rates for the diseases increased between 1950 and 1960, but have since declined
steadily. For example, expressed as percentage of total death rate, the death
rates of heart diseases were 41.7%, 39.6%, and 29.7% for 1960, 1980, and
2000, respectively.
By contrast, the cancer death rates in the U.S. continued to increase
steadily until the middle of the 1990s, when the increase began to slow down.
19
In particular, the death rates for respiratory-system cancer increased
dramatically over the past five decades. Using the 1950 rates as a basis for
comparison, the respiratory-system cancer death rates increased by 191% and
506% for 1970 and 1990, respectively (Table 2.2). By contrast, the increases in
cancer deaths from all causes were 21% and 71% for 1970 and 1990,
respectively. The marked differences in both categories of cancer death rates
are more clearly shown in Figure 2.2. While the reasons for the differences are
not entirely known, it is possible that exposure to increasing levels of air
pollution may play an important role.
In Japan, the level of air pollution has markedly decreased since the early
1970s, but the number of patients with respiratory disease due to air pollution
has increased. Between the late 1950s and 1960s, a large number of patients in
Japan suffered from chronic obstructive lung diseases such as chronic
bronchitis, bronchial asthma, and emphysema. Studies showed that, during
this period, there were many chronic-bronchitis patients in Yokohama and
Kawasaki, two highly industrialized cities near Tokyo that were heavily
polluted with SO 2 and soot. Researchers in Japan concluded that the SO 2
pollution caused acute respiratory diseases and aggravated the condition of
patients already suffering from respiratory disease. One of these respiratory
conditions was even referred to as ‘‘Yokohama and Kawasaki Asthma.’’
34
26
Environmental Toxicology
[16:55 26/8/04 P:/CRC PRESS/4365 MING-HO.751 (1670)/4365-002.3d]
Ref: 4365 MING-HO YU Chap-002 Page: 26 13-30
FIGURE 2.2 Comparison of death rates for cancer of all sites vs. cancer of respiratory system
between 1950 and 2000.
steadily. For example, expressed as percentage of total death rate, the death
rates of heart diseases were 41.7%, 39.6%, and 29.7% for 1960, 1980, and
2000, respectively.
By contrast, the cancer death rates in the U.S. continued to increase
steadily until the middle of the 1990s, when the increase began to slow down.
19
In particular, the death rates for respiratory-system cancer increased
dramatically over the past five decades. Using the 1950 rates as a basis for
comparison, the respiratory-system cancer death rates increased by 191% and
506% for 1970 and 1990, respectively (Table 2.2). By contrast, the increases in
cancer deaths from all causes were 21% and 71% for 1970 and 1990,
respectively. The marked differences in both categories of cancer death rates
are more clearly shown in Figure 2.2. While the reasons for the differences are
not entirely known, it is possible that exposure to increasing levels of air
pollution may play an important role.
In Japan, the level of air pollution has markedly decreased since the early
1970s, but the number of patients with respiratory disease due to air pollution
has increased. Between the late 1950s and 1960s, a large number of patients in
Japan suffered from chronic obstructive lung diseases such as chronic
bronchitis, bronchial asthma, and emphysema. Studies showed that, during
this period, there were many chronic-bronchitis patients in Yokohama and
Kawasaki, two highly industrialized cities near Tokyo that were heavily
polluted with SO 2 and soot. Researchers in Japan concluded that the SO 2
pollution caused acute respiratory diseases and aggravated the condition of
patients already suffering from respiratory disease. One of these respiratory
conditions was even referred to as ‘‘Yokohama and Kawasaki Asthma.’’
34
26
Environmental Toxicology
[16:55 26/8/04 P:/CRC PRESS/4365 MING-HO.751 (1670)/4365-002.3d]
Ref: 4365 MING-HO YU Chap-002 Page: 26 13-30
FIGURE 2.2 Comparison of death rates for cancer of all sites vs. cancer of respiratory system
between 1950 and 2000.