According to a recent article published in the Journal of the National Cancer Institute Advance Access published online on May 12, 2009, it looks as though exposure to formaldehyde could raise one’s risk of lymphohematopoietic malignancies (blood and lymph cancers).
For an extremely statistical look, read the abstract -> http://jnci.oxfordjournals.org/cgi/content/abstract/djp096
I had some exposure to formaldehyde during my twenties. Nobody can say for sure if that was the risk factor for me though. I worked around plastics. A certain type of plastic, called high density polyethylene, gives off fumes that contain formaldehyde when it’s heated to a high temperature. We stood around at a factory with melting HDPE around us all the time.