SigmaDDT Concentrations Research Articles

Preliminary Assessment of Avian Stomach Oils: A Vector of Contaminants to Chicks and Potential for Diet Analysis and Biomonitoring

Bird species from the order Procellariiformes or petrels, including the northern fulmar (Fulmarus glacialis), produce high lipid and high energy content stomach oils from the prey they consume, which enables them to exploit distant marine food sources. Stomach oils are also used as a food source for chicks and for defensive purposes. Samples of stomach oils from two Arctic colonies, St. George Island Alaska, USA and Cape Vera, Devon Island Nunavut, Canada, were collected and analyzed for organochlorine contaminants. SigmaPCB concentrations ranged from 13 to 236 ng g(-1) wet weight (ww) and SigmaDDT concentrations from 5 to 158 ng g(-1) ww and were similar in both sites, though differences in chemical signatures were apparent. Stomach oils are a rich energy source; however, they may also provide a higher dose of contaminants per unit energy than the direct consumption of prey items, as illustrated using mass and energy balance calculations to estimate chick exposure to SigmaDDT for hypothetical stomach oil and whole prey diets. The results of this study suggest that stomach oils are an important vector of organochlorine contaminants to chicks and should be considered in future risk assessments of northern fulmars and other species of petrels. To our knowledge this is the first study of stomach oils as an overlooked vector of organochlorine contaminants to chicks and as a potentially valuable medium for dietary analysis and noninvasive biomonitoring both of petrel dietary exposure and of marine contaminant concentrations.

Residue, Temporal Trend and Half-Life Time of Selected Organochlorine Pesticides (OCPs) in Surface Soils from Bacninh, Vietnam

Selected organochlorine pesticides (p,p'-DDT, p,p'-DDE, p,p'-DDD, alpha,beta,gamma,delta-HCH) were analyzed in the surface soils of Bacninh, Viet Nam. Forty representative soil samples were collected from Bacninh town and three surrounding districts. SigmaDDT concentrations ranged from <0.02 to 160.86 ng g(-1) dry weight, whereas SigmaHCH concentrations ranged from <0.05 to 9.54 ng g(-1) dry weight. The half-life times of SigmaDDT and SigmaHCH are 6.7 and 4.9 years, respectively. The decreasing trends of SigmaDDT and SigmaHCH levels during the period from 1992 to 2006 are observed. There is no recent input of DDT and HCH in the study area.

Passive Air Sampling of Organochlorine Pesticides in Mexico

The spatial and temporal variation of organochlorine pesticides (OCs) in air across Mexico was investigated by deploying passive samplers at eleven stations across the country during 2005-2006. Integrated samples were taken over three-month periods and quantified for DDT compounds, endosulfans, toxaphenes, components of technical chlordane, hexachlorocyclohexanes (HCHs), and dieldrin. Enantiomers of chiral chlordanes and o,p'-DDT were determined on chiral stationary phase columns as an indicator of source and age. Results are discussed in combination with pumped air samples taken at four other stations in southern Mexico during 2002-2004. DDT and its metabolites, endosulfan and toxaphene were the most abundant OCs detected in all sampling sites. Atmospheric concentrations of SigmaDDT (p,p'-DDT + o,p'-DDT + p,p'-DDE + o,p'-DDE + p,p'-DDD + o,p'-DDD) ranged from 15 to 2360 pg m(-3) with the highest concentrations found in southern Mexico and the lowest found in northern and central Mexico. A fresher DDT residue was observed at sites with greater DDT use and in the southern part of the country, as shown from the higher FDDTe = p,p'-DDT/(p,p'-DDT + p,p'-DDE) and nearly racemic o,p'-DDT. This agrees with the former heavy use of DDT in the endemic malarious area of the country. A local hotspot of endosulfan was identified at an agricultural area in Mazatlan, Sinaloa, with a annual mean concentration of SigmaENDO (endosulfans I + II + endosulfan sulfate) = 26,800 pg m(-3). At this site, higher concentrations of SigmaENDO were recorded during the winter (November to February) and spring (February to May) periods. From back trajectory analysis, this coincides with a shift in the air mass coming from the Pacific Ocean (May to November) to the inland agricultural area (November to May). The elevated SigmaENDO observed is likely due to the local agricultural usage. HCHs, chlordanes, transnonachlors, and dieldrin were more evenly distributed across the country likely due to them being aged residues and more diffuse in the environment. In contrast, hotspots of endosulfans, DDTs, and toxaphenes were observed as they were heavily used in localized agricultural or malarious regions of Mexico.

