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| Last Updated:: 27/12/2014

Diseases and Interventions

Environmental sanitation and human health are closely linked. Poor management of human wastes can lead to direct or indirect disease transmission. Presently 2.4 billion people have no access to basic sanitation (WHO/UNICEF, 2000). Poor water, sanitation and personal and domestic hygiene account for 5.7% of the total disease burden or 84 million life years lost per year expressed as DALYs (Disability Adjusted Life Years) (Prüss et al., 2002). Diarrhoea related to poor water and sanitation, is estimated to have killed 2.1 million people in 2000 (90% of the deaths occur in children: 85% in children 0 - 4 years age, and 5% in children 5 - 14 years age) (WHO, 2001; Murray and Lopez, 1996). Sanitation related diseases affect mostly the young and the poor.

This clearly suggests the importance of providing adequate sanitation and the need for preventive measures to combat environmental transmission of pathogens. Sanitation is the primary barrier for preventing the entry of many human pathogens into the environment.

Freshwater resources and especially high quality freshwater resources are becoming increasingly scarce, driven by factors including population growth, urbanisation and global climate change. Rapid population growth, especially in urban areas, increases the production of faecal matter and wastewater. Wastes are often discharged into surface water bodies, untreated or partially treated, potentially impacting the health of all downstream users of the water. Poor sanitation leads to increased disease transmission through drinking water, contaminated food and recreational/occupational contact with contaminated surface waters.

The susceptibility of individuals varies as also the virulence of the organism. Therefore it is important to relate an impact or an intervention to the burden of disease or the reduction of this burden. With this approach, it is necessary also to take into account the most vulnerable groups within a population or within an area. If the main exposure occurs through routes other than environmental ones, interventions on the latter will have less benefit from a general human health point of view. For vulnerable groups, the infective dose may be substantially lower than for the population as a whole. Vulnerability may relate to lower immune response among people with underlying diseases, the elderly or the malnourished. It may also be due to a lack of previous exposure of children, migrants or tourists to the pathogens in question. These groups need special consideration when assessing the impact of and exposure to pathogens through different routes.

Interventions are required to lower the impact on human health of environmental contamination of water bodies and receiving areas caused by human activities. Appropriate interventions may vary according to region and the prevailing socio-economic situation but should be based on a barrier approach to different transmission routes. Many previous and current interventions have failed, at least in developing regions of the world. Interventions at the household level, the industrial level and those related to watershed management must be taken as close to the sources of pollution as possible. Many of the centrally managed facilities have failed partly due to lack of operation and maintenance and partly due to the need for an integrated approach that also focuses on health issues. A household centred approach combined with holistic watershed management may provide a better solution to the problems faced today.

Interventions

Well-planned water and sanitation interventions have been shown to be effective in reducing a number of diseases. For example, Esrey et al., (1991) reviewed the effects of improved water and sanitation on a number of diseases. Based on a review of the best available studies the following results were obtained:

29% reduction in ascariasis;
26% reduction in diarrhoea morbidity;
65% reduction in diarrhoea mortality;
78% reduction in dracunculiasis;
4% reduction in hookworm infection;
77% reduction in schistosomiasis;
27% reduction in trachoma; and
55% reduction in overall child mortality.

The faeces of babies and young children are not considered to be dirty in many societies. However, the faeces of babies and young children are often the most dangerous because they may have a higher concentration of pathogens. It is the faeces of these two groups that are most frequently found in the environment (WHO, 1993). Several studies have shown associations between the incidence of diarrhoea in a household and children defecating in living areas (Han and Moe, 1990; Clemens and Stanton, 1987). Baltazar and Solon (1989) found that the unsanitary disposal of children's faeces was associated with a 34% increase in clinical diarrhoea and a 64% increase in pathogen positive diarrhoea in children from families that did not adequately dispose of their faeces compared to a control group. Sanitation interventions that facilitate the safe disposal of faeces from babies and young children will reduce diarrhoeal disease at the household and community levels.

Interventions to promote personal and domestic hygiene are also effective in reducing disease. In particular, handwashing with soap; after defecation; after handling babies' faeces; before feeding and eating; and before preparing food have significant impacts on diarrhoeal morbidity (WHO, 1993). Huttly (1992) reviewed the effects of handwashing and a combination of handwashing and other hygiene behaviours from several studies in table 3. The median reduction in diarrhoea morbidity due to improved hygiene was 33%.

(Carr and Strauss 2002)


Table: Sanitation options and their containment efficiency

Sanitation option

Containment

Household Community Society
Pit latrine ± - +
VIP latrine    + ± +
No-mix double vault ± + +
Pour-flush latrine + ± +
Septic tanks + ± ±
Sewerage/sewage treatment + ± -


+ good protection
± some protection
- poor protection

 

Improved sources are frequently contaminated with faecal indicator bacteria

 

 

Faecal contamination of drinking water, by source type and MDG region

 

Source: Joint Monitoring Programme Report, 2014