Salmon fall to the inert ingredient within a pesticide mixture used
to fight spruce budworm infestations.
W.L Fairchild in Canada and S.S. Masden in Europe point to an unexpected
cause of the near extinction of Atlantic Salmon: nonylphenol used
as a surfactant in Matacil 1.8D, an insecticide used aggressively
to combat spruce budworm. If confirmed by additional work, this
is likely to become a classic example of endocrine disruption.
research indicates that nonylphenol inteferes with the ability of
salmon smolts to mature physiologically. Exposed to nonylphenol,
they cannot switch their osmoregulatory system from fresh water,
where they hatch, to salt water, into which they migrate in the
first fall of their life. This switch is normally mediated by estrogen.
Apparently nonylphenol's estrogen mimickry disrupts the switch.
Thus when the smolts reach the ocean after migrating downstream,
is a classic case of endocrine disruption for two reasons. First,
as an "inert" ingredient, nonylphenol is supposedly benign.
Second, there is no sign of impact when the smolts are sprayed.
It is only later in life that, when challenged by salt water, that
they reveal their hormonal system has been fatally disrupted.
excellent summary of the research to date on this can be found in
by Janet Raloff in Science News.