Mono(2-ethyl-5-hydroxyhexyl) phthalate-d4 (MEHHP-d4) is a deuterium labeled Mono(2-ethyl-5-hydroxyhexyl) phthalate (HY-133677). Mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) is an oxidative metabolite of Di(2-ethylhexyl) phthalate (DEHP). Mono(2-ethyl-5-hydroxyhexyl) phthalate may protective sperm DNA damage. Di(2-ethylhexyl) phthalate is the predominant plasticizer added to rigid polyvinyl chloride (PVC) to impart flexibility, temperature tolerance, optical clarity, strength and resistance to kinking[1][2][3].