Funny story...
When I entered the bow swap last year I decided I would try a hickory backed ipe for my trade bow. I had been reading up on it and had my design all picked out. At the time, I was limited on my power tools, so when my order came in I carried the piece of ipe I ordered over to my brother's house to have him rip it into bow size slats for gluing. He keeps his table saw in the garage and it was somewhat cool outside so he left the garage door mostly closed with a gap at the bottom. I had about a 7' piece so first we had to cut about 18" off the end, and then rip it. After we made a couple of cuts we noticed this huge cloud of brown dust in the air. I looked over at him and his eyes were almost swelled shut and my head felt like it would explode. He ran over and hit the garage door opener and turned on his fan and yelled. "this wood ain't poison, is it?!?" I felt pretty stupid and said I didn't know. When I got home with the wood I went online and did some more research and found out that the dust can be toxic. We were fine and no serious damage was done, but I am very careful when I work it now. I have made several bows from it and really love the stuff. I hope I never develop any long term allergies that prevent me from working with it.
Another decking material I have recently worked with that doesn't seem as powdery when worked is massuranduba. The color is not quite as pretty, to me, but it seems almost as dense as ipe and has a little more elasticity. I get both of them from the same decking material place online.