sentences:  LEDs are now able to match the brightness and warmer color temperature that consumers desire from their outdoor lighting system.LEDs are increasingly used for street lighting in place of mercury and sodium lamps due to their lower running and lamp replacement costs.However, there have been concerns that the use of LED street lighting with predominantly blue light can cause eye damage, and that some LEDs switch on and off at twice mains frequency, causing malaise in some people, and possibly being misleading with rotating machinery due to stroboscopic effects.