Organohalogen concentrations and a gross and histologic ...

al., 2003). We did not find such a seasonal difference in polar bears probably
due to the fact that only pregnant polar bears den for a long time (we did not
have samples from pregnant polar bears) whereas all other polar bears of
both sexes and age only periodically use shelters (faculative dens) when
environmental conditions are adverse (e.g. Ferguson et al, 2000).
Histological changes in relation to contaminants and BMD
The reason for lack of correlations between organohalogen levels and renal
lesions, could be the relatively large individual variability due to age, sex,
season and genetics, which make the adipose tissue concentration of organohalogens
a poor measure of the individual life long exposure. In addition,
female transference of organohalogens to the offspring reduces the
general body burden which again reduces the value of using body concentration
as a measure of exposure for females (e.g. Polischuk et al, 1995, 2002).
Total exposure which, at least for some effects, is of importance cannot be
detected from body concentrations at late stages of life. The indications of
relations between bone density and renal lesions in adult males could indicate
a dysfunction in the glomerular and tubular reabsorption mechanisms
as indicated by the tubular protein loss (Friberg et al., 1986; WHO, 1992;
Domrongkitchaiporn et al., 2002). However, that BMD in the group of severe
changes should be higher than in the group of mild lesions doesn’t make
sense, and it could therefore be a result of the relatively small sample size.
It was not possible to evaluate whether the possible organohalogen induced
lesions of pluripotent Ito-cells and hepatocytes in the liver tissue of the present
polar bears (Sonne et al., submitted) have contributed to the renal lesions
through a vitamin A release with subsequent toxicity to renal tissue (e.g.
Sato et al., 2001).
Pollution as a co-factor?
The histopathological changes found in glomeruli, tubuli and interstium
were to som degree the same as those reported in Baltic grey seal (Halichoerus
grypus) and ringed seal heavily exposed to PCBs, DDTs and heavy
metals between 1977-1996 (Bergman and Olsson, 1985; Bergman et al., 2001).
These studies suggested the lesions to be a result of age, but based on a lowexposed
reference material from Svalbard, their investigation also indicated
chronic exposure to organohalogens as a plausible etiological factor. Also,
environmentally PCB contaminated bream-fish (Abramis brama) and asp-fish
(Aspius aspius) in a lake in Southern Finland exhibited dilatation of glomerular
capillaries, mesangial edema and adhesions between visceral and
parietal layers of Bowman’s capsule with filling of Bowman’s space (Koponen
et al., 2001). These changes were more or less the same as those found in
the present polar bears.
The renal lesions in the present East Greenland polar bears were all similar
to the histopathological changes in PCB exposed laboratory animals, wild
Baltic seals and wild fish. In addition to this, severe lesions were only found
in adult and old animals, which propose age as the reason for this. But, the
PCB levels in East Greenland polar bears are supposed to have been significantly
higher around 1985 (e.g. Dietz et al., 2004), and therefore organohalogen
exposure could be a co-factor in the development of these present
lesions in adult and old animals. We therefore suggest that age and exposure
to organohalogens are the two major factors in the pathogenesis of the renal
lesions found in the East Greenland polar bears.
171