Enlightening You on Mold and Environmental Contaminants

Aside from providing comprehensive mold inspection services, Holt Analytical is also dedicated to informing property owners about environmental contaminants. That is why we strive to provide invaluable resource materials about these topics.

Common Indoor Molds

  • Aspergillus
  • Cladosporium
  • Basidiospores
  • Penicillium

About These Biological Agents

Whether dead or alive, mold spores often cause adverse health effects. Primarily, this contaminant affects the respiratory systems and induces hay fever-like allergic symptoms. Many of these molds, like S. atra, also produce mycotoxins.

Toxigenic Molds

Mycotoxins are generated and released into the air within the mold spores. Exposure to these contaminants can occur through inhalation, ingestion, or skin contact, resulting in symptoms like the following:

  • Dermatitis
  • Cough
  • Rhinitis
  • Nose Bleeds
  • Cold
  • Flu
  • Headache
  • General Malaise
  • Fever

Allergenic Molds

These contaminants do not usually produce life-threatening health effects. They will most likely affect people who are already allergic or asthmatic.

The human system's responses to allergenic molds tend to be relatively mild. Depending on an individual's sensitivities, the typical allergic reactions include sore throats, eye and nose irritations, and rashes.

How Molds Are Considered Allergenic

Like pollen, mold spores are only significant airborne allergens if they are abundant, easily carried by air currents, and allergenic in their chemical makeup.

Mold spores are almost found everywhere. There are even some areas where they outnumber the amount of pollen in the air. Fortunately, only a few mold types are significant allergens.

Specific Molds That Are Allergenic

Alternaria and Cladosporium (Hormodendrum) are the molds most typically found on the inside and outside of properties throughout the US. Additionally, the following contaminants are common:

  • Aspergillus
  • Penicillium
  • Helminthosporium
  • Epicoccum
  • Fusarium
  • Mucor
  • Rhizopus
  • Aureobasidium (Pullularia)

Mold Counts

This suggests the types and relative quantities of fungi present at a certain time and place. However, these mold counts cannot be used as a constant guide for daily activities.

One reason is that the number and types of spores present in the mold count may considerably change in 24 hours. It may be because weather and spore dispersal are directly related.

Spore Types

Many common allergenic molds are dry-spore types that release their spores during dry, windy weather. However, other fungi need high humidity, fog, or dew. Rain also causes smaller spores to spread into the air but washes out larger spores.

Aside from daily weather changes on mold counts, spore populations differ between day and night as well. It has been shown that dry spores disperse more during daytime than white wet spores spread at night.

Other Mold-Related Disorders

Fungi or their related microorganisms may cause other health problems similar to allergic diseases. Some varieties of Aspergillus may cause different illnesses, such as infections and allergies.

These fungi may stay in the airways or a distant part of the lung and grow until they turn into a compact sphere called "fungus ball." Aspergillus may use this chance to invade the lungs or whole body of people with lung damage or serious underlying illnesses.

Mold Exposure Effects

Some individuals exposed to these fungi can have an asthma attack or contract allergic bronchopulmonary aspergillosis. The latter condition only occurs in a minority of people with asthma. It is characterized by the following:

  • Wheezing
  • Low-Grade Fever
  • Coughing Up of Brown-Flecked Masses or Mucus Plugs

Skin testing, blood tests, x-rays, and sputum examinations for fungi can help establish a proper diagnosis. Fortunately, corticosteroid drugs are usually effective in treating an allergic reaction. However, immunotherapy is not helpful.

Pathogenic Molds

These kinds of mold can produce some type of infection. They may also cause serious health effects to people with suppressed immune systems.

Luckily, healthy individuals can usually resist infection regardless of dose. Cases of high exposure may cause hypersensitivity pneumonitis as well.

Growth Rate

Colonies are moderately fast-growing organisms that effuse grey to blackish brown, suede-like floccose forms with a black reverse. Microscopic morphology has sympodial development of pale brown, pseudoseptate conidia on a geniculate or zig-zag rachis.

Additionally, conidia are produced through pores in the conidiophore wall (poroconidia). These straight, fusiform to ellipsoidal-shaped organisms are rounded at both ends with a smooth to finely roughened texture. They only germinate from the ends as well.

