What Is Alternaria
Alternaria is a genus of filamentous fungi commonly found outdoors on decaying plant material, soil, and vegetation. It enters buildings primarily through air infiltration, open windows, and HVAC systems, making it one of the most frequently detected molds in indoor air samples across North America.
Identification and Testing
Alternaria spores are distinctive under microscopic examination. They appear as large, dark-pigmented, multi-celled structures with a characteristic "shield" or "club" shape. When you conduct air quality testing or surface sampling, a certified laboratory can identify Alternaria using either tape lifts, bulk samples, or spore trap analysis. EPA-approved mold inspection protocols typically include air sampling in occupied spaces and basement areas where moisture accumulation occurs. Spore counts above 1,500 spores per cubic meter in indoor air suggest active colonization or outdoor air infiltration that warrants investigation.
Health Effects and Allergen Properties
Alternaria is classified as a potent allergen. Exposure triggers allergic rhinitis, asthma exacerbation, and hypersensitivity pneumonitis in susceptible individuals. Studies show that people with existing asthma who are sensitized to Alternaria experience significantly increased respiratory symptoms during high spore seasons, typically late summer through fall. The fungus produces proteins that activate IgE-mediated immune responses. Individuals with compromised immune systems or chronic lung disease face elevated risk from prolonged exposure.
Moisture Control and Remediation
Alternaria thrives in environments with relative humidity above 65% and surface temperatures between 68 to 77 degrees Fahrenheit. Remediation begins with moisture control. Identify and repair water intrusion points, install dehumidifiers to maintain indoor humidity below 50%, and ensure adequate ventilation in bathrooms and kitchens. During active remediation, containment protocols isolate affected areas using plastic sheeting and negative air pressure equipment. Workers follow OSHA guidelines for respiratory protection and use EPA-registered fungicides or detergent solutions for surface cleaning. HEPA filtration captures spores during demolition or cleanup of contaminated materials.
Common Questions
- How do I know if I have Alternaria indoors? Visual inspection alone is unreliable. Request air quality testing or surface sampling from a certified mold inspector. Compare indoor air samples to outdoor baseline samples, which is standard EPA practice for diagnosis.
- Can I clean Alternaria myself? Surface contamination under 10 square feet can be cleaned with detergent and water, then dried thoroughly. Larger areas require professional containment and remediation to prevent spore dispersal throughout your home.
- Does fixing the humidity problem eliminate Alternaria? Reducing humidity stops new growth and allows existing colonies to die. However, dead spores and fragments remain allergenic. Professional cleanup removes accumulated spore material and prevents recurrence.