population.