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by Vanessa Graham

It may surprise you to learn that regions with high humidity are not the only places in which you have to worry about mold. While mold spores thrive in dampness and standing water, other factors also contribute to the prevalence of mold in a given area, such as building maintenance and construction practices. Learning more about mold growth is more important now than ever because the number of people in the United States with mold allergies keeps growing, according to a 2011 study by Quest Diagnostics.

Read more about a new technology that can destroy mold.

Why is mold so bad for respiratory health? Which cities should people with mold allergies avoid? Is it possible to protect yourself and your family from the mold in your city? Let us take a closer look at what causes mold growth and why some cities may have more mold than others.

Mold as an allergy trigger

Mold is a type of fungi found both indoors and outdoors. Indoor mold typically grows in the places in your house with the highest humidity, including showers and basements. Mildew is a type of mold that you may find on flat, damp surfaces in your home. While the health effects of mildew may be less severe than other types of mold, you should still take caution and remove it from your home.

Mold thrives in warm, damp environments and spreads through the creation of spores. Mold spores are airborne pollutants that can cause allergic reactions in some people. If you are naturally sensitive to mold, it may trigger respiratory symptoms including red and itchy eyes, runny nose, headaches, skin rashes and sneezing. People with asthma or specific mold allergies may experience more severe reactions to the presence of mold, such as a fever or difficulty breathing.

Are some groups of people more sensitive to mold?

Some people are naturally more sensitive to the presence of mold, including children and people with asthma. The Quest Diagnostics study found that people with asthma were 1.5 times more likely to have a mold allergy and that children under the age of 12 were the most sensitive to mold exposure.

People living with asthma should avoid contact with mold because it could trigger an asthma attack. In some instances, exposure to mold may cause people who are otherwise healthy to develop asthma, according to the CDC. Additionally, there is evidence to support a link between the presence of mold in homes and the development of childhood asthma (Vesper, et. al, 2013).

What causes indoor mold growth?

Indoor dampness and humidity can create a perfect environment for mold growth, either on visible interior surfaces or surfaces hidden inside walls and HVAC systems. Sources of indoor moisture can vary, including leaky roofs, walls and plumbing systems, groundwater entry, damp construction materials, entry of humid outdoor air and insufficient dehumidification, water vapor condensation and floods.

Any situation that causes an unchecked accumulation of moisture can create a breeding ground for mold and bacteria. Mold contamination has been found in homes, schools and office buildings across the United States. The spores created by molds and bacteria can contain allergens and chemicals that may cause respiratory system inflammation when inhaled.

Do mold counts vary by geographic location?

Throughout the years, attempts have been made to understand whether different geographic locations may facilitate different rates of mold growth. A 2011 study suggested that outdoor humidity and precipitation may affect the environment within a building, but that those factors do not affect indoor dampness as much as the structural integrity of the building. If this is true, then mold growth could vary according to building construction and maintenance rather than geographic location (Vesper, et. al, 2011).

The study found that mold growth was evenly distributed in homes throughout the United States, but the authors noted that certain species of mold were found in higher concentrations in specific geographic locations. For example, Aspergillus was found mainly in homes across the eastern United States, while Penicillium was found primarily in the West (Vesper, et. al, 2011). More research is needed to determine whether these differences were due to a difference in climate or in the types of buildings found in those areas.

Worst places to live for a mold allergy sufferer

While some studies argue against a relationship between mold growth and geographic location, there is data to suggest that mold growth concentrations differ from city to city. In 2011, Quest Diagnostics completed a study that compiled laboratory test results from patients seeking medical care to relieve allergy symptoms. Nearly 14 million test results from over 2 million patient visits were analyzed to determine the prevalence of allergen sensitization in 30 of the most populous metropolitan areas in the United States.

The term “sensitization” is used to describe when a patient tests positive for an allergen-specific immunoglobin E (IgE). IgE antibodies in the blood are found at higher levels when your body is sensitive to a particular allergen.

10 Worst cities to live in if you have a mold allergy

Though mold is present in buildings all over the United States, the cities below had the highest percentages of allergy patients that showed sensitization to mold.

10. San Antonio—15%

San Antonio skyline

9. Kansas City—16%

8. Denver—16%

7. Saint Louis—16%

6. Minneapolis-St. Paul—16%

5. Chicago—17%

Chicago city skyline

4. Los Angeles—17%

3. Phoenix—19%

2. Riverside-San Bernardino—20%

1. Dallas—21%

Dallas city skyline

3 Worst states to live in if you have a mold allergy

According to the data in the Quest Diagnostics study, the top 3 worst states for mold allergies are:

  • California, with four cities in the top 20 worst cities for allergy sufferers
  • Ohio, with two cities in the top 20, ranked 8th and 10th
  • Texas, with two cities in the top 20, ranked 1st and 20th

The southwestern United States was found to be the worst region overall for mold allergy sufferers. It is home to four of the top five worst cities for mold sensitization.

Environmental factors that contribute to mold growth

Factors such as climate and the likelihood of natural disasters can contribute to the prevalence of mold allergens in your area. For example, during warmer months when humidity is higher, mold levels are higher. According to the American Academy of Allergy Asthma and Immunology, mold growth typically peaks during July in warmer states and October in colder states. However, mold spores can be found all year in the South and on the West Coast.

Natural disasters, such as hurricanes, tornadoes and floods can cause excess moisture and standing water in buildings. This facilitates mold growth and should be taken into consideration when returning to your home after a natural disaster. For example, harmful concentrations of mold were found in buildings that had sustained water damage during Hurricanes Katrina and Rita (Roa, et. al, 2008).

How to stay safe from the effects of mold

While certain geographic locations may have a higher prevalence of mold growth, the Quest Diagnostics study notes that there are no cities in America that are completely allergen-free. Fortunately, there are steps that you can take to decrease your family’s exposure to mold.

  • Track mold counts—Use a tracker, such as the one provided by the National Allergy Bureau, to monitor mold spore counts in your area. On days when mold spore levels are high, it is best to limit outdoor activity, as well as to keep windows and doors closed as much as possible to prevent outdoor air from entering your home.
  • Wear a pollen mask—If you cannot avoid being outdoors when mold counts are high, consider wearing a pollen mask to decrease the number of mold spores that you inhale. Avoid yard work when mold counts are high.
  • Control humidity levels in your home—Use air conditioners and dehumidifiers to make sure that the relative humidity in your home does not go over 50%.
  • Increase ventilation in your home—Increasing ventilation, especially in bathrooms and cooking areas, can help decrease the concentration of mold spores in your home.
  • Clean regularly and remove visible moldCertain areas in your home are more susceptible to mold growth than others. If you find mold, you can clean it from hard surfaces with soap and water, commercial mold-removing products or a bleach solution of one cup of laundry bleach in one gallon of water. Clean your house regularly and monitor for any dampness or standing water. If you suspect you may have a mold problem, consider a mold inspection.
  • Get an air purifier— Adding an air filter to your home can improve your overall indoor air quality and decrease the concentration of mold allergens in the air that you breathe. There are a few types of air purifier technology that can filter mold. The Molekule technology has been independently verified by a third-party laboratory to destroy airborne mold spores.

Exposure to mold can seriously affect your health, especially if you have asthma or allergies. Whether you live in one of the worst cities for people with mold allergies or not, you can benefit from keeping mold out of your home. Being mindful of the factors that contribute to mold growth and working to improve the air quality of your home can go a long way in protecting your respiratory health.

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