Carbon and nitrogen stable isotope ratios and mercury concentration in the scalp hair of residents from Taiji, a whaling town.

We analyzed stable isotope ratios of carbon (δ(13)C) and nitrogen (δ(15)N) as well as mercury (Hg) concentration in the scalp hair of Japanese who consumed whale meat and those who did not, and investigated the relationships among the δ(13)C and δ(15)N values and Hg concentration. The average δ(15)N and δ(13)C values of whale meat-eaters (10.11‰ and -18.5‰) were significantly higher than those of non-eaters (9.28‰ and -18.9‰), respectively. The average Hg concentration of whale meat-eaters (20.6 µg/g) was significantly higher than that of non-eaters (2.20 µg/g). Significant positive correlations were found between the δ(13)C and δ(15)N values and between the δ(15)N value and Hg concentration in the hair of whale meat-eaters, while the correlation between the δ(15)N value and Hg concentration was not statistically significant in the non-eaters. The consumption of whale meat may increase Hg concentration as well as δ(15)N and δ(13)C values in scalp hair.

Levels of mercury in muscle and liver of star-spotted dogfish (Mustelus manazo) from the northern region of Japan: a comparison with spiny dogfish (Squalus acanthias).

We analyzed mercury (Hg) concentrations in muscle and liver samples of star-spotted dogfish (Mustelus manazo) caught off the northern region of Japan and compared them with those of spiny dogfish (Squalus acanthias) caught in the same region. The average body length of male star-spotted dogfish specimens was significantly smaller than that of female specimens, reflecting the slower growth rate of male fish. Hg concentrations in liver and muscle increased with increases in body length and estimated age of both male and female star-spotted dogfish specimens. However, the relationships between Hg concentration in liver or muscle and body length or estimated age of male specimens differed markedly from those of female specimens, reflecting differences in growth rate and cessation of growth on reaching maturity. Marked increases in Hg concentration in liver of male and female star-spotted dogfish specimens were observed slightly later than increases in Hg concentration in muscle of those specimens due to growth cessation. These marked increases in Hg in liver may reflect increases in Hg due to the formation of mercury selenide. Similar results were previously reported in spiny dogfish specimens, except spiny dogfish showed only trace levels of Hg in liver (Endo et al., Chemosphere 77:1333-1337, 2009). The greater lipid content in liver and the larger liver size in spiny dogfish may explain the much lower levels of Hg observed in liver of spiny dogfish compared with those in the star-spotted dogfish.

Levels of mercury and organohalogen compounds in the muscle and liver of kidako moray eels (Gymnothorax kidako) caught off the southern region of Japan.

We analyzed the levels of total mercury (T-Hg), methylmercury (M-Hg) and Cd in the muscle and liver of kidako moray eels (Gymnothorax kidako) of different body lengths caught off Kochi Prefecture in southern Japan. Furthermore, we analyzed the levels of organohalogen compounds such as polychlorinated biphenyls (PCBs), p,p'-1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE), trans-nonachlor and 2,3,3',4,4',5,5'-heptachloro-1'-methyl-1-2'-bipyrrole (Q1) and stable isotope ratios of carbon (δ(13)C) and nitrogen (δ(15)N) in the muscle of eels. The concentrations of T-Hg and M-Hg in the muscle (edible part) were 0.31±0.08 µg/wet g and 0.25±0.06 µg/wet g (n=26), respectively, and those in large eels exceeded the Japanese legislated levels of T-Hg (0.4 µg/wet g) and M-Hg (0.3 µg/wet g) in fish and shellfish, respectively. The T-Hg and M-Hg concentrations in the liver were markedly higher than those in the muscle, respectively. The ratios of M-Hg to T-Hg in the muscle and liver were about 80 and 60%, respectively, and those ratios tended to decrease with increased body length. The Cd concentrations in the liver tended to increase proportionally with body length, while that in the muscle was trace (around or below 0.03 µg/wet g). The concentrations of PCBs, p,p'-DDE, trans-nonachlor in the muscle tended to increase proportionally with body length, while that of Q1 did not. The δ(13)C and δ(15)N values in the kidako moray eel were markedly higher than those in offshore habit predators reported elsewhere, which may reflect the inshore habitat of this eels.

