Hazard (risk)

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A hazard is any agent that can cause harm or damage to humans, property, or the environment.[1]



Many biological hazards are associated with food, including certain viruses, parasites, fungi, bacteria, and plant and seafood toxins.[2] Pathogenic Campylobacter and Salmonella are common foodborne biological hazards. The hazards from these bacteria can be avoided through risk mitigation steps such as proper handling, storing, and cooking of food.[3] Disease in humans can come from biological hazards in the form of infection by bacteria, antigens, viruses, or parasites.

There is some concern that new technologies such as genetic engineering pose biological hazards. Genetically modified organisms are relatively new man-made biological hazards and many have yet to be fully characterized. For example, corn expressing insecticidal Cry proteins from the bacterium Bacillus thuringiensis was first introduced in 1996 and many of its potential detrimental effects on non-target organisms have yet to be examined.[4]


A chemical can be considered a hazard if by virtue of its intrinsic properties it can cause harm or danger to humans, property, or the environment.[5]

Some harmful chemicals occur naturally in certain geological formations, such as radon gas or arsenic. Other chemicals include products with commercial uses, such as agricultural and industrial chemicals, as well as products developed for home use. Pesticides, which are normally used to control unwanted insects and plants, may cause a variety of negative effects on non-target organisms. DDT can build up, or bioaccumulate, in birds, resulting in thinner-than-normal egg shells which can break in the nest.[3] The organochlorine pesticide dieldrin has been linked to Parkinson's disease.[6] Corrosive chemicals like sulfuric acid, which is found in car batteries and research laboratories, can cause severe skin burns. Many other chemicals used in industrial and laboratory settings can cause respiratory, digestive, or nervous system problems if they are inhaled, ingested, or absorbed through the skin. The negative effects of other chemicals, such as alcohol and nicotine, have been well documented.

Hazards associated with chemicals are dependent on the dose or amount of the chemical. For example, iodine in the form of potassium iodate is used to produce iodised salt. When applied at a rate of 20 mg of potassium iodate per 1000 mg of table salt, the chemical is beneficial in preventing goiter, while iodine intakes of 1200–9500 mg in one dose have been known to cause death.[7]


A mechanical hazard is any hazard involving a machine or process. Motor vehicles, aircraft, and air bags pose mechanical hazards. Compressed gases or liquids can also be considered a mechanical hazard.


A physical hazard is a naturally occurring process that has the potential to create loss or damage. Physical hazards include earthquakes, floods, and tornadoes. Physical hazards often have both human and natural elements. Flood problems can be affected by the natural elements of climate fluctuations and storm frequency, and by land drainage and building in a flood plain, human elements.[8] Another physical hazard, X-rays, naturally occur from solar radiation, but have also been utilized by humans for medical purposes; however, overexposure can lead to cancer, skin burns, and tissue damage.[3]

Hazard vs risk[edit]

The terms "hazard" and "risk" are often used interchangeably. However, in terms of risk assessment, these are two very distinct terms. As defined above, a hazard is any agent that can cause harm or damage to humans, property, or the environment.[1] Risk is defined as the probability that exposure to a hazard will lead to a negative consequence, or more simply, Risk = Hazard x Dose (Exposure).[3] Thus, a hazard poses no risk if there is not exposure to that hazard. Consider the following example from David Okrent's 1980 article, "Comment on Societal Risk":

Three people crossing the Atlantic in a rowboat face a hazard of drowning... Three hundred people crossing the Atlantic in an ocean liner face the same hazard of drowning... The risk to each individual per crossing is given by the probability of the occurrence of an accident in which he or she drowns... Clearly the hazard [drowning] is the same for each individual, but the risk [probability of drowning] is greater for the individuals in the rowboat than in the ocean liner.[9]

Hazard identification[edit]

Mechanical and physical hazards[edit]

Many mechanical hazards (aircraft, motor vehicles) and physical hazards (earthquakes, floods) have already been identified and well described. Hazard identification of new machines and/or industrial processes occurs at various stages in the design of the new machine or process. These hazard identification studies focus mainly on deviations from the intended use or design and the harm that may occur as a result of these deviations. These studies are regulated by various agencies such as the Occupational Safety and Health Administration and the National Highway Traffic Safety Administration.[5]

Biological hazards[edit]

Many biological hazards have also been identified. For example, the hazards of naturally-occurring bacteria such as Escherichia coli and Salmonella, are well known as disease-causing pathogens and a variety of measures have been taken to limit human exposure to these microorganisms through food safety, good personal hygiene and education. However, the potential for new biological hazards exists through the discovery of new microorganisms and through the development of new genetically modified (GM) organisms. Use of new GM organisms is regulated by various governmental agencies. The US Environmental Protection Agency (EPA) controls GM plants that produce or resist pesticides (i.e. Bt corn and Roundup ready crops). The US Food and Drug Administration (FDA) regulates GM plants that will be used as food or for medicinal purposes.

