You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Evaluation of genotoxicity in leukocytes and testis following intra-vasal contraception with RISUG and its reversal by DMSO and NaHCO3 in Wistar albino rats. Evaluation of genotoxicity of RISUG(®) - a vas based contraceptive, was carried out in the present study. Animals were allotted into groups of sham operated control, vas occlusion with RISUG (5-7μl) for 360 days and reversal by DMSO (250-500μl) and 5% NaHCO3 (500μl). Blood samples and testis were collected at 360 days of vas occlusion and 90 days of vas occlusion reversal for comet analysis. Hydrogen peroxide induced samples were used as positive control. Olive moment, tail length and percentage DNA in tail were recorded with minimum variation in all groups for both leukocytes and testis. When compared with positive control the variation was highly significant for both 20μM and 50μM H2O2 (p<0.001). It is concluded that vas occlusion with RISUG at the contraceptive dose regimen is not associated with genotoxicity in leukocytes or the testis of pre- and post-reversal rats.
{"Chemical": ["DMSO", "H2O2", "Hydrogen peroxide", "NaHCO3"]}