to identify which households have access to safe drinking water through “improved water sources”, such as piped water, boreholes, and packaged water.<sup>3</sup> Households with unsafe drinking water typically access “unimproved water sources”, including unprotected well and surface water.

Contaminated water sources can lead to many chronic diseases, particularly in rural areas of developing countries, where a significant percentage of the poor population – more than a quarter in our sample – continues to use surface water as their main source of drinking water (WHO and UNICEF, 2021). Table 2 reports access to improved water sources in our DHS sample, distinguishing between rich and poor non-migrant households residing in rural and urban areas. While 93 percent of households in urban areas have access to improved water sources, that number decreases to around 73 percent in rural areas. Wealth differences further aggravate access to improved water, with only 56 percent of poor rural households having access to improved water compared to 92 percent of their rich counterparts. These statistics imply that those who are most vulnerable to water pollution are poor people residing in rural areas.

**Table 2: Percent share of household’s source of drinking water by urban/rural and wealth**

|**Water source**|**Urban**|**Rural**|**Urban Rich**|**Urban Poor**|**Rural Rich**|**Rural Poor**|
|---|---|---|---|---|---|---|
|Improved drinking water|92.60|73.26|96.66|71.69|92.26|55.65|
|Unimproved drinking water|7.40|26.74|3.34|28.31|7.74|44.35|
|**Total**|**100**|**100**|**100**|**100**|**100**|**100**|

_Notes:_ The household wealth index from DHS<sup>4</sup> was used to divide households into 5 quintiles based on their level of wealth. Rich in the table refers to the richest quintile (quintile = 5) and poor to the poorest quintile (quintile = 1).

The average incidence of DD and stunting among under five-year-old in our sample is 12.6 and 15.5 percent, respectively (Table A1), but there is considerable variation across countries (Table A2). Figure 2a shows the average incidence of DD is particularly high in Latin American, Caribbean and Sub-Saharan African countries, where every fifth child surveyed experiencing DD on average among the top 10 countries.<sup>5</sup> Stunting rates also very greatly across countries, ranging from 29 and 26 percent in Timor-Leste and Madagascar, respectively, to a mere 3 percent in Colombia, The Gambia, and the Dominican Republic (Figure 2b). Stunting rates are generally high in Sub-Saharan Africa and in all Asian countries in our sample.

> 3 The following water sources are included in the JMP definition of improved drinking water sources: piped water, borehole or tube wells, protected dug wells, protected springs, rainwater, and packaged or delivered water. Any other sources are considered as an unimproved water source.

> 4 The Wealth index from DHS is defined after accounting for water, sanitation, and hygiene (WASH) variables. We eliminate the WASH variables to create our own wealth index using the Principal Component Analysis.

> 5 The highest incidence of DD (in percent) was experienced by Bolivia (25.3), Haiti (23.0), Burundi 2.0), Uganda (22.0), Senegal (21.5), Burkina Faso (20.0), The Gambia (20.0), Cambodia (19.8), and Malawi (19.6).

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