Comparison of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in the serum of hypothyroxinemic and euthyroid dogs

Significance of the Topic

The analysis of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in canine serum addresses ongoing concerns about environmental pollutants that disrupt thyroid hormone homeostasis. Domestic dogs, sharing indoor environments with humans yet free from many lifestyle confounders, serve as valuable sentinel species for assessing human exposure and health risks associated with persistent organic pollutants.

Objectives and Study Overview

This study aimed to characterize 14 PBDE and 23 PCB congeners in serum from client-owned dogs and to evaluate their association with hypothyroxinemia. Serum was collected between 2012 and 2016 from 51 dogs attending the University of California, Davis, Veterinary Medical Teaching Hospital, of which 15 exhibited low total T4 levels and 36 were euthyroid controls.

Methodology and Instrumentation

Serum samples (0.25–0.5 ml) underwent formic-acid extraction, SPE cleanup, and silica cartridge purification. Samples were analyzed by gas chromatography–tandem mass spectrometry to quantify PBDE and PCB congeners. Lipid content was determined enzymatically (total cholesterol and triglycerides) and used to normalize analyte levels. Statistical analysis included logistic regression controlling for age to assess the association between congener concentrations and hypothyroxinemia.

Instrumentation Used

• Gas chromatograph coupled with triple quadrupole mass spectrometer (Scion TQ GC/MS/MS)
• Waters Oasis HLB SPE cartridges and Sep-Pak Light Silica cartridges for sample cleanup
• Standard clinical chemistry analyzers for lipid determinations

Main Results and Discussion

All PBDE and PCB congeners were detected in canine serum, confirming ongoing exposure. Median total PBDE and PCB levels were higher in hypothyroxinemic dogs (660 and 1,371 ng/g lipid) than controls, but associations with thyroid status were not statistically significant. BDE-183 showed a near-significant positive odds ratio (OR = 1.05 per ng/g lipid increase; p = 0.068). Possible explanations include dogs’ efficient metabolic debromination of higher-brominated congeners, formation of hydroxylated metabolites with differing thyroid-binding affinities, and high regional PBDE use in California before phase-out.

Benefits and Practical Applications

Domestic dogs provide a practical, non-invasive model for biomonitoring PBDE and PCB exposure. Data from canine populations can inform human health risk assessments, guide public health interventions, and support regulatory decisions on persistent pollutants.

Future Trends and Applications

• Expand analyses to include hydroxylated and methoxylated PBDE/PCB metabolites
• Increase sample sizes and diversity of canine populations for greater statistical power
• Conduct longitudinal and mechanistic studies of pollutant toxicokinetics in dogs
• Integrate canine sentinel data into human epidemiological and exposure modeling efforts

Conclusion

This study confirms ubiquitous canine exposure to PBDEs and PCBs but finds no significant association with hypothyroxinemia. Further research with larger cohorts, expanded analyte panels, and mechanistic endpoints is needed to clarify the role of these contaminants in thyroid disruption and to reinforce the sentinel value of dogs for human health risk assessment.

References

• Lau G, Walter K, Kass P, Puschner B. Comparison of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in the serum of hypothyroxinemic and euthyroid dogs. PeerJ. 2017;5:e3780.