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Mold (American English) or mould (British English), also sometimes referred to as mildew, is a fungal growth that develops on wet materials. Mold is a natural part of the environment and plays an important part in nature by breaking down dead organic matter such as fallen leaves and dead trees; indoors, mold growth should be avoided. Mold reproduce by means of tiny spores. The spores are like seeds, but invisible to the naked eye, that float through the air and deposit on surfaces. When the temperature, moisture, and available nutrient conditions are correct, the spores can form into new mold colonies where they are deposited.There are many types of mold, but all require moisture and a food source for growth.
Mold are ubiquitous, and mold spores are a common component of household and workplace dust. In large amounts they can be a health hazard to humans, potentially causing allergic reactions and respiratory problems.
Some mold produce mycotoxins, chemical components of their cells walls, that can pose serious health risks to humans and animals. "Toxic mold" refers to mold which produce mycotoxins, such as Stachybotrys chartarum .Exposure to high levels of mycotoxins can lead to neurological problems and death. Prolonged exposure (for example, daily exposure) can be particularly harmful. Mycotoxins can persist in the indoor environment even after death of the fungi. They can adhere to dust particles and can spread through the air attached to these dust particles or spores. There must be very specific temperature and humidity conditions in order for fungi to produce mycotoxins.
Symptoms of mold exposure may include nasal and sinus congestion; runny nose, eye irritation; itchy, red, watery eyes, respiratory problems, such as wheezing and difficulty breathing, chest tightness, cough, throat irritation, skin irritation (such as a rash), headache, and persistent sneezing.Immune-compromised people and people with chronic lung illnesses, such as obstructive lung disease, may get serious infections in their lungs when they are exposed to mold. These people should stay away from areas that are likely to have mold, such as compost piles, cut grass, and wooded areas.
Infants may develop respiratory symptoms as a result of exposure to Penicillium , a fungal genus. Signs of mold-related respiratory problems in an infant include a persistent cough or wheeze. Increased exposure increases the probability of developing respiratory symptoms during the first year of life. Studies have indicated a correlation between the probability of developing asthma and exposure to Penicillium.
Mold exposure has a variety of health effects, and sensitivity to mold varies. Exposure to mold may cause throat irritation, nasal stuffiness, eye irritation, cough and wheezing and skin irritation in some cases. Exposure to mold may heighten sensitivity, depending on the time and nature of exposure. People with chronic lung diseases are at higher risk for mold allergies, and will experience more severe reactions when exposed to mold. Damp indoor environments correlate with upper-respiratory-tract symptoms, such as coughing and wheezing in people with asthma.
Mold is found everywhere and can grow on almost any substance when moisture is present. They reproduce by spores, which are carried by air currents. When spores land on a moist surface suitable for life, they begin to grow. Mold is normally found indoors at levels which do not affect most healthy individuals.
Because common building materials are capable of sustaining mold growth and mold spores are ubiquitous, mold growth in an indoor environment is typically related to water or moisture exposure and may be caused by incomplete drying of flooring materials (such as concrete). Flooding, leaky roofs, building-maintenance or indoor-plumbing problems can lead to interior mold growth. Water vapor commonly condenses on surfaces cooler than the moisture-laden air, enabling mold to flourish.This moisture vapor passes through walls and ceilings, typically condensing during the winter in climates with a long heating season. Floors over crawl spaces and basements, without vapor barriers or with dirt floors, are mold-prone. The "doormat test" detects moisture from concrete slabs without a sub-slab vapor barrier. Some materials, such as polished concrete, do not support mold growth.
Significant mold growth requires moisture and food sources and a substrate capable of sustaining growth. Common cellulose-based building materials, such as plywood, drywall, furring strips, finish carpentry, cabinetry, wood framing, composite wood flooring, carpets, and carpet padding provide food for mold. In carpet, organic load such as invisible dust and cellulose are food sources. After water damage to a building, mold grows in walls and then becomes dormant until subsequent high humidity; suitable conditions reactivate mold. Mycotoxin levels are higher in buildings which have had a water incident.
Mold is detectable by smell and signs of water damage on walls or ceiling and can grow in places invisible to the human eye. It may be found behind wallpaper or paneling, on the inside of ceiling tiles, the back of drywall, or the underside of carpets or carpet padding. Piping in walls may also be a source of mold, since they may leak (causing moisture and condensation).
Spores need three things to grow into mold: nutrients - cellulose (the cell wall of green plants) is a common food for indoor spores; moisture - to begin the decaying process caused by mold; and time - mold growth begins from 24 hours to 10 days after the provision of growing conditions.
Mold colonies can grow inside buildings, and the chief hazard is the inhalation of mycotoxins. After a flood or major leak, mycotoxin levels are higher - even after a building has dried out.
