Organometallic Compounds - Organic Pollutants: An Ecotoxicological Perspective - page 167

taBLe 8.2
methyl mercury residues in fish (mg Hg/kg wet weight)

type of fish atlantic ocean Pacific ocean Indian ocean mediterranean Sea

Nonpredators 0.03-0.27 0.03-0.25 0.005-0.16 0.1-0.24

Predators 0.3-1.3 0.3-1.6 0.004-1.5 1.2-1.8.

Source: Data from Environmental Health Criteria 101 Methylmercury.

taBLe 8.3
Bioaccumulation of methylmercury

approximate
Bioaccumulation
factor

cH 3 Hg
(ppm Hg)

duration of
feeding (days) material/Species

Dressed grain 8

Muscle of chickens fed dressed grain 10-40 40-44 2

Chicken tissue fed to goshawks 10-13

Muscle from goshawks fed chicken tissue 40-50 30-47 4

in both cases. This provides further evidence for the slow elimination of methyl mer-
cury by vertebrates and the relatively poor detoxifying capacity of predatory birds
toward lipophilic xenobiotics compared to nonpredatory birds (see Chapters 2 and
5). In a related study with ferrets fed chicken contaminated with methyl mercury, a
somewhat higher bioaccumulation factor was indicated (about sixfold), albeit over
the somewhat longer exposure period of 35-58 days. This provided further evidence
for strong bioaccumulation by predators.
Since the widespread banning of organomercury fungicides, significant levels of
organomercury have continued to be found in certain areas—much of it, presumably,
having been biosynthesized from inorganic mercury. Particular interest has come to
be focused on methyl mercury pollution of the aquatic environment and on levels in
fish and piscivorous birds. In North America, the common loon ( Gavia immer ) has
been identified as a suitable indicator organism for this type of pollution (Evers et
al. 2008). The half-life of methyl mercury in the blood of juvenile loons after moult-
ing has been estimated to be 116 days (Fournier et al. 2002). In another study, the
methyl mercury half-life in blood of another piscivorous bird, Cory's shearwater
( Calonectris diomedea ), was estimated to be 40-60 days (Monteiro and Furness
2001). The ecological effects of methyl mercury on common loons will be discussed
later in Section 8.2.5.
Apart from CH 3 Hg + , other forms of R-Hg + have been found in the natural environ-
ment, which originate from anthropogenic sources but are not known to be generated
from inorganic mercury. These forms have been found in terrestrial and aquatic food
chains. A major source has been fungicides, in which the R group is phenyl, alkoxy-
alkyl, or higher alkyl (ethyl, propyl, etc.). These forms behave in a similar manner