Cleanliness is the absence of dirt, including dust, stains, bad smells and garbage. Cleanliness includes criteria such as health and beauty. § The term Cleanliness derives from the meaning absence of odour, avoidance of and to avoid the spreading of dirt and contaminants to oneself and others. In the case of glass objects such as windows or windshields, the purpose can also be transparency. Washing is one way of achieving cleanliness, usually with water and often some kind of soap or detergent. In more recent times, since the germ theory of disease, it has also come to mean an absence of germs and other hazardous materials. However, dirt may play a useful role in our immune systems. This shift in thinking can be traced back to 1989, when David Strachan put forth the "hygiene hypothesis" in the British Medical Journal. Strachan looked at the records of 17,000 British children and found that the greater number of older siblings they had, the less likely they were to come down with hay fever—a disease which, despite its name, is far more common in the city than the country. Strachan wondered if the older children were bringing home more viral infections to their younger siblings, priming their immune systems so they could better tolerate pollen. The "hygiene hypothesis" has now been linked with asthma, allergies, intestinal diseases including Crohn's disease^{[citation needed]}, childhood leukemia^{[citation needed]} and atopic dermatitis. There is increasing evidence that the less germs people are exposed to as a child, the more likely they are to get sick as adults.

Cleanliness impacts every phase of social interaction, generating potentially profound health-related risks and illnesses.

Early years

The rise of two-income families has led to a commensurate rise in toddlers and infants spending time in day care facilities. Indeed, the number of women with children in the workforce has increased from 44% in 1975 to 65% today.^[1] And as more children enter day care, the number of childhood illnesses has also increased.^[2]

There is little question that daycare before the age of two predisposes children to illnesses of the upper and lower respiratory tract. But we don't yet know the long-term impact of illnesses in early childhood, and that's a very important question. It's possible that some of the infections may be harmful and some may be protective, but that is largely unknown.^[3]

"Daycare syndrome," while not an official illness, is a term referencing illnesses bred from the sharing of contagious germs in day care facilities. According to the Mayo Clinic,^[4] there the five most common and contagious illnesses that children can contract in day care facilities include:

• Colds (upper respiratory infections)
• Stomach flu (vomiting and/or diarrhea)
• Ear infections (otitis media)
• Pink eye (conjunctivitis)
• Sore throat

Other health-related risk and illnesses are associated with daycare, cleanliness, and hygiene.^[2]

Schools

Especially in light of the 2009 rise of the H1N1 virus, schools are getting tough on cleanliness and germs.^[5] To battle the H1N1 virus, the New Jersey School District installed hand sanitizers in all 3,000 of their classrooms. "Students will be washing their hands as many times as they can. That's our preventative method to ensure to the parents and the community and to the students that our children are safe health wise....This is the best way to keep them safe."^[6]

In addition to frequent hand washing, New Jersey schools have instructed teachers to educate students on the following hygiene practices:

• Cover mouth and nose when coughing or sneezing with a tissue.
• Cough or sneeze into your sleeve when a tissues is unavailable.
• Dispose of used tissues properly.
• Wash hands regularly and thoroughly.

Similar practices have been documented in Ohio County Schools,^[5] where libraries and computer labs provide alcohol or sanitary wipes, encouraging students to wipe off shared computer keyboards, mice, and phone handles."

At work

The workplace presents cleaning challenges for both employer and employee.^[7]

For employees, hand sanitizers are an effective cleaning tool, killing 99.9% of most common germs.^[8] At workstations, regular cleaning of computer keyboards, phone handles, and desks also minimizes the risk of germ contamination.

For employers, common areas present a variety of concerns that can be addressed with proper cleaning.

• In rest rooms, touchless hand sanitizers and sensory-activated faucets and toilet flushers prevent the spread of germs.
• While the toilet seat is not the dirtiest spot in a public restroom,^[9] it is perhaps the one receiving the most individual attention. Toilet seat covers^[10] provide a germ-free barrier while preserving excessive toilet paper seat covering rituals.
• Tissues dispensers protect tissues from airborne contaminants.
• Center pull towel dispensers^[11] allow employees to touch only the towel they need, a germ-free system of paper towel distribution. This does have the drawback of using far more paper than most would agree is necessary.

In addition, dust control creates a "safer and healthier environment for employees and customers."^[12] The National Institute for Allergy and Infectious Diseases notes that dust mites are a common cause of perennial allergic rhinitis, an affliction that affects roughly 60 million people in the U.S.^[13]

The Textile Rental Services Association (TRSA) attributes 70% of dust inside the workplace to the outdoors. According to the TRSAA, floor mats placed inside building entrances capture up to 70% of dust debris.

It is a fact that bad quality air causes a vast amount of sickness within the workplace. Air conditioning can contribute to poor air quality. Desks harbour probably the most germs, especially where more and more offices allow staff to eat at their desks rather than canteens. Carpet cleaning can have maximum effects to improve air quality. Bacteria can be removed from desks using the correct cleaning products and implementing a clean desk policy within the workplace.

Industry

In industry, certain processes such as those related to integrated circuit manufacturing, require conditions of exceptional cleanliness which are achieved by working in cleanrooms. Cleanliness is essential to successful electroplating, since molecular layers of oil can prevent adhesion of the coating. The industry has developed specialized techniques for parts cleaning, as well as tests for cleanliness. The most commonly used tests rely on the wetting behaviour of a clean hydrophillic metal surface. Cleanliness is also important to vacuum systems to reduce outgassing.

In the home

Air inside the home has the potential to pose significant health risks.^[14]

"The air within homes and other buildings can be more seriously polluted than the outdoor air in even the largest and most industrialized cities. Other research indicates that people spend approximately 90 percent of their time indoors. Thus, for many people, the risks to health may be greater due to exposure to air pollution indoors than outdoors."^[15]

As such, there are a number of preventative cleaning steps that ensure dust and pollutants do not pose health risks

• Floor mats: These are the first line of dust defense when entering a living area.^[16]
• Vacuums: Traditional vacuum cleaners can force dust airborne, whereas a central vacuum does not blow air in the room being cleaned.
• Mopping: Sweep floors regularly with dust mops, whose materials are specially designed to gather dust.^[17]
• Air Purifiers: These provide additional protection against dust as well as other airborne contaminants
• Outdoor time: The easiest way to avoid pollution inside is to go outside.

Perhaps the biggest breeding ground for germs in the home is the kitchen,^[18] where billions of bacteria can be found. See food safety.

Keeping germs, viruses, and bacteria under control requires diligent cleaning. Dish towels, rags, countertops, and sponges are germ collectors. Regular kitchen cleaning practices include:^[19]

• Clean and disinfect kitchen surfaces with appropriate cleaning solvents.
• After cooking is complete, clean all food prep items in hot, soapy water.
• Wash dish towels and dish rags with soap and hot water between uses.
• Disinfect sponges by running them through the dishwasher or microwave. Replace sponges every two to three weeks.
• Clean appliances regularly.
• Whenever raw meat or eggs have been used, be sure to clean any surfaces that might have been touched in the process.