Introduction:
The first thing that comes to mind when considering a comfortable atmosphere is an optimal temperature, but maintaining the correct humidity levels in the home or workplace is important in keeping oneself healthy. Spending too much time in a humid environment could make one ill, especially those with a pre-existing respiratory infection. For instance, viruses thrive well in environments with humidity levels above 60 %.
What Are the Factors That Influence Air-Borne Infectious Diseases in the Indoor Environment?
The following are the factors influencing the transmission of air-borne diseases in the indoor environment:
-
The number of infected people who produce contaminated aerosols (a suspension of droplets or particles in the air).
-
The length of exposure.
-
Ventilation rate.
-
The number of susceptibles.
-
The settling rate of contaminated aerosols.
-
The survival of the pathogens attached to aerosols.
The humidity in an indoor environment is affected by two of the above factors: the survival of the pathogens attached to aerosols and the settling rate of the contaminated aerosols. Since these two factors play a vital role in determining the humidity, it is clear that the incidence of infectious diseases in an environment with very good ventilation rates is minimal.
How Much Humidity Is Considered Ideal?
The ideal humidity levels for indoor environments should be between 40 % to 60 %. If the humidity level falls below 40 %, it creates a favorable environment for harmful viruses to dwell. Many places like offices, schools, hospitals, and homes have a relative humidity below 20 % during winter. This is because of the dryness induced by traditional, commercial, and residential heating systems which can promote the growth of various harmful infectious agents.
How Are Low Humidity Levels Responsible for Causing Infections in an Indoor Environment?
Low humidity levels can cause infections in the following ways:
-
Aerosols are released by infected people while breathing, talking, coughing, and sneezing. These aerosols are populated with loads of bacteria and viruses embedded in saliva, water, mucous, and dissolved salts.
-
When these exit the airways, the aerosol droplets, which initially had a moisture saturation of almost 100 %, lose nearly 90 % of their weight due to water loss in a dry atmosphere, resulting in high, infectious salt concentrations circulating in the air.
-
If the aerosols are in crystalline form, the infectious agents can remain floating and recirculating in the dry air with a relative humidity of less than 40 %. They can travel considerable distances depending on the air current.
-
If the relative humidity is in the desired range between 40 % to 60 %, the salt concentrations drop to a level where most of the viruses find it hard to survive and become deactivated. The chances of acquiring infections within this ideal range are very scarce.
What Is the Role of Humidity in the Transmission of COVID-19?
The role of humidity in the transmission of the COVID-19 virus is as follows:
-
Dry Respiratory Passage: The cells and mucus lining the airways have a defensive action against the viral agents and other foreign substances that enter the airways. Low humidity levels can dry these cells and mucus linings, interfering with their normal functioning. At low humidity levels, the viral particles tend to populate more at the airway receptor sites, which can increase the chance of infection.
-
The Higher the Humidity Level, the Less the Virus: Researchers have found that viruses have less chance of survival if the humidity in the air is high, which reduces the chance of infection.
-
Low Levels of Humidity: Research shows that coronavirus can thrive for extended periods on surfaces in cold environments. Lower relative humidity combined with colder temperatures increases the risk of acquiring an infection. This is because aerosols dispersed in the air while talking, coughing, sneezing, and singing can linger in an environment with low relative humidity levels, increasing the risk of transmission.
What Are the Various Health Conditions Associated With High and Low Humidity?
In hot conditions, the humidity levels in the outside environment are high. The body sweats to regulate the body temperature. This sweat is expected to evaporate, keeping the body cool. A humid environment makes it difficult for the sweat to evaporate. This can lead to excessive perspiration (sweating), increased respiration, and elevated body temperature (hyperthermia).
The health conditions associated with high humidity are:
-
Diseases of the Respiratory System: High humidity can cause one to contract respiratory diseases like the influenza virus, common cold, and respiratory syncytial virus (RSV).
-
Dermatopathy: High levels of humidity can also make one encounter skin diseases like developing blisters, skin discoloration, skin sloughing (shedding), and skin rashes.
-
Allergic Diseases: A highly humid environment can make one susceptible to developing respiratory problems like asthma, particularly in children.
