Formaldehyde

Also called Methyl aldehyde, Methylene glycol, Methylene oxide, Formalin when dissolved in water, Formol

Toxic, Corrosive, Carcinogen

For more information, see the link

Medical Research Use

 * Preservative of biological tissue
 * disinfectant

Substitutes
Streck Tissue Fixative (also known as Streck Cell Preservative) is the best choice to replace formalin (formaldehyde) for fixation, due to lower health hazard and much lower fire hazard. STF has also been studied and shown to fix tissues as well or better with minor modifications to fixation and staining procedures.
 * Streck Tissue Fixative

The only prohibitive factor could be cost; formaldehyde is exceptionally cheap and STF is considerably more expensive.

. Wardsafe, while more comparably priced with formalin, has much less information available, and while Ward advertises Wardsafe as a fixative, they also note that best results are obtained when first fixing cells with formalin, then preserving with Wardsafe. This method may cut down on the amount of formalin used, and could be considered. More research on Wardsafe and its proprietary ingredients are needed.
 * Wardsafe

Cost aside, is Streck Tissue Fixative a better option because it is safer? yes no

Which of these you more likely to use in lab, considering saftety and price? Formaldehyde STF Wardsafe