World Water Day, on 22 March every year, is about taking action to tackle the water crisis. Today, 1.8 billion people use a source of drinking water contaminated with faeces, putting them at risk of contracting cholera, dysentery, typhoid and polio.
Our recent research looked at efforts to improve water quality in Mexico in the 1990s and we found this had a very significant impact on mortality rates among children.
Improvements in the quality of drinking water made a significant contribution to population health in the late 19th and early 20th century in today’s richer countries. Children were especially vulnerable to diarrhoea and other water-borne diseases, so clean water led to declines in child mortality and, as a result, increases in life expectancy.
Although history has endowed us with knowledge of the benefits of water disinfection, poor water quality and diarrheal diseases remain prevalent in many low- and middle-income countries today. Worldwide, diarrhoea is the second leading cause of child mortality and a leading cause of morbidity.
While this must partly be because of insufficient coverage of chlorination programs, it appears to be partly because the same disinfection technologies that were historically successful today tend to have weaker effects. It is therefore important to identify factors that limit realization of the full potential of water disinfection.
In our new study, we analysed average and local impacts of an abrupt, nationwide municipal water disinfection program that Mexico initiated in 1991, raising the share of the population receiving chlorinated water from 55% to 85% within six months.
On average, the program was associated with a 37 to 48% decline in diarrheal disease deaths among children (over 23,000 averted deaths per year) and was highly cost-effective (about $1,310 per life year saved). However, age (degradation) of water pipes and the patchy coverage of complementary sanitation infrastructure play important roles in attenuating these benefits.
Since, historically, infrastructural investments were made alongside chlorination efforts, this may explain their larger impacts. In our study, we also found some evidence of behavioural responses to the change, such as private household expenditures on disinfectants declined in response to public program efforts, but these are small.
Urban Water Disinfection and Mortality Decline in Developing Countries.
National Bureau of Economic Research Working Paper 23239, March 2017
Sonia Bhalotra (Essex), Alberto Diaz-Cayeros (Stanford), Grant Miller (Stanford), Alfonso Miranda (CIDE), Atheendar S. Venkataramani (Harvard & MGH)