In this paper, we develop a R&based growth model with a pollution externality and a health production sector. We study how healthimpairing pollution affects long term growth, and the effect of an emissions' reduction policy (tax). We show that a tighter environmental tax has positive effects on growth via two channels. On the one hand, it improves workers' health and, thereby, productivity; on the other hand, it induces a reallocation of resources towards R& and, thereby, higher research intensity. The size of the growth effect of a tighter environmental tax, and the level of the optimal environmental tax, are both positivelycorrelated with the weight individuals place on health relative to consumption. As for welfare, a tighter environmental tax brings about utility gains in the long run and, potentially, also in the short run.