Description and Natural Habitats

Bipolaris is a dematiaceous, filamentous fungus. It has a cosmopolitan nature isolated from plant debris and soil. The pathogen also has teleomorphic states in the genus Cochliobolus and produces ascospores.


The genus Bipolaris contains around 45 species that are mostly subtropical and tropical plant parasites. However, several species like B. australiensis, B. hawaiiensis, and B. spicifera — the most well-known pathogens — are well-documented human pathogens.

Clinical manifestations of these species include:

  • Mycotic keratitis
  • Subcutaneous phaeohyphomycosis
  • Sinusitis
  • Peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD)
  • Cerebral and disseminated infections

Pathogenicity and Clinical Significance

Bipolaris is one of the causative agents of phaeohyphomycosis. It can infect both immunocompetent and immunocompromised hosts. The clinical spectrum is diverse and includes:

  • Allergic and Chronic Invasive Sinusitis
  • Keratitis
  • Endophthalmitis
  • Endocarditis
  • Endarteritis
  • Osteomyelitis
  • Meningoencephalitis
  • Peritonitis
  • Otitis Media (in Agricultural Field Workers)
  • Fungemia
  • Cutaneous and Pulmonary Infections
  • Allergic Bronchopulmonary Disease

Apart from being saprophytes on plants, Bipolaris may also be pathogenic to plant species like Graminiae and animals like dogs. It may cause nasal mycotic granuloma in the cattle as well. Luckily, Bipolaris may be isolated as a laboratory contaminant.

Macroscopic Features

Bipolaris colonies grow rapidly. They can reach a diameter of 3-9 cm following incubation at 25°C for seven days on a potato dextrose agar. The colony becomes mature within five days. Its texture is velvety to woolly.

The surface of the colony is initially white to grayish brown. It becomes olive green to black with a raised grayish periphery as it matures. The reverse is also darkly pigmented and olive to black
in color.

Microscopic Features

The hyphae are septate and brown. Conidiophores (4.5-6 µm wide) are brown, simple or branched, geniculate, and sympodial pathogens. They bend at the points where each conidium arises. This property leads to the zigzag appearance of the conidiophore.

About Conidia (Poroconidia)

These organisms are three to six-celled, fusoid or cylindrical shaped, and light or dark brown-colored with a sympodial geniculate growth pattern. The poroconidium (30-35 µm x 11-13.5 µm) is distoseptate and has a scarcely protuberant, darkly pigmented hilum.

This basal scar indicates the point of attachment to the conidiophore. From the terminal cell of the conidium, germ tubes may develop and elongate in the direction of the longitudinal axis of the conidium.

Production and Appearance

The teleomorph production of Bipolaris is heterothallic. Its perithecium is black and has a round to ellipsoidal shape. Meanwhile, the ascospores are flagelliform or filiform and hyaline parts.

They are found in clavate-shaped or cylindrical asci, with each ascus containing eight ascospores.

Laboratory Precautions

No special handling measures are necessary. General laboratory precautions are required.


In vitro susceptibility testing procedures have not been standardized for dematiaceous fungi yet. There are limited data available on the susceptibility of Bipolaris.

This information suggests that itraconazole minimum inhibitory concentrations (MICs) are variable, and voriconazole MICs are considerably low.

Pathogen Treatment

Amphotericin B and ketoconazole are used in the treatment of Bipolaris infections. Some cases, such as sinusitis, may require surgical debridement.

Toxigenic Molds

Mycotoxins can cause serious health reactions in almost anybody. These agents have toxic effects ranging from short-term irritation to immunosuppression and possibly cancer. When toxigenic molds are found, further evaluation is recommended.

The notoriety of Stachybotrys leads some to believe it is the only “toxic mold.” However, many toxigenic mold types have been found during indoor air quality investigations in different parts of the world.

