Organohalogen concentrations and a gross and histologic ...

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small sample size and the effect of seasonal variation. However, there were
tendencies for some compounds to have lower concentrations in females
than in males. As no patterns could be detected in the concentrations of OCs
relative to age in adult animals as observed in other studies (e.g. Norstrom
et al., 1998), the animals were grouped into subadults bears of both sexes
(below 5 years for females and below 6 years for males), adult females (5
years old and above) and adult males (6 years old and above) for statistical
analysis.
ANOVA with the factors sex and age group (sub adult, adult females and
adult males), month (January, February, March, April-July, August and
September) and their interactions were performed to test for differences in
mean OC concentrations. The least square estimates of the marginal means
from the ANOVAs were back transformed to geometric means and plotted
to illustrate the differences among months for each sex and agegroup (Fig.
2). Multivariate analysis of variance (MANOVA, Wilks λ) were performed to
investigate similarities in the patterns of OC (CBs, DDTs, HCHs, chlordane,
chlorobenzene, dieldrin) concentrations among months and sex and age
groups and their interactions. Similarities in the patterns among OC were
further analysed by reorganising the data prior to ANOVA so that the dependent
variable was ln-logarithmically transformed concentrations and the
factors were OC compound, month, sex and age groups and all first order
interactions. Statistical tests of type III were used for both the ANOVA and
the MANOVA.
Data concerning OC concentrations in polar bears from central East Greenland
sampled in 1990 (Norstrom et al. 1998) were made available courtesy of
R. Norstrom (Dept. of Chemistry Carleton University, Ottawa) so that a
comparison could be made of OC concentrations between 1990 and 1999-
2001. An ANOVA on ln-logarithmically transformed concentrations, using
sex and age group (subadult, adult female and adult males), sampling period
and the interactions as factors, was applied to test for differences in
mean OC concentrations. The least square estimates of the marginal means
from the ANOVAs are used to illustrate the differences between the two
sampling periods. For calculation of the half-lives of the analysed contaminants
the standard formula:
A =
−0.
693t
A T
O 1 / 2
Where T 1/2 is the half-life, A 0 is the concentration at time 0, and A is the concentration
after the ellapsed time (t) (Nave 2000). All calculations were performed
using the statistical software package SAS ® (PC-version V8) and
Excel 97 ® was used as a spreadsheet.
Results
Sample Composition
Polar bear tissue samples were collected by local subsistence hunters in the
Ittoqqortoormiit/Scoresby Sound area, central East Greenland between
69˚00’N and 74˚00’N, 19˚00’W and 24˚00’W in 1999-2001, as illustrated in Fig.
1. The total sample of 92 polar bears consisted of 50 subadult bears of both
sexes, 25 adult females, 16 adult males and 4 with unknown sex or sampling
month (Table 1).