Organohalogen concentrations and a gross and histologic ...

BMD analysed by DXA reflects the areal density of hydroxyapatite provided
in g/cm 2 (Fig. 6). In the clinical evaluation of postmenopausal osteoporosis in
e.g. the femoral neck or in the lumbal vertebraes the PC-supported images are
sufficient to establish the diagnosis of osteoporosis. The DXA BMD expresses
the average hydroxyapatite content of both trabecular and cortical bone while
CT or pQCT have the possibility of expressing the hydroxyapatite in g/cm 3
and distinguish between trabecular and cortical bone tissue (e.g. Lind et al.
2003, 2004). We did not have this possibility but a comparative study between
DXA, pQCT and CT is planned as the trabecular and cortical bone tissue may
react differently to e.g. PCB exposure (Ibid.).
Period differences and time trends
First, we compared 41 skulls sampled 1892-1960 with 98 skulls sampled
from 1961-2002. In the preliminary analysis we found that BMD increased
by age in subadults, while there was no age dependency in adults of both
sexes, and that females showed significantly lower BMD than males. In addition,
there were indications of a decrease in skull BMD in old females
(postmenopausal) but this could not be confirmed due to too few observations
in this age/sex group.
For both subadults and adults, the BMD in skulls from the supposed polluted
period (1961-2002) was significantly lower compared to the supposed
non-polluted period (1892-1960). This results were supported by the trend
analysis over the entire period 1892-2002, and are in accordance with time
trend studies of grey seals in the Baltic and the Danish Kattegat harbour
seal. In these, the magnitude of alveolar bone loss (osteoporosis) in mandible
and maxilla was higher in the supposed pollution period (ca. 1960-recent)
compared to the supposed prepollution period (before 1960) (Bergman et al.
1992a, Mortensen et al.1992, Schandorff 1997a). Lind et al. (2003) investigated
the BMD in mandible and radius of the Baltic grey seal by pQCT and found
that radius trabecular bone mineral density was significantly higher in a
fairly low pollution period (1986-1997) compared to a high pollution period
(1965-1985). They also showed that the mandible cortical bone mineral density
was significantly lower in the fairly low pollution period (1986-1997)
compared to the pre-pollution period (1850-1955).
BMD and contaminant levels
The second data exploration of BMD was the relationship between organohalogens
and BMD on an individual by individual basis. In these analysis
we found a negative correlation between ∑-PCBs and ∑-DDTs (and nearly
∑-PBDEs) and BMD in subadults of both sexes while chlordanes and dieldrin
were negative correlated to BMD in adult males. In both mammals and
birds 4,4’-DDT is known to be highly estrogenic active through the estrogen
receptors (ER), while the metabolites 4,4’-DDE and also 4,4’-DDD are less
estrogenic (e.g. Kupfer and Bulger 1980). At the same time the 4,4’-DDE metabolite
is anti-androgenic – and not estrogenic – through DNA/RNA-transcription
blocking effects via ER and/or the androgen receptor (AR) (e.g.
Kelce et al. 1995, Letcher et al. 2002). These changes in gene expression are
critical for normal biological function (cell proliferation and differentiation)
as well as development in the multiple organ systems of mammals. Chlordanes
and dieldrin have been shown to have a modulating effect on cytochrome
P450 (increase) in rodents, dogs and rhesus monkey and on the
37