Stable isotope ratios and mercury levels in red meat products from baleen whales sold in Japanese markets.

We analyzed the δ(13)C, δ(15)N and δ(18)O values and Hg concentration in red meat products originating from the predominant types sold in Japan for human consumption: two populations of common minke (J- and O-types), Bryde's and sei whales in the western North Pacific Ocean, and fin and Antarctic minke whales in the Southern Ocean. The order of the trophic positions, evaluated by δ(15)N values and Hg concentrations, coincided with their known feeding habits: common minke (J-type)=common minke (O-type)> Bryde's ≥ sei ≥ Antarctic minke ≥ fin. The Hg concentrations in the combined samples from the six samples were significantly correlated with their δ(15)N values (γ=0.455, n=66, p<0.05), reflecting overall differences in the trophic level. This correlation was not significant for within-species comparison for the common minke (J- and O-types) or the Bryde's whale, probably reflecting the higher δ(15)N value and lower Hg concentration in the North Pacific Ocean around Japan. Determination of δ(13)C, δ(15)N and δ(18)O could be used to discriminate between the red meat products originating from the whale species in the North Pacific and Southern Oceans. However, the four whale species or populations in the Pacific Ocean could not be discriminated on basis of these values, nor could the two species in the Southern Ocean. Positive correlations between the δ(13)C and δ(15)N values and negative correlations between the δ(15)N and δ(18)O values and the δ(13)C and δ(18)O values, probably reflecting migration patterns, were found in some whale species in the North Pacific and Southern Oceans.

Levels of mercury and organohalogen compounds in Pacific bluefin tuna (Thunnus orientalis) cultured in different regions of Japan.

Contamination levels of total mercury (T-Hg), p,p'-DDE, and polychlorinated biphenyls (PCBs) in akami (leaner meat) and toro (fatty meat) samples from Pacific bluefin tuna cultured in the southern (four locations) and central (three locations) regions of Japan were analyzed. The contamination level of T-Hg in the akami and toro samples from the southern region tended to decrease with an increase in latitude, whereas those of p,p'-DDE and PCBs tended to increase. These spatial trends in contaminants were similar to those reported previously in wild tuna caught off the coast of Japan (Hisamichi et al., in Environ Sci Technol 44:5971-5978, 2010). However, the contamination level of T-Hg in akami and toro samples from one location in the central region was the highest among all seven locations, whereas the contamination level of p,p'-DDE was lower than that from any location studied in the southern region. Thus, contamination levels of T-Hg, p,p'-DDE, and PCBs in the cultured tuna may reflect contamination levels not only in the marine environment but also in prey fish used as bait.

Levels of mercury and organochlorine compounds and stable isotope ratios in three tuna species taken from different regions of Japan.

Levels of mercury (Hg) and organochlorine compounds (OCs), such as PCBs and p,p'-DDE, as well as the stable isotope ratios of carbon (delta 13C) and nitrogen (delta 15N) were compared in Pacific bluefin, yellowfin, and albacore tuna taken from the southern, central, and northern regions of Japan according to tuna species and the region of origin. Levels of Hg and OCs as well as the delta 15N value were the highest in the bluefin tuna, reflecting their higher trophic position and longer life span. The average Hg concentrations tended to be higher in specimens taken in the southern region than in the central and northern regions for bluefin tuna and in the southern region than in the central region for yellowfin and albacore tuna, while the levels of OCs tended to be lower in the southern region except for yellowfin tuna. The spatial differences in Hg and OCs levels found in the three species may reflect geographical differences in the contamination of marine environment around Japan. Negative correlations between delta 13C and delta 15N were found in the yellowfin and albacore tuna, probably reflecting the latitudinal effect, whereas a positive correlation was found in the bluefin tuna, probably reflecting a diet shift during wide-range migration.

Stable isotope ratios of carbon and nitrogen and mercury concentrations in 13 toothed whale species taken from the western Pacific Ocean off Japan.