Uptake of SigmaDDT, arsenic, cadmium, copper, and lead by lettuce and radish grown in contaminated horticultural soils.

Horticultural soils can contain elevated concentrations of selected trace elements and organochlorine pesticides as a result of long-term use of agrichemicals and soil amendments. A glasshouse study was undertaken to assess the uptake of weathered SigmaDDT {sum of the p, p'- and o, p-isomers of DDT [1,1,1-trichloro-2,2- bis( p-chlorophenyl)ethane], DDE [1,1-dichloro-2,2- bis( p-chlorophenyl)ethylene] and DDD[1,1-dichloro-2,2- bis( p-chlorophenyl)ethane]}, arsenic (As), cadmium (Cd), copper (Cu), and lead (Pb) residues by lettuce ( Lactuca sativa) and radish ( Raphanus sativus) from field-aged New Zealand horticultural soils. Concentrations of SigmaDDT, DDT, DDE, Cd, Cu, and Pb in lettuce increased with increasing soil concentrations. In radish, similar relationships were observed for SigmaDDT, DDE, and Cu. The bioaccumulation factors were less than 1 with the exception of Cd and decreased with increasing soil concentrations. Lettuce Cd concentrations for plants grown on four out of 10 assayed soils were equivalent to or exceeded the New Zealand food standard for leafy vegetables of 0.1 mg kg (-1) fresh weight. Concentrations of As, Pb, and SigmaDDT did not exceed available food standards. Overall, these results demonstrate that aged residues of SigmaDDT, As, Cd, Cu, and Pb in horticultural soils have remained phytoavailable. To be protective of human health, site-specific risk assessments and soil guideline derivations for residential settings with vegetable gardens need to consider the produce consumption pathway.

Distribution and Sources of Organochlorine Pesticides in Sediments from Typical Catchment of the Yangtze River, China

Residues of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) and their environmental risks in surface sediments collected from the rivers and lakes in Yangtze River Catchment of Wuhan, China, are investigated in this paper. Based on dry weight (dw), the concentrations of Sigma HCH (alpha-, beta-, and gamma-HCH) and Sigma DDT (p p'-DDT, o p'-DDT, p p'-DDE, p p'-DDD) in sediments ranged from 0.10 to 21.10 ng g(-1) (mean, 4.03 ng g(-1) dw) and 0.79 to 35.61 ng g(-1) dw (average, 6.93 ng g(-1) dw), respectively. Compared with some published guideline values of organochlorine pesticides (OCPs) in sediments, the concentrations of HCHs were at safe levels while the DDT residues would pose adverse biological effects in this studied catchment. The distribution of OCPs in sediments indicated that the input of tributaries was an important factor for OCP residues in the mainstream of the Yangtze River. Levels of OCPs in the sediments were influenced by total organic carbon contents, clay contents, water contents, and pH values of sediments. The present study suggested that historical usage of technical HCH and DDT was the main reason for OCP residues in the sediments from both rivers and lakes. Furthermore, the composition of OCPs reflected additional sources of the holding usage of lindane and fresh inputs of dicofol mixture in this region.

Contamination by Selected Organochlorine Pesticides (OCPs) in Surface Soils in Hanoi, Vietnam

An evaluation of selected organochlorine pesticide residues [p,p'- dichlorodiphenyltrichloroethane (DDT), p,p'- dichlorodiphenyldichloroethylene (DDE), p,p'- dichlorodiphenyldichloroethane (DDD), alpha, beta, gamma and delta- hexachlorocyclohexane (HCH)] in the surface soils of Hanoi, Vietnam was carried out. Sixty representative soil samples were collected from the centre of Hanoi and five surrounding districts. In agricultural areas, SigmaDDT concentrations ranged from < 0.02 to 171.83 ng g(-1) (mean 89.86 ng g(-1)) dry weight, whereas SigmaHCH concentrations ranged from < 0.05 to 20.57 ng g(-1) (mean 8.03 ng g(-1)) dry weight. Investigation of the ratio of different isomers in the soil samples indicates that there has been no recent input of DDT and HCH in the study area.