-
Volatile Organic Compounds: Exposure to volatile organic compounds due to high humidity in the home can result in eczema (a skin disease that leaves the skin red and dry with an urge to scratch), nervous system damage, and even cancer at times.
-
Heart Attack: Since the expelled sweat finds it difficult to evaporate under highly humid conditions, the body tends to produce more sweat to maintain the body temperature and keep the body cool. This can result in dehydration, which can thicken the blood and more pressure may be required to pump the blood throughout the body. This puts a strain on the blood vessels and heart, which can result in a heart attack.
-
Muscle Cramps: Muscle cramps can be caused due to the inability of the body to cool in humid environments. The cramps commonly occur in the legs.
-
Heatstroke: If the body temperature rises above 105 ℃ (Celcius), one may encounter lethargy, confusion, and complete loss of consciousness, which is referred to as heatstroke. Immediate medical intervention is necessary for these conditions.
-
Fainting: Dehydration due to heat exhaustion can result in dizziness and body weakness. It is very important to stay hydrated in humid conditions.
-
Fatigue: A highly humid environment can make one tired.
Low levels of humidity can result in the following health conditions:
-
Dry and Inflamed Mucous Membranes: Under dry conditions, the lining of the mucous membranes in the respiratory tract can also become dry and inflamed, resulting in cold, flu, and other respiratory infections.
-
Flu Relapse: Since the flu viruses and other pathogens can survive longer in low humidity, frequent flu relapse is common in these situations.
-
Skin Problems: Dry air can make the skin itchy and flaky, worsening pre-existing skin allergies.
-
Eye Problems: There may be an imbalance in the moisture levels due to the increased evaporation of tears as a result of the dry air surrounding the eyes, which can irritate the eyes and dry out the film in the eyes, causing impaired vision.
How to Maintain Humidity in the Indoor Environment?
Outside humidity cannot be altered, but humidity at home can be maintained at the optimal levels as follows:
-
Home Humidifiers: The use of home humidifiers during winter can help maintain indoor humidity levels in the optimal range of 40 to 60 %. Though home humidifiers are advantageous, improper use can result in certain health issues. If the relative humidity rises above 60 %, it can encourage the growth of molds in indoor environments. Too much mold growth can cause asthma and other respiratory problems. The water reservoirs of room humidifiers can promote the growth of harmful microbial agents like Legionella or Aspergillus, which can cause other types of infections unsuitable for immunocompromised people. It is advisable to adhere to the industry and manufacturer guidelines when using room humidifiers.
-
Proper Maintenance of Air Conditioners: High humidity at the office or home can be caused due to a poorly functioning air conditioner. Routine clean-up and maintenance are essential to make it work efficiently and effectively.
-
Houseplants: Besides adding a good look, houseplants like tropicals with large leaves can purify the air and maintain humidity by releasing vapor from the leaves, and the soil helps to withhold the water, which slowly evaporates. Other home plants that maintain humidity include philodendrons, palms, and Chinese evergreens.
-
Upgrade Doors and Windows: Inefficient doors and windows can leak out moisture and heat in the winter. This can be overcome by installing efficient and newer doors and windows.
-
Drain the Bathwater Late: Warm water in the bathtub enhances the moisture level in the atmosphere. Draining the water after it turns cool can help maintain adequate moisture levels.
-
Make Use of Shower Steam: After taking a bath in the shower, the bathroom door can be left open so that the shower steam circulates indoors. The bathroom fan should be switched off as these tend to suck the excess moisture from the atmosphere.
-
Hang the Dresses: Avoiding clothes dryers and hanging the clothes will enable the moisture from the clothes to linger inside the home for a while.
-
A Pan or Basin of Water: Keeping basins or pans of water near heating vents or on top of the radiators will slowly evaporate the water into the air. The warmth from the heating system will accelerate this process.
Conclusion:
The humidity levels in the atmosphere play a very important role in acquiring various infections. Both high and low levels of humidity can cause certain health issues. Maintaining the humidity at optimal levels is very crucial. By following certain simple measures at home, the humidity levels at home can be maintained at the needed levels. The smart way to avoid infection is to limit the encounters with infectious agents irrespective of the weather conditions.