Stable isotope ratios of carbon (partial differential(13)C) and nitrogen (partial differential(15)N) and total mercury (T-Hg) concentrations were measured in red meat samples from 11 odontocete species (toothed whales, dolphins, and porpoises) sold in Japan (n = 96) and in muscle samples from stranded killer whales (n = 6) and melon-headed whales (n = 15), and the analytical data for these species were classified into three regions (northern, central, and southern Japan) depending on the locations in which they were caught or stranded. The partial differential(15)N in the samples from southern Japan tended to be lower than that in samples from the north, whereas both partial differential(13)C and T-Hg concentrations in samples from the south tended to higher than those in samples from northern Japan. Negative correlations were found between the partial differential(13)C and partial differential(15)N values and between the partial differential(15)N value and T-Hg concentrations in the combined samples all three regions (gamma= -0.238, n = 117, P < 0.01). The partial differential(13)C, partial differential(15)N, and T-Hg concentrations in the samples varied more by habitat than by species. Spatial variations in partial differential(13)C, partial differential(15)N, and T-Hg concentrations in the ocean may be the cause of these phenomena.

Contamination levels of mercury in the muscle of female and male spiny dogfishes (Squalus acanthias) caught off the coast of Japan.

We analyzed the total mercury (T-Hg) and stable isotopes of (13)C and (15)N in the muscle of spiny dogfish (Squalus acanthias) caught off the coast of Japan. The average body length of the female spiny dogfish sampled (94.9+/-20.2 cm, 50.5-131.0 cm, n=40) was significantly larger than that of the males sampled (77.8+/-10.8 cm, 55.5-94.0 cm, n=35), although the ages of the samples were unknown. The T-Hg concentration in the muscle samples rapidly increased after maturity in the females (larger than about 120 cm) and males (larger than about 90 cm), followed by a continued gradual increase. Contamination level of T-Hg in female muscle samples (0.387+/-0.378 microg(wet g)(-1), n=40) was slightly higher than that in male muscle samples (0.316+/-0.202 microg(wet g)(-1), n=35), probably due to the greater longevity of females. In contrast, the contamination level of T-Hg in females smaller than 94.0 cm in length (0.204+/-0.098 microg(wet g)(-1), n=20) was slightly lower than that in the males, probably due to the faster growth rate of females. Although the partial differential(13)C and partial differential(15)N values in the muscle samples increased with an increase in body length, there were no significant differences between the females (-17.2+/-0.4 per thousand and 12.4+/-0.9 per thousand, respectively) and males (-17.3+/-0.4 per thousand and 12.4+/-0.8 per thousand, respectively). A positive correlation was found between partial differential(13)C and partial differential(15)N values, suggesting trophic enrichment due to the growth.

Halogenated bipyrroles and methoxylated tetrabromodiphenyl ethers in tiger shark (Galeocerdo cuvier) from the southern coast of Japan.

Naturally produced halogenated bipyrroles (HBPs) and methoxylated tetraBDEs (MeO-tetraBDEs) are lipophilic and persistent, and therefore may bioaccumulate with higher trophic levels. In this study, the livers of tiger shark (Galeocerdo cuvier) collected from the southern coast of Japan were investigated for size-related bioaccumulation of natural HBPs and MeO-tetraBDEs in comparison with anthropogenic PCBs and PBDEs. Heptachloro-1'-methyl-1,2'-bipyrrole (Cl7-MBP) and hexahalogenated 1,1'-dimethyl-2,2'-bipyrrole (Br4Cl2-DBP) were present at similar concentration ranges (4-4400 ng/g lipid) in the liver and increased with increasing body length. Two MeO-tetraBDEs, 6-methoxy-2,2',4,4'-tetrabromodiphenyl ether(6-MeO-BDE47), and 2'-methoxy-2,3',4,5'-tetrabromodiphenyl ether (2'-MeO-BDE68) were present at 4- to 6-fold higher concentrations (88 and 58 ng/g lipid, respectively) than BDE-47. In mature tiger sharks, 2,2'-dimethoxy-3,3',5,5'-tetrabromobiphenyl (2,2'-diMeO-BB80) was present at a median concentration of 330 ng/g lipid. Concentrations of 6-MeO-BDE47 were positively correlated to body length (P < 0.01), but no such correlation was observed for 2'-MeO-BDE68 and 2,2'-diMeO-BB80. The concentration ratios (patterns) of PBDE-like natural products in tiger sharks were largely different from that found in other species, such as the bull shark (Carcharhinus leucas), the silvertip shark (Carcharhinus albimarginatus), and the sandbar shark (Carcharhinus plumbeus). The present study suggests thatthe concentrations of natural HBPs in the liver are size (age)-dependent whereas MeO-tetraBDEs have species-specific biomagnification potentials.

