Several molds that grow both indoors and outdoors, produce spores. Mold spores have been likened to the seeds of a dandelion, but they are microscopic in size. Because of their size, mold spores cannot be seen with the human eye save with the aid of a microscope. Mold spores occur in various colors and shapes, such as round, spheroid, banana-shaped or tadpole-shaped. They can occur in enormous quantities depending on the type of mold producing them, and at all times of the year where the environmental conditions allow.
Mold spores are well known for their ability to cause sensitization and allergic responses. Exposure to airborne mold remains the biggest concern when looking at molds and their affects on human health. Mold spores and other fungal structures (e.g. hyphae) contain allergens. These allergens cause mold allergy to sensitive individuals and may also exacerbate asthma. Whether or not the spores are alive, the allergens in and on them may remain allergenic for years.
There is no definite seasonal pattern to mold spores in indoor indoor environments. Growth of mold indoors is determined by the presence/absence of moisture. However outdoor molds are seasonal, first appearing in early spring and thriving throughout summer until fall. Outdoor spore concentration also influences indoor spore concentration as outdoor spores generally infiltrates indoors.
Mold spores are much smaller than pollen grains and easily bypass the normal filtering function of the nose. Inhalation of mold spores into the lung is a common cause of asthma attacks in people who are allergic to molds.
Sources of mold spores
Mold spores come from soil and decaying vegetation, and are everywhere in nature. In houses with evaporative cooling and old carpets, mold can be a problem. Growth of mold in houses increases after a plumbing, roof leak or chronic condensation. Many types of molds are found in soil and house dust.