US Geological Survey


Document Type


Date of this Version



Environ. Sci. Technol. 2015, 49, 7448−7455


U.S. Government Work


Organophosphate triesters are high production volume

additive flame retardants (OPFRs) and plasticizers. Shown to accumulate

in abiotic and biotic environmental compartments, little is known about the

risks they pose. Captive adult male American kestrels (Falco sparverius) were

fed the same dose (22 ng OPFR/g kestrel/d) daily (21 d) of tris(2-

butoxyethyl) phosphate (TBOEP), tris(2-chloroethyl) phosphate (TCEP),

tris(2-chloroisopropyl) phosphate (TCIPP), or tris(1,2-dichloro-2-propyl)

phosphate (TDCIPP). Concentrations were undetected in tissues (renal,

hepatic), suggesting rapid metabolism. There were no changes in glutathione

status, indicators of hepatic oxidative status, or the cholinergic system (i.e.,

cerebrum, plasma cholinesterases; cerebrum muscarinic, nicotinic receptors).

Modest changes occurred in hepatocyte integrity and function (clinical

chemistry). Significant effects on plasma free triiodothyronine (FT3)

concentrations occurred with exposure to TBOEP, TCEP, TCIPP, and

TDCIPP; TBOEP and TCEP had additional overall effects on free thyroxine (FT4), whereas TDCIPP also influenced total

thyroxine (TT4). Relative increases (32%−96%) in circulating FT3, TT3, FT4, and/or TT4 were variable with each OPFR at 7 d

exposure, but limited thereafter, which was likely maintained through decreased thyroid gland activity and increased hepatic

deiodinase activity. The observed physiological and endocrine effects occurred at environmentally relevant concentrations and

suggest parent OPFRs or metabolites may have been present despite rapid degradation.