1,2-benzisothiazol-3(2H)-one 1,1-dioxide

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

The tested chemical saccharin (CAS no. 81-07-2) is for example used in food as a sweetener, flavour and also in formulations for electroplating-bath brighteners and will consequently mainly be released into the environment through wastewater. The available environmental fate and toxicity studies in conjunction with standardized models (EPI suite version 4.1) shows the risk for environmental organisms should be low.

 

Persistence

The ultimate biodegradation estimate in the Biowin model (EPI suite version 4.1) shows that the current compound is moderately biodegradable (biowin 2=0.6, biowin 3=2.8, biowin<0.5).

 

Bioaccumulation potential

The BCF value is estimated to 3.2 L/Kg wet-weight (calculated by EPI suite version 4.1)and Kow <4.5 (Experimentlly determined by UERL lab in India). Henceforth, this compound has low potential of bioaccumulation in fish and food chains.     

 

Environmental fate

According to the fugacity model level III, the most likely environmental fate for this test chemical is soil (i.e. estimated to 69%). However, saccharin is not expected to be persistent in soil due to the estimated short half-life (30 days) (EPI suite version 4.1). Biodegradability was investigated for the read across compound sodium saccharin (CAS no. 128-44-9) in six different types of soils under anaerobic conditions. The half-life in soil was approximately 3 up to 12 days depending on soil type for sodium saccharin (Buerge et al., Environ. Sci. Technicol, 45, (2011) 615-621). The fast degradation in soil is consistent with the high elimination level observed in WWTPs (approx. 90%) for sodium saccharin (Buerge et al., 2011, Environ. Sci. Technicol, 45, 615-621). Henceforth, risk of chronic saccharin exposure terrestrial animals should be very low. There is also low risk for acute toxicity in microorganisms (Stolte et al., Environmntal International 60(2013); 123-127)

 

The Log Koc-value is experimentally determined to -1.353 at 25 ºC (UERL version 4.1). The tested chemical is therefore not expected to adsorb to sediments. Fugacity modelling shows that sediment is not an important environmental fate (less than 0% when estimated by EPI Suite version 4.1). There is also a high removal in sediment face of WWTPs (Subedia and Kannan, Environ. Sci. Technol. 2014, 48). There is low risk of exposure for benthic organisms, given the low Koc-value, low partion potential to sediment, and high removal in WWTPs.

 

According to environmental fate modelling, 31% of the test chemical is partioning into water. The half-life in water is estimated to be 15 days (less than the 40-day-threshold for persistence in water). Both environmental fate and persistence in water was estimated by EPI suite version 4.1. Saccharin is significantly removed from WWTPs (90% removal efficiency) in US. Similar WWTP-results have been reported both from Germany and China. The removal frequency were high both in the sludge- and water face of the WWTP process (Subedia and Kannan, Environ. Sci. Technol. 2014, 48). Volatilization from water surfaces is not expected based upon the test chemicals estimated Henry's Law constant (EPI suite version 4.1). Hence, the current compound is expected to be rapidly degraded in water.

Aquatic toxicity

Based on ECOSAR predictions of acute toxicity for aquatic organisms (for the read-across compound with CAS No. 128-44-9) there is a low risk for chronic toxicity for the current compound since the predicted acute EC50-values values are equal to or higher than 100 mg/L (ECOSAR v1.1). Furthermore when saccharin was exposed to D. magma (48 hours exposure duration) and S. vacuolatus (24 hours exposure duration) the results showed high NOECs, up to 1000 mg/L (Stolte et al., Environmental International 60(2013); 123-127).

 

In two rigours early-life stage test of zebrafish (Danio rerio) saccharin was clearly showing no teratogenic effects after long-term exposure (Selderslaghs et al., Neurotoxicology and Teratology 37 (2013) 44–56; Selderslaghs et al., Reproductive Toxicology 33 (2012) 142– 154). The positive controls were for example acrylamide, bisphenol A (Selderslaghs et al., Neurotoxicology and Teratology 37 (2013) 44–56). Henceforth, long-term exposure to sodium saccharin is based on these result not expected to be a risk for wild fish. The combination of low bioaccumulation potential and short halflife in water further supports low risk of chronic toxicity in fish for the tested chemical.

 

Overall conclusion about persistence, bioaccumulation and toxicity (PBT).

Based on the information described here is saccharine is negative for the P- and B criterion within Annex XIII. There is a low risk for chronic toxicity in freshwater organism for saccharin. The test chemical is regarded to be not classified for carcinogenicity, mutagenicity and reproductive toxicity. Henceforth, the current compound is negative for the T criterion within Annex XIII. For description of the CMR studies see statement letter by Dr. Holst, SSS Europe, Lund.