Allergens are everywhere. Sneezing is not always the symptom of a cold! Sometimes, it is an allergic reaction to something in the air. Health experts estimate that 35 million Americans suffer from upper respiratory tract symptoms that are allergic reactions to airborne allergens. Pollen allergy, commonly called hay fever, is one of the most common chronic diseases in the United States. Worldwide, airborne allergens cause the most problems for people with allergies. And respiratory symptoms of asthma, which affect approximately 11 million Americans, are often provoked by airborne allergens. (National Institute of Allergy and Infectious Diseases 2003).
Allergens are everywhere, Sneezing, Indoor Air Quality
Allergens are everywhere! Except in the most restrictive of environments (e.g., an environmentally controlled, filtered bubble enclosure), allergens are everywhere, and the most commonly recognized allergens are pollen grains and fungal spores. Pollen grains are the male reproductive cells that are dispersed by plants to fertilize the female flower of the species. In 2017, 8.2 percent of adults (over the age of 18) and 8.4 percent of children (under the age of 18) in the United States were diagnosed with “hay fever” due to airborne pollen (Centers for Disease Control and Prevention 2017). Pollen is typically an outdoor allergen but may affect the indoor air when captured and retained within a building HVAC (heating, ventilation, and air conditioning) system.
Fungal spores, as presented herein, include all forms of fungal spores (e.g., mold spores, mushroom basidiospores, and slime molds). Spores are reported to affect more than 20 percent of the U.S. population a number that is purely speculative. The actual number is unknown! Pollen grains and spores must be airborne in order to cause respiratory allergy symptoms, and the total exposures will affect people differently. The higher the exposures, the greater is the number of people affected. Their impact is irrespective of viability, their ability to grow. Nonviable molds may cause allergy symptoms as well as the viable molds they merely stop reproducing and growing. All molds dead or alive are allergens!
The size, shape, and density of the airborne allergens affect their aerodynamic properties, while air humidity, wind direction, wind velocity, and obstructions affect their travel path as well as their travel distance. Temperature, soil types, and altitude may also impact the quantity of airborne allergens. The size of fungal spores ranges from 1 to more than 500 microns in diameter/length, but those that are typically airborne range in size from 1 to 60 microns.
The Cladosporium mold spores typically range between 4 and 20 microns in length. Alternaria spores are around 30 microns in length (ranging from 8 to 500 microns), and Aspergillus/Penicillium spores are around 1 micron in diameter. It should be noted that some spore-producing bacteria are also on the order of 1 micron in size and may appear microscopically to be mold spores and cannot be differentiated without growing the spores in nutrient agar. for differentiation between two molds of similar spore size and shape.
Pollen grains are typically denser and, on average, larger in size than the fungal spores. They range from 14 microns (for stinging nettle) to more than 100 microns in diameter. Tree and weed pollen are more variable. Most, however, fall between 20 and 60 microns. Red cedar and western ragweed pollen are on the low end, around 20 to 30 microns. Scots pine and Carolina hemlock are between 55 and 80 microns. Cedar pollen is around 30 microns in diameter. Giant ragweed pollen grains are around 18 microns in diameter, and noble fir pollen is around 140 microns.
Plant pollen is generally more complicated in design than are the spores. They tend to be spherical or elliptical with surface structures and/or pores, and the interior portions typically have a recognizable arrangement. They may be lobed with a smooth surface or spherical with spicules.
Spore-Producing Fungi and Bacteria Both fungi and fungi-like bacteria produce allergenic spores. Although the most commonly encountered spores in indoor air quality are mold spores, other fungal spores and bacterial spores can and frequently do contribute to the total airborne spore count. Fungi Fungi, numbering more than 100,000 different species, are neither plant nor animal. Lacking in chlorophyll (plant-like) and typically not motile (an animal characteristic), they belong to a kingdom of their own. T
The fungi kingdom consists of molds, yeasts, mushrooms, rusts, smuts, slime holds, and yeasts. Whereas yeasts are single-celled organisms, molds grow into long, tangled strands of cells that multiply, forming visible colonies of varying size, shape, texture, and diameter. Some fungi form complex fruiting bodies that are composed of tightly compacted masses of mold-like filaments and are clearly visible to the naked eye (e.g., mushrooms).
Mold spores are the most commonly referred to fungi. Their cell wall and protective spore surface are composed of polysaccharides (e.g., cellulose) and glucose units containing amino acids (e.g., chitin). The cellulose component is plant-like, and the chitin component is animal-like. It is the outer protective surface of the mold, spores, and growth structures that is thought to be that which elicits an allergic reaction.
For this reason, spores are generally implicated in most allergic conditions; however, sections of the growth structures can be allergenic as well. Mold reproduction involves the release of thousands of allergenic spores, each having the ability to reproduce long, thread-like hyphae that continue to branch and form mycelia. The mycelium, in turn, attaches to a nutrient substrate and grows. As long as the mycelia have nutrients and room to grow, a single mycelium may theoretically expand to a diameter of 50 feet.