We present polarization measurements of more than 250 stars, most of them red giants, in the field of seven metal-poor globular clusters. We find strong spatial variations of the polarization in the fields of NGC 4372, NGC 4833, M4 and NGC 6266, and we conclude that differential reddening is important in these clusters. Mild extinction variations are found across Omega Centauri and M22, while the interstellar medium toward NGC 6397 appears fairly uniform. After taking the foreground polarization component into account, we find no evidence of significant intrinsic polarization in any of the stars observed. We argue that an extreme Population II environment is very deficient in dust. We discuss this result in terms of different mechanisms for mass loss proposed for Population II red giants.
