Infant deaths in Massachusetts for much of the 1800s accounted for more than 20 percent of all deaths, many due to diarrhea, cholera and other gastrointestinal disorders.

But from 1870 to 1930, the infant mortality rate plummeted from around 1 in 5 white infants to 1 in 16 for both Massachusetts and the entire United States.

Studies have shown that the dramatic decline was due to the impact of a clean-water system in Boston and other major U.S. cities at that turn of the 20^th century.

Now, new research by Stanford Health Policy’s Marcella Alsan indicates that effective sewage systems installed in Boston and surrounding municipalities complemented the water treatment plants and had a significant role in protecting the lives of children.

“We were motivated to investigate this because there was a watershed moment when infant mortality began to decline in the U.S. and Massachusetts that we wanted to understand,” said Alsan, an assistant professor in the Department of Medicine, and the country’s only physician who is a tropical disease expert and economist.

“In retrospect, the daunting challenges these engineers and medical professionals faced in designing, financing and executing such a massive project is incredible,” Alsan said in an interview. “It was really inspiring to read the history of how it all came together.”

She and co-author, Claudia Goldin of Harvard University’s Department of Economics, analyzed about 200,000 of infant death certificates in Boston and 54 other Massachusetts municipalities spanning the years 1880 to 1915.

The impetus behind the creation of the Metropolitan Sewerage District was complaints regarding the stench of sewage among Boston’s upper-class citizens.

“The first of a series of hearings was given by the sewerage commission at the City Hall on Friday night,” read a story in an 1875 edition of the Boston Medical and Surgical Journal. “From the statements made it would appear in various parts of the district including most of the finest streets, the stench is terrible, often causing much sickness.”

A joint engineering and medical commission was appointed in 1875 to devise a remedy and a massive drainage project got underway.

Alsan and Goldin found that an overwhelming number of deaths in the greater metropolitan area were due to gastrointestinal disorders, but that this improved significantly when sanitation canals became part of the overall water systems.

“We find robust evidence that the pure water and sewerage treatments pioneered by far-sighted public servants and engineers in the Commonwealth saved many babies,” they write in a working paper. “It must also have enhanced the quality of life for the citizens of the Greater Boston area even if it did not reduce the non-child death rate by much.”

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They acknowledge that the interpretation of their results is intuitive. But it’s an important one to promote because many developing countries today have yet to heed the lesson of combining safe drinking water and improved sanitation systems.

“Without proper disposal of fecal material, the benefits of clean water technologies for the health of children are likely limited,” they write. “Such a result has relevance for today’s low-and middle- income countries.”

The Millennium Development Goal Target 7.C — to halve by 2015 the proportion of the population without sustainable access to safe drinking water and basic sanitation —was only met for water, but not sanitation. Between 1990 and 2015, 2.6 billion people gained access to improved drinking water sources.

Yet despite that progress, one-third of the global population is still using unimproved sanitation facilities, including nearly 1 billion people who are still forced to defecate in the open. This often leads to cholera, typhoid, hepatitis, polio, and worm infestation.

Diarrhea is the third-largest killer of children under 5 in sub-Saharan Africa, and 44 million pregnant women are infected with worms each year due to open defecation, according to the United Nations. Every minute, 1.1 million liters of human excrement enters the Ganges River in India.

The problem of waste disposal likely will be compounded by rapid urbanization occurring in the developing world, said Alsan, and lack of sanitation and the practice of open defecation costs the world’s poorest countries $260 billion a year.

“We think our findings underscore how complementary these infrastructure investments are, and hope that holds lessons for the developing world,” said Alsan. “In all practicality, it’s very hard to ensure the municipal water supply is not contaminated if the sewage infrastructure is neglected.”

Working Paper: Watersheds in Infant Mortality