Congener Groups Research Articles

Plasma organochlorine levels and risk of non-Hodgkin lymphoma in a cohort of men.

Environmental exposure to polychlorinated biphenyls (PCBs) and p,p'-dichlorodiphenyldichloroethylene (p, p'-DDE) has been associated with the risk of non-Hodgkin lymphoma. We conducted a case-control study nested within the Physicians' Health Study, a prospective cohort established in 1982. We measured concentrations of PCBs and p,p'-DDE in baseline blood samples from 205 men later diagnosed with non-Hodgkin lymphoma and 409 age- and race-matched controls. Lipid-adjusted organochlorine concentrations were categorized into quintiles based on the distribution among controls. We used conditional logistic regression to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) for each quintile relative to the lowest quintile. We also evaluated these associations for major histologic subtypes of non-Hodgkin lymphoma. The risk of non-Hodgkin lymphoma was positively associated with the sum of 51 PCB congeners assayed (SigmaPCB); the group of immunotoxic congeners; the individual congeners 118, 138, 153, and 180; and the sum of these 4 congeners. The simple OR for the highest quintile of lipid-adjusted SigmaPCB versus the lowest was 1.9 (95% CI = 1.1-3.2; test for trend, P = 0.001), with similar trends for individual congeners and groups defined as above. Adjustment for height, body mass index, alcohol intake, smoking, and fish intake did not substantially change the effect estimates. No association was observed for p,p'-DDE. There was no evidence of statistical heterogeneity in effects by histologic subtype of lymphoma; however, this analysis was underpowered. These results support the hypothesis of a positive association between PCB exposure and development of NHL in men.

Relationships Between Brominated Flame Retardant Concentrations in House Dust and Serum Hormone Levels in Men

ISEE-0454 Background and Objective: Human exposure to brominated flame retardants (BFRs) is widespread, occurring primarily through diet or contact with indoor dust. There is laboratory evidence of endocrine disruption in animals following exposure to BFRs, but human studies are limited. In this preliminary investigation, we examined the association between BFR levels in house dust and hormone levels in men. Methods: We measured serum hormone levels and BFR concentrations in participant vacuum bag dust from 38 men recruited through a Massachusetts infertility clinic as part of an ongoing study of environmental exposures and male reproductive health. Statistical methods included the calculation of Spearman correlations among BFRs and between BFRs and serum hormone levels, and multivariable linear regression. Results: There were strong correlations (r ≥ 0.80, P < 0.05) among dust concentrations of brominated diphenyl ether (BDE) congener groups with a similar degree of bromination. Positive correlations were found (P ≤ 0.05) between several BDE congeners and serum levels of prolactin and total T3, and between bistribromophenoxyethane and total T3. Hexabromocyclododecane was positively correlated with free androgen index (FAI) (r = 0.46, P = 0.004). Most of these relationships remained statistically significant or suggestive in multivariate linear regression models adjusted for age and BMI. There was a suggestive inverse association between BDE209 and testosterone when adjusting for age, BMI, and serum sex hormone binding globulin (SHBG) (P = 0.09). When dust concentrations of BDE99 were combined with results from a previous analysis of 24 men from the same cohort (n = 62), regression models adjusted for age, BMI, and dust analytical method showed positive relationships between BDE99 and serum estradiol, free T4, and SHBG (P < 0.05). Inverse associations between BDE99 and follicle stimulating hormone (P < 0.05) and FAI (P = 0.11) were also found. Conclusion: This study provides evidence of altered hormone levels in relation to BFR exposure and that house dust may be an important source of human BFR exposure.

Plasma Organochlorine Levels and Risk of Non-Hodgkin Lymphoma in the Physiciansʼ Health Study

