Tobacco use in a cause for risk factor for many diseases; especially those affecting the heart , liver & lungs , as well as many cancers. In 2008 , the WHO has named as tobacco use as the worlds single greatest preventable cause of death. Tobacco epidemic is one of the biggest public health threats the world has every faced , killing more than 8 million people a year around the world . More than 7 million of those deaths are the result of direct tobacco use while around 1.2 million are the result of non - smokers being exposed to 2 - hand smoke.