Air Pollution Disasters

It is very difficult to show the effects caused by continuous exposure to air pollution. However, air pollution with high concentrations have been found to cause acute sickness and death. Also prolonged exposure to small concentrations will also result in adverse effects. It was the major air pollution disasters with their thousands of excess deaths that finally resulted in some control measures.

Some of the major air pollution disasters which occured in this century are summarized below. The excess death rate is estimated from death rates prior to and after the acute period.

Meuse Valley, Belgium, 1930

This is one of the first documented episodes in modern times which aroused worldwide interest occurred in the Meuse Valley of Belgium in December, 1930. Trapped by an inversion, pollutants accumulated in this steep-sided valley of 15 miles length. Coke ovens, steel mills, blast furnaces, zinc smelters, glass factories and sulfuric acid plants produced an estimated SO2 concentration of 8 ppm. It was estimated that the SO2 concentration was reached to 22,600 ug/m3. With in a few days more than 600 people fell ill, and 63 people died from the polluted air. Unfortunately no measurements were made. There seems, however, little doubt that the major culprit was sulfur dioxide which, with the help of fog droplets oxidized to sulfuric acid mist with a particle size small enough to penetrate deeply into the lungs.

Donora, Pennsylvania, 1948

In October 1948 the United States experienced its first pollution tragedy in the small town of Donora in the Manongahela River Valley, 20 miles southeast of Pittsburgh. Effluents from a number of industries such as a sulfuric acid plant, a steel mill, and a zinc production plant became trapped in a shallow valley inversion to produce an unbreathable mixture of fog and pollution. About 6,000 people or 43 percent of the population suffered various degrees of illnesses, such as sore throats, irritation of the eyes, nose, and respiratory tract, headaches, breathlessness, vomiting, and nausea. There were 20 deaths in three days. Again no ambient measurements were made during the disaster. It was suggested that sulfur dioxide reached peak values of about 5,500 ug/m.

Poza Rica, Mexico, 1950

The diasaster which struck Poza Rica, a town of 15,000 people on the Gulf of Mexico, originated from an accident at one of the local factories which recovers sulfur rom natural gas. The release of hydrogen sulfide into the ambient air lasted for only 25 minutes. The spread of the gas under a shallow inversion with foggy and calm conditions killed 22 people and hospitalized 320.

Cincinnati, Ohio. 1968

A similar accidnet with a fortunately less tragic ending occurred on August 25, 1968, in Cincinnati. About 2,500 pounds of SO2 escaped into the air from a burst pipe at a chemical plant located in the northern industrial part of Cincinnati. The release of SO2 started at mid night and lasted for about 8 hours. People who are staying at about 200 meters to the east of the plant were affected. People were awakened by a rotten-egg smell and difficulty in breathing. Fortunately nobody was killed.

London, England, 1953

From December 5 to 8, 1952, London experienced the worst air pollution disaster ever reported. The meteorological conditions were ideal for a pollution. Anti-cyclonic or high pressure weather with stagnating continental polar air masses trapped under subsidence inversions produced a shallow mixing layer with an almost complete absence of vertical and horizontal air motion. Fireplaces and industries supplied the hygroscopic condensation nuclei into the air to form dense fog. The daily temperatures were below the average. With such adverse conditions the concentrations of pollutants reached high values.

With these adverse conditions, elderly people were particulary effected. Deaths from bronchitis increased by a factor of 10, influenza by 7, pneumonia by 5, tuberculosis by 4.5, other respiratory diseases by 6, heart diseases by 3 and lung cancer by 2. When a change in weather finally cleared the fog, 4,000 Londoners had perished in their "pea soup".

Pollution disasters with similarly high concentrations occurred in 1957-1958 and again 1962-1963. But the number of casualties during these disasters were less than that of 1952.

New York, 1953, 1962-1963, 1966

New York City also experienced air pollution disasters. in 1953, 1962-1963 and 1966 causing excess deaths. New York with the nation's highest SO2 concentrations often avoid air pollution disasters because of its excellent ventilation. In December 1962, adverse weather conditions such as low wind speeds and occurrence of shallow inversions, then the SO2 and smoke concentrations which reached peak values were the major reasons. Total deaths increased to 269, which was in excess of even three standard deviations above the expected mortallity for that week.