You may know that the Japanese population is the longest living large population on the planet.
Most Anglos and Germans attribute this to the Japanese diet. That makes no sense to me because diets throughout the world are varied, with Inuit eating only whale meat and blubber much of the year, with no correlation to lifespan or morbidity.
I on the other hand, or anyone who spends a great deal of time in Japan, will notice that the Japanese are easily the cleanest human population on the planet.
Just before New Year's, every year, every retail store including restaurants and bars do a thorough cleaning. In restaurants that means cleaning the stoves and chimneys with steam cleaners. Everywhere you go in a commercial district you will see furniture and flooring on the street being steam cleaned along with the interior.
You will also notice that the underside of nearly all automobiles are just as clean as the outside. The Japanese are the cleanest population on the planet and longest lived. I see a connection.
When I say this to Americans, they invariably tell me about some study that found that children exposed to dirt are less susceptible to asthma and other similar problems. This is Puritanism. Whenever Americans rebel they get dirty. Look at the hippies, look at the Hells Angels. I do not trust studies that come up with pure Puritan results.
On the other hand I notice that hospitals and a few other public places have now become concerned about antiseptic cleaning of hands. This is based on reliable studies that indicate cleanliness in hospital environments results in lower illness rates.
It is hard for Americans to understand what a filthy Third World country we live in. But a trip to Japan with eyes wide open will help explain that America's homeless pooping in doorways and alleys is a low standard of cleanliness.