Risk Assessment and Class-Based Evaluation of Three Phosphate Esters

Abstract

A category approach was used in the evaluation of a group of chemicals (triethyl phosphate, tripropyl phosphate, and tributyl phosphate) in drinking water, in support of determination of safe-harbor level for use by a standard-setting organization. Both non-cancer and cancer endpoints were considered, and risk assessment methodology developed by the U.S. Environmental Protection Agency (USEPA) was used to determine a class-based evaluation level (CBEL) and a total allowable concentration (TAC) in drinking water considered adequately protective of human health. The critical study was a chronic oncogenicity study on tributyl phosphate, with a no-observed-adverse-effect-level (NOAEL) of 9 mg/kg-day. The critical effect, combined incidence of bladder papilloma/transitional cell carcinoma, was likely non-genetic in nature, as supported by the lack of genetic toxicity observed in tributyl phosphate. The effect thus demonstrated a threshold, and this study used an oral reference dose approach and a total uncertainty factor of 100. This conservative analysis demonstrated the TAC should be twenty times greater than the default value of 0.01 mg/L.

PM2.5-Bound Organophosphate Flame Retardants in Hong Kong: Occurrence, Origins, and Source-Specific Health Risks

“…This result can be explained by the high loadings of TCEP and TnBP allocated to the two main sources (plastic processing and waste disposal as well as marine vessels) and the potential carcinogenic risk of these two OPFRs. 61 , 62 In addition, the proportion that plastic processing and waste disposal contributed to CR is consistently slightly higher than that to NCR under each meteorological condition, indicating a more threatening carcinogenic health risk of OPFRs from plastic processing and waste disposal.…”

“…The risk ranking of the four OPFRs is TCEP > TnBP > TEHP > TMPP. Studies have presented the potential carcinogenic risk of TCEP in the kidney and TnBP in the bladder . Apart from these four OPFRs, TCEP and TDCPP have also been reported to pose carcinogenic risks for humans and have even been restricted to use in the EU and part of the U.S. owing to their known carcinogenicity .…”

“…Studies have presented the potential carcinogenic risk of TCEP in the kidney 61 and TnBP in the bladder. 62 Apart from these four OPFRs, TCEP and TDCPP have also been reported to pose carcinogenic risks for humans and have even been restricted to use in the EU and part of the U.S. owing to their known carcinogenicity. 4 However, the SFO data of TDCPP, TCPP, and other potential carcinogenic OPFRs are absent, leading to underestimation of the total CR index of human exposure to PM 2.5 -bound OPFRs calculated in this study.…”

Human Health Risk Assessment of Organophosphate Esters in Urban Topsoils of Shenyang, China

“…The calculated method is the NOAEL divided by 1000 [23]. In short, the RfD of TEP, TPrP, TiBP, TBEP, TCPP, TDCP, TPhP, EHDPP, TCrPs and TPPO was 0.125 [8], 0.009 [25], 0.1 [26], 0.02 [23], 0.01 [21], 0.02 [21], 0.07 [23], 0.005 [27], 0.02 [7] and 0.02 mg/kg-day [21], respectively. The SFO of TnBP, TEHP and TCEP was 0.009, 0.0032 and 0.02 (mg/kg-day) -1 , respectively [21].…”