Water, Sanitation, and Hygiene (WASH)

Water, sanitation, and hygiene, collectively abbreviated WASH, refers to access to safe drinking water, adequate sanitation for the safe disposal of human excreta, and hygiene practices such as handwashing. As a social and environmental determinant of health, WASH is a major factor in the global burden of infectious disease, particularly diarrhoeal disease in low- and middle-income settings.

Definition

WASH denotes the combined provision of safe drinking water, sanitation facilities that safely separate human excreta from contact, and hygiene behaviours, studied in public health as environmental determinants of infectious disease and indicators of health equity.

Scope

The topic covers the public-health rationale for WASH, the diseases linked to inadequate water and sanitation, and the role of WASH access as a measure of equity captured in global monitoring. It treats WASH at the level of populations and services rather than as clinical care for any individual condition. It is reference and educational in nature.

Core questions

• How do unsafe water, inadequate sanitation, and poor hygiene contribute to disease, especially diarrhoeal disease?
• What gains in health can be associated with improvements in water quality, sanitation, and handwashing?
• How is access to WASH measured and tracked across populations?
• Why is WASH considered both a determinant of health and a marker of inequity?

Key concepts

• Faecal-oral transmission
• Safe drinking water versus improved water source
• Improved and safely managed sanitation
• Handwashing and hygiene behaviour
• Diarrhoeal disease burden
• Service ladders and monitoring (JMP)
• Environmental enteric dysfunction

Mechanisms

Inadequate WASH allows pathogens shed in human and animal faeces to reach new hosts through the faecal-oral route, via contaminated water, food, hands, and surfaces. Interrupting this transmission, by treating or protecting water sources, safely containing excreta, and promoting handwashing, reduces exposure to enteric pathogens. The systematic review and meta-regression by Wolf and colleagues quantifies reductions in diarrhoeal disease associated with water and sanitation improvements in low- and middle-income settings.

Clinical relevance

WASH conditions shape the local burden of diarrhoeal and other enteric and water-related diseases that clinicians encounter, and they help explain geographic differences in infectious disease. This entry describes those population-level relationships for educational and reference purposes and is not guidance for treating any individual patient.

Epidemiology

Diarrhoeal disease linked to unsafe water, sanitation, and hygiene remains a leading cause of child mortality in low-income settings, as estimated by Boschi-Pinto and colleagues, and a large share of that burden is considered attributable to inadequate WASH. The WHO/UNICEF Joint Monitoring Programme tracks the still-substantial global gaps in safely managed water and sanitation services and the marked inequities between and within countries.

Evidence & guidelines

The systematic review by Wolf and colleagues (2014) synthesizes the effect of water and sanitation on diarrhoeal disease, and the WHO/UNICEF Joint Monitoring Programme reports provide the standard global monitoring framework and service ladders. The WHO Commission on Social Determinants of Health situates WASH within the wider determinants agenda. These are review, monitoring, and framing documents rather than clinical practice guidelines.

History

The link between water and disease was demonstrated by John Snow's investigation of the 1854 London cholera outbreak, a founding episode of epidemiology. Sanitary reform in nineteenth-century cities followed, and in the twenty-first century WASH was embedded in global targets, first the Millennium Development Goals and then Sustainable Development Goal 6, with the WHO/UNICEF Joint Monitoring Programme tracking progress.

Debates

How large and durable are the health effects of WASH interventions?

Estimates of diarrhoeal-disease reduction from water, sanitation, and hygiene interventions vary by intervention type, study design, and setting, and some large trials have found smaller-than-expected effects, prompting discussion about measurement, compliance, and the combinations of interventions needed.

Key figures

• Sandy Cairncross
• Jamie Bartram
• Annette Pruss-Ustun

Seminal works

• wolf-2014
• boschi-pinto-2008

Frequently asked questions

What does WASH stand for?

WASH stands for Water, Sanitation, and Hygiene, a grouping used in public health to describe access to safe drinking water, adequate sanitation, and hygiene practices such as handwashing.

Why is WASH considered a determinant of health rather than only an environmental issue?

Because access to safe water and sanitation is socially and economically patterned and shapes who is exposed to enteric disease, it is studied as a social and environmental determinant of health and a marker of equity, not merely an engineering concern.