This work examines the distributions of potentially toxic trace elements (e.g., Cu, Zn and As) and assesses the potential hazards of contaminants to environment. Trace elements are released from seawater desalination facility in the Penghu Islands, Taiwan. Temporal trends of trace element concentrations are investigated by comparing biannual concentrations for a 2-year period (2006-2007). Analytical results demonstrate that only As in seawater had an increasing trend after 2006. Further, a hazard index (HI) is applied to assess the potential hazard of contaminants to the environment. The HI (HI =C(95%)/C(allowable)) is defined as the ratio of the 95th percentile for a pollutant concentration (C(95%)) to an allowable concentration for each pollutant (C(allowable)). The hazard index is used to establish a pollutant priority ranking and, then, serves as a useful screening tool for developing strategies for desalination pollution control. In this study, lithe priority is to improve water quality, focus should be placed on Cu (HI = 0.32). On the other hand, if the priority is sediment. quality, the As concentration (HI = 0.51) should be reduced. If the two His (seawater and sediment) are considered together, As (HI = 0.56) becomes the highest-ranking trace element, followed by Zn (HI = 0.54). (C) 2011 Elsevier B.V. All rights reserved.