within three miles of the gas field to flee their homes. The cause of the disaster
reportedly involved a drilling mishap, which broke open a gas well.
3.7.3 CHRONIC EFFECTS
Chronic intoxication is more common than acute episodes of poisoning.
Numerous reports have been published relating chronic effects of both air and
water pollution on living systems. Long-term exposure to relatively low
concentrations of air pollutants, such as SO 2 , smoke, and heavy metals (e.g.,
lead, cadmium, and mercury), may eventually lead to injuries in plants,
animals, or humans. The Minamata Bay incident and itai-itai-byo mentioned
above are examples of chronic effects related to water pollution. More detailed
information is provided in later chapters.
In plants, chronic effects are manifested as impaired growth and development, decreased respiration, chlorosis, necrosis, and other symptoms.
Similarly, chronic effects in animals are reflected in retarded growth, increased
susceptibility to other environmental stresses, and a variety of adverse health
effects, including shorter life spans.
In humans, the health effects of air pollution exposure may occur over a
long period of time. A prolonged exposure to air pollutants such as NO 2 and
O 3 , for instance, may lead to chronic bronchitis and emphysema. In the U. K.,
the combination of SO 2 and smoke pollution is thought to have synergistic
effects with cigarette smoking, causing degenerative diseases.
Results from occupational studies strongly suggest a close association
between air pollution exposure and respiratory cancer. For example, inhalation
of toxic materials, such as arsenic, asbestos, chromium, soot, mustard gas, and
radon, under occupational conditions has been related to lung cancer.
12 In an
effort to assess the association between air pollution and daily outpatient
hospital visits, Xu et al.
13 collected data on nonsurgery outpatient visits at a
community-based hospital in Beijing, China, and on atmospheric SO 2 and total
suspended particle (TSP) levels. Analysis of the data showed increases of 20%
and 17% in nonsurgery outpatient visits to the hospital, in association with
increases in SO 2 and TSP levels, respectively. These observations led to the
conclusion that the existing air-pollution levels in Beijing are associated with
adverse health effects.
Similar observations were made in Hong Kong. Researchers studied the
levels of SO 2 , NO 2 , O 3 , and atmospheric particulate matter less than 10 mm
in diameter (PM 10 ) and found a significant association with daily hospital
admissions for cardiovascular and respiratory diseases, both combined and
separately.
14 Furthermore, the effects of the pollutants on circulatory and
respiratory diseases were stronger for older age groups, with significant excess
of 5 to 10% in those aged 65 or over. Both NO 2 and O 3 were strongly
associated with hospital deaths from cardiovascular and respiratory diseases.
15
42
Environmental Toxicology
[16:54 26/8/04 P:/CRC PRESS/4365 MING-HO.751 (1670)/4365-003.3d]
Ref: 4365 MING-HO YU Chap-003 Page: 42 31-44
reportedly involved a drilling mishap, which broke open a gas well.
3.7.3 CHRONIC EFFECTS
Chronic intoxication is more common than acute episodes of poisoning.
Numerous reports have been published relating chronic effects of both air and
water pollution on living systems. Long-term exposure to relatively low
concentrations of air pollutants, such as SO 2 , smoke, and heavy metals (e.g.,
lead, cadmium, and mercury), may eventually lead to injuries in plants,
animals, or humans. The Minamata Bay incident and itai-itai-byo mentioned
above are examples of chronic effects related to water pollution. More detailed
information is provided in later chapters.
In plants, chronic effects are manifested as impaired growth and development, decreased respiration, chlorosis, necrosis, and other symptoms.
Similarly, chronic effects in animals are reflected in retarded growth, increased
susceptibility to other environmental stresses, and a variety of adverse health
effects, including shorter life spans.
In humans, the health effects of air pollution exposure may occur over a
long period of time. A prolonged exposure to air pollutants such as NO 2 and
O 3 , for instance, may lead to chronic bronchitis and emphysema. In the U. K.,
the combination of SO 2 and smoke pollution is thought to have synergistic
effects with cigarette smoking, causing degenerative diseases.
Results from occupational studies strongly suggest a close association
between air pollution exposure and respiratory cancer. For example, inhalation
of toxic materials, such as arsenic, asbestos, chromium, soot, mustard gas, and
radon, under occupational conditions has been related to lung cancer.
12 In an
effort to assess the association between air pollution and daily outpatient
hospital visits, Xu et al.
13 collected data on nonsurgery outpatient visits at a
community-based hospital in Beijing, China, and on atmospheric SO 2 and total
suspended particle (TSP) levels. Analysis of the data showed increases of 20%
and 17% in nonsurgery outpatient visits to the hospital, in association with
increases in SO 2 and TSP levels, respectively. These observations led to the
conclusion that the existing air-pollution levels in Beijing are associated with
adverse health effects.
Similar observations were made in Hong Kong. Researchers studied the
levels of SO 2 , NO 2 , O 3 , and atmospheric particulate matter less than 10 mm
in diameter (PM 10 ) and found a significant association with daily hospital
admissions for cardiovascular and respiratory diseases, both combined and
separately.
14 Furthermore, the effects of the pollutants on circulatory and
respiratory diseases were stronger for older age groups, with significant excess
of 5 to 10% in those aged 65 or over. Both NO 2 and O 3 were strongly
associated with hospital deaths from cardiovascular and respiratory diseases.
15
42
Environmental Toxicology
[16:54 26/8/04 P:/CRC PRESS/4365 MING-HO.751 (1670)/4365-003.3d]
Ref: 4365 MING-HO YU Chap-003 Page: 42 31-44