Shinsuke Tanabe

PCB problems in the future: Foresight from current knowledge

The present paper overviews the forthcoming PCB problems from current knowledge of their use, environmental contamination and toxicology. From a global point of view, PCB levels in the environmental media and biota are unlikely to decline in the near future due to the greater quantities of PCBs still in use than the quantity that has already escaped into the open environment. Considering all the information on the occurrence, distribution and behaviour of PCBs in the ecosystems, the marine mammals are probably the most vulnerable and possible target organisms in forthcoming long-term PCB toxicity. The recent isomer-specific analyses suggest that the intrinsic toxicity of PCBs principally resulted from the coplanar PCB congeners which may impose a greater toxic threat than chlorinated dioxins and furans to humans and wildlife. The measures necessary to reduce further discharge of PCBs into the environment should be set in motion immediately, otherwise there may be a subsequent deleterious biological impact.

Global contamination by persistent organochlorines and their ecotoxicological impact on marine mammals

The present paper overviews the global contamination by persistent organochlorines and their ecotoxicological implications on marine mammals. The recent pattern of contamination by organochlorine residues in the coastal environment is prominent in tropical regions due to continuous usage in the low-latitude developing countries. The major emission source of organochlorines is probably the tropical belt and large quantities of volatilized contaminants are dispersed through the atmosphere on global terms. Reflecting this, a considerable contamination was observed in open ocean tropical waters as well as in the Arctic and nearby waters. The study of the mass transfer of organochlorines at the air-water interface suggests that the oceanic water bodies, particularly Arctic waters, act as a sink for persistent contaminants. In this regard, the marine mammals, particularly cetaceans, are one of the animal groups receiving high concentrations of persistent organochlorines arising out of a worldwide contamination. They can amplify much greater amounts of toxic contaminants through feeding and also pass them in large quantities from one generation to the next through lactation. Unfortunately, these animals have a smaller capacity for degradation of these contaminants due to the specific mode of cytochrome P-450 enzyme systems. These drug-metabolizing enzyme systems may be related to the possible effects of persistent organochlorines, particularly coplanar PCBs. Furthermore, the residue levels of these contaminants in marine mammals are unlikely to decline in the near future. Considering all these facts, it may be concluded that marine mammals are one of the most vulnerable and possible target organisms with regard to long-term toxicity of hazardous man-made chemicals in the future.

Geographical distribution of persistent organochlorines in air, water and sediments from Asia and Oceania, and their implications for global redistribution from lower latitudes.

Persistent organochlorines in air, river water and sediment samples were analysed from eastern and southern Asia (India, Thailand, Vietnam, Malaysia, Indonesia) and Oceania (Papua New Guinea and Solomon Islands) to elucidate their geographical distribution in tropical environment. The concentrations of organochlorines in these abiotic samples collected from Taiwan, Japan and Australia were also monitored for comparison. Atmospheric and hydrospheric concentrations of HCHs (hexachlorocyclohexanes) and DDTs (DDT and its metabolites) in the tropical developing countries were apparently higher than those observed in the developed nations, suggesting extensive usage of these chemicals in the lower latitudes. CHLs (chlordane compounds) and PCBs (polychlorinated biphenyls) were also occasionally observed at higher levels in the tropics, implying that their usage area is also expanding southward. Distribution patterns of organochlorines in sediments showed smaller spatial variations on global terms, indicating that the chemicals released in the tropical environment are dispersed rapidly through air and water and retained less in sediments. The ratios of organochlorine concentrations in sediment and water phases were positively correlated with the latitude of sampling, suggesting that persistent and semivolatile compounds discharged in the tropics tend to be redistributed on a global scale.

Geographical Distribution and Accumulation Features of Organochlorine Residues in Fish in Tropical Asia and Oceania

Concentrations of persistent organochlorine residues were determined in fish collected from several locations in eastern and southern Asia and Oceania to identify the accumulation features of such residues in tropical aquatic organisms and to elucidate their distribution in tropical developing countries. DDT and its derivatives (DDTs) were the predominantly identified compounds in most locations. In general, the concentrations of organochlorines in tropical fish were lower than those in fish of the temperate regions. Residue levels in fish showed little spatial variability, as reported for tropical sediments. This is different from the patterns observed for air and water in which higher concentrations occur in tropical latitudes compared to mid-latitudes. Compilation of limited available data on the organochlorine residue levels in fish in tropical Asian countries seemed to indicate little temporal variability due to the low levels of accumulation in aquatic organisms, despite the continuous use of these compounds. A short residence time of semivolatile organochlorines in the tropical aquatic environment results in lower levels of accumulation of residues in fish. Examination of walleye pollock (Theragra chalcogramma) collected from the Bering Sea indicated that organochlorine residue levels are declining in temperate water bodies near the Arctic Ocean in recent years.

