Mold spore trapping and respiratory disease exposure

¶ … Mold Spore Trapping

Current Scientific Knowledge

People are exposed to aeroallergens in a variety of settings, both at home and at work. Fungi are ubiquitous airborne allergens and are important causes of human diseases, especially in the upper and lower respiratory tracts. These diseases occur in persons of various ages.

Airborne spores and other fungi particles are ubiquitous in nonpolar landscapes, especially amongst field crops, and often form the bulk of suspended biogenic debris. The term mold often is used synonymously with the term fungi. A more precise definition would specify that molds lack macroscopic reproductive structures but may produce visible colonies. Respiratory illness in subjects exposed to rust and dark-spored imperfecti fungi was described more than 60 years ago, and physicians worldwide now recognize a sensitization to diverse fungi.

Since fungus particles commonly are derived from wholly microscopic sources, exposure hazards are assessed largely through direct sampling of a suspect atmosphere. Because of their small size, fungal emanations present special collection requirements to ensure particle viability for culture-based studies.

Fungi have two basic structures. Yeast grows as single cells by central division of eccentric budding to form daughter units. Most other familiar fungi are composed of branching threads, 3-10 mcm in width, termed hyphae. A mycelium is an aggregate of hyphae. Hyphae are modified to bear the simple reproductive parts of many microfungi and form the structural tissue of fleshy fungi (eg, mushrooms, puff balls).

In general, familiar allergenic molds reproduce asexually. However, two large and distinctive classes, Ascomycetes and Basidiomycetes, also produce innumerable sexual spores for atmospheric dispersion. In its life cycle, a single fungus organism produces both sexual and asexual spores from morphologically different structures, respectively termed perfect and imperfect stages.

Statistics of Occurrence

There are 35 million persons with sinus problems and 15 million persons with asthma reported in the United States alone. Clinically, physicians know that a sinus infection can contribute significantly to the frequency and severity of asthma attacks.

Toxicity of Mold and Physiology of Affectation

The physiology of mucus in individuals with asthma is similar to that of nasal mucus. Mucociliary clearance (MCC) involves cilia and the layers of mucus on the ciliated epithelium and refers to the movement of particles along a desired path for maximum health. In the upper respiratory tract, cilia propel the mucus and its trapped bacteria and particles to the nasopharynx, where it drops to the hypopharynx and is swallowed. The stomach acid then disposes of the unwanted invaders.

In the lower respiratory tract, the cilia that line the trachea and bronchial tree similarly move the mucus blanket up the trachea and into the hypopharynx for swallowing.

The science of rheology investigates the makeup of this liquid and studies its viscosity and elasticity. Two layers of mucus are present over the ciliated cell; an outer, thick, viscoelastic, semisolid mucus layer, which the cilia do not strike directly, is found over a layer of watery serous fluid. Due to the lowered viscosity of the layer of watery serous fluid, the cilia are able to beat normally and to move the watery lower layer, thereby, affecting movement of the upper thick layer. Changes in these properties affect movement of the mucus blanket and play a major role in pulmonary and sinus disease. If the movement of the blanket is slowed, bacteria are able to multiply as the mucus thickens and stagnates.

Mold Infectious Processes

Fungal exposure can also come from a volatile compound (VOC) that a fungi or mold creates through primary or secondary metabolism that then becomes airborne. Note that primary metabolic processes are those necessary to sustain the life of an organism. These volatile compounds may be constantly created as the fungus consumes its food source during the primary metabolic process. VOCs can irritate the mucous membranes of the eyes and respiratory system.

Fungi that consume certain organic sources can release highly toxic gases. For example, a fungus that grows on wallpaper often releases toxic gas arsine directly from the wallpaper that contains arsenic pigments. Thus, fungi and molds can release dangerous materials when they break down the host material. This can cause mucous membrane irritation in sensitized individuals.

Research is demonstrating that fungal-volatile compounds may impact the "common chemical sense" which senses pungency and responds to it. This sense is primarily associated with the trigeminal nerve. The sensory and motor nerves respond to pungency by trying to hold the breath, discomfort, or through sensations such as itching, burning, and skin crawling. Changes in sensation, swelling of mucous membranes, constriction of the respiratory smooth muscle, or dilation of surface blood vessels may be part of fight or flight reactions in response to trigeminal nerve stimulation.

Reactions often include a reduced attention level, general disorientation, lowered reflex time, dizziness, headache, burning sensation in the mucosa, and so on.

Volatile compounds found in or around homes can be responsible for mucous membrane irritants. It is now believed that fungi can add to the already existing compounds when breaking down certain organic substances. A mold-contaminated building may have a significant contribution from fungal contaminants that are added to common VOCs (e.g., building materials, paints, plastics, and cleaning chemicals).