ISEE-0522 Background and Objective: Non-occupational exposure to polychlorinated biphenyls (PCBs) and p,p′-dichlorodiphenyldichloroethylene (p,p′-DDE) may increase the risk of non-Hodgkin lymphoma (NHL). Methods: We conducted a case-control study nested within the Physicians' Health Study, a prospective cohort established in 1982. We measured concentrations of PCBs and p,p′-DDE in baseline blood samples from 205 men diagnosed with NHL and 409 age- and race-matched controls. Lipid-adjusted organochlorine concentrations were categorized into quintiles based on the distribution among controls. We used conditional logistic regression to estimate the rate ratios (RRs) and 95% confidence intervals (CIs) for each quintile relative to the lowest quintile. We also evaluated these associations for major histologic subtypes of NHL. Results: We found significant positive associations for the sum of 51 PCB congeners assayed (ΣPCB), the group of immunotoxic congeners, the individual congeners 118, 138, 153, and 180, and the sum of these four congeners with risk of NHL. The simple RR for the highest quintile of lipid-adjusted ΣPCB versus the lowest was 1.9 (95% CI: 1.1–3.2; P -trend = 0.001), with similar trends for individual congeners and groups defined as above. Adjustment for height, body mass index, alcohol intake, smoking, and fish intake did not substantially change the effect estimates. No association was observed for p,p′-DDE. There was no evidence of statistical heterogeneity in effects by histologic subtype. Conclusions: These results support the hypothesis of a positive association between PCB exposure and development of NHL in men.

Spatial Distribution of Airborne Polychlorinated Biphenyls in Cleveland, Ohio and Chicago, Illinois

Passive samplers were deployed across Cleveland, OH and Chicago, IL to evaluate the spatial variability of airborne PCBs in urban areas. We measured SigmaPCB concentrations, the sum of 151 congeners or congener groups quantified using tandem mass spectrometry, spatial distributions, and congener profiles in two urban areas in the Great Lakes region. Mean SigmaPCB concentrations were significantly different between Cleveland (1.73 +/- 1.16 ng m(-3)) and Chicago (1.13 +/- 0.58 ng m(-3)) during the August 2008 sampling period. Mean congener profiles were compared with commercial Aroclor mixtures and found to be similar to Aroclor 1242 in Cleveland and similar to a mixture of 1242 and 1254 in Chicago. We observed large spatial variation in concentrations and weak or no significant autocorrelation between sites in both cities. "Hot spots" of high SigmaPCB concentrations were identified in both urban areas and the congener profiles at these locations were most strongly correlated to that of PCB Aroclor mixtures. Congener profiles showed important differences including the enrichment of dioxin-like congeners in Chicago.

Polybrominated diphenyl ether contamination levels in fish from the Antarctic and the Mediterranean Sea

Polybrominated diphenyl ethers (PBDEs) concentrations and congener profiles were evaluated in four species of Antarctic fish ( Chionodraco hamatus, Chaempsocephalus gunnari, Gymnoscopelus nicholsi , Trematomus eulepidotes) and in one Mediterranean species (Tuna, Thunnus thynnus). The GC/MS-ECNI analysis revealed that average ∑PBDE concentrations in Antarctic fish species ranged from 0.09 ng g −1 wet weight (wet wt) in G. nicholsi to 0.44 ng g −1 wet wt in C. gunnari . In Mediterranean tuna they were two or three orders of magnitude higher (15 ng g −1 wet wt). The PBDE congener profiles differed between species; low brominated congeners prevailed in Antarctic species while in tuna tetra- and pentabromodiphenyl ethers were the most abundant congener groups (41% and 44%, respectively). These results showed that PBDE levels significantly correlated with the length of the fishes ( r 2 = 0.85, p < 0.01) in C. hamatus, but not with the weight of the fish. Moreover, mean ∑PBDE concentrations in tuna were statistically higher in females than in males (18 and 13 ng g −1 wet wt, respectively; p < 0.05), which was explained by the lower fat contents of the males that just had entered the spawning period. The results of this study confirm that PBDE contamination of the marine environment now occurs on a global scale.

Development of a comprehensive analytical method for the determination of chlorinated paraffins in spruce needles applied in passive air sampling

Conifer needles are used for the monitoring of atmospheric persistent organic pollutants. The objective of the present study was to develop a method for the detection of airborne chlorinated paraffins (CPs) using spruce needles as a passive sampler. The method is based on liquid extraction of the cuticular wax layer followed by chromatographic fractionation and detection of CPs using two different GCMS techniques. Total CP concentrations (sum of short (SCCP), medium (MCCP) and long chain CPs (LCCP)) were determined by EI-MS/MS. SCCP and MCCP levels as well as congener group patterns ( n-alkane chain length, chlorine content) could be evaluated using ECNI-LRMS. For the first time, data on environmental airborne CPs on spruce needles taken within the Monitoring Network in the Alpine Region for Persistent and other Organic Pollutants (MONARPOP) are presented providing evidence that spruce needles are a suitable passive sampling system for the monitoring of atmospheric CPs.

