When I worked in an admin environment we had a policy that noone was to carry anything more than those boxes that contained 5 reams of A4 paper. There was a trolley available for anything heavier than that. This wasn't just about personal safety it was also if you rounded a corner and ran into soneone who was carrying something heavy if could injure two people.

You probably have an occupational health and safety officer somewhere in the organisation. I would contact them and ask for a ruling. Also - if your manager wants it done they can do it!