As seen in the latest Science News(1) ($ subscription article) tadpoles exposed to low levels of a common herbicide (Atrizine) have a greater death rate than ones exposed to higher levels. This finding is another in a series of recent findings(2)($ subscription article) that show that the ill effects of some pollutants are worse when those pollutants are at lower concentrations. The basic reason for why this might be is unknown, but there is some speculation that the hormonal system may be tuned to interact with chemicals only at very low concentrations.
(1) Science News, July 10, 2004; Vol. 166, No. 2, p. 20
(2) Science News, Oct. 12, 2002; Vol. 162, No. 15, p. 228
Other references and sources available from Science News(free access)
Keywords: Pollution, Pesticides, Amphibians
2 comments:
These are all of a class of toxins known as estrogen mimicers, chemicals that are like those that operate at the very lowest level on the minute of cellular life: only in these very small amounts can they get in the door: in larger amounts, they are blocked by the bodies defenses, immune system, inflammation, etc.
Only in the 1990s could be measure parts per billion. The body operates at parts per billion and surely well below that: parts per trillion.
Life developes as certain agents conflicting with that life form are buried, layered, sunk into the sea. It's as if we open all the bottles in the medicine chest,the cleaners and detergents in the laundry and the garange, and spread them about the lawn and then ran barefoot through it.
On the other hand, while these matters are of great and lasting import, our lives are not: they are short and when focused on the miracles at hand, gifts beyond measure or comprehension. Moths of the fields do so very very well unless and until they are drawn to some very bright and rather useless porch light.
So, sorry for leaving a porch light on :-)
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