Paradoxical increases in serum levels of highly chlorinated PCBs in aged women in clear contrast to robust decreases in dietary intakes from 1980 to 2003 in Japan

Exposure to polychlorinated biphenyls (PCBs) is considered to have culminated between 1950 and 1970 in Japan, and exposure through diet, the major exposure route, has decreased significantly over the last 10 years. The primary goal of the present study was to investigate the long-term trends and congener profiles of serum and dietary levels of PCBs using historical samples. Using banked samples collected in 1980, 1995, and 2003 surveys, we determined the daily intakes and serum concentrations of 13 PCB congeners (#74, #99, #118, #138, #146, #153, #156, #163, #164, #170, #180, #182, and #187) in women. The total daily PCB intake [ng/day, geometric mean (geometric standard deviation)] decreased significantly from 523 (2.5) in 1980 to 63 (3.2) in 2003. The serum total PCB level (ng/g lipid) in women <40 years of age decreased significantly from 185 (1.8) in 1980 to 68 (1.8) in 2003. In contrast, the level in women >50 years of age increased significantly from 125 (1.7) in 1980 to 242 (1.7) in 2003. Specifically, the serum concentrations of hexa (#138, #146, #153, #156, #163, and #164) and hepta (#170, #180, #182, and #187) congeners increased significantly. A comparison of the serum PCB levels of women born from 1940 to 1953 revealed that their serum total PCB level was significantly higher in the 2003 survey [242 (1.7), n = 9] than in the 1995 [128 (2.0), n = 17] surveys. This increase in the total PCB level was attributable to increases in the hepta congener groups. Present results suggest a decreased rate of elimination of hepta congeners with aging in females, rather than a birth-generation phenomenon.

Analysis of PCB congeners related to cognitive functioning in adolescents

To investigate the characteristics of PCBs that are linked to cognitive functioning, those congeners that were concurrently found in 271 Mohawk adolescents were grouped according to structure (dioxin-like or non-dioxin-like) and persistence (persistent or low-persistent). After the effects of the congener groups were orthogonalized, regression analyses (controlling for a number of variables found to be related to the cognitive outcomes) examined the relationship of each congener group to scores on three cognitive tests (the non-verbal Ravens Progressive Matrices, the Test of Memory and Learning, and the Woodcock Johnson-Revised). Five subtests from these cognitive tests were found to be associated with one or more PCB congener groups, most often at a moderate level. Two measures of long-term memory (Delayed Recall and Long Term Retrieval) were associated with all four congener groups. Nevertheless, examination of the role of individual congeners in the significantly related congener groups revealed that almost all congeners associated with cognitive outcomes were non-dioxin-like and ortho-substituted. A notable exception was the Ravens test where scores were associated only with dioxin-like congeners. This finding adds to the limited evidence of neurotoxic effects of dioxin-like congeners. Auditory Processing was related only to the persistent congener group. The association of the non-persistent congener group with three cognitive test scores (Delayed Recall, Long Term Retrieval and Comprehension-Knowledge) suggests that the Mohawk adolescents have experienced continuing or recent environmental exposure to PCBs that is sufficient to result in detectable cognitive decrements. Comparison of our findings with those of other human studies was limited by the relative lack of specificity of both PCB measures and cognitive outcome measures in much previous work.

Patterns of Bioaccumulation of Polybrominated Diphenyl Ether and Polychlorinated Biphenyl Congeners in Marine Mussels

Marine mussels (Modiolus modiolus) and sediment from 14 stations near a municipal outfall and three reference locations were analyzed for polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) to evaluate and compare patterns of bioaccumulation of individual congeners between these two groups of chemicals. Of the 47 PBDEs and 209 PCBs analyzed, 34 PBDE and 153 PCB congeners or coeluting groups of congeners were detected in one or more matrices. The predominant PBDE congeners were BDEs 47, 99, 100, and 209, accounting for 80-90% of the total PBDEs in all matrices. PCBs and PBDEs exhibited a parabolic relationship of the biota-sediment accumulation factor (BSAF) versus the log octanol-water partition coefficient(Kow). Below Kow 10(5.5), BSAFs ranged between 1 and 3, reflecting approximate equilibrium between mussels and sedimentforthese relatively water soluble congeners. BSAFs increased with increasing Kow to maximum values of approximately 30-100 for congeners with Kow approximately 10(7) and then declined at higher Kow to a value of approximately 1 for BDE 209. BSAFs for PBDEs were generally 2- to 3-fold higher than those for PCBs of a similar Kow. The calculated BSAFs for PBDE congeners indicate that PBDEs have a pattern of bioaccumulative behavior in mussels similar to that of the PCBs, and that some PBDE congeners may be more bioaccumulative in mussels than PCBs.