Chemical hazards[edit]

A variety of chemical hazards (DDT, atrazine) have been identified as well. However, every year companies produce more new chemicals to fill new needs or to take the place of older, less effective chemicals. Laws, such as the Federal Food, Drug, and Cosmetic Act and the Toxic Substances Control Act in the US, require protection of human health and the environment for any new chemical introduced. In the US, the EPA regulates new chemicals that may have environmental impacts (i.e. pesticides or chemicals released during a manufacturing process), while the FDA regulates new chemicals used in foods or as drugs. The potential hazards of these chemicals can be identified by performing a variety of tests prior to the authorization of usage. The amount of tests required and the extent to which the chemicals are tested varies, depending on the desired usage of the chemical. Chemicals designed as new drugs must undergo more rigorous tests that those used as pesticides.

Environmental hazards[edit]

Natural hazards[edit]

Natural hazard risks have threatened people, society, the natural environment, and the built environment, particularly more vulnerable people, throughout history, and in some cases, on a day-to-day basis. The social, natural and built environment are not only at risk from geophysical hazards such as earthquakes, floods, volcanoes and tsunami, but also from man-made technological hazards including industrial explosions, release of chemical hazards and major accident hazards (MAHs). Man-made hazards include the emergence of risks to people and the built environment in the modern world where hazards are presented by terrorist threats and technological hazards. According to the Red Cross, each year 130,000 people are killed, 90,000 are injured and 140 million are affected by unique events known as disaster.[10]

Recent policy-oriented work into hazard management began with the work of Gilbert White, the first person to study engineering schemes as a means of mitigating flooding in the US. From 1935 to 1967 White and his colleagues led the research into flood defences, and further collaboration on investigation was undertaken at the University of Chicago.[11]

In December 1989, after several years of preparation, the United Nations General Assembly adopted resolution 44/236 proclaiming the 1990s as the International Decade for Natural Disaster Reduction. The objective of that decade was stated in the annex of Resolution 44/236 as follows: "…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."[11]

Mitigating natural hazards[edit]

Methods to reduce risk from natural hazards include construction of prone facilities away from areas with high risk, redundancy, emergency reserve funds, purchasing relevant insurance, and the development of operational recovery plans.[12]

Natural hazard and disaster definitions[edit]

Disaster can be defined as the degree of risk of hazard which has a defined potential to cause significant personal, societal, property, or environmental damage or destruction. Disaster can manifest in various forms, threatening those people or environments specifically vulnerable to disaster. For example, a hurricane making landfall in the southeast United States presents a risk to those people, buildings and environments in the path of the hurricane and within proximity to the hazard where there is a risk, and potentially those who will be involved in the emergency response. Such impacts include death, injury, trauma or post-traumatic stress disorder.

Another popular definition of natural hazard more prominent in the 1960s was the definition given by Burton and Kates (1964) who defined natural disaster as "those elements of the physical environment harmful to Man and caused by forces extraneous to him". This definition is not inclusive of humans as an element of risk or vulnerability and, as such, is not the best definition with regards to modern disaster management practises. If we are to include human factors, which we must do, it is important to recognise man as an element that is at risk of natural hazards and an element which plays a part in mitigating, responding to and living within the realm, in many cases, of natural events that may become hazardous. As McGuire et al. say, "it is only when people and their possessions get in the way of natural processes that hazards exist".[13]

Kates (1978) went on to define environmental hazard as "the threat potential posed to man or nature by events originating in, or transmitted by, the natural or built environment". Keith Smith (1992) says that this definition includes a broader range of hazards ranging from 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 set hazard and the "disaster occurs with an intensity and scale that justifies an emergency response" (Smith, Environmental hazards, 1992).