Accumulation and mother-to-calf transfer of anthropogenic and natural organohalogens in killer whales (Orcinus orca) stranded on the Pacific coast of Japan.

Blubber samples were analyzed for anthropogenic and natural persistent organohalogens in nine killer whales (Orcinus orca) stranded on the northern coast of Japan in 2005. Anthropogenic organohalogens were dominated by DDTs (40-240 microg/g lipid weight (lw)), PCBs (19-68 microg/g lw), and chlordanes (trans-nonachlor, 15-80 microg/g lw). Polybrominated diphenyl ethers (PBDEs) were detected at a range of 0.22-0.64 microg/g lw (BDE-47, 42-74% of SigmaPBDE). For natural organohalogens, mixed halogenated dimethylbipyrroles (Br4Cl2-DBP, 6.4-26 microg/g lw), heptachlorinated methylbipyrrole (Cl7-MBP, 0.5-1.9 microg/g lw), two methoxylated tetrabromodiphenyl ethers (6-MeO-BDE47, 0.11-0.58 microg/g lw; 2'-MeO-BDE68, 0.02-0.06 microg/g lw), and dimethoxylated tetrabromobiphenyl (2,2'-diMeO-BB80, 0.06-0.20 microg/g lw) were present. These concentrations in the blubber were higher in calves than in lactating females, indicating that large quantities of the persistent organohalogens transferred from the mother to the calf through lactation. The mother-to-calf transfer ratios of PCBs and PBDEs were significantly decreased with increasing number of halogen substituents, suggesting that higher halogenated congeners are less transferable.

Hg, Zn and Cu levels in the muscle and liver of tiger sharks (Galeocerdo cuvier) from the coast of Ishigaki Island, Japan: relationship between metal concentrations and body length.

We analyzed Hg, Zn and Cu concentrations in the liver and muscle of tiger sharks (Galeocerdo cuvier) from the coast of Ishigaki Island, Japan. The Hg concentration in the muscle increased proportionally with body length in the tiger sharks, whereas that in the liver increased rapidly after maturity (defined by a length of over 2.7 m). Muscle Hg levels were higher than liver concentrations in immature sharks, with the inverse trend observed in mature sharks. Notably, the Zn and Cu concentrations in the liver tended to decrease with increasing body length. This rapid increase in hepatic Hg concentration concurrent with the onset of maturity in sharks may result from the continuous intake of Hg via food and the slower growth of mature sharks. The high concentrations of the essential metals Zn and Cu in immature sharks may be explained by the physiological demands related to rapid growth.

Contamination levels of mercury and cadmium in melon-headed whales (Peponocephala electra) from a mass stranding on the Japanese coast.

Total mercury (T-Hg), methyl mercury (M-Hg), cadmium (Cd), selenium (Se), zinc (Zn) and copper (Cu) concentrations in the organs of melon-headed whales from a mass stranding on the Japanese coast were analyzed. The mean concentration of T-Hg in the liver (126+/-97 microg/wet g, n=13) was markedly higher than those in kidney (6.34+/-2.36 microg/wet g, n=12) and muscle (4.90+/-2.33 microg/wet g, n=15). In contrast, the mean concentration of M-Hg in the liver (9.08+/-2.24 microg/wet g) was similar to those in the kidney (3.47+/-0.91 microg/wet g) and muscle (3.78+/-1.53 microg/wet g). The mean percentage of M-Hg in the T-Hg found in the liver (13.1+/-10.3) was significantly lower than those in the kidney (58.3+/-15.0) and muscle (78.9+/-8.4). The molar ratio of T-Hg to Se in the liver was effectively 1.0, but those in the kidney and muscle were markedly lower. Conversely, the mean concentration of Cd was markedly higher in the kidney (24.4+/-7.4 microg/wet g) than in the liver (7.24+/-2.08 microg/wet g) and muscle (less than 0.05 microg/wet g). These results suggest that the formation of Hg-Se compounds mainly occurs in the liver after the demethylation of M-Hg, and Cd preferentially accumulates in the kidney of melon-headed whales.

