November 7, 1995

Estimating Lives Saved with UV Water Disinfection Device

Illustrative calculation for Orissa, India

In the following sections, we provide rough estimates of infant lives saved and stunted-growth avoided for children, from one UV disinfection device. These estimates are based on what limited data we could gather, and are only good as order-of-magnitude estimates with one digit accuracy.

Avoiding infant deaths

We take the state of Orissa in India as represent ative of a poor developing country context. Although Orissa does not span the full range of geo-climatic regions in the developing world, it has the high infant mortality, low literacy rates, and poverty levels typical of poor developing countries. Orissa has a population of 32 million (3.7% of India’s population). The fertility rate is 3.7, which indicates that each woman in Orissa bears an average 3.7 children throughout her life. Orissa has an infant mortality rate of 126 deaths per 1000 live births, male literacy of 63%, and female literacy of 35%. (All data from "Census of India 1991", quoted in Development Alternatives Newsletter, Vol. 5, No. 9, p. 4). India’s per capita GNP in 1991 was 330 US dollars (World Bank 1995). Orissa’s would be lower than the Indian average.

Water-borne diseases claim 13 infant lives per hour in Orissa, which equals 113,880 infant deaths per year. (Quoted from Mr. Vinod Alkari, Chief, UNICEF office in Bhubaneswar, at the May 1994 meeting on UV water disinfection, Bhubaneswar, India).

So, in a community of 1000 persons, there are approximately (113,880 / 32 thousand =) 3.56 infant deaths per year from waterborne diseases. This number is higher where drinking water is unsafe (in poor rural communities and city slums), and lower where drinking water is safe (in middle and upper class urban communities).

Assuming that one UV water disinfection device services this community of 1000, we can reduce the infant death rate from waterborne diseases by 30% (1 death) annually. Ideally, the estimate of the reduction should be based on the observed reduction in infant death rate from water-borne diseases in communities supplied with safe drinking water, compared to the rate in matched communities who continue to receive untreated water. However, very few studies of this kind have been undertaken in developing countries. Furthermore, when such studies have been undertaken, the sample size and the duration have been too small to provide adequate statistical power to quantify the reduction well. For a recent review see Mintz et al (Journal of the American Medical Association JAMA, March 22/29, 1995 - Vol. 273, No. 12, pp. 948-953). We assume a reduction of only 30% due to lack of adequate public sanitation and waste disposal, and continued lack of public education in health and hygiene after installation of the UV water disinfection device. If the sanitation, waste disposal and public education in hygiene are provided, the death rate would drop more.

Thus we estimate that one UV disinfection device serving a community of 1000 in Orissa would avoid one statistical infant death annually, saving 15 infants over its 15 year life.

Avoiding Stunted-growth in children

From the data presented in UNICEF WES report "Planning for Health and Socio-Economic Benefits from Water and Environmental Sanitation", summarizing a conference of the same title held in April 1993, a 40% reduction in number of children with stunted growth (from 60% to 20% of the total) appears to be implied by an 80% increase in access (from 0% access to 80% access) to safe water. Assuming that the UV disinfection device improves access to safe water by 80% for a community of 1000 persons, we estimate that over the 15 year life of the device in the community, it will avoid the stunted growth in 40% of the children growing up in this period in the community of 1000. (Since detailed data for Orissa are not available to us at the moment, we use the data for India in the estimate below. Impact in Orissa will be larger.) To estimate the number of children who thus escape stunted growth, we assume a crude birth rate of 29 per thousand per year (the average for India for 1991, ref. Census of India 1991) for this community. In 15 years, there will be born 29 X 15 = 435 children. Of these, some will be lost to infant mortality. This number is given by the infant mortality rate of 79 per 1000 live births for India, applied to these infants. So, (435 X 79 / 1000 =) 34 of these will be lost, 400 will survive. If these have no access to safe drinking water, 60%, i.e., 240, will grow up stunted. If 80% of the children have access to drinking water, then only 20%, or 80, will grow up stunted. The difference, (400-240=) 160 healthy normal-growth children, can be attributed to the UV disinfection device over its 15 year life span.

Summary

One UV device serving a community of 1000 persons in a poor developing country , will, over its service life of 15 years, save the lives of 15 infants from death by waterborne diseases, and avoid stunted-growth in 160 children. If the introduction of the device is accompanied with improved sanitation and waste disposal, and public education in health and hygiene, the impact will be larger. These numbers are order of magnitude estimates with only one digit accuracy.