Page 397 - The Toxicology of Fishes

Liver Toxicity 377

TABLE 7.7
Summary of Application of Fish Liver Histopathology in Major Pollution Monitoring Programs
Pathologic Entity Monitoring Programs Refs.
Liver tumor Recommended for use by the ICES ICES (1989, 1996, 1997)
Hepatic lesions Multidisciplinary surveys by the U.S. National WGBEC (2002)
Marine Service
Fisheries services on the Pacific and Northeast coasts Malins et al. (1988)
Gulf of Mexico integrated monitoring programs Varanasi et al. (1989); Johnson
et al. (1992a,b); Wolfe (1992);
Myers et al. (1993); USEPA (2000)
Macrophage aggregate NOAA marine monitoring programs and U.S. Wolf et al. (1992); Strobel et al. (1999)
National Estuary Program in Virginia estuaries
Lycrosomal integrity North Sea pollution monitoring in Germany Broeg et al. (1999)

ecotoxicological value of the EROD biomarker are significant (Au, 2004). This biochemical biomarker
has proved successful in identifying regions impacted by industrial pulp and paper effluents (Munkittrick
et al., 1991). The use of hepatic EROD induction in fish can be found in regulations in Canada and
Australia (Collier et al., 1992, 1995; Holdway et al., 1994, 1995), and such an approach is considered
potentially suitable for long-term monitoring of the marine environment in Hong Kong (EPD, 2003).
Histocytopathological alterations of fish liver are frequently used in monitoring programs as markers
of fish health. Numerous field studies have reported liver histopathological changes in fish from con-
taminated environments, and liver histopathology has been found to be a sensitive indicator of pollution
stress and impaired fish health (Handy et al., 2002; Schwaiger, 2001; Teh, 1997; Vethaak and Jol, 1996;
Zimmerli et al., 2007). A drawback of liver histopathology to assess toxicant stress can be the qualitative
nature of histological data; however, this can be overcome by using standardized, semiquantitative
evaluation schemes (Bernet et al., 1999).
It is likely that the histocytopathological symptoms described in fish liver may decrease the fitness of
the individual through disturbed metabolic homeostasis and proper functioning of vital biological pro-
cesses (e.g., detoxification). Fish liver pathological symptoms are of significant ecological relevance.
Moreover, hepatic lesions are highly sensitive to pollutant exposure, and certain lesions have been well
correlated with contaminant exposure (Au, 2004). Some histopathological incidences are species specific;
the restrictive natural distributions of many species may make monitoring results not directly comparable
between various locations. Monitoring the presence of liver tumors in young fish may not be suitable
due to a long latent period for disease development. Except for liver tumors that have a well-defined
and validated morphology (Boorman et al., 1997), the technical difficulty is high for symptom diagnosis.
Moreover, certain hepatic lesions, such as macrophage aggregates, relate to a large number of possible
confounding factors (e.g., season, reproductive stage, migration pattern, nutritional conditions). This
makes it necessary to strictly standardize sampling protocols, which sometimes may be difficult. This
problem is further exacerbated by the low incidence of MAs in normal fish livers, and a large sample
size is necessary to discern statistically significant differences between fish population in different sites
or times. In general, the hepatic lesions reviewed are responsive to a variety of pollutants and are therefore
indicative of the general quality of the environment rather than specific types of pollutants. Some
histopathological symptoms of fish livers have already been applied in field monitoring (Table 7.7).
Liver pathologies are currently classified as Category II by the OSPAR Commission, which includes
criteria for quality assurance procedures that are not yet in place although they may be used for monitoring
(WGBEC, 2002).
In contrast, cytological structures (e.g., lipopigments and lysosomes) that occur commonly in most
living cells are easy to identify. The cause-and-effect relationships and detailed mechanisms leading to
the development of most pathological symptoms are becoming clear. Fish hepatic lipopigment has shown
promise as a cytological marker of effects of PAHs and BaP (Au, 2004; Au and Wu, 2001; Au et al.,
1999). Lipopigment content was chosen as one of the battery of biomarkers to assess long-term effects