Relatively sudden and widespread disturbance of the social system and life of a community or region may be caused by one or more of the destructive forces of nature. Natural disasters are usually the result of geophysical or meteorological disturbances, the causes and mechanisms of which are now relatively well understood even though their occurrence and the detailed consequences cannot be predicted. The phenomena which mainly cause disasters are earthquakes and cyclonic storms, usually of tropical origin, but seismic activity under the sea can cause floods far from the centre of disturbance. Besides direct damage due to flooding, wind forces and earth movement, landslips and outbreaks of fire may occur to cause further damage and loss of life. Volcanic activity, besides being the cause of some earthquakes, can also cause damage from lava and ash.

The UNEP data book of 1991 notes that the frequency of natural disasters has increased in recent decade, adding that one reason may be a heightened awareness of disasters through reports in the media. It also suggests that natural disasters are becoming more significant in terms of magnitude and numbers. The most widely accepted reason is that the "hit rate" has increased considerably due to the continuing growth of world population. More than one third of the world's largest and fasting growing cities are now in regions of high seismic risk. Many of these are in developing countries where poor construction methods exacerbate the dangers. Many huge populations of non-urban people are concentrated in regions of environmental risk, such as variable rainfall; thousands of people have migrated to these regions in the past few decades as a result of population pressure and social conflict.

The world's societies and environment are increasingly suffering from the effects of natural disasters. A disaster usually results from the combination of a vulnerable environment and a hazard such as floods, tropical storms, earthquakes, landslides, wild fires, volcanic eruptions, and tsunamis. They can cause the loss of life, property and livelihoods.

Air pollution is the result of the discharge into the atmosphere of foreign gases, vapours, droplets and particles, or of excessive amounts of normal constituents, such as the carbon dioxide and suspended particulate matter produced by the burning of fossil fuels. A growing body of evidence seems to show a consistent association between air pollution and health impairment of varying degrees. Such associations are found between acute pollution exposure and morbidity and mortality; chronic lower-level exposure and morbidity and mortality; exposure and impairment of function and performance; exposure and symptoms of sensory irritation; and exposure and other effects on well-being.

A relatively new feature of the effects of air pollutants is the association with long term global problems. Considerable uncertainty surrounds scenarios relating to the effect of increased levels of carbon dioxide, but some predictions are of major impact on climate. The most significant polluting substances are sulphur dioxide and the oxides of nitrogen produced by power stations burning coal or oil and motor cars. The phenomenon of acid deposition is widespread throughout northern temperate regions, and researchers have associated 'acid rain' with damage to wildlife and wildlife habitats, including freshwaters and forests. Both wet and dry acid deposition is associated with damage to artefacts and materials. More locally, environmental contamination has resulted from long-term use of materials such as asbestos and lead, whose full impact as air pollutants has emerged only recently.

Airborne toxic agents, including micro-organisms and other harmful agents such as respirable dust, may have long-term effects such as genetic damage, carcinogenesis, and shortened life expectancy. The effect on an individual of foreign substances in the ambient environment depends on his health and on the degree and duration of exposure. Symptoms may not be readily distinguishable and their medical assessment is not always easy. Practical difficulties also arise from the inadequacy of long-term sampling procedures and analytical techniques.

The recommendation of maximum permissible limits for international adoption is a complicated procedure. Countries vary greatly in the amount of airborne known toxic and harmful agents workers may be exposed to so that one country may allow exposure to a toxic agent to be up to 90 times greater than the exposure permitted in another country. Permissible limits are normally based on an exposure of eight hours a day for five days a week. Different considerations must apply when people are exposed briefly to high concentrations, when working periods are longer than normal, or when workers are subjected to additional stresses such as high temperatures or poor nutrition.

Chemical agents of warfare include all gaseous, liquid or solid chemical substances which might be employed because of their direct toxic effects on man and animals. (This excludes substances whose effect is primarily physical, such as incendiary weapons, high explosives and smoke). Chemical weapons also include the chemical's precursors, the munitions and devices designed to deliver them, and any equipment specifically designed for their use in warfare.

