On Wed, 25 Aug 1999, Ralph Lewis wrote:
> The LD50 is at best a crude measure of toxicity.
I will concur Ralph. It just happens to be an approximate starting point.
> There is also the problem of large individual differences in toxicity
> between individuals. Phthalate esters cause me a lot of problems but many
> individuals are not as sensitive as I am. In some individuals the P450 liver
> system can handle phthalates apparently and clear them from the body. in
> other individuals the phthalates are not cleared and bio accumulate to very
> toxic levels.
Given that there are multiple P450 enzymes with varying specificities for different molecules and multiple polymorphisms within those enzymes I would assume this to be the case.
Francis Collins has noted that every individual has ~5-8 significant genetic defects. Nobody is completely immune. Some defects happen to interfere with eating, others with activity, others with biohazards, etc., etc.
> It is also interesting to look at the UN report on toxic exposure levels
> across various countries. The vary quite a bit.
A good point. Afalotoxin (sp?), a fungus that grows on peanuts (and is carcinogenic, in part because it will mutate a specific critical base in the p53 gene), is at relatively low levels in the U.S., but is responsible for significant amounts of cancer in China.
This raises the *fundamental* problem with genetic variance, "equality", safety regulations and a host of other factors. Should all children in a playground be required to play as "safely" as a child with one of the various blood clotting genetic defects? [Perhaps so that the child with the gene defect is not made to feel "disabled" or "handicapped"???]
Should all consumers be required to pay the expense of "special" food or "special" food processing techniques or "natural/organic" food because there are individuals in the population who are disadvantaged due to the genetic lottery?
[Ralph, I hope you undertand that I am strongly sympathetic for the problems you have to deal with due to this situation. I just feel that the proper solution is *not* to impose generic solutions to this problem on the general population.]
Just as I have to watch out for a car dealer selling me a lemon, I should have to watch out for a restaurant serving me foods high in phthalates if I am sensitive to them.
The solution in the AgBio-GeneTherapy debate is for the "organic" growers and the ag-purists to be paying the bill to certify their questionably scientific perspective (just as a person with a clotting defect has to pay the price of "playing safer") -- the solution is *not* to impose those costs on people who disagree with those perspectives (as would be the case if foods had to be labeled "genetically engineered", causing consumers who didn't know anything about science to boycott them in fear that they represented a risk). This is the same cost the people with normal blood clotting would be forced to endure if they were required to follow minimal-likelyhood-of-accident play practices.
Robert