PCB Accumulation Research Articles

Arctic terrestrial ecosystem contamination

Limited data have been collected on the presence of contaminants in the Arctic terrestrial ecosystem, with the exception of radioactive fallout from atmospheric weapons testing. Although southern and temperate biological systems have largely cleansed themselves of radioactive fallout deposited during the 1950s and 1960s, Arctic environments have not. Lichens accumulate radioactivity more than many other plants because of their large surface area and long life span; the presence and persistence of radioisotopes in the Arctic is of concern because of the lichen → reindeer → human ecosystem. Effective biological half-life of cesium 137 is reckoned to be substantially less than its physical half-life. The database on organochlorines in Canadian Arctic terrestrial mammals and birds is very limited, but indications are that the air/plant/animal contaminant pathway is the major route of these compounds into the terrestrial food chain. For terrestrial herbivores, the most abundant organochlorine is usually hexachlorobenzene followed by hexachlorocyclohexane isomers. PCB accumulation favours the hexachlorobiphenyl, pentachlorobiphenyl and heptachlorobiphenyl homologous series. The concentrations of the various classes of organochlorine compounds are substantially lower in terrestrial herbivore tissues than in marine mammal tissues. PCBs and DDT are the most abundant residues in peregrine falcons (a terrestrial carnivore) reaching average levels of 9.2 and 10.4 μg · g −1, respectively, more than 10 times higher than other organochlorines and higher than in marine mammals, including the polar bear. Contaminants from local sources include metals from mining activities, hydrocarbons and waste drilling fluids from oil and gas exploration and production, wastes from DEW line sites, naturally occurring radionuclides associated with uranium mineralization, and smoke containing SO 2 and H 2SO 4 aerosol from the Smoking Hills at Cape Bathurst, N.W.T.

Indications of P450 monooxygenase activities in beluga ( Delphinapterus leucas) and narwhal ( Monodon monoceros) from patterns of PCB, PCDD and PCDF accumulation

Selective accumulation of PCDDs, PCDFs and PCB congeners was investigated in beluga ( Delphinapterus leucas), narwhal ( Monodon monoceros) and several species at the same trophic level in two areas of Canada. There was a much higher relative abundance of meta-para-unsubstituted PCBs in the cetaceans compared with other species. This suggests that activity of cytochrome P450 monooxygenase enzymes causing CYP2B-type metabolism was relatively low in beluga and narwhal. Lower relative levels of 2,3,7,8-TCDD occurred in beluga from both areas, and selective reduction of toxic non- ortho PCBs occurred in the highly PCB-contaminated St Lawrence beluga. These compounds are potent inducers of cytochrome P450 CYP 1A-type enzymes, suggesting that such an enzyme with the capability of metabolizing TCDD-like substrates is present in beluga and narwhal. SIMCA principal components analysis of PCB congener patterns showed that the two cetaceans were in a statistically significant different class than the other species. Variables (congeners) with the greatest separation power between classes were mainly those defined by the selective metabolism rules.

Organochlorines in different fractions of sediments and in different planktonic compartments of the Belgian continental shelf and the Scheldt estuary

PCB levels in sediments (bulk and fraction <63 μm), suspended matter and zooplankton from the Belgian continental shelf of the North Sea and the Scheldt estuary were evaluated in relation to their organic carbon content, their lipid content and, for sediments, their particle size distribution. PCB accumulation mechanisms are discussed, considering the importance of direct contamination (adsorption onto the cell surfaces, absorption through the cell walls and partitioning into the cell lipids) for suspended matter and sediments, and of indirect contamination through the food for zooplankton. Geographical and seasonal variations are described.

Dietary accumulation of PCBs from a contaminated sediment source by a demersal fish ( Leiostomus xanthurus)

Accumulation and dietary transfer of PCBs from contaminated harbor sediments were studied in a laboratory food chain consisting of sediments, polychaetes ( Nereis virens) and a predatory fish ( Leiostomus xanthurus). The study was conducted in two phases to distinguish dietary uptake from PCB accumulation resulting from sediment exposure alone. In phase I fish and polychaetes were separately exposed to field-collected PCB contaminated sediments (5.2 μg/g dry weight as Aroclor 1242 and 1254) in flow-through sea-water systems for 40 days to allow organisms to attain steady state concentrations. In Phase II the dietary fraction of PCB accumulation was determined by selectively feeding exposed and control groups of fish polychaetes having a known PCB body burden. In addition the effect of direct sediment contact on PCB accumulation by L. xanthurus was investigated. Results demonstrate that contaminated sediments can serve as a source of PCBs for uptake and trophic transfer in marine systems. Fish exposed to PCB-contaminated sediments and fed a daily diet of polychaetes from the same sediment accumulated more than twice the PCB whole-body residues than fish exposed to similar conditions but fed uncontaminated polychaetes. The dietary contribution of PCBs accounted for 53% of the total body burden measured in fish fed for 20 days, and this percentage appeared to be increasing. Results also indicate that fish isolated from direct contact with PCB-contaminated sediment do not significantly ( P ≤ 0.05) accumulate PCB residues when compared with fish allowed contact with sediment.