Nerve agents (chemicals of the same family as organophosphorus insecticides) are the most lethal of the classical chemical warfare agents, killing by poisoning the nervous system and disrupting bodily functions. Blister agents (such as mustard gas) burn and blister the skin (causing more casualties than any other agent in the first world war). Vesicants are blistering and tissue-injuring agents which produce injuries similar to burns, although the mechanism behind the injury is different. Choking agents (such as phosgene) are highly volatile liquids. Toxins (such as mycotoxins and botulin toxin) are biological substances chemical substances produced biologically (although many of them have also been synthesized) which are very highly toxic. Tear gas and harassing agents are sensory irritants causing pain in the eyes, tear flow, and severe irritation of the upper respiratory tract (and have been widely used as riot control weapons); they can also cause skin irritation, nausea and vomiting. Psycho-chemicals are drug-like chemicals intended to cause temporary mental derangement, including psychosis. Cyanides (blood agents) cause headaches, weakness, disorientation and nausea in low doses; higher doses are acutely lethal causing circulatory effects, seizures and respiratory and cardiac failure. Incapacitating agents produce physiologic or mental effects, or both. They render individuals incapable of performing normal activities. DZ (3-quinuclidinyl benzilate) is the most commonly used. It is pharmacologically related to anticholinergic drugs and is present within some over-the-counter sleeping medications. Tear gases are used primarily for riot control and cause irritation to the eyes, respiratory tract, and skin. Herbicides may also be used to poison or defoliate plants.

Despite the availability of scientific methods in agriculture and animal husbandry, present methods of farming tend to yield a much smaller percentage than is potentially feasible with proper crop rotation, more plant varieties, plant nutrients, fertilisers and proper pest control. In many villages in the developing nations only a little over 50% of the arable land is used for agricultural production, which leaves much land uncultivated that could possibly produce profitable crops. In many rural areas, even with plentiful rainfall, dependence on subsistence farming has resulted in only short-range agricultural planning.

With existing traditional farming methods, it is difficult to meet family food requirements. Continuous soil erosion, limited means of fertilization, inadequately cultivated fields, and uncontrolled grazing practices all work to create minimally-productive farmland. Farmers tend to have little experience in poultry-keeping or in mechanized farming methods because of the inaccessibility of training centres where they might learn modern farming methods.

Because of the low-yield farming methods, much of the village employment is cyclical rather than continual. Sometimes residents are blocked by outside ownership which controls their markets and brings minimal economic returns to the farmer. Land cultivation is often done with animal powered-single furrow ploughs; the farmers depend on regular rains to supply water where there is no irrigation system. Chickens, pigs, goats, cows, geese, ducks and rabbits live in family yards and are raised for home consumption only - these animals freely forage for food throughout a village since there is usually no common grazing land. Without proper upbreeding of present stock and a larger variety of animals, profitable animal husbandry is not possible.

Organized crime are acts carried out for profit or power, by more than two people acting together over a long or indeterminate period, through the abuse of commercial structures, the use of violence or intimidation, and having an effect on political life, the media, public administration, justice or the economy. More simply put, organized crime is perpetrated by any group having a corporate structure who primary objective is to obtain money through illegal activities, often surviving on fear and corruption. Groups are increasingly crossing national borders. Mafia-type organizations are also coming to resemble multinational companies. Their statutory objective is to make money. The are irregular only in that they have recourse to crime to do so.

Organized crime are acts carried out for profit or power, by more than two people acting together over a long or indeterminate period, through the abuse of commercial structures, the use of violence or intimidation, and having an effect on political life, the media, public administration, justice or the economy. More simply put, organized crime is perpetrated by any group having a corporate structure who primary objective is to obtain money through illegal activities, often surviving on fear and corruption.

Organized crime can be segmented into four types: (a) the criminal gang, usually predatory mobile gangs involved in armed robbery, kidnapping and some kinds of drug trafficking; (b) the criminal syndicates cater to a specific segment of the population providing forbidden goods or services like drugs, sex and gambling; (c) criminal rackets extort money or business concessions from legitimate or illegitimate organizations including business and trade unions; and (d) criminal political machines. These types can overlap and any one criminal organization might be involved in one or all of these types.

Organized crime is difficult to eliminate for three main reasons: (a) Although individuals can be arrested and convicted, they can also be quickly replaced in the organization; (b) Although the criminal code penalizes individual acts or persons, is generally powerless to tackle the conspiracy of a permanent, sometimes international, well-structured organization; (c) As long as the public continues to demand certain services (such as gambling, drugs and prostitution) which are illegal or semi-legal, criminal entrepreneurs will find it profitable to employ the same techniques as industry in order to be profitable and efficient, which includes being efficient at avoiding prosecution. Techniques used include both the sound organization (usually on military lines with a chain of command up to the general staff) and the communications systems (international, national, local and field based) that effective operations require.