Different Species Of Mold: Which Types Can Harm You?

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Mold. It starts out as a few black spots on a shower curtain or along the edge of the tub and grows into a big, dark, fuzzy spot on a basement wall. Or, it may start out as a soft dark spot on a piece of fruit and the next day an entire head of lettuce is black and slimy. These molds are just a few examples of the thousands of types of fungi that grow in warm, damp and humid environments.

Mold Health Concerns

Mold is found everywhere. It grows all year long and can be found both indoors and outdoors. Any area that is warm and humid should be checked for mold. Here are a few places where mold can be found around your house and yard:

  • Shaded areas that stay damp. The north side of a house or under a tree are two examples.
  • Areas where leaves and other plant material are left to decompose.
  • Bathrooms that are poorly ventilated.
  • Walls of underground basements, especially during the rainy seasons.
  • Food that has spoiled in the refrigerator.
  • After a flood. This is when mold causes the most severe problems.

For most people, mold is just an unsightly occurrence around the home. But, for people with allergies and lung illnesses, mold can be an irritant. Some of the symptoms of mold exposure include a stuffy nose, itchy eyes, wheezing and skin irritation. People that have a severe mold allergy or who have chronic lung problems may also experience a fever or a shortness of breath.

Common Types Of Household Mold

The most common indoor molds are Cladosporium, Penicillium, Aspergillus, and Alternaria.

Alternaria is a common fungus found on many types of fruits, vegetables and other plants. It starts out as a small and round dark spot which is covered with a black and fuzzy growth. It is known by many names including carrot leafblight, tomato early blight, broccoli headrot, fruit rot and fruit spot. Alternaria infections usually occur during periods of heavy rain or dew. Plants that are weak, stressed or damaged are more likely to be affected. To prevent alternaria mold in the garden plant seeds that are resistant to blight, rotate crops and control weeds.

Aspergillus is a common mold found in both indoor and outdoor environments. Indoors, aspergillus is found in household dust and building materials. Outdoors, aspergillus lives in the soil, on plants and in decaying organic matter. Aspergillus rarely causes infections in people with healthy immune systems. People with lung problems, such as asthma or cystic fibrosis, or a weakened immune system may experience pneumonia, pulmonary aspergillosis or fungus ball.

Cladosporium is a common mold that looks like black pepper. Cladosporium is non-toxic but can cause the most allergy symptoms. Indoors, it thrives in damp and dark environments. It prefers to grow on non-porous surfaces such as window frames, tile grout, toilet tanks and refrigerators. It is also found on fiberglass duct liners, food, paint and textiles. Outdoors, it is found on dead plants, woody plants, straw and in the soil.

Penicillium is a common mold that is found in dust, has a greenish color and a powdery texture. It is characterized by its heavy and musty odor. Outdoors, penicillium is found in composting and rotting vegetation. Indoors, it grows on food items and on water damaged building materials. It can become a problem because it grows in moist fabrics, wallpaper and wallpaper glue, chipboard, carpet and behind paint. Foods that are susceptible to penicillium include apples, cheese, herbs, cereal, nuts, onions and citrus.

Tips For Reducing Mold In The Home

Persons that are extremely sensitive to mold should avoid outdoor areas where mold is likely to grow, such as damp and wooded areas or around compost piles. Inside the home, mold can be kept to a minimum by reducing humidity levels and increasing ventilation in wet rooms like the bathroom, kitchen and basement. Other places that are likely to have mold include antique shops, flower shops, greenhouses, saunas and vacation homes that are closed up during part of the year.

No matter what type of mold may be lurking in your home, all molds have potential health effects and all molds are removed using the same methods. There are many commercial cleaning products that claim to remove mold. Another alternative is to use soap, water and a scrub brush. For severe cases of mold, use a solution of 1 cup bleach in 1 gallon of water.

When using bleach, follow these tips:

  • Do not mix bleach with household cleaning products. Combining bleach with ammonia or other cleaning solutions can cause toxic fumes.
  • Ventilate the room where the bleach will be used. Open the windows and turn on a fan to remove the fumes from the air.
  • Wear protective clothing, especially latex gloves and protective eye wear.

Here are some ways in which mold can be prevented before it turns into a problem:

  • Keep indoor humidity levels low. Running the air conditioner, a dehumidifier or a fan will help dry the air.
  • Add a mold inhibitor to paint. Mold inhibitors are especially useful in bathrooms, kitchens and other rooms that are damp.
  • Clean items that are susceptible to mold on a regular schedule. Toilets, showers and refrigerators are susceptible to mold growth.
  • Fix water leaks around the home. Check water pipes, windows and roofs for leaks and condensation.
  • Avoid the use of carpet in damp rooms, such as bathrooms and basements.
  • If there has been water damage, replace carpets and upholstered furniture that has been soaked. Mold can quickly grow after a flood, hurricane or other natural disaster that causes water damage.

Mold is a problem in every environment and it is impossible to completely rid of home of mold and its spores. The best defense against mold is to keep humidity levels low, fix any water leaks around the home, ventilate damp rooms such as bathrooms and clean up the mold as soon as it appears.

Last Updated: March 21, 2013
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About Coletta Teske Coletta Teske has 25 years' experience in tech journalism, as well as home and gardening topics. She has freelanced for Fortune 500 companies such as Boeing and Microsoft, published more than two dozen computer books for Prima Publishing and Macmillan, and worked as a freelance correspondent for West Hawaii Today. Coletta has been an avid gardener since she was 2 years old. While living in Hawaii, she achieved a lifelong dream of becoming a certified master gardener.

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