VOCs in general can result in symptoms that include lowered attention span, headaches, lack of concentration, and dizziness.

Reaction to Mold Odors

Some individuals have very strong reactions to the smells given off by molds. Among humans, there is a high degree of variation in ability to detect these odors. Certain individuals can detect low levels of VOCs, while others can only detect relatively high levels. Those individuals who are particularly susceptible to mold odors may react with headache, nasal stuffiness, nausea, or even vomiting.

Asthmatics often exhibit extreme symptoms when exposed to certain mold-induced odors.

Toxicities

Molds also produce secondary metabolites such as antibiotics and poisonous substances produced by a fungus known as mycotoxins. Sometimes it is possible to isolate antibiotics from the molds themselves in order to utilize some of their properties in fighting infections.

Secondary metabolisms are not necessary for maintaining the existence of a mold - either by creating energy or synthesizing structural components, informational molecules, or enzymes. They do, however, function to provide molds with advantages over other mold and bacteria and are toxic to certain plant and human cells.

Toxic conditions exist when a human is exposured to these mycotoxins - either through ingesting mycotoxin-containing mold spores or with skin contact to toxic mold itself.

Mycotoxins are nearly all cytotoxic (substances produced by microorganisms that are toxic to individual cells), which disrupt various cellular structures such as membranes, and interrupt important processes, including protein, RNA, and DNA synthesis.

Mycotoxins vary in the danger they pose for humans. Mycotoxins pose a threat to larger organisms, not because they are specifically targeting them, but rather because these large organisms inadvertently come across the byproduct of the competing molds all battling for the same ecological niche.

Numerous mold types produce mycotoxins, including some found indoors in contaminated homes and office buildings. Another factor that determines the mycotoxins that are produced by specific molds usually depends on the materials or organisms that they grow on.

It used to be thought that dangerous molds were primarily contaminants in foods. This notion is quickly changing. Recently, researchers have become more concerned with multiple mycotoxins that develop from many types of mold spores growing in moist indoor environments.

Health effects from exposures to such mold mixtures can differ from those related to single mycotoxins in controlled laboratory exposures. Although it is difficult to predict how exposure to multiple toxigenic molds can affect an individual - a synergetic effect can occur - the following table provides possible poor health effects from mycotoxin exposure to multiple molds indoors.

Problems with:

Results in:

Vascular System

Increased vascular fragility, the possibility of hemorrhaging into body tissues.

Possible molds include: aflatoxin, satratoxin, and roridins

Digestive System

Diarrhea, vomiting, intestinal hemorrhaging, liver necrosis, liver fibrosis

Aflatotoxin produces damage to mucous membranes

Respiratory System

Respiratory distress, hemorrhaging from the lungs and surrounding lung tissues

Cutaneous System

Rash, burning sensations, sloughing of skin

Urinary System

Painful and burning urination, increase in infections of the urethra, bladder, and kidneys

Reproductive System

Infertility and changes in the reproductive cycles, menses, and sperm motility

Immune System

Many mycotoxins can produce changes or weakenings of the immune system and can shorten the life span of those with compromised immunity systems (i.e, HIV / AIDS).

Table 1.1. Mycotoxins and their effects on human physiology

Unfortunately, not all types or species of molds have been tested for the presence of mycotoxins. The production of toxins varies according to the type of mold, the substrate on which it grows, and seasons of the year.

National Allergy Bureau

This agency considers mold counts in the air 0-900 as low, 2500 as moderate, 25,000 as high, and above 25,000 as very high. At "high" levels most individuals with any sensitivity will experience symptoms. Acceptable levels for individual species vary since species toxicity varies widely as does spore size, weight, and other features, which affect risk to building occupants.

Allergies are probably the most common reaction to contact with molds. Atopic individuals (i.e., those experiencing allergic reactions that are hereditary) who are exposed to mold, mold spores, or mold byproducts may manifest allergic reactions once they become sensitized to the particular strain of toxic mold.

The reactions can run the spectrum, from very mild and temporary reactions to acute, chronic, and end-system illness.

According to The Institute of Medicine:

in 5 Americans suffer from allergic rhinitis - the most common chronic disease in human beings in 9 Americans suffer from allergen-related sinusitis in 10 Americans have allergen-related asthma in 11 Americans suffer from allergic dermatitis

Approximately 1 in 100 Americans suffer from serious chronic allergic diseases

Nonimmune Enzyme Detoxification

Nonimmune triggering of the vessel wall may occur. Complement may be triggered directly through the alternate pathway by molds, foods, or toxic chemicals. Mediators such as kinins and prostaglandins may also be directly triggered. These reactions then cause vascular spasm with resultant hypoxic release of lysozyme, which further accelerates the cycle with more spasm and hypoxia. Eventually, if left untreated and exposed to the triggering pathogen, end-organ failure will occur.

