Sodium hypochlorite is a chlorine compound often used as a disinfectant or a bleaching agent; in these solutions, sodium hypochlorite is stabilized with sodium hydroxide, resulting in caustic solutions with a range of sodium hypochlorite concentration and pH. A frequently referenced hazard of these solutions is the decomposition byproduct chlorine gas (Cl2, CASRN: 7782-50-5), which occurs at room temperature.
A review of available sources identified the following: a WEEL-STEL (15-minutes), rat LC50 (no duration listed), and rat oral LD50 toxicity data. The State of New Jersey has adopted the National Institute for Occupational Safety and Health (NIOSH) airborne exposure limit (REL) and the immediately dangerous to life and health (IDLH) limit for chlorine as applicable to sodium hypochlorite; as such, chlorine AEGLs (CASR: 7782-50-5) were also evaluated as TEEL bases. Additionally, a survey of available material safety data sheets indicates sodium hypochlorite solutions have a NFPA/HMIS rating of 3, therefore a HHR = 3 was also evaluated as a TEEL basis (Section 3.4.4). Data sources were selected according to the hierarchy listed in Table 3.1. Toxicity data were selected according to type of exposure, species, and route based on the hierarchies stated in Sections 3.3.1, 3.3.2, and evaluated using factors in Tables 3.2, 3.3, and 3.4.
The most preferred source identified during research for the chemical of interest TEEL-1 basis is the WEEL-STEL, 0.66 ppm (2 mg/m3) which is comparable to the AEGL-1 (60-minute) for chlorine, 0.5 ppm (1.5 mg/m3). Comparison of TEEL values calculated from Table 3.5 (left) and chlorine AEGLs (right) yields the following:
WEEL-STEL (NaClO) vs. AEGLs (Cl2) Comparison:
TEEL-1 = 0.66 ppm vs. AEGL-1 = 0.5 ppm
TEEL-2 = 7.3 ppm vs. AEGL-2 = 5.0 ppm
TEEL-3 = 44 ppm vs. AEGL-3 = 20 ppm
The lowest toxicity-based TEEL estimates were double these values; therefore, none were selected as bases. An HHR = 3 yielded a TEEL-3 of 26 ppm, on the same order as the AEGL-3. Considering these analyses, the comparable magnitudes of TEELs derived from an exposure limit and assumed HHR=3, the high reliability and preference of AEGLs as a source, and conservatism, it is recommended that the AEGLs for chlorine be adopted as TEEL bases.
• TEEL-1 = AEGL-1 60-minute Chlorine (CASRN: 7782-50-5)
• TEEL-2 = AEGL-2 60-minute Chlorine (CASRN: 7782-50-5)
• TEEL-3 = AEGL-3 60-minute Chlorine (CASRN: 7782-50-5)
This review generated TEEL values that are significantly more conservative than those in Rev. 29A due to a change in bases. The Rev. 29A TEEL-3 and TEEL-2 values were derived from a rat oral LD50 exposure, while the current recommendation uses chlorine AEGL-3 and AEGL-2 values, an inhalation hazard of sodium hypochlorite decomposition. The Rev. 29A TEEL-1 values are based on the WEEL-STEL (15 minute), while the current recommendation uses the chlorine AEGL-1 as a more reliable source with a comparable value.