Loyola University Chicago

Healthy Homes & Healthy Communities

Mold & Moisture

What is it?

Molds are fungi. (CDC)

Molds are living organisms that grow naturally, particularly in warm, damp, humid conditions where there is little air movement. There are hundreds of thousands of different types of mold. (Green and HH)

Molds typically consist of a network of threadlike filaments that infiltrate the surface on which the mold is growing. (NCHH)

Where is it found?

Molds can be found both indoors and outdoors. They are found in every environment, but they grow best in warm, damp and humid conditions. (CDC)

Outdoors they can be found in shady, damp areas or places where vegetation is decomposing such as compost piles, cut grass, and wooded areas. Indoors they can be found where humidity levels are high, such as basements and showers. (CDC)

Mold can enter homes through open doorways, windows, vents, and heating and air conditioning systems. Mold in the air outside can also attach itself to clothing, shoes, bags, and pets and be carried indoors. (CDC)

Mold will grow in places with a lot of moisture. It grows well on paper products, cardboard, ceiling tiles, and wood products. Mold can also grow in dust, paints, wallpaper, insulation, drywall, carpet, fabric, and upholstery. (CDC)

Places you might find mold:

  • Around leaky sinks in bathrooms and kitchens.
  • In wet or damp basements and crawl spaces; in attics under leaky roofs.
  • Under wallpaper or carpet.
  • On windows and walls where condensation collects; in or around air conditioners. (GHH)

What causes it?

Molds reproduce via spores which spread easily and can survive harsh environmental conditions that do not support mold growth, such as dry conditions. (CDC)

Moisture is the key factor determining mold growth in the home, influencing both the type of mold present and the extent of mold colonization. (NCHH)

How does mold affect health?

Individuals who are sensitive to molds can suffer from symptoms such as nasal stuffiness, eye irritation, wheezing or coughing, throat irritation or skin irritation when exposed. Severe reactions to molds include fever and shortness of breath. (CDC)

In 2004, the Institute of Medicine found there was sufficient evidence to link indoor exposure to mold with upper respiratory tract symptoms, cough and wheeze in otherwise healthy people and with asthma symptoms in people with asthma. (CDC)

Some types of mold produce toxic substances known as mycotoxins, which can cause health problems when they are inhaled, absorbed through the skin, or ingested. (NCHH)

  • Mycotoxin production varies depending on environmental conditions such as moisture level, temperature, and substrate concentration. As a general matter, toxin-producing molds have higher water requirements than most household molds. (NCHH)
  • Skin rashes, fatigue, dizziness, flu-like symptoms, nausea, respiratory and eye irritation, immune-suppression, birth defects, lung inflammation, and cancer have been associated with exposure to mycotoxins. (NCHH)

Why is this a prevalent toxin?

Structural issues with aging buildings, natural damage (flooding), etc.

Effective Interventions

Inside homes, mold growth can be slowed by controlling humidity levels and ventilating showers and cooking areas. (CDC)

Mold growth can be removed from hard surfaces with commercial products, soap and water, or a bleach solution of no more than 1 cup of bleach in 1 gallon of water. (CDC)

The key to mold control is moisture control. When addressing mold problems, one must address the source of the moisture problem or the mold problem may simply reappear. (Green and HH)

  • Maintaining a dry home can prevent mold growth, prevent a hospitable environment for dust mites, roaches and rodents, and reduce indoor allergens. (Green and HH)