Far-field microscopy was used to noninvasively measure the room-temperature optical properties of single dye molecules located on a polymer-air interface. Shifts in the fluorescence spectrum, due to perturbation by the locally varying molecular environment, and the orientation of the transition dipole moment were correlated to variation in the excited-state lifetime. The lifetime dependence on spectral shift is argued to result from the frequency dependence of the spontaneous emission rate; the lifetime dependence on dipole orientation was found to be a consequence of the electromagnetic boundary conditions on the fluorescent radiation at the polymer-air interface.