Environmental Engineering Reference
In-Depth Information
been the practice in the past. For example, in a study published in 2012, Brenda Eskenazi
and colleagues looked for associations between impaired neurobehavioural development
in five- to seven-year-old children (whose parents were agricultural workers in southern
California) and their prenatal and postnatal exposure to one of the brominated flame-re-
tardant family of substances (PBDE). They found “associations between maternal PBDE
levels during pregnancy and evidence of deficits in children's attention, fine motor coordin-
ation and cognitive functioning at both ages”. In addition, the children's PBDE levels (not
the mothers' blood levels in pregnancy) “were associated with lower scores for full-scale
IQ, particularly processing speed, verbal comprehension and perceptual reasoning”. The
researchers also found that each ten-fold increase in the children's total measured PBDE
levels wasassociated withatleast 4.5times higheroddsofthechild beingrated byteachers
as at least moderately hyperactive and impulsive.
It is very difficult to summarize exactly what the PCB cohort studies mean in the Arc-
tic context, partly because (as we shall see) in utero exposure to mercury has been associ-
ated with similar outcomes and partly because cohort studies conducted in the Arctic have
always used quite small sample sizes. Clearly, there is sufficient evidence from the studies
conducted outside theArctic togenerate concern,butwewill understand alittle morewhen
we complete our mercury review.
Organophosphate pesticides were considered to be an alternative to organochlorines,
such as DDT. They have a much greater acute toxicity than most organochlorines, but they
rapidly degrade on exposure to sunlight and in air and soil. They function by blocking
the activity of an enzyme called acetylcholinesterase that is essential for nerve function
in many species, including insects and mammals. They are not POPs in the context of the
CLRTAP protocol and the Stockholm Convention because of their lack of environmental
persistence and there is no evidence they are responsible for any problems in the Arctic.
However, I thought they deserved a quick mention here because studies have associated
them with similar cognitive outcomes following the prenatal exposure we have seen for
PCBs and mercury. This clearly indicates the need for a more rigorous toxicological ex-
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