Figure 22.6: Jet contrails block sunlight. ( 9 )spotted. Soybeans and other crops have reduced productivity. In developing nations, where
getting every last bit of food energy out of the agricultural system is critical, any loss is
keenly felt. Many of these nations, like China and India, also have heavy air pollution.
Some pollutants have a positive effect on plant growth. Increased CO 2 seems to lessen
ozone damage to some plants and it may promote growth. Unfortunately, CO 2 and other
greenhouse gases cause other problems that harm the ecosystem and reduce growth of some
plants.
Other air pollutants damage the environment (Figure22.7). NO 2 is a toxic, orange-brown
colored gas that gives air a distinctive orange color and an unpleasant odor. Nitrogen and
sulfur-oxides in the atmosphere create acids that fall as acid rain. Human health suffers
in locations with high levels of air pollution. Lead is the most common toxic material for
humans and is responsible for lead poisoning. Carbon monoxide is a toxic gas and can kill
peopleinpoorlyventilatedspaces, liketunnels. Nitrogenandsulfur-oxidescauselungdisease
and increase rates of asthma, emphysema, and viral infections like flu. Ozone also damages
the human respiratory system, causing lung disease. High ozone levels are also associated
with increased heart disease and cancer. Particulates enter the lungs and cause heart or
lung disease. When particulate levels are high, asthma attacks are more common. By some
estimates, 30,000 deaths a year in the United States are caused by fine particle pollution.
Although not all cases of asthma can be linked to air pollution, many can. During the 1996
Olympic Games, Atlanta, Georgia closed off their downtown to private vehicles. As a result,
ozone levels decreased by 28%. At the same time, there were 40% fewer hospital visits for
asthma.
Lung cancer among non-smokers is also increasing. One study showed that the risk of being
afflicted with lung cancer increases directly with a person’s exposure to air pollution. The