Brominated flame retardants: a novel class of developmental neurotoxicants in our environment?

Abstract

Brominated flame retardants are a novel group of global environmental contaminants. Within this group the polybrominated diphenyl ethers (PBDE) constitute one class of many that are found in electrical appliances, building materials, and textiles. PBDEs are persistent compounds that appear to have an environmental dispersion similar to that of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT). Levels of PBDEs are increasing in mother's milk while other organohalogens have decreased in concentration. We studied for developmental neurotoxic effects two polybrominated diphenyl ethers, 2,2',4,4'-tetrabromodiphenyl ether (PBDE 47) and 2,2',4,4',5-pentabromodiphenyl ether (PBDE 99)--congeners that dominate in environmental and human samples--together with another frequently used brominated flame retardant, tetrabromo-bis-phenol-A (TBBPA). The compounds were given to 10-day-old NMRI male mice, as follows: PBDE 47, 0.7 mg (1.4 micromol), 10.5 mg (21.1 micromol)/kg body weight (bw); PBDE 99, 0.8 mg (1.4 micromol), 12.0 mg (21.1 micromol)/kg bw; TBBPA, 0.75 mg (1.4 micromol), 11.5 mg (21.1 micromol)/kg bw. Mice serving as controls received 10 mL/kg bw of the 20% fat emulsion vehicle in the same manner. The present study has shown that neonatal exposure to PBDE 99 and PBDE 47 can cause permanent aberrations in spontaneous behavior, evident in 2- and 4-month-old animals. This effect together with the habituation capability was more pronounced with increasing age, and the changes were dose-response related. Furthermore, neonatal exposure to PBDE 99 also affected learning and memory functions in adult animals. These are developmental defects that have been detected previously in connection with PCBs.

Developmental neurotoxicity of polybrominated diphenyl ether (PBDE) flame retardants

“…Control mice display habituation, a decrease in locomotion, rearing and total activity variables in response to the diminishing novelty of the test chamber over 60-min. Thus, the investigators interpret their results (initial hypoactivity and late hyperactivity) as a decrease in habituation caused by PBDEs (Eriksson et al 2001). An alternative interpretation might be that the decreased activity at the beginning of the session is a possible sign of increased anxiety or arousal, and the elevated activity later in the session is simply the animals finally beginning to explore their environment, as controls did at the beginning of the session.…”

“…A Swedish group has carried out most studies on developmental neurotoxicity of various PBDEs (see Table 7; Eriksson et al 2001;Viberg et al 2003a;2003b;2007a). Their experimental protocol involves direct exposure of neonatal mice or rats to PBDEs, as a single oral dose, usually on post-natal day (PND) 10.…”

“…3 shows a typical profile of locomotor activity in these experiments. Three variables are measured: horizontal locomotor activity, rearing, and total activity (Eriksson et al 2001). Mice exposed to PBDEs display significant less activity than controls during the first 20-min.…”

Organohalogen contaminants and metabolites in cerebrospinal fluid and cerebellum gray matter in short-beaked common dolphins and Atlantic white-sided dolphins from the western North Atlantic

“…Studies with experimental animals have indicated that pre-and postnatal exposure to PBDEs impairs motor activity and cognitive behavior. Exposure of neonatal rats to BDE-47 (the most prominent PBDE congener in CSF and cerebellum GM) caused poor performance in horizontal locomotor activity (Eriksson et al, 2001). In addition to the effects on the cerebellum, exposure of neonatal rats to some PBDEs (e.g., BDE-153) impairs learning and memory and decreases hippocampal cholinergic receptors (Viberg et al, 2003).…”

Assessing reproductive and endocrine parameters in male largescale suckers (Catostomus macrocheilus) along a contaminant gradient in the lower Columbia River, USA

“…The most prominent PBDE congeners found in the environment, humans, birds of prey and other wildlife are BDE-47, BDE-99, and BDE-100 (Eriksson et al, 2001;Chen and Hale, 2010;Nilsen et al, 2014-in this issue), with some inter-regional differences. At sites furthest downstream on the LCR, sperm quality values in LSS were the lowest.…”