From the American Acadmy of Pediatrics:
Burns are among the most common accidental injuries in infants and children, and scalding injuries occur most frequently. Children commonly are burned by hot liquids spilled from a table or stove, but approximately 3,800 injuries and 30 deaths each year are reported to be due to burns from tap water that is too hot. The amount of contact time required to produce a third-degree burn is less than parents may realize.
Water Temperature Time Until Third-degree Burn Occurs:
150?F 2 seconds
140?F 6 seconds
130?F 30 seconds
120?F 5 minutes
Therefore, the Consumer Product Safety Commission has recommended that all water heaters be set to 120?F. Parents should call their local electric or gas companies for instructions on adjusting the temperature. Parents who live in apartments should talk with their building managers about having the temperature lowered because the hot water heaters in most apartment buildings are set at higher temperatures to provide hot water to all tenants. In addition to setting hot water heaters to a lower temperature, parents should hand-test water before bathing children and infants, and young children never should be left unsupervised in the bathroom.