Fourteen street dust samples were collected from Hamedan, western Iran. Street dust samples received different amount of heavy metal pollution. The samples analyzed for total cadmium (Cd), copper (Cu), lead (Pb), nickel (Ni) and zinc (Zn) and binding forms of heavy metal were determined in five fractions. The results showed Cd was the only metal present appreciably, 25.21 and 25.92%, in the exchangeable and carbonates fractions respectively and Cu was the only metal predominantly associated, 31.77%, with organic fraction. Zn, 45.84%, was present mainly in the Fe-Mn oxide fraction and the residual fraction was the most dominant solid phase pool of Ni and Pb respectively with 42.56 and 41.31%. The order of apparent mobility and potential metal bioavailability for these contaminated street dust samples is: Cd>Zn>Cu>Pb>Ni. The risk assessment code results showed very high risk for Cd, medium risk for Cu, Pb and Zn and low risk for Ni.
