Activated charcoal is an excellent material for filtering toxic gases. Activated charcoal were used by workers at the WTC site after 9/11. It has also been incorporated into many Japanese cigarette filters. While more than 70% of cigarettes sold in Japan use activated charcoal filters ("charcoal filters"), less than 1% of cigarette products sold in USA have this.
Japan has significantly lower lung cancer rates than the United States.* However, there is no hard evidence to show a direct link between charcoal filters and reduction of lung cancer rates.
Charcoal filters can also modify the taste of cigarettes by absorbing more chemicals. As a result, many consumers in the United States have rejected it.
Currently I am smoking Mild Seven Lights Charcoal Filter, which a friend of mine has given me. And indeed, it tastes like shit. Here are some reasons that I can think of why charcoal filters have gained wide acceptance in Eastern Asia: (a) Consumer education. (b) The government-owned tobacco monopoly, JT (Japan Tobacco), has less to worry about competition or their bottom line. While the Japanese government has more control over what goes into the smokers' lungs, they chose healthier filters for them.
If interested, JT cigarette products are available at street vending machines (no ID required) for smokers on their next visit to the Western pacific.
*
Wynder, E.L. and Hoffman, D., Smoking and Lung Cancer: Scientific Challenges and Opportunities, Cancer Research, 54, 5284-5295 (1994).