Hazard


A hazard is an agent which has the potential to cause harm to a vulnerable target. Hazards can be both natural or human induced. Sometimes natural hazards such as floods and drought can be caused by human activity. Floods can be caused by bad drainage facilities and droughts can be caused by over-irrigation or groundwater pollution. The terms "hazard" and "risk" are often used interchangeably however, in terms of risk assessment, they are two very distinct terms. A hazard is any agent that can cause harm or damage to humans, property, or the environment. Risk is defined as the probability that exposure to a hazard will lead to a negative consequence, or more simply, a hazard poses no risk if there is no exposure to that hazard.
Hazards can be dormant or potential, with only a theoretical probability of harm. An event that is caused by interaction with a hazard is called an incident. The likely severity of the undesirable consequences of an incident associated with a hazard, combined with the probability of this occurring, constitute the associated risk. If there is no possibility of a hazard contributing towards an incident, there is no
several ways. One of these ways is by specifying the origin of the hazard. One key concept in identifying a hazard is the presence of stored energy that, when released, can cause damage. Stored energy can occur in many forms: chemical, mechanical, thermal, radioactive, electrical, etc. Another class of hazard does not involve release of stored energy, rather it involves the presence of hazardous situations. Examples include confined or limited egress spaces, oxygen-depleted atmospheres, awkward positions, repetitive motions, low-hanging or protruding objects, etc. Hazards may also be classified as natural, anthropogenic, or technological. They may also be classified as health or safety hazards, by the populations that may be affected, and the severity of the associated risk. In most cases a hazard may affect a range of targets, and have little or no effect on others.
Identification of hazards assumes that the potential targets are defined, and is the first step in performing a risk assessment.

Characteristics

include long term environmental deterioration such as acidification of soils and build-up of atmospheric carbon dioxide to communal and involuntary social hazards such as crime and terrorism to voluntary and personal hazards such as drug abuse and mountain climbing. Environmental hazards usually have defined or common characteristics including their tendency to be rapid onset events meaning they occur with a short warning time, they have a clear source of origin which is easily identified, impact will be swift and losses suffered quickly during or shortly after on-set of the event, risk of exposure is usually involuntary due to location or proximity of people to the hazard and the "disaster occurs with an intensity and scale that justifies an emergency response".
Hazards may be grouped according to their characteristics. These factors are related to geophysical events which are not process specific:
  1. Areal extent of damage zone
  2. Intensity of impact at a point
  3. Duration of impact at a point
  4. Rate of onset of the event
  5. Predictability of the event
Natural hazards may be defined as "extreme events that originate in the biosphere, hydrosphere, lithosphere or atmosphere" or "a potential threat to humans and their welfare" which include earthquake, landslide, hurricane and tsunamis. Technological and man made hazards include explosions, release of toxic materials, episodes of severe contamination, structural collapses, and transportation, construction and manufacturing accidents etc. A distinction can also be made between rapid onset natural hazards, technological hazards and social hazards which are described as being of sudden occurrence and relatively short duration, and the consequences of longer term environmental degradation such as desertification and drought,.
In defining hazard Keith Smith argues that what may be defined as hazard is only a hazard if there is the presence of humans to make it a hazard and that it is otherwise merely an event of interest. In this sense the environmental conditions we may consider hostile or hazardous can be seen as neutral in that it is our perception, human location and actions which identify resources and hazards within the range of natural events. In this regard human sensitivity to environmental hazards is a combination of both physical exposure and human vulnerability.
Smith states that natural hazards are best seen in an ecological framework in order to distinguish between natural events as natural hazards. He says "natural hazards, therefore, result from the conflict of geophysical processes with people and they lie at the interface what has been called the natural events system and the human interface system." He says that "this interpretation of natural hazards gives humans a central role. Firstly through location, because it is only when people and their possessions get in the way of natural processes that hazard exists."
A natural hazard can be considered as a geophysical event which when it occurs in extremes and a human factor is involved that may present a risk. In this context we can see that there may be an acceptable variation of magnitude which can vary from the estimated normal or average range with upper and lower limits or thresholds. In these extremes the natural occurrence may become an event that presents risk to the environment or people. Smith says "most social and economic activities are geared to some expectation of the 'average' conditions. As long as the variation of the environmental element remains fairly close to this expected performance, insignificant damage occurs and the element will be perceived as beneficial. However when the variability exceeds some threshold beyond the normal band of tolerance, the same variable starts to impose a stress on society and become a hazard." Thus above average wind speeds resulting in a tropical depression or hurricane according to intensity measures on the Saffir–Simpson scale will provide an extreme natural event which may be considered a hazard.

Classification

Hazards can be classified as different types in several ways. One of these ways is by specifying the origin of the hazard. One key concept in identifying a hazard is the presence of stored energy that, when released, can cause damage. Stored energy can occur in many forms: chemical, mechanical, thermal, radioactive, electrical, etc. Another class of hazard does not involve release of stored energy, rather it involves the presence of hazardous situations. Examples include confined or limited egress spaces, oxygen-depleted atmospheres, awkward positions, repetitive motions, low-hanging or protruding objects, etc.
Hazards may also be classified as natural, anthropogenic, or technological. They may also be classified as health or safety hazards and by the populations that may be affected, and the severity of the associated risk.
In most cases a hazard may affect a range of targets, and have little or no effect on others. Identification of hazards assumes that the potential targets are defined.

