Mental illnesses are characterized by disorders of the psyche, or mind. The view of objective reality is impaired, as are also the patient's self-correctness, his attitudes towards others and his behaviour. Some mental diseases are the result of primary affection of the brain, followed by a disturbance of the body as a whole. Others are caused by diseases of particular organs, with secondary disturbance of mental functions. They may be manifested in a variety of disorders: false sensory impressions, disturbances in thinking or mood, disturbances of consciousness and memory, and intellectual decline. Three types of mental illness are delineated; the psychoses (including schizophrenia and manic-depressive psychosis) constituting the most important group. The second group are nervous and mental disorders, including neuroses, psychopathies, and other nonpsychotic diseases. The third category is mental retardation.

The course of mental disease varies from single or rare attacks with complete remission, to severe, chronic psychoses with gross disorganization of mental activity and deterioration into feeblemindedness.

Significant mental disorder is clinically defined as a significant behavioural or psychological dysfunction that is associated with (a) present distress (a painful symptom) or (b) disability or impairment of functioning or (c) with a significantly increased risk of suffering death, pain, disability or an important loss of freedom. Another definition of mental illness is a non-organic, social-psychological disorder in which the individual is unable to protect his ego or social self sufficiently to participate in ordinary social life and obtain at least a minimal degree of social and psychological rewards.

Malaria is a parasite of red blood cells and the world's number one infectious disease. It is caused by infection of the liver with parasites of the genus Plasmodium, transmitted by the bite of infected anopheline mosquitoes Anopheles bifurcatus. The parasites cause the rupture of red blood cells and, in its worse cases, life-threatening anaemia, coma or death. The disease is characterized clinically by recurrent paroxysms of chills, high fever, seizures, sweating and prostration. It can lead to anaemia, kidney failure or rupture of the spleen. In man, malaria is produced by four specific parasites: Plasmodium vivax, P. malariae, P. ovale and P. falciparum. Falciparum malaria is the most life-threatening and has a fatality rate in untreated cases of 25%; it is transmitted by its African mosquito vector Anopheles gambiae.

Malaria is worsening in many parts of the world. It is a major threat to health and development, is primarily an environmental and socio-economic problem. Past reliance on narrow strategies is increasingly seen as the reason for the resurgence of this debilitating disease. The P. falciparum] parasite has continued to evolve resistance to almost all drugs in use (chloroquine, sulfadoxine/pyramethamine, and mefloquine). In areas of mosquito control, research with bed nets impregnated with pyrethroid insecticide offers hope of at least partial control of transmission of the disease in certain epidemiological situations. However, many people cannot afford the mosquito nets, which cost $5-10. Patients can usually be saved if they receive prompt medical treatment, but many of them cannot afford doctor's fees or the cost of travel, in total often less than $20.

Pollution immediately or eventually involves the hydrological cycle of the earth, because even pollutants emitted into the air and those present in the soil are washed out by precipitation. Water is considered polluted when it is altered in composition or condition so that it becomes less suitable for any or all of the functions and purposes for which it would be suitable in its natural state. This definition includes changes in the physical, chemical and biological properties of water, or such discharges of liquid, gaseous or solid substances into water as will or are likely to create nuisances or render such waters harmful to public health, safety or welfare, or to domestic, commercial, industrial, agricultural, fish or other aquatic life. It also includes changes in temperature, due to the discharge of hot water.

Pollution may be accidental (sometimes with grave consequences) but is most often caused by the uncontrolled disposal of sewage and other liquid wastes resulting from domestic uses of water, industrial wastes containing a variety of pollutants, agricultural effluents from animal husbandry and drainage of irrigation water, and urban run-off. The deliberate spreading of chemicals on the land to increase crop yields, or the addition of chemicals to water to control undesirable organisms, is another cause of pollution. Examples are the application of chemical fertilizers, and of pesticides for the control of aquatic weeds, insects and molluscs. Problems are compounded when national boundaries are involved, and cooperation in the management of transboundary waters is becoming essential.

Illiteracy is the inability to read and write. A person is defined as illiterate if he cannot, with understanding, both read and write a short and simple statement on his everyday life; and as functionally illiterate if he cannot engage in all those activities in which literacy is required for the effective functioning of his group and community, and also for enabling him to continue to use reading, writing and calculation for his own and the community's development. Lack of such abilities prevents individuals from going about their daily activities in modern society, seeking suitable employment, or moving about normally with comprehension of the usual printed expressions and messages they encounter. Its consequences include inability to take up basic social services, fill in even simple forms, and understand traffic instructions or other danger signs.

The multiplicity of languages is a major dividing factor in world society, reinforcing geographical, socio-economic (especially caste or class), political, ideological, professional and religious separatism. It prevents or hinders communication and the spread of education, and therefore aggravates international misunderstanding and mutual suspicion. Multilingualism within a country results in poor communications between members of different language communities and between those communities and the government. It can lead not only to mistrust and to political tension, but also to poor levels of literacy and problems in the judiciary when different languages may be used and transcripts required in order for a case to be heard at all.

Language barriers impede international communication in general and individuals in particular by rendering them unable to speak and correspond with whomever they wish, or read the periodicals and books they want to read. Bilingualism enables people to participate fully and directly in world culture and universal dialogue; monolingualism leaves the individual with a more parochial, and fearful, worldview.