Testing for lead In school drinking water: A summary of sampling protocols
Low level lead exposure has been linked to neurobehavioral and cognitive effects in children.1 No “safe” level of lead exposure exists and efforts should be made to reduce exposures to as low as possible. The phasing out of lead in gasoline, residential paints, and solder in food cans has substantially decreased blood lead levels among the general population, but residual sources still exist. Exposures can occur through lead in dust, water, air, soil, food, and consumer products. The relative contribution of water to total exposures increases with increasing lead levels in water and with increasing consumption of water with elevated lead levels.
Water leaving a treatment plant generally has low lead concentrations, but lead can enter drinking water through leaching from lead service lines and lead-containing building plumbing components, such as fittings, solder, and galvanized pipes. The degree of leaching is influenced by water chemistry, smoothness of flow, and water use patterns. Characteristics such as pH, alkalinity, the presence/absence of corrosion inhibitors, stagnation time, and water temperature all influence the corrosiveness of water. Stagnant water will generally have higher water lead levels since the longer water is in contact with leadcontaining components, the greater potential there is for leaching. In schools, intermittent water use throughout the day promotes stagnation, lack of laminar flow and leaching if lead-containing components are present.
Testing for lead in school water can help to ensure that lead levels are below an acceptable level, assess the potential for lead exposure, as well as identify the source(s) of contamination where elevated lead levels are found. The sampling protocol used to test for lead influences how results are interpreted. Understanding key aspects of sampling procedures can allow for more appropriate testing of lead in school water. Here we summarize four Canadian protocols for sampling lead in school water, including those from Ontario and Québec, which require annual testing of lead in school water, and two from Health Canada. Two guidance documents from the United States Environmental Protection Agency (EPA) and the California EPA are also discussed. This document is intended for public health practitioners and policy makers who are interested in understanding and potentially developing sampling protocols for lead in school drinking water.