Reactivity of Group 5 Bielement Clusters with H2

Bielement metal clusters composed of the group 5 elements, A(n)B(m) (A, B = V, Nb, Ta), were prepared in the gas phase over the wide n and m ranges. We measured reactivities of the attachment reaction of the neutral clusters to H(2), which were plotted as a function of a map with n and m. The clusters with n + m = 4 and 5 were found to be more reactive than the other clusters. The measurement of the ionization energies reveals that there is no strong correlation between the reactivity and the ionization energy. In addition, the reactivities of the cations, A(n)B(m)(+), were also highest at n + m = 4 and 5. These findings suggest that the electronic structure does not totally determine the reactivity of the neutral clusters. On the other hand, theoretical calculations for A(n)B(m) (n + m = 4) reported by Metha et al. showed that the optimized geometrical structures of the congener group 5 bielement clusters do not change significantly by changing n and m within n + m = 4. Hence, it is highly likely that the pyramidal (n + m = 4) and bipyramidal (n + m = 5) structures of A(n)B(m) determine the high reactivity of the clusters.

Particle-size-fractioned transfer of dioxins from sediments to water columns by resuspension process

Particle-size-fractioned transfer of dioxins from sediments to water columns by resuspension process was investigated, using supernatant samples obtained from shaking experiments of sediment–water pairs simulating natural disturbances. The concentrations (dry-matter mass basis) of individual compounds ( C fraction ) in two particle size fractions (0.1–1 and 1–10 μm) in the supernatants were generally slightly higher than those in the original sediment ( C sed ). C fraction / C sed ratios ranged from 0.45 to 5.9 (median 1.5) without consistent differences among congener groups or consistent correlations against the number of chlorine atoms. The dioxin concentrations in the water column associated with the remaining sediment particles can therefore be estimated by those in the original sediment and by the concentration of suspended sediment particles in the water. The concentration of each compound in the remaining sediment particles (mostly 0.1–10 μm in size) can be roughly estimated by multiplying the concentration in the original sediment by 1.5.

Revision of Ilyocryptus Sars, 1862 (Cladocera: Ilyocryptidae) of Brazil with description of two new subspecies

Analyzing numerous samples from Brazil, we found only three previously described species of Ilyocryptus (Cladocera: Anomopoda: Ilyocryptidae): I. paranaensis paranaensis Paggi, 1989, I. sarsi Stingelin, 1913 and I. spinifer Herrick, 1882. Two new taxa, being Neotropical subspecies of the species previously described from Palaearctic, I. cuneatus brasiliensis subsp. nov. and I. silvaeducensis paraensis subsp. nov., are described. Maps of Brazilian records are provided for each species using both original and literature data. Most part of records of Brazilian ilyocryptids concerns I. spinifer, which is among the most common cladocerans in the Neotropics, while other taxa occur significantly rare. I. spinifer has a wide distributional range. “I. sarsi” seems to be a group of close topical congeners, quite possible that I. sarsi s. str. is an exclusively Neotropical taxon. Three other recorded species are Neotropical endemics. We believe that previous records of I. sordidus (Lévin, 1848) from Brazil were misidentifications, probably of two newly described taxa, or I. sarsi.

High serum PCBs are associated with elevation of serum lipids and cardiovascular disease in a Native American population

We have investigated the relationships among the concentration of total serum polychlorinated biphenyls (PCBs), various PCB congener groupings, and three pesticides to total serum lipids in humans with and without self-reported cardiovascular disease. Blood samples were obtained from 335 adult Akwesasne Mohawks, and were analyzed for 101 PCB congeners, mirex, dichloro-diphenyl-dichloro-ethylene (DDE), and hexachlorobenzene (HCB), as well as serum triglycerides and cholesterol. Structural equation modeling, following the definition of latent variables by means of confirmatory factor analysis, was used to analyze the relationships between serum lipids with PCBs and heart disease. There were significant associations among PCBs, lipids, age, and body mass index (BMI), a fact which justified the application of the structural equation model. Gender of the participant was unrelated to any of the remaining study variables. The results of this study are consistent with a model in which age is considered as both an exogenous explanatory variable and a biological driving mechanism for the acquisition of PCBs. Moreover, the results of this study are consistent with the conclusion that PCBs, acting through P450 enzymes, are directly responsible for increased synthesis of cholesterol and triglycerides, substances known to be major risk factors for cardiovascular disease.