Age-dependent accumulation of heavy metals in a pod of killer whales (Orcinus orca) stranded in the northern area of Japan.

Mercury (Hg), cadmium (Cd), iron (Fe) manganese (Mn), zinc (Zn) and copper (Cu) concentrations in the liver, kidney and muscle of nine killer whales (including three calves) that stranded together in the northern area of Japan were determined. The Hg and Cd concentrations were found at trace levels in the calf organs, and increased with age. The Fe concentration in the muscle was significantly lower in the calves than in the mature whales and also increased with age. In contrast, Mn and Cu concentrations in the muscle were significantly higher in the calves than in the mature whales, and changes in the Zn concentration relative to age were unclear. These results suggest minimal mother-to-calf transfer of the toxic metals Hg and Cd and accumulation of these metals in the organs with age, while the essential metals Mn and Cu were found at higher concentrations in the muscle of calves than in mature whales.

Distribution of total mercury, methyl mercury and selenium in pod of killer whales (Orcinus Orca) stranded in the northern area of Japan: comparison of mature females with calves.

Total mercury (T-Hg) and selenium (Se) concentrations in liver, kidney and muscle from a pod of killer whales including five mature females and three calves stranded in the northern area of Japan were analyzed. In the mature female, contamination level of T-Hg in the liver sample (62.2+/-21.9 microg/wet g) was markedly higher than that in kidney sample and muscle sample. The molar ratio of T-Hg to Se in the liver sample was approximately 1, and those in the kidney and muscle samples were markedly lower than 1. These results suggest that the formation of HgSe compound increases the hepatic accumulation of mercury (Hg). In contrast, contamination level of T-Hg in the calf organs was much lower than that in the mature female organs. These results suggest that the transfer of Hg from the mother to the fetus via placenta and/or to calf via milk is trace.

Total mercury, methyl mercury, and selenium levels in the red meat of small cetaceans sold for human consumption in Japan.

We surveyed the total mercury (T-Hg) and methyl mercury (M-Hg) levels in red meat products (n = 160) from small cetacean species sold for human consumption in markets throughout Japan from 2000 to 2003. Genetic identification showed that the red meat products originated from nine species: false killer whale, bottlenose dolphin, short-finned pilot whale, striped dolphin, rough-toothed dolphin, Risso's dolphin, pantropical spotted dolphin, Baird's beaked whale, and Dall's porpoise. T-Hg and M-Hg concentrations in all red meat products exceeded the provisional permitted levels of T-Hg (0.4 microg/wet g) and M-Hg (0.3 microg/ wet g) in fish and shellfish set by the Japanese government, respectively. The average M-Hg level in the most contaminated species (false killer whale) was 11.5 microg/wet g, and that in the least contaminated species (Dall's porpoise) was about 1.0 microg/wet g, exceeding or equaling the Codex guideline of M-Hg in predatory fishes (1.0 microg/wet g). Contamination levels of T-Hg and M-Hg differed considerably among samples of the nine species and among individuals of a particular species. The highest M-Hg was about 26 microg/ wet g in a sample from a striped dolphin, 87-times higher than the permitted level. The consumption of only 4 g of this product would exceed the provisional tolerable weekly intake of M-Hg for someone of 60 kg body weight (1.6 microg/kg-bw/ week). Although a high correlation between T-Hg and selenium (Se) was observed in these products, the molar ratio of T-Hg to Se was substantially higher than 1. The consumption of red meat from small cetaceans, therefore, could pose a health problem for not only pregnant women but also for the general population.