GENTECH archive


RE: Substantial equivalence - what is it?

I am trying to be objective about GMOs and foods. My gut reaction is that
research, in a laboratory, is good. However I am wary about releasing GMOs
into the environment or feeding them to the population en masse.

One criticism of the anti GM lobby is that they are unscientific,
irrational and almost hysterical. However a central plank of GM food
regulation appears to be "substantial equivalence" and so far I have not
seen any strong defence of this term. In fact, so far, it appears to be
pseudo science with no real substance.

I wrote;
>I don't see how such a term can have any scientific meaning unless it
>relates to specific properties of the organism which can be measured. The
>word "substantially" also implies that there is some way of knowing if
>differences in the measured properties are significant or not.

There were three reasons that I wrote the above;

1. New Scientist 8/May/1999 - Even with the right gene, you might not see
This article stated "Colour blindness may be caused by genes being in the
wrong order, rather than being faulty, say vision researchers in Seattle".

If gene order can have quite a profound effect on an organism what are the
implications for "substantial equivalence" ?

2. New Scientist 15/May/1999 - Fiendish Fungus, a hybrid blight is running
amok in Europe's woodlands. The article tates that two species of
Phytophthora, relatives of potatoe blight, have hybridised to to create an
offspring that that has killed 10% of the Alders in southern England and
Wales, and is steadily killing 2% of the population each year. Fungi rarely
hybridise in nature, because species that evolve in the same environment
have evolved barriers to prevent it. "But fungi that are geographically
isolated don't accumulate barriers to reproduction. so if you bring them
together there is more risk of hybridisation" says Brasier.

The above is an example of the problems that can be caused just by
physically relocating organisms. Can we pedict the effect of gene transfer
when we release "substantially equivalent" organisms ino the wild ?

3. BSE. This is really my main concern with GM. BSE, to me, show up a
profound lack of knowlege of what could happen when we modify natural
systems. The 
prion protein PrP exists in two different conformational forms. PrPc is
thought to be the benign form of the protein and is found in normal,
healthy cells. However, PrPsc is thought to be the infectious "scrapie"
form which causes neurodegenerative diseases. The only difference between
PrPc and PrPsc is that the protein is folded in a different way. I imagine
that in terms of "substantial equivalence" PrPc and PrPsc would be regared
as totally equivalent. Yet one is benign and the other caused a massive
food related disaster which is still not really understood. What are the
implications of this for "substantial equivalence" ?

Unless somebody can throw some light on this the term "substantial
equivalence" seems to be very subjective and rather missleading.