Due to increased concerns regarding the potential for contamination of drinking water supplies, considerable efforts have been devoted towards enhanced monitoring capabilities of priority inorganic and organic pollutants. Bench-scale experiments were designed and performed at the U.S. Environmental Protection Agency (U.S. EPA) Test & Evaluation (T&E) Facility in Cincinnati, Ohio, on a number of contaminants that are potential threats to the drinking water supply. The experiments were conducted to determine the dose-response (sensitivity) threshold concentrations for water-quality sensors when exposed to these contaminants. The types of contaminants included pesticides, herbicides, and lead compounds. The specific contaminants used for this study were commercial malathion (Real KillT™), neat glyphosate, commercial glyphosate (Roundup™), aldicarb, potassium ferricyanide, nicotine, lead nitrate, dimethylsulfoxide, sucrose, colchicine, dicamba, and anhydrous sodium thiosulfate. The test compounds were selected to simulate some of the properties of chemical and biological agents. One multi-parameter monitor and one free-chlorine monitor were used to represent typical sensors in use at water distribution systems. The parameters monitored were chloride, free chlorine, specific conductance, turbidity, ammonia-nitrogen, nitrate-nitrogen, oxidation-reduction potential (ORP), and pH. The bench-scale tests were conducted in a reaction vessel (4-liter beaker) using 3.5 liters of Cincinnati tap water. The tests were designed to evaluate the responses of several water quality sensors to a number of potential contaminants [added in the increment of 0.2 milligram per liter (mg/L) every minute]. Each test was carried out for 20 minutes. The study provided the minimum detection levels of the contaminants for various water quality parameters, which were compared to life-threatening toxicity concentrations for drinking water. Of all the parameters, free chlorine was the single most sensitive indicator in the study. In addition to free chlorine, specific conductance, ammonium-N, nitrate-N, ORP, chloride, and pH also showed sensitivity for detection. Based on the study results it can be concluded that commercially available single and multiparameter monitors can trigger (below life-threatening toxicity concentrations) and provide warnings when drinking water is contaminated by toxic contaminants below life-threatening levels (dose). Of all the parameters, chlorine was the single most important indicator of the study. Multiple parameters crossed the threshold limits for several contaminants namely, neat glyphosate, commercial glyphosate (Roundup™), potassium ferricyanide, and anhydrous sodium thiosulfate Includes 4 references, tables, figures.