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Recycling pesticide bottles: a risk?

Manufacturers bottle many toxic pesticides in high-density polyethylene (HDPE). Because such contents can permeate this plastic, labels instruct consumers not to reuse the bottles. Yet people dispose of so many plastic pesticide containers-1 million a year in Canada alone-that waste managers have begun recycling pesticide-impregnated HDPE into building materials, such as fence posts. Researchers at the University of Guelph in Ontario now report that a technique adopted recently to limit pesticide leaching from this plastic "is not as effective as it could be in limiting pesticide penetration."

Manufacturers usually dissolve oily pesticides in a solvent to ease their dispersal. However, the solvent degrades HDPE, helping pesticides enter and leach out of the plastic. To stem the resulting losses from evaporation, pesticide makers have turned to fluorination-where fluorine atoms swap places with hydrogen in the plastic's molecules, forming a solvent barrier.

However, notes Graham M. O'Brien, "the containers we looked at, the industry standard for packaging these pesticide formulations, didn't form a complete barrier." These plastics still incorporated pesticides at "quite high levels"-up to 1 gram of solvent-based herbicide, such as trifluralin or 2,4-D, per 350 grams of plastic. By contrast, HDPE produced by a more stringent, but expensive, fluorination technique allowed one-thousandth or less of that amount to permeate-yielding truly negligible levels.

Few companies use this more expensive technique for pesticide bottles, he noted, because the old type "appeared to be doing its job"-cutting product losses from evaporation.

Guelph studies published earlier this year found that plastic from recycled pesticide containers can leach detectable, albeit insignificant amounts, of the toxic compounds. However, O'Brien observes, pesticides that are more mobile or more highly concentrated than those studied may still present problems. That's why he argues that only the better-fluorinated pesticide containers should be recycled if any resulting products will be used in watery environments or where extensive human contact can occur.
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Title Annotation:Environment; high density polyethylene bottles used to package pesticides leach toxic compounds when recycled
Author:Raloff, Janet
Publication:Science News
Article Type:Brief Article
Date:Nov 25, 1995
Words:313
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