Food sources for mold in buildings include cellulose-based materials such as wood, cardboard and the paper facing on drywall and organic matter such as soap, fabrics, and dust containing skin cells. If a house has mold, the moisture may originate in the basement or crawl space, a leaking roof or a leak in plumbing pipes. Insufficient ventilation may accelerate moisture buildup. Visible mold colonies may form where ventilation is poorest and on perimeter walls (because they are nearest the dew point).
If there are mold problems in a house only during certain times of the year, the house is probably too airtight or too drafty. Mold problems occur in airtight homes more frequently in the warmer months (when humidity is high inside the house, and moisture is trapped), and occur in drafty homes more frequently in the colder months (when warm air escapes from the living area and condenses). If a house is artificially humidified during the winter, this can create conditions favorable to mold. Moving air may prevent mold from growing, since it has the same desiccating effect as low humidity. Mold grow best in warm temperatures, 77 to 86 °F (25 to 30 °C), although growth may occur between 32 and 95 °F (0 and 35 °C).
Removing one of the three requirements for mold reduces (or eliminates) new mold growth: moisture; food for the mold spores (for example, dust or dander); and warmth since mold generally does not grow in cold environments.
HVAC systems can produce all three requirements for mold growth. The air conditioning system creates a difference in temperature, encouraging condensation. The high rate of dusty air movement through an HVAC system may furnish ample food for mold. Since the air-conditioning system is not always running, warm conditions are the final component for mold growth.
An observation of the indoor environment should be conducted before any sampling is performed. The area should be surveyed for odors indicating mold or bacterial growth, moisture sources, such as stagnant water or leaking pipes, and water-damaged building materials.This can include moving furniture, lifting (or removing) carpets, checking behind wallpaper or paneling, checking ventilation ductwork and exposing wall cavities. Efforts typically focus on areas where there are signs of liquid moisture or water vapor (humidity), or where moisture problems are suspected. Often, quick decisions about the immediate safety and health of the environment can be made by these observations before sampling is even needed. The United States Environmental Protection Agency (EPA) does not generally recommend sampling unless an occupant of the space has symptoms. In most cases, if visible mold growth is present, sampling is unnecessary. Sampling should be performed by a trained professional with specific experience in mold-sampling protocols, sampling methods and the interpretation of findings. It should be done only to make a particular determination, such as airborne spore concentration or identifying a particular species.
Before sampling, a subsequent course of action should be determined.
In the U.S., sampling and analysis should follow the recommendations of the Occupational Safety and Health Administration (OSHA), National Institute for Occupational Safety and Health (NIOSH), the EPA and the American Industrial Hygiene Association (AIHA). Types of samples include air, surface, bulk, dust, and swab.Multiple types of sampling are recommended by the AIHA, since each has limitations.
Air is the most common form of sampling to assess mold levels. It is considered to be the most representative method for assessing respiratory exposure to mold.Indoor and outdoor air are sampled, and their mold spore concentrations are compared. Indoor mold concentrations should be less than or equal to outdoor concentrations with similar distributions of species. A predominant difference in species or higher indoor concentrations can indicate poor indoor air quality and a possible health hazard. Air sampling can be used to identify hidden mold and is often used to assess the effectiveness of control measures after remediation. An indoor mold air sampling campaign should be performed over the course of at least several days as the environmental conditions can lead to variations in the day-to-day mold concentration. Stationary samplers assess a specific environment, such as a room or building, whereas personal samplers assess the mold exposure one person receives in all of the environments they enter over the course of sampling. Personal samplers can be attached to workers to assess their respiratory exposures to molds on the job. Personal samplers usually show higher levels of exposure than stationary samples due to the "personal cloud" effect, where the activities of the person re-suspend settled particles. There are several methods that can be used for indoor mold air sampling.
For more detailed information on air sampling methods for indoor mold, see Bioaerosol.
Surface sampling measures the number of mold spores deposited on indoor surfaces. With swab, a cotton swab is rubbed across the area being sampled, often a measured area, and subsequently sent to the mold testing laboratory. The swab can rubbed on an agar plate to grow the mold on a culture medium. Final results indicate mold levels and species located in the suspect area. Surface sampling can by used to identify the source of mold exposure. Molecular analyses, such as qPCR, may also be used for species identification and quantification. Swab and surface sampling can give detailed information about the mold, but cannot measure the actual mold exposure because it is not aerosolized.
Bulk removal of material from the contaminated area is used to identify and quantify the mold in the sample. This method is often used to verify contamination and identify the source of contamination.Dust samples can be collected using a vacuum with a collection filter attached. Dust from surfaces such as floors, beds, or furniture is often collected to assess health effects from exposure in epidemiology studies. Researchers of indoor mold also use a long-term settled dust collection method where a dust cloth or petri dish is left out in the environment for a set period of time, sometimes weeks. Dust samples can be analyzed using culture-based or culture-independent methods. Quantitative PCR is a DNA-based molecular method that can identify and quantify fungal species. The Environmental Relative Moldiness Index (ERMI) is a numerical that can be used in epidemiological studies to assess mold burdens of houses in the United States. The ERMI consists of a list of 36 fungal species commonly associated with damp houses that can be measured using qPCR. Like swab and surface sampling, bulk and dust sampling can give detailed information about the mold source, but cannot accurately determine the level of exposure to the source.