Engineering a regulatory region of jadomycin gene cluster to improve jadomycin B production in Streptomyces venezuelae

Streptomyces venezuelae ISP5230 produces a group of jadomycin congeners with cytotoxic activities. To improve jadomycin fermentation process, a genetic engineering strategy was designed to replace a 3.4-kb regulatory region of jad gene cluster that contains four regulatory genes (3' end 272 bp of jadW2, jadW3, jadR2, and jadR1) and the native promoter upstream of jadJ (P(J)) with the ermEp* promoter sequence so that ermEp* drives the expression of the jadomycin biosynthetic genes from jadJ in the engineered strain. As expected, the mutant strain produced jadomycin B without ethanol treatment, and the yield increased to about twofold that of the stressed wild-type. These results indicated that manipulation of the regulation of a biosynthetic gene cluster is an effective strategy to increase product yield.

Distribution characteristics of polychlorinated biphenyls (PCBs) in coastal areas of Okinawa Island, Japan

Surface sediment and seawater samples were collected from coastal areas around Okinawa Island from September 2001 to May 2002. The samples were analyzed for total polychlorinated biphenyl (PCB) levels and homolog composition. The results show that total PCB levels ranged from 0.32 to 128.7 ng/g (dry wt.) in sediment and 1.59 to 2.48 ng/L in seawater. The levels exceed the Environmental Quality Standard (EQS) for water pollution of Japan. The distribution of PCB homolog showed different patterns in the sediments and seawaters. Penta-chlorobiphenyls (CBs) comprised the main congener group in seawater, while hexa-CBs were more abundant homologs in the sediments. The heavily contaminated sites featured higher CBs, including penta-CBs, hexa-CBs, and hepta-CBs, than those in less contaminated sites where tri-CBs dominated. This study provides current distribution and geochemical behavior of PCBs in the coastal areas around Okinawa Island.

Factors Influencing the National Distribution of Polycyclic Aromatic Hydrocarbons and Polychlorinated Biphenyls in British Soils

The polycyclic aromatic hydrocarbons (PAHs) naphthalene, acenaphthylene, acenaphthene, fluorene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, ideno[1,2,3,-cd]-pyrene, dibenz[a,h]anthracene, benzo[g,h,i]perylene and the polychlorinated biphenyls (PCBs) 8, 18, 28, 29, 31, 52, 77, 101, 105, 114, 118, 123, 126, 128, 138, 141, 149, 153, 156, 157, 163, 169, 170, 171, 180, 183, 187, 189, 194, 199, 201, 206, and 209 were measured in -200 rural soils across Great Britain (GB). Dominance of soil PAH profiles by heavier compounds (4-6 rings) provided initial evidence for the importance of source in governing soil PAH concentrations. No relationship was found between soil organic matter (SOM) and sum concentration of total and "heavy" PAHs, although there was a weak positive relationship with lighter compounds. A spatial statistical technique showed that highest soil PAH concentrations were usually found close to industrial/urban centers where presumably source intensity is highest. PCBs clustered into seven groups, five of which contained a single "dioxin like" PCB, one contained lighter congeners (2-4 chlorines), and one contained heavy congeners (5-10 chlorines). Linear regressions with SOM explained up to 24.3% of variation for the sum concentration of penta- to deca- congeners, but <1% for the lighter congener groups. No significant relationships were found with latitude. Spatial statistical techniques showed clusters of high soil PCB concentrations predominantly in west and south east GB, either associated with urbanized areas or on the West coast.

PCDD/PCDF Isomer patterns in waste incinerator flyash and desorbed into the gas phase in relation to temperature

The influence of temperature on the PCDD and PCDF isomer profiles of a municipal waste incinerator flyash and the PCDD/PCDF desorbed from the ash under an inert atmosphere was investigated using a bench-scale reactor. Exposure to temperatures of 250 °C and above resulted in significant changes in the distribution of isomers within most dioxin and furan congener groups. The PCDD content tended to become more evenly distributed across the range of isomers than was the case for the raw flyash, while the PCDF content became concentrated across a relatively lower number of isomers. In most cases the desorbed PCDD/PCDF were mainly mono- to tri-chlorinated, and hence had a relatively low I-TEQ value. The isomer profiles of the desorbed species were also influenced by temperature. There were some significant differences between the PCDF isomer profiles of the desorbed species and those of the treated flyashes under the same conditions, but no clear differences between the PCDD isomer profiles.

