Figure 22.7: Smog in New York City. ( 12 )study concluded that no level of air pollution should be considered safe. Exposure to smog
also increased the risk of dying from any cause, including heart disease.
Children are more vulnerable to problems from breathing dirty air than adults because their
lungs are still growing and developing. Children take in 50% more air for their body weight
thanadults. Childrenspendmoretimeoutsideinunfilteredairandaremorelikelytobreathe
hard from playing or exercising. One study found that in the United States, children develop
asthma at more than twice the rate of two decades ago and at four times the rate in Canada.
Adults also suffer from air pollution-related illnesses that include lung disease, heart disease,
lung cancer, and weakened immune systems. The asthma rate worldwide is rising 20% to
50% every decade.
Especially dangerous are pollutants that remain in an organism throughout its life, called
bioaccumulation. In this process, an organism accumulates the entire amount of a toxic
compound that it consumes over its lifetime. Not all substances bioaccumulate. A person
who takes a daily dose of aspirin only has that day’s worth of aspirin in her system, because
aspirin does not stay within her system. When a compound bioaccumulates, the person has
all of that compound she’s ever eaten in her system. Compounds that bioaccumulate are
usually stored in the organism’s fat.
Mercury is a good example of a substance that bioaccumulates. Bacteria and plankton store
all of the mercury from all of the seawater they ingest. A small fish that eats bacteria and
plankton accumulates all of the mercury from all of the tiny creatures it eats over its lifetime.
A big fish accumulates all of the mercury from all of the small fish it eats over its lifetime.
The organisms that accumulate the most mercury are the large predators that eat high on
the food chain. Tuna pose a health hazard to anything that eats them because their bodies
are so high in mercury. This is why the government recommends limits on the amount of