GUELPH, ON / ACCESSWIRE / June 4, 2021 / ZEN Graphene Solutions Ltd. ('ZEN' or the 'Company') (TSXV:ZEN)(OTC PINK:ZENYF), a Canadian, next-gen nanomaterials technology company and Trebor Rx Corp. (Trebor) are pleased to announce successful inhalation safety testing results of ZENGuardTM-enhanced surgical masks and submission of these results to Health Canada. Testing was completed by NanoSafe Inc.…