The not-so-deadly Bt corn

[John Shuey]

Just a note that almost all modern toxicity testing includes assessments of both
acute and chronic effects.  The news report definitely answers the acute impact
under normal field condition (none under study conditions) but does does not
fully investigate chronic effects (limited to larval weight gain over time).
Most obviously missing in the analyses are the potential reproductive impacts of
exposure.  Does anyone know if the study simply hasn't progressed that far, or
has the study ended?

John


> -----Original Message-----
> From: Paul Cherubini [mailto:monarch at saber.net]
> Sent: Wednesday, August 29, 2001 11:15 PM
> To: leps-l at lists.yale.edu
> Subject: Re: The not-so-deadly Bt corn
>
> Monday August 27 7:08 PM ET
>
> Study: Biotech Corn OK for Monarchs
>
> By MAURA KELLY, Associated Press Writer
>
> CHICAGO (AP) - A new study found that pollen from genetically
> altered corn poses little risk to monarch butterfly larvae, contradicting
> previous findings that led to calls to curb the spread of bio-engineered
> crops.
>
> The larvae digest the pollen when they eat milkweed. A 1999 lab study
> at Cornell University showing that pollen from the corn could poison larvae
> caused a public outcry in Europe and rallied environmentalists to demand
> limits on the crops.
>
> But the latest study, which will be discussed Wednesday at a meeting
> of the American Chemical Society, found that the larvae usually do not
> eat enough pollen for it to harm them.
>
>  ``It's a negligible risk at best. They must consume considerable amounts
> of pollen to show an effect, and that amount of pollen rarely exists in
> nature,''
> said Mark K. Sears, chairman of the Department of Environmental
> Biology at the University of Guelph in Canada.
>
> Sears and a team of scientists looked at how far pollen traveled in a
> cornfield, if monarch larvae were exposed to it and how much of it
> the larvae typically ate. The research, funded mostly by the Canadian
> government, took place on corn fields in Canada, Iowa, Maryland and
> Minnesota between 1999 and 2000.
>
> The scientists saw no adverse effects except when larvae ate
> about 4,000 pollen grains. At that point, they began to eat and gain weight
> more slowly than larvae that ate corn pollen that was not genetically
> altered.
>
> The symptoms suggested that their stomach linings were breaking
> down, Sears said.
>
> However, because there is an average of only 120 pollen grains per square
> centimeter of a milkweed leaf, ``it's highly unlikely that larvae are going
> to
> be exposed to that much pollen to cause a measurable effect,'' Sears said.
>
>
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