As energy efficiency and stricter environmental standards become increasingly important in the policy sphere, LED, or light emitting diode, lighting has had much success. The Energy Independence and Security Act of 2007 established a higher minimum efficiency standard for medium screw base light bulbs, which effectively eliminates incandescent bulbs that are 100W or less from the market .
Instead of only converting 10% at most of their energy to light like incandescent bulbs, LED bulbs convert 60% of their energy to light, resulting in decades more use from just one bulb. From daylight to white, red to blue, and immediately bright to a soft glow, a growing variety of colors and dimming options are available to match your mood. On top of that, LED bulbs are now available for your home for under $10. 
With all of these benefits, there must be some kind of drawback, right? Compact florescent light bulbs (another energy efficient alternative to incandescents) contain mercury vapor, which emits UV rays when in contact with an electric current. Cracks in the bulbs coating allow these rays to escape into your living room and come in contact with your skin, potentially causing skin cancer. Opponents of LED bulbs claim they contain the same UV rays and therefore are a risk, when in fact the light source of a LED bulb is a blue light source that poses no danger. 
So if it doesn’t emit UV rays, why are there concerns of LED bulbs causing cancer? According to a study published in the journal Environmental Science and Technology, “excessive levels” of arsenic, lead, copper, and nickel, among other potentially harmful substances are found in LED bulbs . When the bulbs are broken, these chemicals are released as gas and liquid, meaning when you clean one up you could be ingesting arsenic.  Experts suggest wearing protective clothing and disposing of cleaning materials as hazardous waste just to be safe.
However, despite this downside, in comparison to current technology LED bulbs seem to be the best choice. Every technology poses some kind of risk, especially those with chemical reactions and an electrical current. At least with LEDs there is a much greater gain in energy and economic efficiency than in posing a potential danger to health.
Potential Environmental Impacts of Light-Emitting Diodes (LEDs): Metallic Resources, Toxicity, and Hazardous Waste Classification
Seong-Rin Lim, Daniel Kang, Oladele A. Ogunseitan, and Julie M. Schoenung
Environmental Science & Technology 2011 45 (1), 320-327