Limits on Dust in Rich Clusters of Galaxies from the Color of Background Quasars

I measure the V - I color distribution of two samples of radio-selected quasars. Quasars from one sample are projected on the sky within 1° of a rich foreground Abell cluster of galaxies, while quasars from the other sample are more than 3° from any such cluster. There is no significant difference between the color distribution of the two samples. The 90% upper limit on the relative reddening between the two samples is E ( B - V ) = 0.05 mag. This result limits the allowed quantity of smoothly distributed dust in rich clusters and contradicts previous indications of the existence of such a component.