Bacteria
are microscopic organisms that are found in water, on solid
surfaces, and in air. Most of them are not harmful to men and play a major
role in element cycling, which is crucial in sustaining life on planet Earth.
However, there is a group of bacteria that are causative agents of many
diseases in humans (tuberculosis, typhoid fever, plague, anthrax, etc.).
Legionella pneumophyla is a bacterium that causes respiratory infection
and is often cited as an example of microbial dissemination from sources
within buildings. There are also bacteria that are not pathogenic but may
cause allergies. In our homes, they live in cooling coils and in air
ducts of air-conditioning systems. Some of them produce volatile organic
compounds (VOC) that contribute to the musty odor in homes and cars. More
research is needed to understand their effect on human health.
Molds are microorganisms that live everywhere, especially in humid and warm environments. They form filaments called hyphae, which penetrate the surface on which they grow, or form aerial mycelia that bears reproductive structures - spores. Mold spores are easily detached and made airborne by air flow, vacuuming, walking on a carpet or sitting on a couch. In indoor environments they grow in air-conditioning ducts, carpets, pots of house plants, etc. They produce and release millions of spores which are small enough to stay airborne threatening to invade the human respiratory system. There is scientific proof of a direct correlation between presence of mold spores and wheezing and asthma. The mold Strachybotris atra found in home environments on high cellulose materials has been linked to a fatal pulmonary disorder in young infants.
Even though the Dust Mites are so small that they can not be seen with the unaided eye, they are there polluting the air in your home or office. House Dust Mites live in carpets, mattresses, pillows, stuffed toys and upholstered furniture. A typical used mattress may have up to 1 million mites. They feed on human skin scales and need a moist and worm climate. Their fecal droppings are the main allergen in asthmatics. If you have pets, the likelihood that your home is contaminated with Dust Mites is even greater.
There is a group of chemicals called volatile organic chemicals (VOC) that are important indoor air pollutants. The major source of VOC in indoor air is modern building materials. With time VOC are depleted by "off gassing". Later, VOC can be reintroduced into home environment by the use of cleaning materials. Besides VOC, formaldehyde is another common indoor air chemical pollutant. Its source can be traced to the new furniture, tobacco smoke and certain insulation foams. VOC and formaldehyde cause eye, throat and skin irritation, headache, nausea, vomiting and coughing.