Based on energy source

;Biological hazard:
;Chemical hazard:
;Ergonomic hazard:
;Mechanical hazard:
;Physical hazard:
;Psychosocial hazard:

Based on origin

;Natural hazards:
"…to reduce through concerted international action, especially in developing countries, the loss of life, property damage, and social and economic disruption caused by natural disasters, such as earthquakes, wind-storms, tsunamis, floods, landslides, volcanic eruptions, wildfire, grasshopper and locust infestations, drought and desertification and other calamities of natural origin."

;Anthropogenic hazards:
;Technological hazards:
;Sociological hazards:
;Environmental hazards:

Based on effects

;Health hazards:
;Safety hazards:
;Economic hazards:
;Environmental hazards:

Disasters

can be defined as a serious disruption, occurring over a relatively short time, of the functioning of a community or a society involving widespread human, material, economic, societal or environmental loss and impacts, which exceeds the ability of the affected community or society to cope using its own resources. Disaster can manifest in various forms, threatening those people or environments specifically vulnerable. Such impacts include loss of property, death, injury, trauma or post-traumatic stress disorder.
Disaster can take various forms, including hurricane, volcano, tsunami, earthquake, drought, famine, plague, disease, rail crash, car crash, tornado, deforestation, flooding, toxic release, and spills. These can affect people and the environment on the local regional level, national level or international level where the international community becomes involved with aid donation, governments give money to support affected countries' economies with disaster response and post-disaster reconstruction.
A disaster hazard is an extreme geophysical event that is capable of causing a disaster. 'Extreme' in this case means a substantial variation in either the positive or the negative direction from the normal trend; flood disasters can result from exceptionally high precipitation and river discharge, and drought is caused by exceptionally low values. The fundamental determinants of hazard and the risk of such hazards occurring is timing, location, magnitude and frequency. For example, magnitudes of earthquakes are measured on the Richter scale from 1 to 10, whereby each increment of 1 indicates a tenfold increase in severity. The magnitude-frequency rule states that over a significant period of time many small events and a few large ones will occur. Hurricanes and typhoons on the other hand occur between 5 degrees and 25 degrees north and south of the equator, tending to be seasonal phenomena which are thus largely recurrent in time and predictable in location due to the specific climate variables necessary for their formation.
Major disaster, as it is usually assessed on quantitative criteria of death and damage was defined by Sheehan and Hewitt having to conform to the following criteria:
This definition includes indirect losses of life caused after initial onset of the disaster such as secondary effects of, e.g., cholera or dysentery. This definition is still commonly used but has the limitations of number of deaths, injuries and damage. UNDRO defined a disaster in a more qualitative fashion as:
an event, concentrated in time and space, in which a community undergoes severe danger and incurs such losses to its members and physical appurtenances that the social structure is disrupted and the fulfillment of all or some of the essential functions of the society is prevented.

As with other definitions of disaster, this definition not only encompasses social aspect of disaster impact and stresses potentially caused but also focuses on losses, implying the need for an emergency response as an aspect of disaster. It does not however set out quantitative thresholds or scales for damage, death or injury respectively.

Status of a hazard

Hazards are sometimes classified into three modes or statuses:
The terms "hazard" and "risk" are often used interchangeably. However, in terms of risk assessment, these are two very distinct terms. A hazard is an agent that can cause harm or damage to humans, property, or the environment. Risk is the probability that exposure to a hazard will lead to a negative consequence, or more simply, a hazard poses no risk if there is no exposure to that hazard.
Risk can be defined as the likelihood or probability of a given hazard of a given level causing a particular level of loss of damage. The elements of risk are populations, communities, the built environment, the natural environment, economic activities and services which are under threat of disaster in a given area. The total risk according to UNDRO 1982 is the "sum of predictable deaths, injuries, destruction, damage, disruption, and costs of repair and mitigation caused by a disaster of a particular level in a given area or areas.
David Alexander distinguishes between risk and vulnerability saying that "vulnerability refers to the potential for casualty, destruction, damage, disruption or other form of loss in a particular element: risk combines this with the probable level of loss to be expected from a predictable magnitude of hazard." As hazards have varying degrees of severity, the more intense or severe the hazard, the greater vulnerability there will be as potential for damage and destruction is increased with respect to severity of hazard. Ben Wisner argues that risk or disaster is "a compound function of the natural hazard and the number of people, characterised by their varying degrees of vulnerability to that specific hazard, who occupy the space and time of exposure to the hazard event.".
Another definition of risk is "the probable frequency and probable magnitude of future losses". This definition also focuses on the probability of future loss whereby degree of vulnerability to hazard represents the level of risk on a particular population or environment. The threats posed by a hazard are:
  1. Hazards to people – death, injury, disease and stress
  2. Hazards to goods – property damage and economic loss
  3. Hazards to environment –loss of flora and fauna, pollution and loss of amenity

    Marking of hazards

Hazard symbols or warning symbols are easily recognisable symbols designed to warn about hazardous materials, locations, or objects, The use of hazard symbols is often regulated by law and directed by standards organisations. Hazard symbols may appear with different colors, backgrounds, borders and supplemental information in order to specify the type of hazard and the level of threat. Warning symbols are used in many places in lieu of or addition to written warnings as they are quickly recognized and more universally understood, as the same symbol can be recognized as having the same meaning to speakers of different languages.