Epoxy resins contains epichlorohydrin, an alkylating agent and bisphenol A, an oestrogenic endocrine disrupter (can give guys tits). The epichlorohydrin is a lachrymator hence it makes your eyes water, throat sore etc.and a suspect human carcinogen so it will also be alkylating your DNA. I have never been sure why they get away with selling it under the classification of HARMFUL / irritant / sensitiser rather than as a suspect carcinogen (totally different chemical risk phrases). However if you try to buy bulk eg 25L drum you will have freight / shipping problems as you move up to larger quantities and it gets expensive / restrictive to ship around (as expected for a carcinogenic liquid).
So make sure you have good ventilation and avoid skin exposure. Chemical masks (ie charcoal)are ok if they fit. Dust masks are no use at all. Air-line fed respirators are best. It gives dense vapour (it's halogenated) so it will persist in pits and sumps, eg your basement. I try to do all layup in the garage with the doors open.
There is epoxy -and there is epoxy. The skin toxicity/sensitization depends on the choice of hardener and type of solvent if any. Most good epoxies for our interest have very very low volatiles content, so no need for a respirator with small to moderate quantities in controlled reactions. Unless mixed with nonpolar solvents, low volatiles epoxies will not go through the skin. This substantially mitigates concern about alkylating and estrogenic effects. No need to be terribly afraid of epoxies. You do need to know about the chemistry of the specific product you use. You do need to protect your skin. It can give a rash, if you are over-exposed or sensitized. You don't need a respirator to laminate small things like kiteboards. Unless you throw in a lot of solvent or other nasty additives. Or let your mix exotherm. You do need a respirator or a P95 mask for sanding it. Epoxy is ok, but you need to be sophisticated about it, and it is well worth using protection.
Thanks for that answer about the contents of the Epoxy- IÂ´ve experienced some strange reactions when i once got some epoxy on may hands. My nipples/chest area got sore and sensitive, and i had some sleeping disturbances. I knew there was stuff in there that was effecting hormones so i was aware of what happened and made sure i never touch the stuff again- use gloves - sometimes 2 sets.
Read " Our Stolen Future" if you want the whole story about those chemicals.
If you are past your pro-creative years, then there is minimal risk- but if you are planning on having children, or if your women is carrying- then you should be extremely careful. According to scientists in book above, the chemicals effect embryonic development- and development later in life and are transgenic- those problems are inherited. They effect the number and condition of your semen too. Cancer is the least of the problems.