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Distinguishing between soluble and particulate lead in drinking water is useful in understanding the mechanism of lead release and identifying remedial action. Typically, particulate lead is defined as the amount of lead removed by a 0.45-mu m filter. Unfortunately, there is little guidance regarding selection of filter membrane material and little consideration to the possibility of the sorption of dissolved lead to the filter. The objective of this work was to examine the tendency of 0.45-mu m syringe filter materials to adsorb lead. Tests were performed withwater containing 40 and 24 mu g/L soluble lead at pH 7 buffered with 50 mg C/L dissolved inorganic concentration (DIC). The amounts of lead sorbed greatly varied by filter, and only two filter types, polypropylene and mixed cellulose esters, performed well and are recommended. Great care must be taken in choosing a filter when filtering soluble lead and interpreting filter results.