PCB dynamics in Hudson River striped bass. II. Accumulation from dietary sources

Young-of-year striped bass were administered known doses of 14C-labeled Aroclor 1254 in natural food ( Gammarus tigrinus) by gavage. PCB accumulation from the gut and elimination from the whole-body were determined empirically for single-dose and multiple-dose studies. The data have been applied to models describing absorption site kinetics and fluctuations in whole-body burden at ‘steady state’. Those variables critical to the calculation and understanding of bioaccumulation factors, namely growth, metabolic rate, and dose, are discussed in the context of the kinetic model results.

A mathematical model of PCB bioaccumulation in plankton

In batch experiments exposing individual plankton constituents to Aroclor 1254 PCB, the rate at which the organism approaches partitioning equilibrium appears to be partly size-dependent while the extent of PCB accumulation is species-specific. The sorptive desorptive kinetics of PCB in these experiments can be described mathematically by a first-order expression. Employing this expression in a model plankton food web permits examination of the role of feeding and sorptive processes in determining PCB body burden under various environmental conditions. When ingestion rates exceed desorption and excretion rates, a consuming organism accumulates PCB above levels predicted by equilibrium partitioning relationships. Feeding-induced oscillations in PCB body burden could thus obscure the reduction of soluble PCB concentration which determine a “baseline” PCB body burden. Unless referenced to a specific set of biological and environmental conditions, the importance of direct partitioning from water vs. food uptake appears to be a moot topic.

Patterns of PCB accumulation by fry of lake trout.

A study examining the accumulation pattern of PCBs by lake trout fry exposed through the period of yolk absorption and the onset of feeding is presented. The PCB uptake pattern was examined by exposing the fry to a nominal concentration of 50 ng/l PCB (Aroclor 1254) for 48 days. The fry were sampled and analyzed for PCB concentration seven times during the exposure. The patterns of PCB concentration in the lake trout fry appeared similar, regardless of how the data were expressed (wet weight concentration, dry weight concentration, or body burden). PCBs in exposed fry increased slowly, peaked at day 32 (just before yolk absorption was complete) and decreased by day 48. Although these patterns appeared similar, important differences in the relative changes in PCB levels of exposed fry became evident when the different ways of expressing the uptake data were compared. It was determined that physiological changes in the fry through yolk absorption and initial feeding were responsible for the differences between PCB levels based on wet weight, dry weight, and body burden.

Implications of short-term PCB uptake by small estuarine copepods (genus Acartia) from PCB-contaimined water, inorganic sediments and phytoplankton

PCB uptake by adult copepods of the genus Acartia exposed to 14 C-labeled PCB-contaminated water, inorganic suspended sediments, and phytoplankton was determined. PCB uptake from water and inorganic particles followed an asymptotic function, with apparent equilibrium values reached after about 36 h. Copepods fed PCB-contaminated phytoplankton showed a substantial increase in PCB accumulation relative to unfed copepods, despite similar PCB concentrations in the water. Significantly greater mortality was observed among copepods fed contaminated phytoplankton than among copepods without phytoplankton. These experiments indicate that phytoplankton provide an important vehicle for PCB uptake at the herbivore trophic level.

Accumulation of polychlorinated biphenyl (phenoclor DP6) by estuarine fish.

Fish intoxicated for 30 days by Phenoclor DP6 added either to water or food revealed an accumulation of PCB in all tissues measured. The highest concentration was found in the liver. There was a higher accumulation of PCB from water than from food. Little or no Phenoclor DP6 was metabolized by these fish. The results provide important data on the PCB accumulation in food chains.

A comparative study on accumulation and elimination of tetrachlorobiphenyl isomers in mice

The presence and persistence of polychlorinated biphenyls (2CB's) in various global ecosystems have been well recognized (FISHBEIN 1972). Considerable papers have dealt with the PCB accumulation and elimination during a long term oral exposure (CURLEY et al. 1971; BURSE et al. 1974). Whereas only limited data are available on the bioaccumulation of individual chlorobiphenyl isomers of known structure (JAN et al. 1975; GAGE et al. 1976). This study was undertaken to obtain the systematic information on the accumulation and elimination of all the possible isomers of symmetrically substituted tetrachlorobiphenyl (TCB) in connection with their structures.

Effect of dam's diet on PCB accumulation in nursing Osborne Mendel pups.

Upon parturition, dams were fed high fat or high carbohydrate diets to which 1, 10, and 30 ppm of Aroclor 1254 were added to study the effect of diet on fat and PCB accumulation in nursing pups. The percentage of body fat in the carcasses of 0, 8, and 16 day old pups ranged from 2.2 to 18.2% and from 1.2 to 12.0% for animals suckled by dams fed high fat and high carbohydrate rations, respectively. Accumulation of Aroclor 1254 expressed as ppm wet weight or as total PCB's per pup was similar for animals nursed by dams fed either the high fat or high carbohydrate ration, but pups from dams fed a high carbohydrate ration also had significantly less body fat. Therefore, transfer of PCBs via the milk appears to be more a function of the amounts of PCB's consumed by the dam than the diet's ability to increase the percentage of body fat in the pups.