Regional disparities in the burden of disease attributable to unsafe water and poor sanitation in China
Elizabeth J Carlton, Song Liang, Julia Z McDowell, Huazhong Li, Wei Luo & Justin V Remais
Volume 90, Number 8, August 2012, 578-587
Table 1. China-specific scenarios of exposure to water and sanitation facilities and associated relative risk (RR) of diarrhoea
|Exposure scenarioa||Description||RR of diarrhoea||Reference for RR|
|I||There is no transmission of diarrhoeal disease from unsafe water or sanitation.||1.0b||–|
|II||Centralized, treated drinking water is piped to each residence AND improved sanitation facilities are appropriately installed.c,d||2.5||Mead et al.
|IV||Drinking water is available from centralized piped systems, but treatment is incomplete or nonexistent (hence only partially improved) AND improved sanitation facilities are appropriately installed.c,d||4.5||Cao
|Va||No improved or partially improved drinking water is available BUT improved sanitation facilities are appropriately installed.c,d||5.2||Cao
|Vb||Partially improved drinking water is available BUT improved sanitation is not.c,d||6.8||Xing et al.
|VI||No improved or partially improved drinking water or improved sanitation is available.c,d||11.2||Xing et al.,
a For comparability, we have numbered our scenarios to indicate similarities with previous work.11
b Reference group.
c Improved sanitation includes a sewer connection (typically seen in urban areas), a triple compartment septic tank, an anaerobic biogas digester, a double barrel funnel type septic tank, and a urine-separating toilet with a septic tank. The latter four designs, found in rural areas, reduce pathogen loads through extended residence times as well as physical and chemical inactivation of pathogens, depending on soil and weather conditions.29,30 Unimproved sanitation includes unprotected stool pits and the absence of any sanitation system.
d Improved drinking water is defined as water that comes from centralized piped water systems that are treated regularly. Partially improved drinking water also comes from centralized piped water systems, but treatment is irregular or nonexistent. Untreated wells and surface water sources were classified as unimproved.
e In light of typical Chinese access to safe water and sanitation facilities, we have omitted Scenario III as previously defined by Prüss et al. (i.e. access to water and sanitation facilities with improved drinking water quality through piped water systems or point-of-use treatment or improved personal hygiene).11 Improved sanitation and piped water access are included in China-specific Scenarios IV and II, and the widespread practice of consuming hot water or tea leads to point-of-use drinking water treatment in most households.