Distribution and sources of polycyclic aromatic hydrocarbons in sediments from Kyeonggi Bay, Korea

Abstract Sixty-six sediment samples were collected from Kyeonggi Bay, Korea, in December 1995 and analysed for a suite of 2–6 ring polycyclic aromatic hydrocarbons (PAHs). Sediments were collected in the Han River estuary, Incheon Harbour, from nearshore locations adjacent to large industrial complexes south of Incheon, and along transects toward the open sea. Concentrations of PAHs (9.1–1400 ng g −1 dry wt with an average of 120 ng g −1 ) were positively correlated with organic carbon (OC) content and negatively correlated with mean sediment grain size. The highest PAH concentrations were in samples from inner Incheon Harbour basins; these levels decreased within a short distance from these heavily industrialised waterways. The sources of PAHs were determined to be primarily combustion in nature based on the distribution of alkylated homologs to parent compounds. Overall, sediment PAHs in Kyeonggi Bay were lower than those in the United States and Europe. The potential for biological effects due to PAHs alone is expected to be low based on comparisons of individual and ΣPAH concentrations with effects-based and equilibrium partitioning-based sediment quality guidelines/criteria.

PCBs and chlorinated hydrocarbon pesticides in Antarctic atmosphere and hydrosphere

Abstract PCBs and chlorinated hydrocarbon pesticides such as DDTs and HCHs (BHCs) were measured in air, water, ice and snow samples collected around the Japanese research stations in Antarctica and adjacent oceans during December 1980 to March 1982. The atmospheric concentrations of chlorinated hydrocarbons decreased in the transport process from northern lands to Antarctica, but the compositions of PCBs, DDT compounds and HCH isomers were relatively uniform throughout this process. Regional and seasonal variations were found in aerial concentrations of these pollutants at Syowa Station and adjacent seas in Antarctica. Chlorinated hydrocarbons were also detected in snow, ice, lake water and sea water samples, in which rather high concentrations were found in snow and ice samples. This suggests that snow and ice serve as media of supply of these pollutants into Antarctic marine environment. Most interestingly, the concentrations of DDTs and higher chlorinated biphenyls were much lower in sea water under fast ice than in that from outer margin of pack ice. This indicates that the active removal of these pollutants is occurred in the sea under fast ice, and that is strongly associated with high primary productivity. It is, therefore, presumed that the concentrations of PCBs and DDTs in marine organisms living under fast ice in Antarctica could be lower than those in other oceans.

Contamination and toxic effects of persistent endocrine disrupters in marine mammals and birds

In recent years, several species of marine mammals and birds have been affected by uncommon diseases and unusual mortalities. While several possible causative factors have been attributed for these events, a prominent suspect is exposure to man-made toxic contaminants. Particularly, some of these man-made chemicals can disrupt normal endocrine physiology in animals. At CMES, our studies focus on exposure and toxic effects of endocrine disrupting chemicals, particularly organochlorines, in higher trophic level wildlife. Endocrine disrupting chemicals, such as organochlorine insecticides, polychlorinated biphenyls, organotins etc. are found in tissues of a wide variety of wildlife. Extremely high concentrations have been found in animals afflicted with diseases and/or victims of mass mortalities. Elevated contamination by organochlorines has been found in open sea animals such as cetaceans and albatrosses, which seemed to be attributable to their low capacity to metabolize toxic persistent contaminants. Significant correlations between biochemical parameters (serum hormone concentrations and cytochrome P450 enzyme activities) and residues of endocrine disrupting chemicals were found in some species of marine animals, which indicates that these chemicals may impose toxic effects in animals even at the current levels of exposure. In general, water birds and marine mammals accumulated the dioxin-like compounds with much higher concentrations than humans, implying higher risk from exposure in wildlife. The future issues of endocrine disrupting chemicals in humans and wildlife will have to be focused in developing countries.

Butyltins in muscle and liver of fish collected from certain Asian and Oceanian countries

