Water, sanitation and hygiene (WASH) interventions such as provision of clean piped drinking water, enhanced facilities for excreta disposal and the promotion of hand-washing with soap are frequently implemented to improve health (especially with relation to infectious diseases) and children's development outcomes. There are no published systematic reviews investigating the impact of WASH interventions on medium- to long-term markers of health in childhood such as measures of physical growth and nutritional sufficiency. This review will assess the strength of evidence linking WASH interventions with measures of child nutritional status.
Description of the condition
In 2010 it was estimated that approximately 925 million people worldwide were undernourished (insufficient calorie availability) (FAO 2010), and global estimates of people with specific nutrient insufficiencies (for example iron and iodine) are in excess of 2 billion (SCN 2004). A lack of calories, minerals and vitamins is estimated to be the underlying cause of 35% of all child deaths and 11% of the global disease burden (Black, Allen, et al 2008). This figure includes estimates of the negative effects of undernutrition on pregnant women, which can cause poor foetal growth (intra-uterine growth retardation) and low birthweight. The Millennium Development Goal 4 (MDG 4) is to reduce by two thirds the mortality rate of children less than 5 years of age and current evidence suggests that the achievement of good nutritional status is crucial for the attainment of this goal.
In low-income countries over 27% of children under the age of 5 years (147 million) suffer from chronic undernutrition manifested as short height for their age (or stunting) and 23% (126 million) are underweight (low weight for age); by far the largest numbers of undernourished children live in South Asia and Sub-Saharan Africa. The period from conception to 24 months of age is widely recognised as a critical window for the prevention of chronic undernutrition (Black, Allen, et al 2008). The long-term consequences of chronic undernutrition include reduced school attendance and diminished health, economic and gender potential. One target for Millennium Development Goal 1 (MDG 1) is to reduce by half the proportion of people who suffer from hunger, but to date progress towards this goal has been slow (Unicef 2008).
There are both direct and indirect causes of undernutrition in children. The two direct immediate causes of undernutrition are inadequate dietary intake and disease, which interact in a complex manner and manifest as either chronic undernutrition (short height or stunting) or in acute situations as severe thinness (or wasting). Underlying these immediate causes are a multitude of indirect factors that contribute to nutritional status such as food security, child-care practices, maternal education, access to health services and water, hygiene and sanitation conditions. Ultimately, these factors are embedded in the larger political, economic, social and cultural environment.
Nutritional status in children is normally evaluated by assessing physical growth performance (via anthropometry) or micro-nutrient status (clinical signs of deficiency or blood measures). Various standardised methods are available for the assessment of nutritional status.
Description of the intervention
The integral role in health of safe water, sanitary disposal of human waste and personal hygiene has long been recognized (Fewtrell, Kaufmann, et al 2005). One target for Millennium Development Goal 7 (MDG 7) is to reduce by half the proportion of people without access to safe drinking water and basic sanitation. Activities linked to this goal aim to reduce the prevalence of infectious diseases and thereby improve nutritional status, especially in children. However, discourse around efforts to reach the MDG 7 targets is often not linked directly to health.
Currently approximately 2.6 billion people do not have access to improved sanitation, that is sanitation which ensures the hygienic separation of human excreta from human contact, and they rely on facilities such as unsafe flush or pour flush (to the street, yard, plot, open sewer, ditch or other location), a pit latrine without a slab or platform, a bucket and hanging latrine. Approximately 1.1 billion people have no sanitation facilities at all and have to practice open defecation (WHO/UNICEF 2010). Approximately 884 million people do not have access to improved drinking water sources (WHO/UNICEF 2010). Progress towards MDG 7 is on track for access to safe water but will fall well short for provision of basic sanitation (WHO/UNICEF 2010) and there are major differences between and within countries and regions.
Water, sanitation and hygiene (WASH) interventions are defined in this review as follows.
Water quality is any intervention to improve the microbiological quality of drinking water, including removing or inactivating microbiological pathogens (via household, community, or water source level water treatment systems involving filtration, sedimentation, chemical treatment, heat treatment or ultraviolet (UV) radiation) and protecting the microbiological quality of water prior to consumption (residual disinfection, protected distribution, improved storage). The effects of chemical contaminants (that is arsenic, fluoride) are not included in this review.
Water quantity or supply is any intervention to provide a new or improved water supply or improved distribution (installation of a new hand pump or household connection), or both.
Sanitation is interventions to introduce or expand the provision or use of facilities for excreta disposal (flush or pour flush to piped sewer system, septic tank or pit latrine; ventilated improved pit (VIP) latrine; pit latrine with slab; or composting toilet).
Hygiene is interventions that promote adoption of or increased practice of hand-washing with soap after defecation and disposal of child faeces prior to preparing and handling food and before eating (group discussions, media campaigns, leaflets, songs, pictorial stories, dramas etc.).
How the intervention might work
The causes of poor nutritional status in children are numerous and complicated and are both direct and indirect. The overall conceptual framework of the manner in which poor water supply and quality and also poor sanitation and hygiene might impact on child nutritional status identifies both direct pathways, namely diarrhoea (Briend 1990; Guerrant, Oriá, et al 2008), tropical enteropathy (Humphrey 2009) and nematode infections (Pruss-Ustun and Corvalan 2006); and indirect pathways, namely the time taken to collect water at long distances from the home, the purchase of water from water vendors and contamination of groundwater by poisonous metals (Figure 1). This review will focus on those pathways exemplified in Figure 2.
Why it is important to do this review
Several reviews have been published on the impact of sanitation interventions on diarrhoea incidence, the most recent of which is a Cochrane review that reports some evidence for effectiveness (Clasen, Boestoen, et al 2010). A further recent Cochrane review on the impact of hand-washing to prevent diarrhoea (Ejemot, Ehiri, et al 2008) reported that these interventions can reduce diarrhoea by approximately one third. The links between diarrhoea and other enteric infections and child nutritional outcomes are already well established (Pruss-Ustun and Corvalan 2006; Checkley, Buckley, et al 2008; Guerrant, Oriá, et al 2008).
However, work published thus far focuses only on the impact of WASH interventions on the incidence of childhood diarrhoea, and there are no published systematic reviews investigating the effect of WASH interventions on child nutritional status. The current review will therefore evaluate the strength of evidence linking WASH interventions with measures of child nutritional status. Indirect effects of improved nutritional status (such as improved Intelligence Quotient (IQ) levels, school performance, school attendance) will not be included in the review. Linking up the to-date distinct evidence base will help identify the role of WASH interventions in improving child health in efforts to meet the MDG 7 targets and will help establish priorities for future research.