Transplacental transfer of organochlorines in california sea lions (Zalophus californianus)

The transplacental transfer of organochlorines (OCs) in California sea lions (Zalophus californianus) was investigated by analyzing blubber samples from 20 female sea lions and their fetuses during the last trimester of pregnancy. A rapid, high-performance liquid chromatographic, photodiode-array method was used to measure blubber concentrations of polychlorinated biphenyls (PCBs), including dioxin-like congeners, as well as DDTs and hexachlorobenzene. Summed values of PCBs (sigmaPCBs), of DDTs (sigmaDDTs), and of PCB toxic equivalents (sigmaPCB TEQs) were calculated from these data. The ratios of mean blubber concentrations of fetal sigmaPCBs to maternal blubber concentrations of sigmaPCBs were 0.45 by wet weight and 0.97 by lipid weight, but these ratios varied widely among mother-fetus pairs. Mean ratios of fetal sigmaDDTs to maternal sigmaDDTs were 0.53 by wet weight and 1.12 by lipid weight. Fetuses were classified into two age groups, based on date of recovery, to examine differences in OC transfer because of gestational age. Fetal to maternal ratios for individual PCB congeners, DDT compounds, and sigmaPCBs, sigmaDDTs, and sigmaPCB TEQs were lower among premature compared with late-term fetuses. These ratios increased for both groups as the logarithmic n-octanol/water partition coefficient (log Kow) for each compound decreased. Linear predictions for sigmaPCB and sigmaDDT concentrations in fetal blubber could be obtained using the sigmaPCB and sigmaDDT concentrations in maternal blubber, maternal and fetal blubber lipid content, maternal mass, and maternal age. Fetal TEQ was explained by maternal TEQ and maternal age. The ability to predict contaminant concentrations in fetal blubber from maternal parameters is important for developing risk assessment models for marine mammals.

Atmospheric Organochlorine Pesticide Concentrations Near the Great Lakes: Temporal and Spatial Trends

As a part of the Integrated Atmospheric Deposition Network, atmospheric organochlorine pesticide concentrations were measured in both the gas and particle phases at seven sites near the Great Lakes. Much higher organochlorine pesticide concentrations were found in the gas phase compared to that in the particle phase. Long-term decreasing trends were observed for most pesticides in both phases. Two different seasonal trends were observed in the particle phase: (a) in-use pesticides, such as endosulfan, showed higher concentrations in the summer, a time corresponding to their agriculture use, and (b) restricted organochlorine pesticides, such as lindane, showed higher particle-phase concentrations in the winter, presumably due to their enhanced partitioning from the gas phase to particles. Generally, Chicago had the highest concentrations of chlordanes, dieldrin, and sigmaDDT, suggesting that urban areas could be sources of these compounds to atmosphere. Point Petre had the highest concentrations of endosulfan, likely due to its agricultural application in Southern Ontario.

A Worldwide Survey of Polychlorinated Dibenzo-p-dioxins, Dibenzofurans, and Related Contaminants in Butter

The main source of human exposure to persistent organic pollutants (POPs) is, in general, food. In this study, 64 butter samples from 37 countries were analyzed to assess the global contamination of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs), hexachlorobenzene (HCB), and 2,2-bis (4-chlorophenyl)-1,1,1-trichloroethane (DDT) together with its major metabolites. The objectives of the study were to assess the presence of major organohalogen contaminants in butter, to trace geographical differences, and to determine toxic equivalents (TEQs) of PCDDs/Fs and dioxin-like PCBs in butter. The highest PCDD/F concentrations were found in butter from Korea with an average of 1.4 pg TEQ g(-1) lipid weight (l.w.). from PCDD/F and an additional contribution from the non- and mono-ortho-PCBs of 0.55 pg TEQ g(-1) l.w. Belgian butter showed average levels of 0.53 and 1.2 pg TEQ g(-1) l.w. for PCDDs/Fs and PCBs, respectively, but one sample of Belgium butter had a total TEQ level as high as 4.0 pg TEQ g(-1) l.w. Three out of five butter samples from Portugal showed similarly high PCDD/F TEQ levels. The sigmaPCB levels in European butter appeared to be somewhat higher than in the samples from the rest of the world. The average contribution of CB-153 to the total PCB concentration was 22% (SD 6.4, coefficient of variation 29%). Generally, the PCBs contributed around 60% of the total TEQ value, with CB-126 contributing approximately half of this value. This shows the important TEQ contribution from dioxinlike PCBs to the total TEQs. The highest HCB levels were found in butter samples from Russia, Ukraine, Belgium, and Slovenia. Low levels of HCB in butter were generally found in the Southern Hemisphere. Butter samples from countries from Eastern Europe had elevated sigmaDDT concentrations, with a particularly high concentration in Ukraine butter, followed by some Russian samples, Brazil, and the U.S.

