Abstract: Samples of surface dust were collected from 41 representative urban parks in Tianjin. The health risk of heavy metals in surface dust was evaluated using human health risk assessment model established by U.S. EPA. The results showed that the pollution of heavy metals was serious. The average concentrations of Cu, Pb, Cr, Cd and Ni in the samples were 113.18, 63.32, 103.18, 1.14 and 40.58 mg·kg^-1 respectively, which all exceeded the background values in the soils of Tianjin. The direct ingestion of dust via hand-mouth contact behaviors was the major exposure pathway for health risk and the amount of chronic daily average exposure was in order of hand-mouth direct ingestion > dermal uptake > inhalation. The non-cancer risk of exposure was Cr > Pb > Cu > Ni > Cd, while the cancer risk of exposure was Ni > Cr > Cd. Non-cancer risk was higher for children than for adults. All the risks were lower than the average risk thresholds of the heavy metals, and would not cause noncarcinogenic or carcinogenic health hazard to human body, while its potential ecological hazard on children should be considered.

Key words: Angelica dahurica, isoimperatorin, total coumarin., trace element, imperatorin