An agency within the World Health Organization (WHO) has classified air pollution as a leading environmental cause of cancer. Air pollution, which is already associated with heart and lung diseases, is now being classified in the same category as UV radiation and tobacco smoke. Since the majority of air pollution is created from sources such as car exhaust, power generation, and the heating of buildings, it could be summarized that the main source of air pollution is energy. With this information about the devastating effects that air pollution has on human health, it is becoming even more apparent just how necessary it is for places across the globe to include sources of clean, renewable energy into their energy infrastructures. Renewable energy reduces air pollution and greenhouse gas emissions, including carbon dioxide, nitrous oxide, and methane. In light of this troubling information, cities with dirty air should take an accelerated approach to cleaning up their act. This is particularly important for cities with economies that heavily rely on travel and tourism. After all, people are not going to want to visit a place that is detrimental to their health.