Reduction of Organochlorine Residues in Goshawk Eggs (Accipiter gentilis) from Northern Germany (1971–2002) and Increasing Eggshell Index

We investigated unhatched eggs (n = 57) of Goshawks (Accipiter gentilis) from the period 1988--2002 and compared them with eggs (n = 134) from 1971--1978. Mean concentrations of PCBs, sigmaDDT and HCB in the earlier period were (mg kg(-1) lipid weight) 50.1, 126.6, and 117.7, while the values from the later period were statistically significantly lower: 27.7, 4.1, 0.1, respectively. Nevertheless, the concentration of PCB is relatively constant during the last 8-10 years. The variability of residues was lower within clutches than among clutches. No age-dependent accumulation in eggs could be demonstrated. A statistically significant lower shell index was measurable for the period 1971--1978, while this index during 2001--2002 was relatively high as it was during the late 18th century. We are suggesting a threshold value for effect concentrations on shell index. Residues of the DDT-group had an influence on the number of fledged young per nest site.

An evaluation of the success of dredging as remediation at a DDT‐contaminated site in San Francisco Bay, California, USA

Lauritzen Canal, a portion of San Francisco Bay near Richmond, California, USA, was heavily contaminated with dichlorodiphenyltrichloroethane (DDT) and dieldrin as a result of releases from a pesticide-formulating firm. In 1996 and 1997, 82,000 m3 of contaminated sediment was removed from the canal by dredging. This study evaluated the success of the dredging based largely on body burdens of DDT and its metabolites (sigmaDDT) in resident biota, with some data on sediment- and water-contaminant levels and sediment toxicity testing. Sediment disturbance during dredging introduced a pulse of sigmaDDT into the Lauritzen Canal ecosystem, and body burdens of fish and invertebrates increased 2- to 76-fold, depending on the species. Approximately 1 1/2 years after remediation, 11 of 14 indicators showed contamination comparable with or worse than the contamination that existed prior to dredging. Monitoring of mussels up to four years postdredging suggests some modest improvement, although the sigmaDDT body burden of canal mussels remained far above the norm for San Francisco Bay. The elevated sigmaDDT body burdens in biota that persisted for years after remediation reflect recent exposure and are not merely a result of slow metabolic elimination of the sigmaDDT pulse associated with dredging. Sediment sigmaDDT concentrations were low immediately after dredging, but within months, the canal bottom became covered with a veneer of fine sediment as contaminated as that that had been removed. The source of this material has not been conclusively established, but we suspect it came from slumping and erosion from the flanks of the canal beneath docks and around pilings where dredging was not done. In retrospect, either capping in place or more thorough dredging may have been more successful in reducing pesticide exposure of the biota, although there were difficulties associated with both alternatives.

Chemical and biochemical composition of caviar from different sturgeon species and origins.

The chemical and biochemical composition of caviar in 22 specimens of wild caught and of 2 farmed animals were measured. The results include grain size, protein and fat content, fatty acid composition of triglycerides and phospholipids, as well as the concentrations of relevant heavy metals and chlorinated hydrocarbons. The average protein content varied between 26.2 and 31.1% (wet weight) and fat from 10.9 to 19.4% (wet weight) with lowest values for caviar from farmed sturgeon. The triglycerides and phospholipids contained more n-3 fatty acids, especially eicosapentaenoic and docosahexaenoic acid than n-6 fatty acids. The copper and zinc concentrations varied between 1.20 and 1.69 and 10.3 and 12.4 mg/kg (wet weight), respectively. These values reflect the elevated requirement of sturgeons for these components. Lead content varied between 0.06 and 0.15 mg/kg (wet weight). The cadmium concentrations were less than 5 micrograms/kg (wet weight) leading to the conclusion that no accumulation took place in the eggs. The concentrations of sigma DDT and sigma PCB were extremely high in caviar from Huso huso compared to the samples of the other species thus reflecting the different food habits leading to increased bio-accumulation.

