Workshop on the Social and Economic Aspects of Weather

Impact of Weather on Health
Gib Parrish
Center of Disease Control
Atlanta, GA
rgp1@cdc.gov

Introduction
The adverse impact (mortality and morbidity) of certain types of weather events on health is significant, and considerable effort is directed at reducing this impact. In these efforts, it is important to have a good understanding of the number of people affected by each weather event and the ways in which each event produces its adverse effects. Such understanding is crucial to the implementation of measures to prevent adverse effects from similar weather events in the future. Table 1 shows deaths from weather events and earth movements in the U.S. 1979-94.

Lack of Common Definitions
To determine the number of people affected by a weather event, one must decide which deaths, injuries, and illnesses should be counted and be aware of good sources of information on health affects. At present, there is no generally accepted definition of what constitutes a weather-related death, injury, or illness. Furthermore, those attempting to assess the impact of weather events may use different sources of information. As a result, it may be difficult to compare the impacts of different weather events on mortality and morbidity, and different groups may report dissimilar numbers of persons affected by the same weather event.

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Scenarios
Each of the following scenarios presents a death that occurred at the time of or shortly after a weather event. Even among medical examiners, who are usually responsible for investigating and determining the cause of deaths due to injuries and violence and who were asked to review these scenarios at a recent meeting, there is often disagreement on what constitutes a "disaster-related" death. Mortality data from several eastern U.S. cities affected by the 1993 heat wave reinforce this point.

1. Roof trusses from a neighbor's home were blown off during a hurricane, penetrating the roof of the decedent's home, striking her in the head. She died from blunt head injury.

2. During a hurricane, a 72 year old man with a history of heart disease was in his garage lifting a piece of plywood to repair a storm-damaged window, when he collapsed and died immediately. Cause of death was cardiac dysrhythmia.

3. Two days after a flood, a family was still without power. Because the decedent was afraid of the dark, her mother left a candle burning in her bedroom. During the night, the candle fell over and started a fire. The decedent died from carbon monoxide poisoning.

4. 15 days after a tornado occurred, a workman was asphyxiated when a storm-felled tree trunk toppled back over, trapping him beneath its roots.

5. The decedent - armed and apparently intent on looting a storm-damaged home - approached, shot at, but missed a homeowner; but the homeowner, defending his property, and himself, shot the would-be robber in the head.

6. A husband shot and killed his wife and then himself 6 months after a hurricane; they were still living in temporary housing and their marriage had become unstable.

7. The decedent was from another state. He was in the area providing relief efforts to victims who were displaced by a flood when he was stung by a hornet and died from anaphylactic shock. The decedent had no known history of allergies or previous exposure to stinging insects.

Relationship of death to disaster in seven scenarios, as judged by medical examiners at the annual meeting of the National Association of Medical Examiners, Charleston, South Carolina, 1994.

Death related to disaster? If yes, directly or indirectly?

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Proposed Definition
To determine whether a death, injury, or illness is related to a weather event, the health effect must be temporally and geographically related to the weather event, and make causal and biological sense. Thus, in counting people affected by weather, one must establish reasonable geographic and time frames, and assess the nature of the circumstances and health effects:

• Time Frame - One should establish an explicit starting and ending date for counting health effects. For example, for a weather event such as a hurricane in which preparations, including evacuation, can be made and for which physical destruction of the natural and built environment is extensive and, therefore, clean-up after the event is often prolonged, the time period could extend from one or more days prior to the event to two or more months after the event. For an event with little or no advanced warning and little clean-up, for example, a severe hail storm, the time frame may start with the event and end the same day.

• Geographic Frame - One should establish the geographic area in which people may be affected by the weather event. For example, an affected person must have been present in the county or counties affected by a tornado to be counted.

• Circumstances - A death, injury, or illness is directly related to a weather event if it is caused by the direct environmental effect(s) of the weather. A death, injury, or illness is indirectly related to a weather event if it is caused by unsafe or unhealthy conditions that occurred because of the anticipation or occurrence of the weather event. These conditions include the loss or disruption of usual services, personal loss, and disruption of an individual's lifestyle. We divide these indirect effects into those caused by (1) unsafe or unhealthy conditions that caused a loss or disruption of usual services (including medical care services) or (2) temporary or permanent displacement, property damage, or other personal loss or stress.

• Biological Sense - For a death, injury, or illness to be related to a weather event, the circumstances leading to the health effect and the reported health effect must make causal and biological sense. For example, a lung cancer which results in someone's death two days after a hurricane could not be causally related to the weather event. It is possible, however, that the death of someone whose medical care for lung cancer was disrupted by the hurricane could be attributed to the hurricane.

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Source of Information

Mortality

• Death certificates are completed by physicians, medical examiners, coroners, and funeral directors for each death in the United States and filed with state or local registrars. The selected data from the filed certificates are compiled at the state and national level and form the basis of state and national mortality statistics. Causes of death are classified and coded using the International Classification of Diseases. See listing of weather related categories below.

• Medical examiners or coroners are responsible for investigating and certifying the cause of most deaths that are sudden, unexplained, or caused by injuries, including those related to weather events. Their records usually contain more detailed and complete information on the cause and circumstances of weather related deaths than do death certificates, and their records are usually available more quickly than are data from death certificates.

• Newspapers often provide reports of weather related deaths.

• Red Cross workers who respond to disasters usually compile information on persons affected by the disaster.

• The National Weather Service gathers information on weather related morbidity and mortality, which is published monthly.

A Rapid Epidemiologic Assessment (Noji 1997, p. 48) following a disaster may be used to estimate

• overall magnitude of the impact of the disaster (geographic extent, number of affected persons, and estimated duration)
• impact on health (e.g., number of casualties)
• integrity of health services delivery systems
• specific health care needs of survivors
• disruption of other service sectors (power, water, sanitation) that contribute to public health
• extent of response to the disaster by local authorities

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References
The Public Health Consequences of Disasters, edited by Eric K. Noji, Oxford University Press, New York, 1997.

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