In Monday’s post I mentioned how much I loved London when I visited – but London wasn’t always such an appealing place. During the Industrial Revolution, it was filthy and polluted. The stench was appalling, and an episode of particularly foul smells from the Thames River in 1858 was known as the “Great Stink.” Life expectancy in England’s urban areas was markedly lower than in the countryside.

This filthy environment was the site of a public health breakthrough. During the 1854 cholera epidemic in London, the physician John Snow mapped the cholera cases from an outbreak in the Soho district and realized that those falling ill got their water from the same pump on Broad Street. At the time, the prevailing theory held that cholera spread through the air, rather than water, so Snow’s assertion of the pump’s role in the cholera epidemic wasn’t immediately embraced. He finally convinced community leaders to remove the pump’s handle to prevent further exposure. This story is widely told in introductory public health classes when explaining how to study diseases in populations (and it was an obvious choice when we were wondering what to name a public health blog).

It was later reported that the well feeding the Broad Street Pump was adjacent to a cesspit in which the diapers of baby suffering from cholera were washed. John Snow didn’t identify the mechanism of the disease exactly, but he hit upon the main problem: a contaminated water supply. Today, we know that drinking water contaminated with the feces of an infected person will spread cholera and other diarrheal diseases. But this knowledge hasn’t stopped diarrheal illnesses from claiming 1.5 million lives each year.

“Flying Toilets” in the Kibera Slum
In many parts of the world, sanitation facilities are inadequate or nonexistent. One of the oft-cited examples of inadequate sanitation comes from the Kibera slum in Nairobi, where some slum dwellers without adequate toilet access defecate in plastic bags and throw them outside. The bags then become a health hazard, especially in the rainy season.

Many slums do have shared latrines or pay toilets, but rarely in sufficient numbers – in Kibera, the BBC reports that the average is one toilet per 2,000 residents. Some facilities require payment, which can fund their upkeep but discourage residents from using them. Others deteriorate and become unusable. Not having a toilet in one’s home can be dangerous as well as inconvenient; women, in particular, risk being assaulted as they walk down unlit alleys to visit toilets at night.

A new product called the Peepoo may help alleviate the flying toilet problem; it’s a biodegradable bag coated with a chemical that reportedly turns feces into fertilizer. If the bags’ contents can be made valuable, entrepreneurs might be willing to collect them. But there will still need to be a system for getting human waste – even in a transformed state – out of the crowded slum and into gardens.

Spreading Sanitation
The Millennium Development Goals are a useful metric for seeing how the world’s doing on things like clean water and education. The sanitation target focuses on halving the proportion of the global population without access to improved sanitation facilities. (I should note that inadequate sanitation is a problem in rural as well as urban areas, but it can be a more visible – and smellable – problem in cities.)

An “improved” sanitation facility is defined as “adequate excreta disposal facilities (private or shared, but not public) that can effectively prevent human, animal, and insect contact with excreta.” Toilets connected to public sewer systems or septic systems qualify, as do many latrines. Latrines that use an open pit or require manual removal of excreta don’t qualify, nor do public latrines, because they are rarely maintained adequately and may not be accessible at all times.

In 1990, only 54% of the world’s population used improved sanitation facilities; the MDG target aims to bring that number up to 77% by 2015. In 2008, however, that number had only reached 61%. The increase represents 1.3 billion people who gained access to improved sanitation facilities between 1990 and 2008, but the World Health Organization/UNICEF Joint Monitoring Program estimates that we’ll still end up missing the target by one billion people.

As a commenter on Monday’s post pointed out, just installing sanitation facilities in areas that previously lacked them isn’t necessarily sufficient. People who grew up defecating in open areas or into plastic bags may not see a good reason to start using new facilities instead, and there are stories of newly built latrines being turned into storage sheds. Having learned from less-than-successful experiences, aid organizations are now supporting “demand-driven” water and sanitation services, in which governments and donors focus on creating demand rather than supplying hardware. See this post for more on creating demand for sanitation facilities.

Cities and Sewage
Here in the US, many people don’t think about what happens to their feces after they flush. In our densely populated areas, toilets are connected to a sewage system that brings waste to a sewage treatment plant, where harmful organisms and other contaminants are removed. (Wikepedia has an in-depth description and a nice diagram of how this happens if you want details.) The end result is solid sewage sludge – which can be landfilled, incinerated, or treated for use as fertilizer – and liquid effluent, which is discharged into a waterway.

Many of the US’s older cities have inadequate sewage systems, though, which can end up discharging untreated sewage directly into streets or surface waters when there’s a broken pipe or equipment failure or when a big storm dumps large amounts of water into the system in a short time. In some cases, the sewage can even end up in people’s basements or lawns. These related problems are known as Sanitary Sewer Overflows (that’s when an equipment failure leads to a discharge) and Combined Sewer Overflows (which arise because stormwater and sewage feed into the same pipes, and a heavy rainfall can overwhelm the system’s capacity). Cities are aware of these problems and are working to replace problematic systems, but such infrastructure work is resource-intensive, and residents aren’t always thrilled about paying to fix problems they weren’t aware of in the first place.

We’re also seeing concerns arise about chemical substances that sewage treatment plants weren’t designed to treat but that are becoming more common in our sewage, like pharmaceutical residues and nanoparticles. Substances that are designed to kill bacteria might affect the beneficial bacteria used in wastewater treatment plants. And if these substances survive the treatment process, they’ll either end up in the sewage sludge or discharged effluent, which means they could be applied to a field or end up in a waterway that supplies drinking water.

So, even in a country where we take our sanitation system for granted, old and new challenges still exist. The task of keeping us safe from our shit will remain one of our most important undertakings.