Effects of trophic position and lipid on organochlorine concentrations in fishes from subarctic lakes in Yukon Territory

Concentrations of organochlorines in lake trout (Salvelinus namaycush), burbot (Lota lota), and northern pike (Esox lucius) from subarctic lakes in Yukon Territory varied significantly among populations, and these differences could not be ascribed to size or age of the fishes. For each species, lipid content and trophic positioning (measured by stable nitrogen isotope ratios; delta 15N) were significantly different across populations, and the latter differences could not be attributed to variable delta 15N at the base of the food webs. Across lakes, concentrations of up Sigma PCB, Sigma DDT, chlorinated bornanes (CHB), chlordane ( Sigma CHL), chlorobenzenes ( up Sigma CBZ), and hexachlorocyclohexane ( Sigma HCH) in lake trout and northern pike muscle and burbot liver were significantly related to their delta 15N. The slopes of these log organochlorine - delta 15N relations were greatest for more lipophilic contaminants ( Sigma PCB, Sigma DDT, CHB), indicating that they bioaccumulate to a greater degree than less lipophilic contaminants. Lipid significantly predicted organochlorine concentrations both within and among populations of lake trout, and the slopes did not vary significantly with contaminant lipophilicity. Among-lake differences in Sigma HCH in trout muscle were removed by adjusting concentrations by the covariate lipid. Lipid-adjusted concentrations of CHB, Sigma PCB, Sigma DDT, Sigma CHL, and Sigma CBZ in lake trout remained significantly different between lakes, and these differences were attributed to variable food chain lengths.

Effects of trophic position and lipid on organochlorine concentrations in fishes from subarctic lakes in Yukon Territory

Concentrations of organochlorines in lake trout (Salvelinus namaycush), burbot (Lota lota), and northern pike (Esox lucius) from subarctic lakes in Yukon Territory varied significantly among populations, and these differences could not be ascribed to size or age of the fishes. For each species, lipid content and trophic positioning (measured by stable nitrogen isotope ratios; delta 15N) were significantly different across populations, and the latter differences could not be attributed to variable delta 15N at the base of the food webs. Across lakes, concentrations of up Sigma PCB, Sigma DDT, chlorinated bornanes (CHB), chlordane ( Sigma CHL), chlorobenzenes ( up Sigma CBZ), and hexachlorocyclohexane ( Sigma HCH) in lake trout and northern pike muscle and burbot liver were significantly related to their delta 15N. The slopes of these log organochlorine - delta 15N relations were greatest for more lipophilic contaminants ( Sigma PCB, Sigma DDT, CHB), indicating that they bioaccumulate to a greater degree than less lipophilic contaminants. Lipid significantly predicted organochlorine concentrations both within and among populations of lake trout, and the slopes did not vary significantly with contaminant lipophilicity. Among-lake differences in Sigma HCH in trout muscle were removed by adjusting concentrations by the covariate lipid. Lipid-adjusted concentrations of CHB, Sigma PCB, Sigma DDT, Sigma CHL, and Sigma CBZ in lake trout remained significantly different between lakes, and these differences were attributed to variable food chain lengths.

Concentrations of chlorinated organic compounds in biota and bed sediment in streams of the San Joaquin Valley, California.

Samples of resident biota and bed sediments were collected in 1992 from 18 sites on or near the floor of the San Joaquin Valley, California, for analysis of 33 organochlorine compounds. The sites were divided into five groups on the basis of physiographic region and land use. Ten compounds were detected in tissue, and 15 compounds were detected in bed sediment. The most frequently detected compound in both media was p,p'-DDE. Concentrations of SigmaDDT (sum of o,p'- and p, p' forms of DDD, DDE, and DDT) were statistically different among groups of sites for both tissue and sediment (Kruskal-Wallis, p < 0.05). Concentrations in both media were highest in streams draining the west side of the valley. Concentrations of SigmaDDT in tissue were significantly correlated with specific conductance, pH, and total alkalinity (p < 0.05), which are indicators of the proportion of irrigation return flows in stream discharge. Concentrations in sediment on a dry-weight basis were not correlated with these water-quality parameters, but total organic carbon (TOC) normalized concentrations were significantly correlated with specific conductance and pH (p < 0.05). Regressions of the concentration of SigmaDDT in tissue, as a function of SigmaDDT in bed sediment, were significant and explained up to 76% of the variance in the data. The concentration of SigmaDDT in sediment may be related to mechanisms of soil transport to surface water with bioavailability of compounds related to the concentration of TOC in sediment. The results of this study did not indicate any clear advantage to using either bed sediment or tissues in studies of organochlorine chemicals in the environment. Some guidelines for protection of fish and wildlife were exceeded. Concentrations of organochlorine chemicals in biota, and perhaps sediment, have declined from concentrations measured in the 1970s and 1980s, but remain high compared to other regions of the United States.

