Page 323 - Fundamentals of Air Pollution 3E

III. Meteorological Conditions during Historic Pollution Episodes 279

valley. Those affected were primarily elderly persons who had lung or heart
problems. However, some previously healthy persons were among the
seriously ill. There were no measurements of pollutants during the episode,
but the five Liege University professors who participated in the subsequent
inquiry indicated that part of the sulfur dioxide was probably oxidized to
sulfuric acid.
Roholrn (2), in discussing the episode, noted that 15 of the 27 factories
in the area were capable of releasing gaseous fluorine compounds and
suggested that the release of these compounds was of significance.
During the 30 years prior to the episode, fogs lasting for more than 3
days had occurred only five times, always in the winter, in 1901, 1911,
1917, 1919, and 1930. Some respiratory problems were also noted in 1911.
Industrial activity was at a low level in 1917 and 1919.
It is prophetic that Firket (1), in speaking about public anxiety about
potential catastrophes, said, "This apprehension was quite justified, when
we think that proportionately, the public services of London, for example,
might be faced with the responsibility of 3200 sudden deaths if such phe-
nomenon occurred there" (p. 1192). In 1952, such a catastrophe occurred
(see Section III/C).

B. Donora, Pennsylvania

A severe episode of atmospheric pollution occurred in Donora, Pennsyl-
vania, during the period Ocotober 25-31, 1948 (3). Twenty persons died,
17 of them within 14 hours on October 30.
During this period, a polar high-pressure area remained nearly station-
ary, with its center in the vicinity of northeastern Pennsylvania. This caused
the regional winds, both at the ground and through the lowest layers,
to be extremely light. Donora is southeast of Pittsburgh and is in the
Monongahela River valley. Cold air accumulated in the bottom of the river
valley and fog formed, which persisted past midday for 4 consecutive days.
The top of the fog layer has a high albedo and reflects solar radiation, so
that only part of the incoming radiation is available to heat the fog layer
and eliminate it (Fig. 18-3, left). During the night, longwave radiation leaves
the top of the fog layer, further cooling and stabilizing the layer (Fig. 18-
l
1
3, right). Wind speeds at Donora were less than 3.1 m s~ (7 mi h" ) from
the surface up to 1524 m (5000 ft) for 3 consecutive days, so that pollutants
emitted into the air within the valley were not transported far from their
point of emission. Maximum temperatures at Donora at an elevation of
232 m (760 ft) mean sea level were considerably lower than those at the
Pittsburgh airport, elevation 381 m (1250 ft), indicating the extreme vertical
stability of the atmosphere. In the vicinity of Donora there were sources of
sulfur dioxide, particulate matter, and carbon monoxide. Previous recorded
periods of stagnation had occurred in Donora in October 5-13, 1923 and
October 7-18, 1938.