Major environmental hazards are estimated to threaten 5 to 15% of a country's population from day to day. Sometimes, for example in countries such as Tanzania and Ethiopia where drought is a major threat, the figure can rocket dramatically to over 90%. Hazard perception describes the way man comes to understand the extent to which he lives at risk from harmful states and processes in his environment. When studied, it reveals a striking paradox. Man not only chooses to live in hazardous areas, such as the Californian Earthquake Belt, but is also prepared to return to a devastated area even though the hazard may strike again. The rebuilding of Managua in the same location after the Nicaragua earthquake of December 23-24, 1972, which killed between 4 000 and 6 000 people and affected 75% of the population economically, is only one outstanding example. Another is the return of the Tristan da Cunha islanders after the volcanic eruption of 1961.
So far most research has been on natural hazards but study of manmade hazards and, by extension, social hazards is increasing. Examples of natural hazards are drought, landslides, hurricanes and earthquakes.
Manmade hazards include problems of pollution such as the dumping of toxic waste on land and oil spills at sea, while among the social hazards are technological accidents and breakdowns in social services.
All environmental hazards, whether natural or manmade, are the result of the interaction between the physical environment and society. A flood may be of natural origin but it is not defined as a hazard until it threatens human activities on the floodplain. The amount of damage caused by the flood really depends on how men use the floodplain. Clearly, the cost is likely to be greater if the floodplain is a residential or industrial area than if it is open agricultural or recreational land.
None the less, hazard research has shown that in the USA, for example, the building of flood protection works has only encouraged further residential and industrial development of floodplains. As a result, when a major flood next occurs, the cost of the damage is increased rather than decreased.
Research into natural hazard perception has focused on the individual's estimation of the size and likelihood of the next hazard "event" and on his awareness of alternative actions open to him. In areas of high mobility (for example, urban areas) or where a population is relatively new, people may be unaware of the existence of a particular hazard and thus may unwittingly contribute to it. More commonly, however, people are aware of the possibility of a major hazard but do not regard it as threatening them personally. They fail to adjust to the magnitude and frequency of natural hazards because they cannot see their environment, and their place in it, objectively. Hazard perception is therefore looked at in terms of personal characteristics.
These include cultural and social background, personality, socioeconomic variables like age and sex, and status within the community. Also important, of course, are an individual's relation to the hazard and his experience of hazards in the past.
Before any adjustment can occur, hazard perception must reach some threshold level of awareness. The choice of adjustment is then related to the individual's evaluation of the risk to himself and the cost to him of possible alternatives. Plainly, a major factor in this evaluation is the individual's experience of past hazards (variables like age, sex and income being less important).
Those who have experienced a flood or an earthquake in the past are more likely to expect one in the future and to make appropriate adjustments, especially if the last hazard event was recent or very serious. And yet, paradoxically, it is quite common for individuals to deny or denigrate the existence and likelihood of hazards. Thus they tend to forget past hazards, recalling them as less serious than they actually were. The tendency is for future hazards to be seen as occurring not at random but in cycles or pairs, and it is commonly supposed that a recent natural disaster means that another one will not occur for some time (like the gambler's fallacy). So it is the subjective way we perceive hazards which enables us to cope with the threat and uncertainty which they, in fact, constantly represent.
The research on which these results are based now covers some 15 natural hazards in 20 countries. Comparative studies of tropical cyclone perception have been carried out in, for example, Bangladesh, Puerto Rico, the Virgin Islands and the USA, while drought perception has been studied in Australia, Brazil, Kenya, Mexico, Nigeria, Tanzania and the USA. What these studies reveal is that the hazard perceptions described above are often similar in different societies and for different hazards. To give an example, peasant cultivators in Oaxaca in Mexico and suburban residents of floodplains in the USA both subscribe to the view that natural hazards occur in cycles of a few years.
As already pointed out, hazard perception is related to hazard adjustment. The number of possible hazard adjustments considered has been found to vary from seven in a study of drought in Yucatan, Mexico, to 264 in a study of floods in Sri Lanka. Response to hazard can be looked at in different ways: in terms of adjustments before, during and after the event or according to the level of adjustment (individual, community, regional, national and international). The range of adjustments beforehand can include technical development (for example, dams on rivers, drought-resistant crops, sea walls, earthquake resistant buildings and sophisticated hazard prediction and warning systems).
It may also include social adjustment such as the mutual-help practiced by many peasant and tribal societies, and the state and private insurance schemes in industrial countries, where the level of adjustment also tends to move from the individual and local community to regional and national bodies. In extreme disasters, international aid is forthcoming.
Manmade hazards are usually more difficult to perceive directly. They tend to pervade large, ill-defined areas and last for longer periods of time than most natural hazards. It is therefore harder to imagine them as discrete events for which one can see a cause and determine effects. Many hazards, such as chemical pollutants, are not perceived by people directly but through the measurements of scientific instruments.
They are more likely to result in ill-health and reduced life expectancy than sudden death.
Thus perception of manmade hazards differs from that for natural hazards. The threshold of awareness is higher and response is often a "caretaker" one. That is, decisions are taken by one group (usually a national government) on behalf of another (the population at risk). Where the individual cannot perceive a hazard directly, his awareness of it comes largely through information he receives about it.
Both the amount of information he has and his effectiveness in influencing or determining decisions related to the hazard, tend to be related to his position and role in society. An individual's social characteristics have more influence over his perception of manmade hazards than over that of natural hazards. Thus it has been found that the very people who are most at risk from air pollution in our cities those who are old, poor and live in the most polluted areas-are the ones who feel least able to respond to the threat by either protecting themselves, moving away from the hazard or influencing decision makers in government to take action for them.
Some researchers, recognizing that for many manmade hazards public awareness is low and possible adjustments constrained both by restricted scientific information and governmental environmental policies, have begun to focus on the hazard perception of professional decision makers in science and government.
They have shown important differences in the ways risks are assessed and adjustments adopted by the general public and professional administrators.
Work in hazard perception is broadening in two main directions. It is increasingly concerned with the social, political and psychological processes involved in the communication and evaluation of hazard information. It is also seeking to place hazard perception within the more general context of risk assessment, perception of uncertainty, and judgmental processes in relation to the environment, both physical and social.