Isomer-specific analysis of polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) in red fox and human adipose tissue from central Italy.

The general exposure of humans and foxes to polychlorinated biphenyls (PCBs) and DDT in Italy was determined by analysis of adipose tissue samples collected from 1991-1992. sigma PCB concentrations varied between 1.0 and 2.6 micrograms/g (wet wt.). sigma DDT concentrations ranged from 1.6 to 5.0 micrograms/g (wet wt.). About thirty-five PCB congeners were identified in most samples. PCB congeners of IUPAC Nos. 138, 153, and 180 were the most abundant compounds, accounting for an average of 50% of the sigma PCBs in humans and 64% in foxes. Generally, higher chlorinated biphenyls and those with a 2,4,5-chlorine substitution in one ring and at least one substitution in the 4-position of the other ring were preferentially accumulated. Coplanar PCB congeners were detected at considerable concentrations and there is no sign of decline in their concentrations with respect to previously reported data. IUPAC Nos. 118, 156 and 126 were the main contributors to toxicity in humans and foxes. The significant contribution of mono-ortho congeners in humans and non-ortho congeners in foxes suggests that differences in metabolic potential may affect the PCB toxicity pattern.

Mercury, DDT and PCB in the Atlantic Walrus (&lt;i&gt;Odobenus rosmarus rosmarus&lt;/i&gt;) from the Thule District, North Greenland

Tissue samples of 69 Atlantic walruses ( Odobenus rosmarus rosmarus ) were collected in the Thule district, North Greenland, in May-July 1975 and 1977. The mean concentration of total mercury in liver was 1.78 mg/kg (SD=1.54; N=46), wet weight basis, with the mean percentage of methyl mercury being 5.5%. The mean concentration in muscle was 0.08 mg/kg (SD=0.05; N=58; mean age = 10.9 years; range: 1-26 years; neonates excluded). In neonates (N=9) the mean concentration of total mercury was 0.31 mg/kg (SD=0.45) in liver (19.9% methyl mercury) and 0.06 mg/kg (SD=0.03) in muscle. Mean Sigma DDT and PCB concentrations in blubber of 28 walruses (mean age = 7.4 years; range: 0-19 years) were 0.063 mg/kg (SD=0.080) and 0.221 mg/kg (SD=0.207), respectively. In males the concentration of Sigma DDT and PCB increased with age. In females there was no correlation between the concentration of Sigma DDT and age, while there was a negative correlation between the concentration of PCB and age. The values of mercury concentrations are low compared with values for seals in Greenland and the eastern Canadian Arctic, and the values of organochlorine concentrations are the lowest reported for pinnipeds. Key words: Mercury, DDT, PCB, Atlantic walrus, Odobenus rosmarus rosmarus , North Greenland

Mercury and chlorinated hydrocarbons in zoobenthos of Lake Päijänne, Finland.

The average amounts of mercury, PCBs, and sigma DDT (primarily DDE), found in macrozoobenthos, on the wet basis, in Lake Päijänne, Finland, for the time period 1972-1974, were 79 ng/g, 29 ng/g, and 8 ng/g, respectively. Lindane was found in negligible amounts in only 2% of the samples examined; aldrin was present in 10% of the samples; no dieldrin was detected. Mercury and PCB concentrations varied regionally in the lake. PCB and sigma DDT concentrations were greater in the predatory bottom animals than in the herbivores or detritus feeders, and the amounts of chlorinated hydrocarbons were greater in profundal animals than in littoral animals. No significant correlation was apparent between the amount of residues found and the weight of the animal (e.g. Anodonta). A significant positive correlation was evident in the amounts of PCBs and sigma DDT in most of the taxonomical groups. Spongilla lacustris and Anodonta piscinalis were excellent species for monitoring purposes.