The first step in solving an indoor mold problem is to remove the moisture source;new mold will begin to grow on moist, porous surfaces within 24 to 48 hours. There are a number of ways to prevent mold growth. Some cleaning companies specialize in fabric restoration, removing mold (and mold spores) from clothing to eliminate odor and prevent further damage to garments.
The effective way to clean mold is to use detergent solutions which physically remove mold. Many commercially available detergents marketed for mold cleanup include an EPA-approved antifungal agent.
Significant mold growth may require professional mold remediation to remove the affected building materials and eradicate the source of excess moisture. In extreme cases of mold growth in buildings, it may be more cost-effective to condemn the building than to reduce mold to safe levels.
The goals of remediation are to remove (or clean) contaminated materials, preventing fungi (and fungi-contaminated dust) from entering an occupied (or non-contaminated) area while protecting workers performing the abatement.
The purpose of cleanup is to eliminate mold and remove contaminated materials. Killing mold with a biocide is insufficient, since chemicals and proteins causing reactions in humans remain in dead mold. The following methods are used.
Equipment used in mold remediation includes: moisture meter: measures drying of damaged materials; Humidity gauge: often paired with a thermometer; borescope: Camera at the end of a flexible snake, illuminating potential mold problems inside walls, ceilings and crawl spaces; digital camera: Documents findings during assessment; personal protective equipment (PPE): Respirators, gloves, impervious suit, and eye protection; thermographic camera: Infrared thermal-imaging cameras identify secondary moisture sources.
During mold remediation in the U.S., the level of contamination dictates the protection level for remediation workers.Contamination levels have been enumerated as I, II, III, and IV:
After remediation, the premises should be reevaluated to ensure success.
According to the EPA, residential mold may be prevented and controlled by cleaning and repairing roof gutters, to prevent moisture seepage into the home; keeping air-conditioning drip pans clean and drainage lines clear; monitoring indoor humidity; drying areas of moisture or condensation and removing their sources; ensuring that there is adequate ventilation by installing an exhaust fan in your bathroom; treating exposed structural wood or wood framing with an EPA-approved fungicidal encapsulation coating after pre-cleaning (particularly homes with a crawl space, unfinished basement or a poorly-ventilated; attic).
Mold health issues are potentially harmful effects of molds.
A mold or mould is a fungus that grows in the form of multicellular filaments called hyphae. In contrast, fungi that can adopt a single-celled growth habit are called yeasts.
Indoor air quality (IAQ) is the air quality within and around buildings and structures. IAQ is known to affect the health, comfort and well-being of building occupants. Poor indoor air quality has been linked to sick building syndrome, reduced productivity and impaired learning in schools.
Sick building syndrome (SBS) is a common worldwide health concern, where people in a building suffer from symptoms of illness or become infected with chronic disease from the building they work in or reside in. Many cases involving fatalities have been examined involving the deposition of infectious disease bearing particles throughout a building or structure. In all cases, the outbreaks are a direct result of inadequate cleaning, and maintenance, or defects with the construction materials or assembly process. In many cases the building itself is too damaged to recover, as the materials themselves are decaying from mold or rot. The phenomenon is found worldwide in buildings with lower than adequate maintenance or other economic concerns. Health professionals recommend anyone living in an older building with medical conditions, to use HEPA air filters for indoor use to minimize airborne particulate introduced from outside the living space. Many cases of Norwalk virus and Norovirus outbreak have been traced back to cruise ships and hotels with food service in unsanitary conditions or substandard restroom cleanliness protocols. Certain symptoms tend to increase in severity with the time people spend in the building; often improving over time or even disappearing when people are away from the building. The main identifying observation is an increased incidence of complaints of symptoms such as headache, eye, nose, and throat irritation, fatigue, and dizziness and nausea from exposure to harmful chemicals released by toxic black mold. Some symptoms are linked to the average amount of time spent in a building, such as mold spore and dust inhalation. SBS is also used interchangeably with "building-related symptoms", which orients the name of the condition around patients symptoms rather than a "sick" building. A 1984 World Health Organization (WHO) report suggested up to 30% of new and remodeled buildings worldwide may be subject of complaints related to poor indoor air quality.
Environmental remediation deals with the removal of pollution or contaminants from environmental media such as soil, groundwater, sediment, or surface water. Remedial action is generally subject to an array of regulatory requirements, and may also be based on assessments of human health and ecological risks where no legislative standards exist, or where standards are advisory.
