Several adsorbents have been tried out by researchers to remove different pollutants from wastewater. However, the adverse effect of these biosorbents on the treated water and the possibility of leaching new pollutants to the treated water have not been investigated. A batch technique was employed to study this phenomenon. Three agricultural wastes namely sawdust, dates stones and palm fibers were investigated. The possible leaching of total dissolved solids (TDS) and organic compounds in the form of chemical oxygen demand (COD) from these substances to water were investigated. The effect of water pH and particle size of these biosorbents on the extent of the leaching process was studied. The results indicate high release of both TDS and COD for the three biosorbents. A COD value as high as 230 mg l-1 was obtained, while the highest TDS leached was 29 mg l-1. DS was found to have the highest leaching ability, followed by SD and PF. The highest leaching was obtained at high pH and small particle size of the adsorbent.