CHAPTER 13 • Mercury in Marine Environments
257
13.6.3
Human Exposure to Mercury in some Fish Eating Communities
The best known of the poisoning incidences was at Minamata Bay on the south-west
coast of Kyushu (Takeuchi 1972; Smith and Smith 1973; D'Itri 1991), where residents
showing symptoms relating to the peripheral and central nervous systems were noted
in the 1950S. By 1956 it was established that the disease was caused by the consumption of contaminated shell fish and fish from Minamata Bay. The source of the contamination was a plastics factory using mercuric chloride as catalyst. Evaluation of
the incident makes it appear most likely that the contamination was not only inorganic mercury but also methyl or other alkylated mercury compounds.
In a number of marine fish eating coastal and island communities, studies have
been carried out to assess levels in seafood, human exposure and consequences
for health. These include Greenland (Hansen et al. 1976), UK (Haxton et al. 1979) Iceland (Johannes son et al. 1981), Seychelles (Matthews 1982), Singapore (Foo et al. 1988),
Maldives (Renzoni 1989), Canada (WHO/IPCS 1990), the Mediterranean (Renzoni 1992;
Renzoni et al. 1998; Franchi et al. 1994), Minamata (Harada et al. 1998), the Faroe Islands (Weihe et al.I997; Grandjean et al.1997, 1998) and Madeira (Renzoni 1992; Renzoni
et al.1998; Gaggi et al. 1996). Some of the more recent case studies are discussed briefly
below.
13.6.3.1
The Mediterranean
As discussed above (Section 1342), many marine organisms living in the Mediterranean Sea have higher mercury body burdens than do the same species living in the
Atlantic or other Oceans (Stoeppler et al. 1979; Bernhard 1985,1988). Species from the
North Tyrrhenian Sea show particularly enhanced mercury in most species. The correlation between body weight and total mercury concentrations in the tissues (wet
weight) of the Norwegian lobster from this area, is shown in Fig. 13.6. Positive correlations between mercury levels in benthic crustaceans and mollusks and those in sediments have been demonstrated for the eastern Mediterranean (Hornung et al. 1984).
Because of the high levels of mercury in fish and seafood tissue, there are risks of high
mercury intake, since many residents in the coastal areas consume, on average, more
than 4 seafood meals per week. An investigation of mercury in hair from residents of
fishing villages along the Tyrrhenian Sea (Table 13.4) demonstrated a positive correlation with the number of meals consumed (Renzoni 1992; Renzoni et al. 1998), in addition, a few values over 50 Ilg g -I were found. These individuals were investigated further and positive correlations were found between mercury in blood and chromosomal
aberrations (Franchi et al. 1994).
13.6.3.2
Present Day Exposure in the Minamata Area
A study of present day inhabitants (ages 32-82 years) of the Minamata area (Harada
et al. 1998) showed that of the 185 subjects only 6 had total mercury in scalp hair
>10 Ilg g-I. There was an upward trend correlated with the intake of seafood (Table 13.5).
257
13.6.3
Human Exposure to Mercury in some Fish Eating Communities
The best known of the poisoning incidences was at Minamata Bay on the south-west
coast of Kyushu (Takeuchi 1972; Smith and Smith 1973; D'Itri 1991), where residents
showing symptoms relating to the peripheral and central nervous systems were noted
in the 1950S. By 1956 it was established that the disease was caused by the consumption of contaminated shell fish and fish from Minamata Bay. The source of the contamination was a plastics factory using mercuric chloride as catalyst. Evaluation of
the incident makes it appear most likely that the contamination was not only inorganic mercury but also methyl or other alkylated mercury compounds.
In a number of marine fish eating coastal and island communities, studies have
been carried out to assess levels in seafood, human exposure and consequences
for health. These include Greenland (Hansen et al. 1976), UK (Haxton et al. 1979) Iceland (Johannes son et al. 1981), Seychelles (Matthews 1982), Singapore (Foo et al. 1988),
Maldives (Renzoni 1989), Canada (WHO/IPCS 1990), the Mediterranean (Renzoni 1992;
Renzoni et al. 1998; Franchi et al. 1994), Minamata (Harada et al. 1998), the Faroe Islands (Weihe et al.I997; Grandjean et al.1997, 1998) and Madeira (Renzoni 1992; Renzoni
et al.1998; Gaggi et al. 1996). Some of the more recent case studies are discussed briefly
below.
13.6.3.1
The Mediterranean
As discussed above (Section 1342), many marine organisms living in the Mediterranean Sea have higher mercury body burdens than do the same species living in the
Atlantic or other Oceans (Stoeppler et al. 1979; Bernhard 1985,1988). Species from the
North Tyrrhenian Sea show particularly enhanced mercury in most species. The correlation between body weight and total mercury concentrations in the tissues (wet
weight) of the Norwegian lobster from this area, is shown in Fig. 13.6. Positive correlations between mercury levels in benthic crustaceans and mollusks and those in sediments have been demonstrated for the eastern Mediterranean (Hornung et al. 1984).
Because of the high levels of mercury in fish and seafood tissue, there are risks of high
mercury intake, since many residents in the coastal areas consume, on average, more
than 4 seafood meals per week. An investigation of mercury in hair from residents of
fishing villages along the Tyrrhenian Sea (Table 13.4) demonstrated a positive correlation with the number of meals consumed (Renzoni 1992; Renzoni et al. 1998), in addition, a few values over 50 Ilg g -I were found. These individuals were investigated further and positive correlations were found between mercury in blood and chromosomal
aberrations (Franchi et al. 1994).
13.6.3.2
Present Day Exposure in the Minamata Area
A study of present day inhabitants (ages 32-82 years) of the Minamata area (Harada
et al. 1998) showed that of the 185 subjects only 6 had total mercury in scalp hair
>10 Ilg g-I. There was an upward trend correlated with the intake of seafood (Table 13.5).