I called a professor who specializes in sanitation to discuss World Toilet Day.

He said, "You're asking about my favorite thing — indoor plumbing."

Yeah, Kellogg Schwab, a professor at Johns Hopkins Bloomberg School of Public Health who specializes in wastewater contaminants, left me no choice. I had to ask: Why is it your favorite thing?

Here's what he said: "Close your eyes and imagine you're on the 6^th floor of the 9-story building where I work, with 2,500 students and 800 faculty when it's full. And imagine there's no indoor plumbing and you had the immediate need to defecate and you had to go down six flights of stairs and outside ... and maybe even put a quarter in to use a privy that is perhaps a hole in the ground. One: Would you make it? And two: Would you even want to?"

He convinced me. Indoor plumbing is pretty amazing.

And while clean, indoor toilets are ubiquitous in many parts of the world — we just take them for granted — they're an impossible dream for vast numbers of Earthlings. The United Nations reports that 3.6 billion people do not have access to a safe and effective toilet. And 673 million engage in what's known as "open defecation" — squatting outdoors, according to a joint report by WHO and Unicef.

And then there's the "flying toilet."

Jane Otai, an advocate in Kenya for safe toilets in schools and program lead for the Empowered Girls Initiative, explains: "The Mathare slums have public toilets which are shared by about 100 people per toilet block. These toilets are so filthy, never washed and the walls are 'painted' with human feces. Due to this poor state of the toilets, many people decide to defecate in plastic bags and throw these at night to wherever they will land. This is known as flying toilets.

"You will find these in alleys and ditches while some land on the roofs of structures. Some of the flying toilets find their way into the Nairobi river, which is the only source of water for the residents who cannot afford to pay for water sold by vendors. It's a horrible sight and stench."

And when fecal matter is not treated to remove pathogens, it can spread diarrheal and other diseases.

The health problems that stem from a lack of sanitary toilets are compounded when there's no running water for handwashing.

"I don't want you making my sandwich with contaminated hands," says Schwab.

So toilets are serious business. When the U.N. set its "millennial goals" back in 2000, one of them was: "access to proper sanitation, including toilets or latrines" by the year 2015. We didn't make it.

Now the U.N.'s Sustainable Development Goals call for safe toilets for all by 2030. And experts agree: Again, we're not going to make it. "We are seeing pockets of success but not at the pace and scale that we need," says Hope Randall, a spokeswoman for the Defeat Diarrheal Disease (DefeatDD) Initiative at the health nonprofit PATH.

World Toilet Day, established by the U.N. in 2013 and held on Nov. 19, is meant to draw attention to our planet's toilet inadequacies.

Schwab has another idea for bringing the problem of toilet inequity to the fore: talk s****.

"We still have a hard time saying it, but we have to talk about s***. My medical colleagues are saying 's***' is not a negative word. The idea is 's***' is a word that will make people perk their ears up."

He has a point. If Schwab were to ask you to Google "fecal matter flow diagrams" to see where waste starts out, including how much is treated to address health threats and how much is not treated, you'd probably just yawn.

But when he suggested that I Google "s***-flow diagrams for cities" ... I got right to it. And was bombarded with 2.4 million-plus results and an awesome definition of a s***-flow diagram from Wikipedia: "a high level technical drawing used to display how excreta moves through a location ... The diagram has a particular focus on treatment of the waste, and its final disposal or use. SFDs are most often used in developing countries."

So yes, words can get you to think about toilets.

So can humor. "Playfulness helps people engage in the conversation. I don't think it cheapens it," says Randall. "In my experience once you draw people in with something that rewards them with laughter" you can pivot to a serious conversation.

(Editors note: That's why we're illustrating this story with toilet signs. They can be pretty funny.)

But toilet signs can also be frustrating.

The signs that urge "no open defecation" — well, as Otai puts it, if there's nowhere to go, what's the point? She'd rather see a sign that says "please use this facility" posted next to a clean, well-lit public toilets. And it should be free. Some public toilets in Kenyan charge 5 Kenyan shillings — the equivalent of about 4 U.S. cents. For a poor family in a Kenyan slum with, say, five kids, that could be a deal breaker.

Then there's the launch this year of a new ... um ... character. Her name is Poo Guru. She's the brainchild of the Defeat Diarrheal Disease (DefeatDD) Initiative at PATH. The goal is for this brown animated character to educate the world about the need for many many many more toilets.

They made Poo Guru female because the U.N. and other sanitation specialists agree that women and girls suffer more from lack of toilets because of menstrual needs and vulnerability to sexual violence if defecating outside, especially in the dark.

And while Poo Guru is just an animated character bearing positive sanitation messages at this time, the hope is that she will appear at conferences — as a statue of some sort. And wearing a sticker that says: "I talk s***."