Environmental Engineering Reference
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ability to maintain sustained attention in a cohort of four-year-old children. The mothers
came from a non-Arctic community where fish formed a major part of the diet and where
aquatic PCB pollution was known to have occurred. The researchers found that “[p]renatal
exposure to PCBs was associated with less efficient visual discrimination processing and
more errors in short-term memory scanning but not with sustained attention.” Surprisingly,
although a greater exposure to PCBs must have occurred during breastfeeding, this source
did not contribute to the reduced cognitive performance. Therefore, the window for sus-
ceptibility appeared to be located within the time of embryonic development. In 1996 and
2003, Joseph and Sandra Jacobson published results after looking at the same types of cog-
nitive endpoints for the same children now aged 11 years. Prenatal exposure to PCBs via
umbilical cord blood was associated with lower verbal IQ scores, memory and (this time)
their ability to maintain attention. The most highly exposed children were three times as
likely to have lower IQ scores and twice as likely to be at least two years behind in reading
comprehension. Again, there was no relationship to PCB exposure via breast milk.
Similar cohort studies have been carried out in other parts of the world, but the results
between areas and cohorts have been quite variable, perhaps reflecting different method-
ologies. In the Faroese cohort we will look at in relation to mercury exposure, Philippe
Grandjean and colleagues looked for neuropsychological outcomes of prenatal exposure to
PCBsinseven-year-oldchildren.PCBlevelsinumbilicalcordbloodathighconcentrations
were associated with similar types of cognitive deficits as reported by the Jacobsons, but
there was evidence of confounding with mercury levels also present in the cord blood. In
Arctic foods used by northern indigenous peoples, these two toxic substances are almost
always found together.
Recently, several researchers have been using cohort studies to examine outcomes re-
lated to POPs that were not included in the original CLRTAP POPs protocol and Stock-
holm Convention. Most are not members of the original “legacy” organochlorines but do
include several substances that are already now being addressed in the two international
agreements. These studies reinforce the justification for the actions taken, but they are also
exposing the need for a much more precautionary approach to chemical regulation than has
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