If global warming continues unabated, extreme heat waves that now occur once every 20 years are projected to occur about every other year by the end of the century in much of the country. Urban areas such as Philadelphia, Chicago, and Indianapolis will likely experience the worst effects. Higher temperatures and the associated stagnant air masses, interacting with pollution from vehicles and industry, are also expected to increase the frequency and intensity of conditions conducive to smog formation. Children, the elderly, and the poor are particularly vulnerable to respiratory, cardiovascular, and heat-related illnesses exacerbated by these conditions.
Conversely, reducing our emissions through a shift to cleaner forms of energy will not only help slow global warming but will also improve air quality, reducing the cases of asthma and other respiratory illnesses that result from high levels of ozone and airborne particulates. Such cuts in emissions will also reduce the amount of mercury and other heavy metals—by-products of coal-fired power plants—that enter our air, water, and food.