What are molds?
Molds are microscopic fungi that live on plant or animal matter. No one knows how many species of fungi exist but estimates range from tens of thousands to perhaps three hundred thousand or more. Most are filamentous organisms and the production of spores is characteristic of fungi in general. These spores can be air-, water-, or insect-borne.
How do molds affect people?
Some people are sensitive to molds. For these people, exposure to molds can cause symptoms such as nasal stuffiness, eye irritation, or wheezing. Some people, such as those with serious allergies to molds, may have more severe reactions. Severe reactions may occur among workers exposed to large amounts of molds in occupational settings, such as farmers working around moldy hay. Severe reactions may include fever and shortness of breath. People with chronic illnesses, such as obstructive lung disease, may develop mold infections in their lungs.
Where are molds found?
Molds are found in virtually every environment and can be detected, both indoors and outdoors, year-round. Mold growth is encouraged by warm and humid conditions. Outdoors they can be found in shady, damp areas or places where leaves or other vegetation is decomposing. Indoors they can be found where humidity levels are high, such as basements or showers.
Bacteria and Viruses
Airborne bacteria (and viruses) are a common source of respiratory infection and a particular threat to infants, the elderly and those with compromised immune or cardiovascular systems, including people with allergies, asthma, AIDS and heart disease. Some serious infectious diseases are spread through airborne bacteria or viruses, including whooping cough, meningitis and anthrax.
How large are the bacteria and viruses that threaten human health? According to the Pennsylvania State University Department of Aerobiological Engineering airborne pathogens database, health-threatening bacteria and viruses range in size from .018 micron to as large as 1.325 microns.
Airborne pathogens larger than .1 micron include:
- Chickenpox virus (Varicella zoster) at .12 to .2 micron
- Smallpox virus (Poxvirus variola) at .14 to .3 micron
- Whooping cough bacteria (Bordetella pertussis) at .2 to .3 micron
- Pneumonia bacteria (Mycoplasma pneumoniae) at .2 to .3 micron
- Bronchitis bacteria (Chlamydia pneumoniae) at .2 to .4 micron
- Meningitis bacteria (Haemophilus influenza) at .2 to .3 micron
- Tuberculosis bacteria (Mycobacterium tuberculosis) at .2 to .6 micron
- Diphtheria bacteria (Corynebacteria diphtheria) at .3 to .8 micron
- Scarlet fever bacteria (Streptococcus pyogenes) at .6 to 1.0 micron
- Otitis media bacteria (Streptococcus pneumonia) at .8 to 1.0 micron
- Anthrax bacteria (Bacillus anthracis) at 1.0 to 1.25 microns
When it comes to filtration, bacteria and viruses have not been proven to behave in exactly the same way as non-living particles. Some pathogens can move on their own, and some have slimy coatings that may affect a filter's ability to capture them. Furthermore, home air cleaners may not always be used under ideal conditions (24 hours per day, in a sealed room appropriate to the unit's tested air volume capacity). All of these variables may affect any system's ability to filter bacteria and viruses.
Some examples of virus inactivation through heat
Numerous studies have been conducted on the inactivation of viruses through heat application. For instance, the HIV virus in the blood will die when exposed to 170°F for only 0.006 seconds. In another study, "parvovirus" and "phage phiX174" were completely inactivated when exposed to 266°F for 90 seconds. In the case of herpes viruses, elevated temperatures inhibit the release of proteins necessary for a successful infection.
Airborne viruses are no different. A study of respiratory syncytial virus (the main cause of wheezing in children less than 2 years old) showed that when the virus is exposed to 149°F for 45 minutes, its infection capacity is decreased, and the conformational proteins are transformed, reducing the activity of substances responsible for inflammation, hypersensitivity and airway damage.
The SARS virus (causative agent of Severe Acute Respiratory Syndrome) has thermosensitive (heat-sensitive) proteins in its envelope, which can be fully denatured at 131°F, the same temperature at which the SARS virus was proven to be inactivated. Similarly, the proteins that are essential for the transmission of infectious influenza viruses are sensitive to variations in pH and temperatures between 131°F and 158°F.
Dust mites are microscopic insects and one of our health's largest enemies. They cause over 70% of all respiratory allergies. Unlike pollens that provoke allergies during spring, dust mite allergies can be felt all year long. In cold weather, dust mite allergies are intensified because people spend more time indoors. Dust mites bite generally at night and can cause skin rashes mainly in children.
Studies performed by the University of Virginia show that children exposed to dust mites in their early ages have more chances to develop asthma.
Asthma is the third major cause of hospitalization in children under 15. Underestimating the severity of an acute attack poses the greatest threat to children with asthma. Unfortunately, one study of children found that nearly 40% of them were unaware of asthmatic symptoms when they occurred. Asthma is especially serious in children, particularly those younger than five because their airways are very narrow. These immature airways have less reserve for air exchange and don't respond as well as adults to bronchodilators (drugs that open the airways). Sadly, the hospitalization and fatality rates among children and young adults with asthma are on the rise.