As you can imagine, cigarette smoke contains many impurities that are inhaled in great numbers directly into the lung. For this reason, the alveolar spaces of the smoker contain numerous scavenger cells (macrophages) that are filled with engulfed (phagocytized) particles of impurities and debris, as illustrated in Picture of scavenger cells in a smoker's alveolus Under the microscope, with this high magnification, you can actually see the black and brown engulfed particles in the alveolar scavenger cells. Indeed, smoker's lung may have so much of this particulate material that the lung looks gray-black to the naked eye. Most of the time, you don't need a microscope to tell if someone is or was a heavy smoker. A naked eye examination of a smoker's lung will usually reveal an enlarged gray-black lung with enlarged air spaces (the emphysema, as you saw in Figure 4 and will see again in Figure 8).
Adverse air quality can kill many organisms including humans. Ozone pollution can cause respiratory disease , cardiovascular disease , throat inflammation, chest pain, and congestion . Water pollution causes approximately 14,000 deaths per day, mostly due to contamination of drinking water by untreated sewage in developing countries . An estimated 500 million Indians have no access to a proper toilet,   Over ten million people in India fell ill with waterborne illnesses in 2013, and 1,535 people died, most of them children.  Nearly 500 million Chinese lack access to safe drinking water.  A 2010 analysis estimated that million people died prematurely each year in China because of air pollution.  The WHO estimated in 2007 that air pollution causes half a million deaths per year in India.  Studies have estimated that the number of people killed annually in the United States could be over 50,000.