In light of the growing concern about mold contamination and health issues, safety professionals should be prepared to deal with these issues. This information has been written for Caltex dealers with the basic understanding they will need to answer those questions. However, please note that the information in this article is a simplification and compilation of information from several sources, meant to give a general overview of mold hazards and how to deal with them. The remediation industry is currently in a state of flux, and there are few true guidelines published. We have attempted to cull the best of the industry’s current standards in this article, but they may be subject to change as a consensus emerges.

Mold Facts

• Invisible - 4-80 microns
• Fungi : the correct term for molds, mildew, mushrooms, yeast, rusts, and smuts
• Fungi is everywhere in our environment
• Most types require free water to begin colonization
• Requires an external food source
• Releases spores for reproduction
• Cell fragments, spores, and cell by-products may be allergenic, infectious, and toxigenic
• Estimated 100,000+ species, but currently only about 100 species are identified as pathogenic to humans

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Primary Requirements For Mold Growth

• Moisture
• Nutrient source
• Proper Temperature
• "Starter" Spore or Colony
• Time

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Basic Informaiton

In the common vernacular the terms mold and fungus are often used interchangeably. However, in the scientific community molds are just one of the categories of non-green plant-like organisms (along with mildew, mushrooms, yeast, rusts, and smuts) that fall under the heading of fungus. Since molds make up the largest component of the fungal classification with over 60,000 identified species, the two terms often are interchanged indiscriminately. Regardless of the type of fungal matter, they all share the characteristics of being able to grow without the benefit of sunlight. This means that the only things necessary for fungus to proliferate are a viable seed (known as a spore), a nutrient source, moisture, and the right temperature. This explains why fungal infestation is often found in damp, dark, and hidden spaces. Light and air circulation have a tendency to dry things out, making the area inhospitable for the fungus.

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FUNGI

Fungi may be while, grey, red, yellow, black, brown, or greenish and have cells bound by rigid walls usually formed of chitin and glucans, which are tough proteins. Fungi may be single-celled or multicellular. Yeasts are single-celled fungi that reproduce by budding. Multicellular fungi, such as mushrooms, mold and mildew, are formed of microscopic, branched filaments called hyphae. Groups of hyphae form one or more colonies can form a visible mass called a mycelium. Fungi also produce large numbers of spores on their hypahe. Spores are small, light particles capable of producing a mature fungus. Most of the fungi found growing indoors are commonly called molds.

Fungi have complex lifecycles that may include both sexual and asexual stages. Spores can be produced by meiosis during the sexual stage, resulting in unique spores that have half as much genetic material as the parent cells. Spores can also be formed asexually by mitosis, simple cell division. Asexual spores are called sporangiospores if they are formed internally or conidia if they are produced externally.

Fungi can grow in many habitats, under wide variety of environmental conditions. However, there are two basic requirements for all mold growth.

1. Moisture

   The first requirement for fungal growth is moisture. Fungi need a moisture source to begin growth, and at least some moisture to continue growing. Fungi require moisture to process nutrients, The moisture to sustain growth can cone from high relative humidity for some species of fungi, such as Cladosporium, while others, such as Stachybotrys, require actual water (known as "free water").

2. External Food Source

   The second requirement of mold growth is an external food source. These sources can range from simple sugars and starches to complex carbon-containing substances. Indoors, these sources include wallpaper paste, cellulose from paper and fabrics, animal skin, and wood. Fungi release enzymes to digest these substances into glucose, which is then absorbed. This process requires a source of water, nitrogen, and numerous elements. If these basic requirements are present, as they are in many instances of water damage, fungi can grow in a wide variety of climates.

Most fungi are saprobic, meaning they live on non-living organic material. These fungi are a major factor in decomposition. A few fungi are dedicated parasites, and require a living host to survive. Some other fungi can become parasitic, but only under unusual circumstances, such as when the host is weakened by illness. A small number of fungi are symbiotic, living in partnership with another organism. These include lichens and fungi that grow around tree roots.

Fungi can spread in two ways. A good analogy for these two methods of growth is dandelions will grow there, just as mold will grow in a house if conditions are right. Dandelions can grow locally by physically expanding and growing larger, or they can spread further by producing seeds that are carried by the wind.

Many species of fungi act like the dandelion. Once they gain a foothold, they can spread rapidly across a surface as long as there is sufficient moisture. This is similar to the dandelion increasing in size across the base. If the moisture source becomes insufficient, many mold species will enter sporation phase, where they produce and release huge numbers of spores into the air. It has been estimated that a single colony of Penicllium 2.5 centimeters in diameter could contain as many as 400,000,000 microscopic spores. These spores are the equivalent of the seeds produced by the dandelion in the analogy.

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Common Types of Fungi

While there are thousands of types of fungal spores, some are more common than others, especially in certain environments. Some of the most common spores are Cladosporium, ascospores, basidiospores, and Alternaria.

Cladosporium

Cladosporium is the most prevalent mold in the Midwestern section of the United States. The dark mold that can be found growing on the seal of refrigerator doors is often Cladosporium. Cladosporium grows in so many areas because it does not need much moisture and can grow on a wide variety of materials, It is a mold commonly associated with hay fever and asthma.

Ascospores

Ascospores are also a very common type of mold. There are many different species of ascospores, and they are found both outdoors and inside. They are generally not toxic, but can cause allergies if the exposure concentration is high enough.