A mycotoxin is a toxic secondary metabolite produced by organisms of the fungus kingdom and is capable of causing disease and death in both humans and other animals. The term 'mycotoxin' is usually reserved for the toxic chemical products produced by fungi that readily colonize crops.
An air purifier or air cleaner is a device which removes contaminants from the air in a room to improve indoor air quality. These devices are commonly marketed as being beneficial to allergy sufferers and asthmatics, and at reducing or eliminating second-hand tobacco smoke. The commercially graded air purifiers are manufactured as either small stand-alone units or larger units that can be affixed to an air handler unit (AHU) or to an HVAC unit found in the medical, industrial, and commercial industries. Air purifiers may also be used in industry to remove impurities from air before processing. Pressure swing adsorbers or other adsorption techniques are typically used for this.
A humidifier is a device, primarily an electrical appliance, that increases humidity (moisture) in a single room or an entire building. In the home, point-of-use humidifiers are commonly used to humidify a single room, while whole-house or furnace humidifiers, which connect to a home's HVAC system, provide humidity to the entire house. Medical ventilators often include humidifiers for increased patient comfort. Large humidifiers are used in commercial, institutional, or industrial contexts, often as part of a larger HVAC system.
Stachybotrys chartarum, also known as black mold or toxic black mold, is a variety of microfungus that produces its conidia in slime heads. It is sometimes found in soil and grain, but the mold is most often detected in cellulose-rich building materials from damp or water-damaged buildings. S. chartarum was originally discovered on the wall of a house in Prague in 1837 by Czech mycologist August Carl Joseph Corda. It requires very high moisture levels in order to grow and is associated with wet gypsum material and wallpaper.
Radon mitigation is any process used to reduce radon gas concentrations in the breathing zones of occupied buildings, or radon from water supplies. Radon is a significant contributor to environmental radioactivity.
Structural dampness is the presence of unwanted moisture in the structure of a building, either the result of intrusion from outside or condensation from within the structure. A high proportion of damp problems in buildings are caused by ambient climate dependent factors of condensation and rain penetration. Capillary penetration of fluid from the ground up through concrete or masonry is known as Rising Damp and is governed by the shape and porosity of the construction materials through which this evaporation limited capillary penetration takes place. Structural damp, regardless of the mechanisms through which it takes place, is exacerbated by higher levels of humidity.
Bioaerosols are a subcategory of particles released from terrestrial and marine ecosystems into the atmosphere. They consist of both living and non-living components, such as fungi, pollen, bacteria and viruses. Common sources of bioaerosols include soil, water, and sewage.
Mold prevention is a conservation activity that is performed in libraries to protect books and other materials from deterioration caused by mold growth. Mold prevention consists of different methods, such as chemical treatments, careful environmental control, and manual cleaning. Preservationists use one or a combination of these methods to combat mold spores in library collections.
Indoor bioaerosol is bioaerosol in an indoor environment. Bioaerosols are natural or artificial particles of biological origin suspended in the air. These particles are also referred to as organic dust. Bioaerosols may consist of bacteria, fungi, viruses, microbial toxins, pollen, plant fibers, etc. Size of bioaerosol particles varies from below 1 µm to 100 µm in aerodynamic diameter; viable bioaerosol particles can be suspended in air as single cells or aggregates of microorganism as small as 1–10 µm in size. Since bioaerosols are potentially related to various human health effects and the indoor environment provides a unique exposure situation, concerns about indoor bioaerosols have increased over the last decade.
Dry rot treatment refers to techniques used to eliminate dry rot fungus and alleviate the damage done by the fungus to human-built wooden structures.
Wallemia sebi is a xerophilic fungus of the phylum Basidiomycota.
Aspergillus versicolor is a slow-growing filamentous fungus commonly found in damp indoor environments and on food products. It has a characteristic musty odor associated with moldy homes and is a major producer of the hepatotoxic and carcinogenic mycotoxin sterigmatocystin. Like other Aspergillus species, A. versicolor is an eye, nose, and throat irritant.
Soil stabilization a general term for any physical, chemical, mechanical, biological or combined method of changing a natural soil to meet an engineering purpose. Improvements include increasing the weight bearing capabilities, tensile strength, and overall performance of in-situ subsoils, sands, and waste materials in order to strengthen road pavements.
The conservation and restoration of bone, horn, and antler objects is the preservation of objects made from or containing these organic materials by preventive methods and treatments. Because these materials are both versatile and durable, they have been used throughout history for various tools and/or ornamentation including clothing, jewelry, and decorative art. These objects can be found in personal collections as well as cultural institutions and their collections.
Cladosporium ear rot is a disease that affects maize. The disease is caused by the saprophytic fungus Cladosporium herbarum and is characterized by black or dark green fungal growths that cause black streaks on kernels.