F, E Dewailly, G Muckle and P Ayotte. 2003. Time trends
of persistent organic pollutants and heavy metals in umbilical cord
blood of inuit infants born in Nunavik (Quebec, Canada) between
1994 and 2001. Environmental
Health Perspectives, on line 2 July 2003.
analysis of trends in body burdens of Inuit infants born in eastern
arctic Canada reveals dramatic decreases in concentrations of several
persistent organic pollutants, most notably PCBs, DDT, DDE and HCB.
Lead and mercury were reduced, but there were no trends evident
for chlordanes. The scientific team that conducted the work attributed
the decline to a combination of world-wide efforts reining in the
emmissions of the compounds, plus local changes in diet.
did they do? In this paper, Dallaire et al.
combine data from two studies by the same research team in
the Canadian arctic that measured umbilical cord blood of
Inuit infants over the period 1994-2001. The samples come
from three villages on the eastern shore of the Hudson Bay
laboratory techniques were "rigorously the same for the
entire study period," with a total of 251 samples analyzed
for 14 PCB congeners, 11 chlorinated pesticides (aldrine,
a-chlordane, g-chlordane, cis-nonachlor, p,p'-DDE, p,p'-DDT,
hexachlorobenzene, mirex, oxychlordane, trans-nonachlor and
b-BHC), lead and mercury. Slightly different sample sizes
were obtained for each different contaminants.
organochlorine measurements were reported per gram of lipid.
to right: The location of villages Puvirnituq, Inukjuaq and
Kuujjuarapik on the eastern shore of Canada's Hudson Bay.
adapted from Dallair et al. 2003.
did they find? With the exception of chlordane and two
of 14 PCB congeners, all measured contaminants decreased significantly
over the time period of the samples.
two metals measured, lead and mercury, both declined by more
than 8% per year, as did total PCBs, DDT and DDE. HCB's decrease
was somewhat less, 6.4% per year. These calculations were adjusted
statistically to take into account the village of residence,
the age of the mother, parity, and the season of birth, factors
all known to influence contaminant concentration.
time course of DDE decline (graph to left) was similar to
that of DDT (not shown) and PCBs (graph to right).
shown are the average concentrations for each birth year,
adjusted as noted above.
does it mean? The organochlorine contaminants studied by
Dallaire et al., and mercury, have reached relatively high
concentration levels within cord blood because of long-range atmospheric
transport and subsequent contamination of native foods eaten by
Inuit. Because those foods typically come from the top of the food
chain, bioaccumulation has been especially intense, leading to high
levels in Inuit mothers.
source of high lead is less clear, but is possibly due to lead poisoning
from lead shot and bullets used to kill game.
et al. acknowledge that two possible factors may be contributing
to the declines they are reporting in contamination of umbilical
cord blood: increasing control of emissions leading to lower contamination
of the food chain, and changes in diet away from contaminated native
foods. Unfortunately, they lack sufficient data on contamination
trends in native foods to be able to distinguish between these two
intepretations with certainty. They believe that both trends are
contributing. Indeed, in their estimation, "the decline is
mainly due to a diminution of food contamination and, to a lesser
extent, to dietary changes."
declines they observe in the organochlorines and lead are consistent
with observations elsewhere and with expectations based on bans
and restrictions now in place for these chemicals for several decades.
mercury trend is more puzzling. Insufficient data are available
from arctic animals to establish trends, although a study from 1981-1994
noted an increase. Data from elsewhere in the world to not show
a strong decrease. Indeed the decrease in Dallaire et al.
is not the result of a gradual decrease, as with the organochlorines,
but (as they note) instead two low years in 1998 and 2000.
summary, these data establish that infants born to Inuit mothers
along the eastern shore of Hudson Bay are experiencing less contamination
in the womb now than in the early 1990s. This is good news. The
only caveat to that assessment arises from concerns about the nutritional
impact of shifting to market foods, with added carbohydrates, junk
food, pork, chicken, milk products, and other “foreign”
et al. end by calling for additional international efforts
to reduce environmental inputs. This study's data indicate that
decades of efforts to reduce releases of persistent organic
pollutants into the environment are paying off with reduced
exposures in the womb.