Tris(1-chloro-2-propyl) phosphate (TCPP). Tris(1-chloro-2-propyl) phosphate (TCPP) is a colourless liquid used as a flame retardant, mainly in polyurethane foams. It is not volatile. Its solubility in water is 1.6 g/litre, it is soluble in most organic solvents, and it has a log octanol/water partition coefficient of 2.59. Analysis is by gas chromatography/mass spectrometry (GC/MS). Concentration of TCPP from water prior to analysis can be achieved using XAD resin, followed by extraction with various organic solvents. TCPP is manufactured from propylene oxide and phosphorus oxychloride. Annual worldwide demand exceeded 40 000 tonnes in 1997. TCPP is not readily biodegraded in sewage sludge inocula. It is rapidly metabolized in fish. Traces of TCPP have been detected in industrial and domestic effluents but not in surface waters. It has not been detected in surveys of sediments. Traces of TCPP have been detected in raw peaches, raw pears and fish. No data are available on the kinetics and metabolism of TCPP in mammals. TCPP is of low to moderate acute toxicity by the oral (LD50 in rats = 1017-4200 mg kg body weight), dermal (LD50 in rats and rabbits is > 5000 mg/kg body weight) and inhalation routes (LC50 in rats is > 4.6 mg/litre). Rabbit eye and skin irritancy studies have indicated that TCPP is either non-irritant or mildly irritant. A skin sensitization study showed that TCPP has no sensitizing properties. The reproductive toxicity, irnmunotoxicity and carcinogenic potential of TCPP have not been investigated. The results of in vitro and in vivo mutagenicity studies investigating an appropriate range of end-points indicate that TCPP is not genotoxic. TCPP has been investigated for potential delayed neurotoxicity in hens. There was no evidence of delayed neurotoxicity when two oral doses (each of 13 230 mg/kg body weight) were given 3 weeks apart. No studies of the effects of TCPP on humans are available. Toxicity values for organisms in the environment are available, LC50 values ranging from 3.6 to 180 mg/litre. The no-observed-effect concentrations for algae, daphnids and fish are 6, 32 and 9.8 mg/litre, respectively. Tris(1,3-dichloro-2-propyl) phosphate (TDCPP). Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) is a viscous colourless liquid used as a flame retardant in a range of plastic foams, resins and latexes. It is not volatile. Its solubility in water is 0.1 g/litre, it is soluble in most organic solvents, and it has a log octanol/water partition coefficient of 3.8. Analysis is by GC/MS. Concentration of TDCPP from water prior to analysis can be achieved using XAD resin, followed by extraction with various organic solvents. TDCPP is manufactured from epichlorohydrin and phosphorus oxychloride. The commercial product is predominantly TDCPP with trace amounts of tris (2,3-dichloropropyl) phosphate. Annual worldwide demand was 8000 tonnes in 1997. TDCPP is not readily degraded in sewage sludge inocula. Studies have demonstrated limited degradation of TDCPP in natural waters. It is rapidly metabolized by fish. Bioconcentration factors are low (3-107). The half-life of elimination in killifish is 1.65 h. in vivo. Traces of TDCPP have been detected in sewage effluent, river water, seawater, drinking-water, sediment and in fish. TDCPP has been found in some samples of human adipose tissue. Kinetic studies in rats using 14C-labelled TDCPP showed the radiolabel to be distributed throughout the body following oral or dermal administration. The major metabolise of TDCPP identified in the urine of rats was bis(1,3-dichloro-2-propyl) phosphate. Elimination of the radiolabel was primarily in faeces and urine, with a small amount in expired air as CO2. TDCPP is of low to moderate acute toxicity by the oral route (LD50 in rats = 2830 mg/kg body weight) and of low acute toxicity by the dermal route (dermal LD50 in rats is > 2000 mg/kg body weight). In a 3-month study in mice, an exposure of approximately 1800 mg/kg body weight per day caused death within one month. The noobserved-effect level (NOEL) for the study was 15.3 mg/kg body weight per day; the lowest-observed level (LOEL) for increased liver weight was 62 mg/kg body weight per day. The sensitization potential of TDCPP has not been investigated. The potential for TDCPP to affect human male reproductive ability is unclear in view of testicular toxicity in rats but a lack of effect on male reproductive performance in rabbits. The possible effect on female reproduction has not been investigated. A teratology study on rats showed fetotoxicity at an oral dose of 400 mg/kg body weight per day; there was maternal toxicity at doses of 100 and 400 mg/kg body weight per day. No teratogenicity was seen. Overall, the mutagenicity data show that TDCPP is not genotoxic in vivo. The carcinogenicity of TDCPP has been investigated in a single 2-year feeding study. It was carcinogenic (increased occurrence of liver carcinomas) at all exposure levels that were tested (5-80 mg/kg body weight per day) in both male and female rats. Kidney, testicular and brain tumours were also found. In addition, there were nonneoplastic adverse effects in bone marrow, spleen, testis, liver and kidney. The effects in the kidney and testis occurred at all exposure levels. Only animals in the highest dose and control groups were evaluated for effects in the bone marrow and spleen. It was impossible, therefore, to determine whether there was a dose-response relationship for these effects in these organs. TDCPP exposure produced some indications of immunotoxicity in mice but only at high doses. Limited human studies following occupational exposure are available but they add little to the knowledge of the safety aspects of TDCPP.