The EGR system routes a number of the exhaust gases (6 ? 10%) from the EGR valve, last on the Intake System, and ultimately within the combustion chamber. The exhaust gases are inert i.e. they cannot burn in the combustion chamber; also, the exhaust gases take up a number of the space which would preferably be taken with the intake air. This reduces the volume of intake air readily available for the combustion process during each Power Stroke; which in turn decreases the peak combustion temperatures. This brings about lower NOx emissions. Sunglasses allow better vision in bright daylight, and may protect one's eyes against damage from high levels of ultraviolet light. Typical sunglasses are darkened for protection against bright light or glare; some specialized glasses are clear in dark or indoor conditions, but turn into sunglasses when in bright light. Most sunglasses do not have corrective power in the lenses; however, special prescription sunglasses can be ordered. Specialized glasses may be used for viewing specific visual information (such as stereoscopy) or 3D glasses for viewing three-dimensional movies. Sometimes glasses with no corrective power in the lenses are worn simply for aesthetic or fashion purposes. Even with glasses used for vision correction, a wide range of designs are available for fashion purposes, using plastic, wire, and other materials. In September 2004 the EU implemented legislation that banned using over 1,000 chemicals of concern in personal care products. The prohibited chemicals were those known or strongly suspected of causing cancer, mutation, or birth defects. The EU ban has served being a wake-up demand many US companies who market a few overseas. In response some companies have replaced toxins in their goods, for example phthalates, parabens, and formaldehyde with non-toxic alternatives.