  The observation of the interstellar 1.809 MeV decay-line of radioactive 26Al
by the imaging gamma-ray telescope COMPTEL have let to the conclusion, that
massive stars and their subsequent core-collapse supernovae are the dominant
sources of the interstellar 26Al abundance. Massive stars are known to affect
the surrounding interstellar medium by their energetic stellar winds and by the
emission of ionising radiation. We present a population synthesis model
allowing the correlated investigation of the gamma-ray emission characteristics
with integrated matter, kinetic energy and extreme ultra-violet radiation
emission of associations of massive stars. We study the time evolution of the
various observables. In addition, we discuss systematic as well as statistical
uncertainties affecting the model. Beside uncertainties in the input stellar
physics such as stellar rotation, mass loss rates or internal mixing
modifications due to a unknown binary component may lead to significant
uncertainties.