Short- and medium-chain chlorinated paraffins in biota from the European Arctic — differences in homologue group patterns

Congener and homologue group patterns of chlorinated paraffins (CPs) in biota can be influenced by different processes, but these are not well studied yet. Short- (SCCPs) and medium-chain chlorinated paraffins (MCCPs) were quantified in liver from Arctic char and seabirds (little auk and kittiwake) collected at Bear Island (European Arctic) as well as in cod from Iceland and Norway. CP concentrations were between 5 and 88 ng/g wet weight (ww) for SCCPs and between 5 and 55 ng/g ww for MCCPs with one exception of 370 ng/g measured in a liver sample from little auk. The SCCP homologue group patterns were compared with those of technical mixtures and of SCCPs present in cod liver from the Baltic Sea. The latter showed a more common SCCP homologue distribution (sum of C11 and C12>60%) in contrast to cod liver from the Northwest of Europe, which had a high abundance of C10 and C12 congeners. Seabirds from Bear Island contained an equally distributed SCCP homologue group pattern. In Arctic char, the SCCP distribution was closer to technical products, but with a high proportion (average of 18.9%) of C10 congeners. A comparison of C10/C12 ratios confirmed the higher abundance of C10 congeners in samples from higher latitudes. For the first time, MCCPs could be detected in Arctic samples. The average proportion of C14 congeners was 65.8%. The C14/C15 abundance ratio was similar to technical mixtures. High-chlorinated CPs (Cl>7) were also detectable. The average chlorine content of the SCCPs was 61.9% (59.0–63.3%), and that of the MCCPs 55.8% (54.5–57.4%).

Congener group patterns of chloroparaffins in marine sediments obtained by chloride attachment chemical ionization and electron capture negative ionization

Congener group patterns of technical short chain and medium chain chloroparaffins (SCCP and MCCP) were determined by electron capture negative ionization (ECNI) and chloride attachment chemical ionization (CACI) mass spectrometry (MS). In contrast to CACI–MS, congener patterns obtained by ECNI showed always a shift to the next higher chlorinated congener and carbon chain length group. Consequently, the calculated molecular masses and chlorine contents were higher for ECNI (factor 1.10 ± 0.03 and 1.09 ± 0.03, respectively). ECNI/CACI ratios in sediment samples from the North and Baltic Sea were also slightly higher. However, a more pronounced shift of the congener pattern for a given carbon chain length to congeners with 2–3 more chlorine atoms was observed. SCCP and MCCP concentrations obtained by ECNI–MS were in the range of 8–63 ng g −1 (North Sea) and 22–149 ng g −1 dry weight (Baltic Sea). MCCP levels were highest in all samples (MCCP/SCCP factor 1.1–3.2).

Persistent organic pollutants in Alaskan ringed seal (Phoca hispida) and walrus (Odobenus rosmarus) blubber

Since 1987, the Alaska Marine Mammal Tissue Archival Project (AMMTAP) has collected tissues from 18 marine mammal species. Specimens are archived in the National Institute of Standards and Technology's National Biomonitoring Specimen Bank (NIST-NBSB). AMMTAP has collected blubber, liver and/or kidney specimens from a number of ringed seals (Phoca hispida) from the areas near Nome and Barrow, Alaska and walruses (Odobenus rosmarus) from several locations in the Bering Sea. Thirty-three ringed seal and 15 walrus blubber samples from the NIST-NBSB were analyzed for persistent organic pollutants (POPs). The compounds determined included PCBs (28 congeners or congener groups), DDT and related compounds, hexachlorobenzene (HCB), hexachlorocyclohexane isomers (HCHs), chlordanes, dieldrin, and mirex. POP concentrations in ringed seal blubber were significantly higher in Barrow than in Nome when statistically accounting for the interaction of age and gender; HCB, however, was not statistically different between the two locations. Unlike males, POP concentrations and age were not significantly correlated in females probably as a result of lactational loss. POP concentrations in walrus blubber were lower than in ringed seal blubber for SigmaPCBs, chlordanes, and HCHs, but higher for dieldrin and mirex. POP concentrations in ringed seals and walrus from Alaska provide further evidence that the western Arctic tends to have lower or similar POP concentrations compared to the eastern Canadian Arctic.