Adequate nutrition, safe drinking water and adequate sanitation are vital for the prevention of serious disease and the maintenance of good health and high labour productivity. In most parts of the world, nutrition has improved over the past 25 years, as reflected in declining infant and child mortality rates and in declining percentages of the total population suffering from undernutrition. But the improvements in child nutritional status in the 1970s ceased, on average, in the 1980s. Some 100 million children under the age of five show protein energy malnutrition; more than 10 million suffer from the severe form that is normally fatal if not treated. The estimated number of people suffering from severe undernutrition, with calorie intakes providing an energy level less than 1.2 times the basal metabolic rate (BMR), increased from 320 million in 1980 to 348 million by 1984 in 89 developing countries (excluding China). The number below 1.4 BMR increased from 475 to 512 million (figure 12.3). (BMR = i.o is the energy needed under resting and fasting conditions. It varies with body weight and sex.) The proportion of the population that is undernourished fell in the early 1980s in Asia, North Africa, and Central America, but there was no overall improvement in South America. The proportion rose sharply in sub- Saharan Africa, which has suffered long-term declining food availability per capita and increased malnutrition, due to economic stress and severe drought. Within regions, economic stress in the 1980s has been strongly associated with malnutrition, based on a recent survey of 33 countries (16 in Africa, 6 in Asia, and in Latin America and the Caribbean).

Assuming that the recent pattern of income distribution and food consumption relative to per capita income continues, FAO estimates that the total number of people suffering acute malnutrition will increase slightly to 353 million (in 89 developing countries) by the year 2010, and the number below 1.4 BMR will increase to 532 million. To reduce these numbers significantly, the system of income and food distribution will need improvement in many countries, and food production will need to accelerate.

Adequate nutrition is but one facet of disease prevention and health maintenance. A safe water supply and adequate sanitation are also necessary. Percentages of the population that have access to safe drinking water supply and adequate sanitation increased in many developing countries from 1975 to 1985, although variations in national interpretations of these concepts and changes in the number of countries reporting on them to WHO limit the comparability of the data, both between countries and over time. Of 89 countries surveyed in 1985, 73 per cent of the urban population and 42 per cent of the rural population had safe supplies of drinking water, compared with 74 per cent of the urban population (in 76 countries) and only 19 per cent of the rural population (in 69 countries) in I975-19

Although the percentage served did not increase much in the urban areas, the number of people served increased greatly, along with the total urban population. The percentage of urban populations with adequate sanitation increased from 51 per cent in 60 countries in 1975 to 61 per cent in 65 countries in 1985. In rural areas, adequate sanitation increased from 11 to 15 per cent over the 10-year period.

In 1985, the only groups of countries in which less than 74 per cent of the urban population had safe drinking water were the least developed countries (52 per cent) and Southeast Asia (49 per cent). In contrast, less than 50 per cent of the rural population had safe water in all of the developing regions, except Western Asia and the Mediterranean. The percentage of the urban population with adequate sanitation in 1985 was more diverse, although the only country groups averaging less than 55 per cent were South Asia (34 per cent) and the least developed countries (44 per cent). The rural percentages were mostly between 15 and 35 per cent, but only 3 per cent in South Asia.

With the slowdown in economic growth in many developing countries in the 1980s, it has become apparent that few of them have reached the ambitious target of 100 per cent water supply and sanitation coverage originally set for the end of 1990, as the goal of the International Drinking Water Supply and Sanitation Decade (1981-1990). Based on the cross-section relation between percentages served and per capita GDP in 1985, and on the baseline projections of GDP growth for 1990 and the year 2000, relatively small increases from 1985 to 1990 and the year 2000 will occur in the percentages of safe water and adequate sanitation in most regions. Additional increases of a few percentage points could be expected with higher total investment in a scenario for more rapid economic growth. But large increases in coverage would also require an increase in water supply and sanitation as a share of total investment. It might also require significant reductions in average unit costs, or increased efforts to raise sufficient revenues from taxes and user charges to cover the costs of construction, operation and maintenance.

Meeting the goal of 100 per cent coverage is a serious challenge. Although countries with average tariffs equal to or higher than costs of production have seen significant progress, the poorer regions, including Africa and the least developed countries have not. For most regions the most serious constraints on meeting the goal have been funding limitations and inadequate cost recovery frameworks, insufficient trained personnel and unsatisfactory operation and maintenance.

It was calculated in the 1980s that if low-cost technologies are used, construction costs for safe drinking water and adequate sanitation facilities for 100 per cent of the population by the year 2000 could be less than 1 per cent of annual GDP during the period from 1986 to the year 2000 in most of the developing countries. The cost would be higher, 1 to 2 per cent, in sub- Saharan Africa. These low-cost technologies include public standpipes rather than individual house connections for water supply, and non-water- borne sanitation (dry-pit privies, night-soil collection, etc.). Water- borne sewage systems for urban areas would cost considerably more to construct, but might have lower costs for operation and maintenance.