Wash off of imidacloprid and fipronil from turf and concrete surfaces using simulated rainfall

► Surface run-off of pesticide and degradation products from turf and concrete surfaces was measured. ► Maximum concentrations were observed in the initial run-off from the first rainfall event. ► Cumulative mass losses were described by both power and linear functions of the cumulative surface run-off depth. ► Degradation byproducts in the runoff contributed significantly to the total toxicity of the runoff.