Basidiospores

Basidiospores are another broad category of spsores.They are nearly as common as ascospores, and are also found both outside and in. Basidiospores are generally not toxic, but, like ascospores, they can cause allergies.

Alternaria

The fourth common type of mold is Alternaria. Alternaria is the most common mold found in bathrooms, where it grows around the edges of showers and toilets. It is also found in dust and on window frames. Alternaria is generally not toxic, but can cause allergies in some people.

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Molds caused by water damage

The molds that are found in houses with water damage can be different from the normal molds mentioned above. Molds often found in water-damaged buildings include Asperiguillus, Penicillium, Stachybotrys, and Fusarium. These molds require higher levels of moisture than the common indoor and outdoor molds, and they are linked to much more severe health effects.

Asperigllus and Penicillium

Asperigllus and Penicilliumare the more common molds found in water-damaged buildings. They are similar in configuration and spore size and often appear together in samples. Asperigllus and Penicillium grow quickly on water-damaged materials such as wallboard and carpeting. Often within 48 to 72 hours after the first water intrusion. Some species of Asperigllus and Penicillium can produce toxins, including aflatoxin, which is an extremely potent carcinogen. Nearly all species are highly allergenic to humans.

Stachybotrys

Stachybotrys is the most well known of the toxic molds, and, as such, it requires somewhat more detail than the other toxic molds discussed here. For this reason, a more detailed article on Stachybotrys is included at the end of this Topic.

Fusarium

Fusarium is another mold that is found in some water-damaged buildings. Like Stachybotrys, it requires high levels of moisture, so it is often found in humidifiers and other areas of standing water. Also like Stachybotrys, Fusarium produces potent mycotoxins. Fusarium mycotoxins particularly affect the nervous system, causing headaches, memory loss, coma, and death.

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The Prevalence of Fungus and Risk Assessment

Many forms of fungus can be found throughout the natural world. People from the earliest of times have recognized not only the presence of fungus but have learned to distinguish between beneficial forms and harmful forms of these materials. The ancient Egyptians understood that the fungus called yeast was necessary if bread was to rise or beer and wine were to ferment. Many Asian nations have used dried black or green fungus for thousands of years as a seasoning for soups and sauces. There are types of mushrooms and truffles that have been known as delicacies since before the golden age of Greece. Blue cheese receives its characteristic marbling and taste from a mold. In the modern era, a common bread mold was manipulated to create the first class of disease-fighting antibiotics.

However, just as mankind learned early on how to identify the good fungi, the bad ones were known as well. The book of Leviticus in the Bible contains some of the earliest known instructions for the proper procedures to deal with mold growth on interior surfaces. Ancient Roman texts document the dangers of eating moldy grain. The great potato famine of 1845-1847 was a result of a fungus called "Late Blight" and led to an estimated 750,000 deaths. A more recent occurrence of serious fungal destruction was the death of thousands of people in the former Soviet Union in the 1940s due to their ingestion of grain that was contaminated with the mold Stachybotrys atra. This is the same mold that some doctors link to the death of infants in Cleveland, Ohio, and around the country. Stachybotrys can produce serious injury after ingestion or inhalation through internal poisoning which causes hemosiderosis, bleeding in the lungs.

Since mold, mushrooms and yeast can be beneficial or harmful it becomes crucial to have some understanding of the conditions that would result in a hazard due to a fungal contamination. In other words, if there’s a little bit of black mold in the corner of the shower stall, is it serious enough that people should run screaming from the building? What about a thick patch that covers half of a two foot by four foot ceiling tile and has gray spidery tentacles beginning to creep out of a black mass? Does it make a difference if these situations are in the crawlspace? The crawlspace of a factory versus the crawlspace of a school? Is the musty/mildew odor an indication of significant levels of contamination? What if you cannot find a visible source for the smell? While each situation of potential mold exposure has to be evaluated individually, there are several important items to consider in every case.

All visible interior sources of mold, or the characteristic musty/mold odors, should be investigated carefully. A small amount of visible mold or transient odors can often signal greater infestation that is hidden above ceiling tiles, below carpet, inside HVAC systems or between wall components. Such visible mold also is a sure sign of a moisture source. The investigation/hazard assessment should identify possible causes of structural or plumbing leaks, or reasons for elevated humidity levels (i.e., inadequate air conditioning capacity, spraying, mixing or cooking processes, unvented shower rooms, etc.).

The location of fungal contamination has a great impact on a mold risk assessment. The most significant problems are cases where mold is in an air stream. Therefore, any mold contamination of an HVAC system, particularly the supply ductwork, needs to be addressed promptly. Mold in or near occupied spaces is the next priority. Even mold in less frequently entered areas, such as basements, crawlspaces, attics or service rooms, should be addressed as doors, floors, and walls usually do not create airtight barriers necessary to contain the microscopic spores.

The amount of mold also factors into a mold risk assessment. While any mold should be cleaned up, larger quantities may require the use of safety equipment to protect the workers and engineering controls to protect the building occupants. Many organizations suggest that patches of mold smaller than 2-3 square feet can be cleaned with minimal precautions (NYCDH Section 3.3). Contamination up to 30 square feet requires personal protective equipment and controlled activities (OSHA 6-9). Mold infestation greater than 30 square feet normally demands site specific engineering controls such as dust partitions, air filtering devices, special cleaners.

Although controversial, many mold remediation specialists treat certain species differently. Because of their ability to produce mycotoxins, molds such as Stachybotrys and Fusarium many times are approached from a more conservative standpoint—including the use of negative pressure enclosures for their removal.