Triggering of the enzyme detoxification systems also may occur in any organ but more frequently in the liver and respiratory mucosa.

Diagnosis

Controversy still exists regarding the exact criteria for diagnosis and the exact regimen for treatment. Although not perfected, recent evidence supports the theory that AFS (allergic fungal sinusitis) represents an immunologic, rather than infectious, disease process. An improved understanding of this underlying disease process has lead to an evolution in the treatment of AFS and other mold-related problems.

Medical therapy has begun to shift from an emphasis on systemic antifungal therapy to various forms of topical treatment and immunomodulation. Likewise, surgical treatment of AFS, still a crucial component of the overall treatment plan of the patient, has shifted from radical to a more conservative but complete, usually endoscopic, approach.

Although important, surgery alone does not lead to a long-term disease-free state. A comprehensive management plan incorporating medical, surgical, and immunological care remains the most likely means of providing long-term disease control for AFS. The exact combination continues to be strongly debated.

Treatment

Injection therapy for inhalants such as toxic molds may help alleviate a chemically-induced hypersensitivity. These can be done daily, but usually are given every four to seven days. Vitamin and mineral supplementation is often necessary to replace any deficiencies occurring from direct toxic damage, an increased metabolism required for detoxification, or competition with direct absorption.

Toxologic Mechanisms

There are many potential sources for unwanted moisture in buildings. For example, improperly maintained air conditioning systems that create excessive condensation can be a breeding ground and distribution mechanism for mold particles possibly from rubbing against the spores themselves. Skin is generally a good barrier against particles. Since mycotoxins stay with the particles, the skin is not a significant route of exposure for mycotoxins.

Mold growth may be found in walls, ceilings and floor cavities when standing water is produced in a building or gets in and stays for more than a few days. Sources for water to support molds and other fungi in homes include plumbing leaks, gaps in roofs, siding or masonry, poorly sealed windows, porous slabs and foundations, inadequate drainage, and faulty roof drains and downspouts.

Poor ventilation and/or air circulation combined with high indoor humidity from showers, cooking or other activities can result in condensation that promotes mold growth on cooler surfaces. Poorly insulated walls may also provide a surface for condensation and mold growth in buildings that do not have general humidity problems.

Surface moisture on unseasoned framing lumber, appearing as the wood dries, may create conditions for mold growth. Note: once the moisture content of the wood falls below 20%, mold growth can no longer be supported. Depending on the climate, framing lumber will dry to below 20% moisture content during the construction and before the building is enclosed.

In instances where wood is chronically exposed to water, wood decay fungi can invade. Decay fungi can penetrate more deeply and attack the structural polymers in the fiber, reducing the strength of the wood.

Other conditions can increase the amount of mold spores in the indoor air of buildings. Homes with exposed-dirt crawl spaces and basements tend to have more airborne mold spores than homes without. With the right humidity conditions, some molds can grow on house dust.

It is not surprising, then, that poor housekeeping and high indoor humidity are both associated with increased levels of airborne mold spores.

The biggest source of indoor mold spores is often the outdoor air. Higher levels of indoor mold spores tend to be found in homes with yards having dense and overgrown landscaping.

Indoor mold levels are generally lower in buildings with forced-air heating systems (as opposed to window ventilation) and lower still when these systems include a well-maintained and properly functioning air conditioning system.

Mold spore levels outdoors vary with the season and weather. They may be very high in the growing season or approach zero when snow covers the ground. Except for the snow-cover conditions, mold spores in normal indoor environments are usually between 20-50% of the outdoor levels.

Summary

Molds play an important role in nature by breaking down organic materials. We routinely encounter mold spores as part of everyday life, in both outdoor and indoor environments. In most cases, the body's immune and respiratory systems normally provide defense mechanisms that protect it from health effects of regular exposure to molds. Inhalation of molds can result in a wide range of health effects in some circumstances. Infections are possible in immunecompromised people. Allergic responses to molds include hay fever and asthma, and many people with allergies are also allergic to mold. The amount of mold that must be inhaled to cause an allergic response is unknown. Toxic effects from inhalation of mold may occur in situations where there is prolonged exposure to exceedingly high airborne mold concentrations, such as in an agricultural setting.

Many molds co-exist with humans without measurable problems in respiratory, systemic, or other systemic reaction. Those molds that do affect the human respiratory and other bodily systems can be the source for chronic, deleterious, even deadly diseases.

The awareness and subsequent addressing, testing, treatment, management, and research of toxic molds (e.g., Stachybotrys chartarum, Aspergillus versicolor, tricothecene toxicosis, Stachybotrys atra, and so on) continues and with the eminent experts in the field of autoimmunology, allergens, and others, the broad array of mold-based toxins will be catalogued, diagnosed, and treatable in the near future.