Two-Generation Oral (Diet) Reproductive Toxicity Study of Resorcinol Bis-Diphenylphosphate (Fyrolflex RDP) in Rats

Comparative Metabolism and Toxicokinetics of 14C-ResorcinoI Bis-Diphenylphosphate (RDP) in the Rat, Mouse, and Monkey

As part of a comprehensive program to examine the safety and toxicokinetics of the flame retardant, resorcinol bis-diphenylphosphate (RDP), the metabolism and toxicokinetics of RDP was determined after exposure of rats and monkeys to 14C-RDP via intravenous, inhalation, oral, or dermal routes. The metabolism of RDP was also determined in mice. Blood, urine, and fecal samples were collected at specified times for the quantification of 14C levels. Expired air was collected from rats. Excreta samples were quantitatively extracted. Chromatographic profiles of urinary and fecal metabolites were generated for multiple animals from each group. The major metabolites were isolated and then purified by a multistep chromatographic process. Structures of urinary and fecal metabolites were determined by HPLC-mass spectrometry (MS), MS-MS, and MS-MS-MS techniques. The metabolic pattern in all three species is complex. In certain urine and feces samples, radioactivity was associated with more than 30 HPLC peaks. There was little interanimal variability in metabolic profiles. No differences between species or sexes were apparent. The parent molecule, RDP, was present in significant amounts only in the feces of animals exposed by inhalation or gavage; this appears to reflect unabsorbed ingested material. Structures of all major urinary and fecal metabolites (representing 5% of the administered dose) in rats and primates were identified. The major fecal metabolites were resorcinol diphenylphosphate (RDP half ester), hydroxy-RDP half ester, dihydroxy-RDP, and hydroxy-RDP. Major urinary metabolites were identified as resorcinol, resorcinyl glucuronide, and resorcinyl sulfate. A small amount of 14CO2 was expired. This study confirms that RDP is metabolized in an identical manner by rats, mice, and primates, and that the rat and mouse are appropriate surrogates (animal models) in which to assess the toxicity of RDP. In both rats and primates, the highest peak plasma concentration (Cmax) and greatest area under the curve (AUC) was obtained with intravenous (TV) administration. In rats the Cmax for inhalation, oral, and dermal exposures were 42%, 10%, and 1%, respectfully. The AUC values for these three routes were 60%, 58%, and 15% of the IV AUC. Approximately 20% of the dermal dose was absorbed in the rat whereas primates absorbed only 10% of the applied dermal dose. Tissue accumulation and retention of radioactivity was minimal, indicating complete clearance of the administered dose.

Persistence, bioaccumulation, and toxicity of halogen-free flame retardants

Polymers are synthetic organic materials having a high carbon and hydrogen content, which make them readily combustible. Polymers have many indoor uses and their flammability makes them a fire hazard. Therefore, flame retardants (FRs) are incorporated into these materials as a safety measure. Brominated flame retardants (BFRs), which accounted for about 21% of the total world market of FRs, have several unintended negative effects on the environment and human health. Hence, there is growing interest in finding appropriate alternative halogen-free flame retardants (HFFRs). Many of these HFFRs are marketed already, although their environ- mental behavior and toxicological properties are often only known to a limited extent, and their potential impact on the environment cannot yet be properly assessed. Therefore, we undertook this review to make an inventory of the available data that exists (up to September 2011) on the physical-chemical properties, pro- duction volumes, persistence, bioaccumulation, and toxicity (PBT) of a selection of HFFRs that are potential replacements for BFRs in polymers. Large data gaps were identified for the physical-chemical and the PBT properties of the reviewed HFFRs. Because these HFFRs are currently on the market, there is an urgent need to fill these data gaps. Enhanced transparency of methodology and data are needed to reevaluate certain test results that appear contradictory, and, if this does not provide new insights, further research should be performed. TPP has been studied quite extensively and it is clearly persistent, bioaccumulative, and toxic. So far, RDP and BDP have demonstrated low to high ecotoxicity and persistence. The compounds ATH and ZB exerted high toxicity to some species and ALPI appeared to be persistent and has low to moderate reported ecotoxicity. DOPO and MPP may be persistent, but this view is based merely on one or two studies, clearly indicating a lack of information. Many degradation studies have been performed on PER and show low persistence, with a few exceptions. Additionally, there is too l ittle information on the bioaccumulation potential of PER. APP mostly has low PBT properties; however, moderate ecotoxicity was reported in two studies. Mg(OH)₂, ZHS, and ZS do not show such remarkably high bioaccumulation or toxicity, but large data gaps exist for these compounds also. Nevertheless, we consider the latter compounds to be the most promising among alternative HFFRs. To assess whether the presently reviewed HFFRs are truly suitable alternatives, each compound should be examined individually by comparing its PBT values with those of the relevant halogenated flame retardant. Until more data are available, it remains impossible to accurately evaluate the risk of each of these compounds, including the ones that are already extensively marketed.