Are quasars dusty

Two separate techniques have been applied to estimate the amount of dust in the line of sight toward a number of quasars. No evidence for dust was found. Estimates of the dust-to-gas ratio in the emission-line region of quasars suggest that it is much less than the value in our Galaxy. These results provide strong evidence against dust theories of the infrared emission from quasars. The possible relationship between quasars and galaxies is discussed. Finally, a new upper limit on the dust content of the intergalactic medium is obtained.