Concentrations of butyltin residues were determined in muscle tissue of fish collected from local markets and sea food shops in India, Bangladesh, Thailand, Indonesia, Vietnam, Taiwan, Australia, Papua New Guinea and the Solomon Islands. Contamination levels were determined in the Asia-Pacific region and human exposure was estimated. Similarly, corresponding liver samples of fish muscle collected in Australia, Papua New Guinea and the Solomon Islands were analyzed to obtain information on partitioning of butyltin compounds between muscle and liver tissues. Butyltin compounds were detected in most of the samples which suggested widespread contamination in Asia and Oceania. The concentrations of butyltin compounds were, on average, an order of magnitude higher in liver than in muscle. Residue concentration of Sigmabutyltin in liver was found to be correlated significantly (p < 0.02) with those in muscle. Intensive ship-scrapping activities, sewage disposal and antifouling paints are considered the major sources of butyltins in this region. Increased proportions of MBT over DBT and TBT in samples from most locations indicated degradation of TBT to MBT in fish tissues during storage at 4 degrees C in the dark over 1-2 years. The possibility that fish have been subject to increased exposure to MBT and that TBT degrades to MBT quite rapidly in tropical environments are also considered. Butyltin concentrations in fish from Asia and Oceania were lower than those reported for Japan, Canada and the USA. Although the number of samples analyzed from each country was small, it is tentatively suggested that intake of butyltins by humans via consumption of fish in these countries was < 25% of the tolerable daily intake of 250 ng kg bw(-1) day(-1). To our knowledge, this is the first study reporting on butyltin pollution in developing Asian countries.

Critical evaluation of polychlorinated biphenyl toxicity in terrestrial and marine mammals : increasing impact of non-ortho and mono-ortho coplanar polychlorinated biphenyls from land to ocean

Residues of potentially toxic non-ortho chlorine substituted coplanar 3,3′,4,4′-tetra-,3,3′,4,4′,5-penta-, 3,3′,4,4′,5,5′-hexachlorobiphenyl and their mono- and di-ortho analogs (2,3′,4,4′,5-penta-, 2,3,3′,4,4′-penta-, 2,3,3′,4,4′,5-hexa-and 2,2′,3,3′,4,4′-hexa-, 2,2′,3,4,4′,5-hexa-chlorobiphenyl) were determined in humans, dogs, cats (terrestrial), a finless porpoise (Neophocoena phocoenoides-coastal), Dalls porpoises (Phocoenoides dalli,dalli), Bairds beaked whales (Berardius bairdii) and killer whales (Orcinus orca-open ocean). Among the coplanar polychlorinated biphenyl (PCB) congeners, the concentration of the di-ortho congeners was the highest and the non-ortho congeners was the lowest. However, all three coplanar PCBs occurred at significantly higher levels than toxic polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). The relative bioconcentration and metabolic capacity of terrestrial and marine mammals to these chemicals, suggest that the toxic threat of coplanar PCBs increases from land to ocean, but the reverse is true for PCDDs and PCDFs. The toxic threat of coplanar PCBs to higher aquatic predators such as cetaceans was principally assessed by 2,3,7,8-T4CDD Toxic Equivalent Analysis which is based on the induction of arylhydrocarbon hydroxylase (AHH) and ethoxyresorufinO-deethylase (EROD). Analysis indicates, in particular, that the bioaccumulation of toxic 3,3′,4,4′,5-penta- and 2,3,3′,4,4′-pentachlorobiphenyls in carnivorous marine mammals is a cause for considerable concern.

CONGENER PROFILE AND TOXICITY ASSESSMENT OF POLYCHLORINATED BIPHENYLS IN DOLPHINS, SHARKS AND TUNA COLLECTED FROM ITALIAN COASTAL WATERS

Abstract Bottlenose and Rissos dolphins found dead along the Italian coast in 1992 were analysed for the presence of PCB isomers and DDT. High concentrations of PCBs (90–1400 μg/g wet wt) were detected in the blubber of stranded carcasses. The concentrations were higher than those found in animals showing reproductive failure and physiological impairment following prolonged PCB exposure, suggesting that the contamination by PCBs as well as DDT may be a major causative factor for the large-scale deaths of dolphins in the Mediterranean Sea. The 2,3,7,8-TCDD toxic equivalents estimated for bottlenose and Rissos dolphins were 18.8 and 20.8 ng/g, respectively, with a major contribution from mono-ortho PCBs. The monoortho congeners of IUPAC Nos 105, 118 and 156 accounted for most of the toxicity exerted by PCBs in these dead dolphins. An increase in the proportion of non-ortho coplanar PCB congener of IUPAC No. 169 to No. 126 with an increase in the total PCB concentration in the blubber suggested a strong induction of drug metabolizing enzymes. It is possible to use CB-169 CB-126 concentration ratio to indicate whether there has been a strong activation of cytochrome P450 enzyme system in severely exposed/contaminated dolphin populations. The total PCB concentrations in the adipose fat of sharks from Italian coasts ranged from 70 to 4000 ng/g wet wt and that of DDT from 14 to 300 ng/g wet wt. In bluefin tuna, the total PCB and DDT concentrations were 170–2200 and 56–780 ng/g wet wt, respectively. These values were comparable to those reported for the same species in the Mediterranean Sea during the 1970s, suggesting the existence of PCB sources near this marine ecosystem.