Mold Education Hub

Indoor mold refers to the growth of fungi in indoor environments, particularly in areas that are damp or have high levels of moisture.

Mold is a natural part of the environment and plays a crucial role in breaking down dead organic matter in nature. However, when it grows indoors, it can pose health risks and should be avoided.

Mold reproduces through tiny spores that float through the air and deposit on surfaces. When the conditions are right, including the right temperature, moisture, and available nutrients (such as organic matter like dust), these spores can form new mold colonies.

Water-damaged buildings can house various microorganisms, including bacteria, molds, and other toxins. Some common molds found in such environments include Stachybotrys chartarum, Penicillium, and Aspergillus species.

In addition to molds, bacteria can also be present in water-damaged buildings. These bacteria can produce endotoxins, which can trigger inflammatory responses in humans.

Actinobacteria, commonly found in water-damaged buildings, are known to produce compounds that can affect human biology, and their metabolites have antibiotic activity, which can disrupt the gut and respiratory system microbiomes, leading to various health issues.

Toxins found in water-damaged buildings often include substances produced by these microorganisms. For instance, gram-negative endotoxin and beta-D-glucan have been detected in water extracts from water-damaged building materials.

Mold grows in homes when mold spores land on a wet or damp spot and begin growing. They can grow on a variety of materials including ceiling tiles, wallpaper, insulation material, wood, and carpet. Bathrooms, basements, HVAC systems, and laundry rooms are typically high-humidity areas prone to mold growth.

Indoor mold growth is often related to water or moisture exposure and can be caused by various factors such as flooding, leaky roofs, poor building maintenance, or indoor plumbing problems, but also high humidity environments. Common building materials are capable of sustaining mold growth, and mold spores are ubiquitous, making mold growth a common issue in many indoor environments.

Mold can grow in various places in a home, especially in areas that are damp and have poor ventilation, including the kitchen, bathroom, bedroom, living room, basement, attic, laundry room, HVAC system, wall cavities, ceiling, and garage.

See our free MoldCo Home & Health Guide for a more comprehensive home inspection checklist on the signs of potential mold in your home.

Mold is common in homes, especially in places where there is poor ventilation, high humidity, or dampness. According to the U.S. Centers for Disease Control and Prevention (CDC), molds can be found in virtually any environment, year-round.

Some compelling stats and facts:
Mold stats:
50% of buildings have some degree of water damage.
85% of office buildings have past water damage (EPA).
45% of office buildings have current leaks (EPA).
50% prevalence of dampness and mold in a study across 12,842 homes (Spengler).
24 to 48 hours for mold to develop following water intrusion (EPA).
87% of environmental exposure occurs indoors (NHAPS).
30% of remodeled and new buildings have indoor air quality issues (WHO).
21% of American asthma cases could be associated with dampness and mold (WHO).
96% of chronic sinus infections are a direct result of mold overexposure (Mayo Clinic).
24 to 48 hours for mold to develop following water intrusion (EPA).
87% of environmental exposure occurs indoors (NHAPS).
30% of remodeled and new buildings have indoor air quality issues (WHO).
24% of the population has a genetic susceptibility to mold (Dr. Shoemaker).
21% of American asthma cases could be associated with dampness and mold (WHO).
96% of chronic sinus infections are a direct result of mold overexposure (Mayo Clinic).
14,000 people daily in the US are affected by water damage (III).

As a first step, see our free MoldCo Home & Health Guide for a more comprehensive home inspection checklist on the signs of potential mold in your home.

Regions or climates that are especially susceptible to mold growth are those that are warm, humid, and damp.

The most common states for mold exposure, particularly for those with mold allergies, are California, Ohio, and Texas. This is based on data from a study by Quest Diagnostics, which found that these states had the highest number of cities ranked among the top 20 worst cities for allergy sufferers (although the health impacts from mold go beyond an allergy issue).

In California, 4 cities were in the top 20, while Ohio and Texas each had 2 cities in the top 20. The southwestern United States was identified as the worst region overall for mold allergy sufferers, housing 4 of the top 5 worst cities for mold sensitization.

The cities with the highest percentages of allergy patients showing sensitization to mold are as follows:

1. Dallas—21%
2. Riverside-San Bernardino—20%
3. Phoenix—19%
4. Los Angeles—17%
5. Chicago—17%
6. Minneapolis-St. Paul—16%
7. Saint Louis—16%
8. Denver—16%
9. Kansas City—16%
10. San Antonio—15%

Other states with high mold prevalence include Florida, Oklahoma, South Carolina, Nevada, Arizona, South Dakota, Tennessee, and Kansas. These states are more susceptible to mold growth due to factors such as high humidity, annual precipitation, and water damage. However, it's important to note that mold can grow in any state, especially in areas with high humidity and rainfall, and homes with water damage.

