The document discusses: the effect of our air environment on fitness and human health, specifically the effects on the lungs and the thermal effects of water immersion. The principle air pollutants of concern in large cities and their environs include ozone, sulfur dioxide, carbon monoxide, lead, and particulates or aerosols (including the politically important acid aerosol precursors of acid rain). Although studies generally consider the outdoor environment in the context of air pollution, there is also a considerable body of evidence describing the health effects of indoor-air contaminants, of which those of major concern for human health include secondary tobacco smoke, carbon monoxide, nitrogen dioxide, wood smoke, formaldehyde, radon, and volatile organic compounds.