Infamous Toxic Contaminants

According to studies by Burge (1986), Smith et al. (1992), Hirsh and Sosman (1976), Verhoeff et al. (1992), Miller et al. (1988), and Gravesen et al. (1999), the most frequently found outdoor molds that exceed the acceptable levels are:

  • Aspergillus
  • Penicillium
  • Stachybotrys
  • Cladosporium

The toxicity levels of Penicillium, Aspergillus, and Stachybotrys are especially harmful when people are exposed to these contaminants indoors.


These mold species are common indoors, even in clean environments. According to studies by Burge (1986), Miller et al. (1988), and Flannigan and Miller (1994), they can be problematic when indoor spore levels are higher than outdoors.

Penicillium spores have the highest concentrations of mycotoxins. Mycelium, the vegetative portion of the mold, can also contain the poison. The viability of spores is not essential to toxicity. Because of this fact, a dead spore can still be a source of the toxin.


This species is fairly prevalent in problematic buildings. Its genus contains several toxigenic molds, such as A. parasiticus, A. flavus, and A. fumigatus.

About These Toxigenic Species

A. parasiticus and A. flavus produce aflatoxins, the most extensively studied mycotoxins. It is among the most toxic substances. They can adversely affect the liver, brain, kidneys, and heart. Chronic exposure leads to potent carcinogens in the liver.

Aflatoxins are also teratogenic, according to studies by Smith and Moss (1985) and Burge (1986). Based on research by Smith and Moss (1985), symptoms of acute aflatoxicosis are fever, vomiting, coma, and convulsions.

Read About A. Flavus

This toxic mold is found indoors in tropical and subtropical regions. A. flavus is also occasionally detected in specific environments like flowerpots.

Explore More About A. Fumigatus

It is found in many indoor spaces. This mold is often associated with an infectious disease called aspergillosis. However, the species does produce poisons that only been examined using simple toxicity tests, according to studies by Betina (1989).

Additionally, recent work has found several tremorgenic toxins in the conidia of this species, as researched by Land et al. (1994).

See More About A. Versicolor

This is a more common Aspergillus species found growing on wallpaper, wooden floors, fiberboards, and other construction materials in wet buildings. It does not produce aflatoxins but does produce a less potent toxin.

This pathogen is called sterigmatocystin, the precursor to aflatoxins according to Gravesen et al. (1994).

A. Versicolor Exposure Signs and Symptoms

Symptoms of aflatoxin ingestion are well described. However, symptoms of environmental contraction, like being in a moderately contaminated building, are not known but are undoubtedly less severe due to reduced exposure.

Additionally, the potent toxicity of these agents requires prudent prevention of exposures. This precaution is especially warranted when levels of Aspergilli indoors exceed outdoor levels by a significant amount.

Find Out More About A. Ochraceus

This toxic mold produces ochratoxins, which are also produced by some penicillia. According to studies conducted by Smith and Moss (1985), ochratoxins are carcinogenic and damage the kidneys.


Stachybotrys chartarum (atra) has been discussed in the popular press. It has been the subject of several building-related illness investigations.

The mold is not readily measurable from air samples. This is because its spores are sticky and not easily aerosolized when wet.

Mold Sampling

Because Stachybotrys does not do well with other molds or bacteria, it is easily overgrown in a sample. This is especially true since it does not grow ideally on standard sampling media.

Its inability to compete may also result in Stachybotrys being killed off by other organisms in the sample mixture.


Stachybotrys may not be viable and won't be identified in a cultured sample media when physically captured. Sampling this mold may not be feasible even though it is present in the environment, and people who breathe it can have toxic exposures.

Sampling Precautions

Take a surface sample, such as tape or bulk, whenever evidence of black mold is found. This organism has a high moisture requirement, so it grows vigorously where water has accumulated from roof, wall, or plumbing leaks and chronically wet areas.

Black mold is often hidden within the building envelope and inside wall cavities. When Stachybotrys is detected in the air, it should be searched out in walls or other hidden spaces where it is likely growing in abundance.

Mold Growth

This mold has a very low nitrogen requirement. It can grow on wet hay and straw, paper, wallpaper, ceiling tiles, carpets, and insulation material.

Contact Us for More Info

For additional details about mold types, inspection services, and more, feel free to get in touch with us. It would be our pleasure to help you learn more about possible biological contaminants in your property and how they may affect your health.