Thyroid disruption and oxidative stress in American kestrels following embryonic exposure to the alternative flame retardants, EHTBB and TBPH

Christopher Goodchild; Natalie K Karouna-Renier; Paula F P Henry; Robert J Letcher; Sandra L Schultz; Catherine M Maddox; Thomas G Bean; Lisa E Peters; Vince Palace; Kim J Fernie

doi:10.1016/j.envint.2021.106826

Thyroid disruption and oxidative stress in American kestrels following embryonic exposure to the alternative flame retardants, EHTBB and TBPH

Environ Int. 2021 Dec:157:106826. doi: 10.1016/j.envint.2021.106826. Epub 2021 Aug 24.

Authors

Affiliations

¹ U.S. Geological Survey, Eastern Ecological Science Center, Patuxent Research Refuge, Beltsville, MD 20705, USA; Department of Biology, University of Central Oklahoma, Edmond, OK 73034, USA.
² U.S. Geological Survey, Eastern Ecological Science Center, Patuxent Research Refuge, Beltsville, MD 20705, USA. Electronic address: nkarouna@usgs.gov.
³ U.S. Geological Survey, Eastern Ecological Science Center, Patuxent Research Refuge, Laurel, MD 20708, USA.
⁴ Ecotoxicology & Wildlife Health Division, Science & Technology Branch, Environment & Climate Change Canada, Carleton University, Ottawa, Ontario K1A 0H3, Canada.
⁵ U.S. Geological Survey, Eastern Ecological Science Center, Patuxent Research Refuge, Beltsville, MD 20705, USA.
⁶ Department of Environmental Science and Technology, University of Maryland, College Park, MD 20740, USA.
⁷ Faculty of Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.
⁸ International Institute of Sustainable Development - Experimental Lakes Area, Winnipeg, Manitoba R3B 0T4, Canada.
⁹ Ecotoxicology & Wildlife Health Division, Science & Technology Branch, Environment and Climate Change Canada, Burlington, Ontario L7S 1A1, Canada. Electronic address: kim.fernie@canada.ca.

PMID: 34438233
DOI: 10.1016/j.envint.2021.106826

Abstract

Brominated flame retardant chemicals, such as 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EHTBB) (CAS #: 183658-27-7) and bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH) (CAS #: 26040-51-7), have been detected in avian tissues and eggs from remote regions. Exposure to EHTBB and TBPH has been shown to cause oxidative stress and altered thyroid function in rodents and fish, yet no controlled studies have examined potential adverse effects of exposure in birds. Because flame retardants have been detected in wild raptors, we used American kestrels (Falco sparverius) as a model raptor to determine whether in ovo exposure to EHTBB or TBPH affected growth, hatching success, oxidative stress, or thyroid function. We exposed kestrel embryos to nominal concentrations (10, 50, or 100 ng g^-1 egg weight) of EHTBB and TBPH via egg-injection on embryonic day 5. Embryonic exposure (~23 d) to EHTBB increased thyroid gland mass, reduced glandular colloid and total thyroxine (T4) in hatchling males and females, whereas deiodinase enzyme activity increased in males but decreased in females. Hatchlings exposed to TBPH in ovo exhibited reduced colloid and increased oxidative stress. Although exposure to EHTBB and TBPH caused several physiological effects (e.g., heart and brain mass), only exposure to 50 ng g^-1 EHTBB appeared to reduce hatching success. Our results suggest these flame retardants may be hazardous for predatory birds. Future research should evaluate long-term survival and fitness consequences in birds exposed to these chemicals.

Keywords: American kestrel; Firemaster 550®; Flame retardant; Oxidative stress; Thyroid.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Animals
Falconiformes*
Female
Flame Retardants* / toxicity
Male
Oxidative Stress
Thyroid Gland
Thyroxine / toxicity

Substances

Flame Retardants
Thyroxine