Hazards were grouped by Hewitt and Burton (1971) according to their characteristics. These were factors related to geophysical events which were not process specific (Smith, 1992). They were: 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[11]

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 (Wisner et al., unknown) where the international community becomes involved with aid donation, governments give money to support affected countries' economies with disaster response and reconstruction post-disaster. In defining hazard it is important to distinguish between natural hazards which may be defined as "extreme events that originate in the biosphere, hydrosphere, lithosphere or atmosphere" (David Alexander, 2000) or as Keith Smith (1992) says, "a potential threat to humans and their welfare" and technological hazards which include earthquake, landslide, hurricane and tsunamis and technological and man made hazards including explosions, release of toxic materials, episodes of severe contamination, structural collapses, and transportation, construction and manufacturing accidents etc. There is also a distinction to be made between rapid onset natural hazards, technological hazards and social hazards and the consequences of environmental degradation such as desertification and drought, which are described as being of sudden occurrence and relatively short duration (McGuire, et al., 2002). Another distinction to be made as outlined by Keith Smith (1992) is that of the distinction between hazard and risk. We have defined hazard above but Keith Smith the distinction is that risk "has the additional implication of the chance of a particular hazard actually occurring" and thus define risk as "the probability of hazard occurrence'. Major disaster, as it is usually assessed on quantitative criteria of death and damage was defined by Sheehan and Hewitt (1969) having to conform to the following criteria:[11]

  • At least 100 people dead,
  • at least 100 people injured, or
  • at least $1 million damage.

This definition has the added benefit of including 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 (in $) (Smith, 1992). UNDRO (1984) 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 fulfilment 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 has the added benefit of focusing on losses, implying the need for an emergency response as an aspect of disaster (Smith, 1992). It does not however set out quantitative thresholds or scales for damage, death or injury respectively.

In defining hazard, whether it be as an "act of God" or "act of man," Keith Smith argues that what may be defined as a natural hazard is not in fact a hazard unless there is the presence of humans to make it a hazard and that it is merely an event of scientific interest. In this sense the environmental conditions we may consider hostile or hazardous can really be seen as neutral in that it is our 'perception, human location and actions which identify resources and hazards with the range of natural events. In this regard human sensitivity to environmental hazards is a combination of both physical exposure (natural and/or technological events at a location related to their statistical variability) and human vulnerability (in regard to social and economic tolerance of the same location). (Keith Smith, environmental hazards, 1992)

Keith 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." (Keith Smith, environmental hazards, 1992)

We can regard hazard then as a geophysical event which when it occurs in extremes and a human factor is involved may be called risk of hazard. In this context we can see that there may be an acceptable variation of magnitude (Smith, 1992) which can vary from the estimated normal or average range with upper and lower limits or thresholds. In these extremities the natural resource will become an event that presents risk to the environment or people. Keith Smith (Smith, 1992) 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 Sapphire Simpson Scale will provide an extreme natural event or hazard.

Most commonly time is linear according to medieval thought not cyclical as in such thinkers as Plato and Aristotle (Alexander, 2000). A disaster can be defined as an event occurring in time and space which affects the lives or welfare of a population or presents risk to the environment. David Alexander defines hazard as an extreme geophysical event that is capable of causing a disaster (Alexander, 2000). He says that 'extreme' in this case 'signifies a substantial departure in either the positive or the negative direction from a mean or a trend' thus flood disasters can result from unusually high precipitation and river discharge, whereas drought "stems from unusually low values" (Alexander, 2000). The fundamental determinates of hazard and indeed the risk of such hazards occurring is timing, location, magnitude and frequency (Alexander, 2000). Magnitudes of earthquakes for instance are measured on the Richter scale from 1 to 10, whereby each increment of 1 increases in severity and significance tenfold. The magnitude-frequency rule states that 'over a significant interval of time there will be many small events and few large ones (Alexander, Wolman, & Miller, 2000; 1960) giving a short return period for small events and long return period of larger events. 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 (Alexander, 2000). In the North Atlantic Ocean they develop in the late summer and autumn for instance. This is because of the easterly perturbations known as easterly waves (Alexander, 2000) (Elsner, 1994) (Pulwarty, 1997).


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 (Alexander, 2000). David Alexander outlined the elements of risk (Alexander, Confronting catastrophe, 2000) as populations, communities, the built environment, the natural environment, economic activities and services which are under threat of disaster in a given area. Risk can be equated with a simple equation, although it is not mathematical. 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. Mathematically it can be written as

Total risk = (Sum of the elements at risk) x (hazard x vulnerability)

David Alexander (Alexander, 2000, p.13) 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 (which can be considered as the manifestation of the agent that produces the loss)." (Wisner, et al., 1994). As hazard have varying degrees of severity (Wisner, et al., 1994) 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." (Wisner, et al., 1994). This is simplified into a non mathematical equation:

R = H x V

Risk, vulnerability and hazard are the three factors or elements which we are considering here in this pseudo equation. Another definition of risk given by Factor analysis of information risk which may be related to disaster is 'the probable frequency and probable magnitude of future losses. Again this definition focuses on the probability of future loss whereby degree of vulnerability to hazard represents the level of risk on a particular population, built environment or environment. The relationship between severity of environmental hazard, probability and risk. Hazard severity will obviously vary it is necessary to outline threats posed by hazard. These 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 (Smith, 1992)

Prioritization of hazards[edit]

SMAUG model – a basis for prioritizing hazard risks[edit]

In emergency or disaster management the SMAUG model of identifying and prioritizing risk of hazards associated with natural and technological threats is an effective tool. SMAUG stands for Seriousness, Manageability, Acceptability, Urgency and Growth and are the criteria used for prioritization of hazard risks. The SMAUG model provides an effective means of prioritizing hazard risks based upon the aforementioned criteria in order to address the risks posed by the hazards to the avail of effecting effective mitigation, reduction, response and recovery methods.[14]

Seriousness can be defined as "The relative impact in terms of people and dollars." This includes the potential for lives to be lost and potential for injury as well as the physical, social and as mentioned, economic losses that may be incurred

Manageability can be defined as "the relative ability to mitigate or reduce the hazard (through managing the hazard, or the community or both)". Hazards presenting a high risk and as such requiring significant amounts of risk reduction initiatives will be rated high.[14]

Acceptability - The degree to which the risk of hazard is acceptable in terms of political, environmental, social and economic impact

Urgency - This is related to the probability of risk of hazard and is defined in terms of how imperative it is to address the hazard [14]

Growth - This is the potential for the hazard or event to expand or increase in either probability or risk to community or both. Should vulnerability increase, potential for growth may also increase.

An example of the numerical ratings for each of the four criteria is shown below:[15]

Manageability High = 7+ Medium = 5–7 Low = 0–4
Urgency High = >20yr Medium = <20yr Low = 100yrs
Acceptability High priority - poses more significant risk low priority - Lower risk of hazard impact
Growth High = 3 Medium = 2 Low = 1
Seriousness High = 4-5 Medium = 2-3 Low = 0-1

See also[edit]


  1. ^ a b Sperber, William H. (2001). "Hazard identification: from a quantitative to a qualitative approach". Food Control. 12: 223–228. doi:10.1016/s0956-7135(00)00044-x. 
  2. ^ Natio-clearnal Restaurant Association. (2008). Servsafe Essentials, 5th edition.
  3. ^ a b c d Ropeik, David (2002). Risk. New York, New York, USA: Houghton Mifflin Company. ISBN 0-618-14372-6. 
  4. ^ Jensen, P.D.; G.P. Dively; C.M. Swan; W.O. Lamp (2010). "Exposure and nontarget effects of transgenic Bt corn debris in streams". Environmental Entomology. 39 (2): 707–714. doi:10.1603/en09037. 
  5. ^ a b Jones, David (1992). Nomenclature for hazard and risk assessment in the process industries. Rugby, Warwickshire, UK: Institution of Chemical Engineers. ISBN 0-85295-297-X. 
  6. ^ Song, C.; Kanthasamay, A.; Anatharam, V.; Sun, F.; Kanthasamy, A.G. (2010). "Environmental neurotoxic pesticide increases histone acetylation to promote apoptosis in dopaminergic neuronal cells: relevance to epigenetic mechanisms of neurodegeneration". Mol Pharmacol. 77: 621–632. doi:10.1124/mol.109.062174. 
  7. ^ Agency for Toxic Substances & Disease Registry. (2004). Toxicological profile of iodine. Retrieved from http://www.atsdr.cdc.gov/toxprofiles/tp158-c3.pdf.
  8. ^ Smith, Keith (2001). Environmental Hazards: Assessing risk and reducing disaster. New York, New York, USA: Routledge. ISBN 0-415-22464-0. 
  9. ^ Okrent, David (1980). "Comment on Societal Risk". Science. 208 (4442): 372–375. doi:10.1126/science.208.4442.372. 
  10. ^ David Alexander, 2000
  11. ^ a b c d Keith Smith, environmental hazards, 1992
  12. ^ Craig Taylor, Erik VanMarcke, ed. (2002). Acceptable Risk Processes: Lifelines and Natural Hazards. Reston, VA: ASCE, TCLEE. ISBN 9780784406236. 
  13. ^ McGuire,2002, p 10
  14. ^ a b c Annex B – SMUG model for prioritizing hazards
  15. ^ Chatham Islands Civil Defense Emergence Management Plan 2005–2010