Tree of Heaven can be hazardous with over-exposure, The sap and sawdust can cause myocarditis-like symptoms that impact your heart. This has happened with prolonged exposure (such as a work crew cutting a lot of them down over a few days) and seems to be exasperated when the sap is exposed to cuts or abrasions on the skin. Cutting one tree of heaven down should be safe, but you will likely want to wear gloves and, if you are concerned, even a mask to prevent inhalation of sawdust.