It's important to note that environmental factors such as climate and the likelihood of natural disasters can contribute to the prevalence of mold allergens in a given area. For instance, mold levels are typically higher during warmer months when humidity is higher. However, mold spores can be found all year.

See our free MoldCo Home & Health Guide for a more comprehensive home inspection checklist on the signs of potential mold in your home.

The Environmental Relative Moldiness Index (ERMI) quantifies 36 molds, which are divided into two groups.

Group 1 consists of molds associated with water-damaged homes, while Group 2 consists of molds commonly found in homes regardless of water damage.

Group 1: Water Damage Molds
1. Aspergillus flavus/oryzae
2. Aspergillus fumigatus
3. Aspergillus niger
4. Aspergillus ochraceus
5. Aspergillus penicillioides
6. Aspergillus restrictus
7. Aspergillus sclerotiorum
8. Aspergillus sydowii
9. Aspergillus unguis
10. Aspergillus versicolor
11. Aureobasidium pullulans
12. Chaetomium globosum
13. Cladosporium sphaerospermum
14. Eurotium (Asp.) amstelodami
15. Paecilomyces variotii
16. Penicillium brevicompactum
17. Penicillium corylophilum
18. Penicillium crustosum
19. Penicillium purpurogenum
20. Penicillium spinulosum
21. Penicillium variabile
22. Scopulariopsis brevicaulis/fusca
23. Scopulariopsis chartarum
24. Stachybotrys chartarum
25. Trichoderma viride
26. Wallemia sebi


Group 2: Common Indoor Molds
27. Acremonium strictum
28. Alternaria alternata
29. Aspergillus ustus
30. Cladosporium cladosporioides1
31. Cladosporium cladosporioides2
32. Cladosporium herbarum
33. Epicoccum nigrum
34. Mucor and Rhizopus group
35. Penicillium chrysogenum1
36. Penicillium chrysogenum2

Toxic mold refers to certain mold species that produce mycotoxins, which can cause serious health issues in humans. While all molds can cause health problems, especially in people with allergies or asthma, toxic molds are known for their potential to cause more severe health effects.

Some common health issues from mold exposure include:
Fatigue, weakness, aches, muscle cramps, unusual pain, ice pick pain, headache, light sensitivity, red eyes, blurred vision, tearing, sinus problems, cough, shortness of breath, abdominal pain, diarrhea, joint pain, morning stiffness, memory issues, focus/concentration issues, word recollection issues, confusion, disorientation, skin sensitivity, mood swings, appetite swings, sweats (especially night sweats), temperature regulation or dysregulation problems, excessive thirst, increased urination, static shocks, numbness, tingling, vertigo, metallic taste, and tremors.

Common types of toxic mold include:
1. Stachybotrys: Often referred to as "black mold," it can cause flu-like symptoms, diarrhea, headaches, memory loss, and severe respiratory damage.

2. Chaetomium: Commonly found in water-damaged homes, it thrives in wet, dark environments such as drywall, wallpaper, baseboards, and carpets.

3. Aspergillus: This mold family consists of almost 200 species, with at least 16 of them causing illnesses in humans, including lung infections, inflammation, and asthma attacks.

4. Penicillium: Some species of Penicillium are harmful, while others are used in producing cheese and medicine.

5. Alternaria: A well-known allergy-causing mold, it is present in high amounts in many climate zones during the spring and summer. It can cause skin, eye, and respiratory infections.

6. Cladosporium: This mold can cause respiratory issues, inflammation, and allergic reactions.

7. Fusarium: Fusarium mold can cause infections, inflammation, and allergic reactions.

8. Acremonium: A toxigenic mold that can cause infections and other health issues.

9. Aureobasidium: An allergenic mold that can cause skin, nail, and eye infections.

10. Mucor and Rhizopus group: These molds can cause respiratory issues and allergic reactions.

It's important to note that mold affects individuals differently, and not all mold species are harmful to everyone. However, prolonged exposure to toxic mold can lead to serious health issues.

If you think you may be impacted, as a next step, take our at-home mold test, and free MoldCo Health and Home Questionnaire.

The terms "toxic mold" and "non-toxic mold" can be misleading. All molds are capable of causing health issues, but the severity and type of health problems can vary greatly depending on the type of mold and the individual's immune response.

It's important to note that the color of the mold does not indicate its toxicity. Black mold, for instance, can refer to several species of mold.

In general, all molds should be treated as potential health risks, and their presence in the home should be addressed promptly. As a first step, see our free MoldCo Home & Health Guide for a more comprehensive home inspection checklist on the signs of potential mold in your home. If you suspect a mold problem in your home, it's recommended to contact a mold remediation professional.