Mold is common both indoors and outdoors. Many encounter mold in their homes, leading to concerns about its health impact. A frequent concern is whether mold can cause cancer. This article clarifies the scientific understanding of mold exposure and its relationship to human health, specifically addressing its link, or lack thereof, with cancer.
Addressing the Cancer Question
Exposure to common indoor molds is not directly linked to cancer in humans. Major health organizations, including the U.S. Environmental Protection Agency (EPA) and the World Health Organization (WHO), do not classify common indoor mold as a carcinogen. Research lacks strong epidemiological evidence supporting a direct causal link between typical indoor mold exposure and cancer.
Mold exposure most frequently causes respiratory problems and allergic reactions, not cancerous growth. While mold has been theorized to indirectly contribute to cancer by suppressing the immune system or causing chronic inflammation, this lacks clinical support for common indoor exposures. Therefore, for most people encountering mold in their homes, cancer should not be the primary concern.
Mycotoxins and Their Carcinogenic Potential
Some types of mold produce toxic compounds known as mycotoxins. These mycotoxins differ from common household mold. While common molds like Cladosporium, Penicillium, and Alternaria are not associated with cancer, certain species, such as Aspergillus flavus and Aspergillus parasiticus, produce potent mycotoxins called aflatoxins.
Aflatoxins are classified as Group 1 carcinogens by the International Agency for Research on Cancer (IARC). These toxins commonly contaminate agricultural crops like maize (corn), peanuts, cottonseed, and tree nuts, especially in warm, humid regions. Exposure to aflatoxins primarily occurs through the ingestion of contaminated food products or by consuming meat or dairy from animals that have eaten contaminated feed.
Chronic exposure to high levels of aflatoxins, particularly through contaminated food sources, is a well-documented risk factor for liver cancer. For instance, populations in sub-Saharan Africa, Latin America, and Asia, where food contamination by aflatoxins and fumonisins is prevalent, show a heightened risk of liver cancer. This type of exposure, often involving consistent consumption of contaminated staple foods, differs significantly from inhaling spores from typical household mold growth.
Common Health Effects of Mold Exposure
While common indoor mold is not linked to cancer, it can cause other health problems. The most frequently reported symptoms are allergic reactions and irritation. Individuals may experience sneezing, a runny nose, red and itchy eyes, or a skin rash. These allergic responses can be immediate or delayed.
Mold exposure can also cause respiratory issues. People with asthma may experience worsening of their symptoms, including coughing, wheezing, and shortness of breath. Even for individuals without pre-existing allergies or asthma, mold can cause irritation of the eyes, skin, nose, throat, and lungs. In more severe cases, prolonged exposure to damp, moldy environments has been associated with hypersensitivity pneumonitis, an inflammation of the lungs. Individuals with compromised immune systems or underlying respiratory conditions may be more susceptible to these effects.