Mold-spore distribution and weather
Mold spores are microscopic reproductive structures produced by filamentous fungi, commonly found in environments with moisture, oxygen, and organic material. These spores are distributed through air, water, and animals, and their presence can significantly impact human health, particularly through allergic reactions and respiratory infections. In temperate and tropical regions, mold spores are more abundant, with higher spore counts occurring year-round in warmer climates compared to seasonal occurrences in colder areas.
The relationship between weather and mold-spore distribution is increasingly significant due to climate change. Rising temperatures are expected to lead to an increase in mold spore populations, potentially heightening allergy-related health issues and exacerbating conditions such as asthma. Certain molds, such as those causing coccidioidomycosis and histoplasmosis, may spread into new geographic areas as the climate warms. Additionally, the increase in mold-related plant diseases could negatively affect plants' ability to absorb carbon dioxide, further contributing to climate change. Overall, managing mold populations effectively may depend on addressing the broader issue of global warming.
Subject Terms
Mold-spore distribution and weather
Definition
Mold spores are reproductive structures of filamentous fungi (molds). A single microscopic mold filament, called a hypha, forms a mat that is called a mycelium. Mycelia are visible without a microscope. Molds are very common organisms and can be found where there is moisture, oxygen, and food they need. Molds can be seen on bread, cheese, or fruit. Hot spots of mold growth can be found in basements and bathrooms (especially shower stalls), house plants, and even air conditioners. Molds grow on fallen leaves, rotting logs, certain grasses, and weeds. They can alsobe found in barns, dairies, bakeries, and greenhouses.
The mold mycelium produces reproductive branches above the surface of the mold. These branches carry spores called conidia that function by the distribution of mold by air, water, and animals. Among different molds, spores—employed in asexual reproduction—vary in size, shape, and color. Each spore can germinate to start a new mold, which in turn produces millions of spores. Spores are very tough structures: they are resistant to drying, freezing, heating, and some chemicals.
The majority of the mold spores are disseminated by air. A sample of air may contain up to 2 million spores per cubic meter, but on average, about 10,000 spores inhabit one cubic meter of air. The amount of mold spores in the air in some areas is greater than the amount of pollen. Certain types of mold spores can cause various allergic reactions in humans, such as irritations of the eyes, nose, and throat. About 20 to 30 percent of the population develops allergic responses after exposure to these mold spores. The most common allergenic spores in the United States are Alternaria cladosporium, Aspergillus, Fusarium, Mucor, Rhizopus, and Penicillium.
In some people, exposure to mold spores leads to asthma. Some mold spores, if they reach lungs, can cause infections called mycoses. Systemic mycoses are the most serious category of mold infection. The host becomes infected by inhaling spores that germinate in the lungs. In the United States, two of the most common mold infections of that type are coccidioidomycosis, caused by Coccidioides immitis, and histoplasmosis, caused by Histoplasma capsulatum. Mild coccidioidomycosis may go unnoticed or produce symptoms similar to those of pneumonia or tuberculosis. The human immune system normally destroys mold spores and neutralizes mold infections. In some cases, however, more serious coccidioidomycosis develops and lesions of the skin, bones, joints, internal organs, and brain (meningitis) occur. Progressive histoplasmosis symptoms include lung cavities, sputum production, night sweats, and weight loss.
Significance for Climate Change
The weather and mold-spore distribution are closely related. Spore count is usually higher in temperate and tropical regions than in the polar and northern regions. In colder climates, molds are present in the air during the period between late winter and late fall. In warmer climates, mold spores are found throughout the year. It is likely that warmer temperatures due to global warming will result in an increase and even abundance of mold spores and, therefore, a considerable increase of allergic reactions. Repeated exposure to a massive amount of mold spores (100 million per cubic meter) can cause serious allergy-related health problems, including chills, fever, dry cough, breathlessness, weight loss, and even permanent lung damage.
Global warming is believed to be a major factor in the explosion of mold-related asthma and mold infections. For instance, the causative agent of coccidioidomycosis can be found in geographical areas with high summer temperatures and mild winters. In the southwestern regions of the United States, where this climate prevails, an estimated 80 percent of inhabitants are currently infected. Infectious disease specialists suggest that global warming will cause the further expansion of the geographic ranges of coccidioidomycosis infection.
Scientists predict that climate change could also increase the spread of histoplasmosis, which at present afflicts about 500,000 people annually. Another example of mold-spore infection spreading as a result of climate change is the infection caused by Cryptococcus gattii. Though previously it was only seen in Australia and other subtropical regions, this mold is spreading in Canada’s Vancouver Island and the Pacific Northwest. It can cause serious human infection of the lungs and brain.
In addition, molds are the cause of numerous plant diseases. The increase of plant fungal diseases due to global warming may have a negative impact on plants’ ability to take up carbon dioxide (CO2), a greenhouse gas, thereby increasing the CO2 concentration of the atmosphere and contributing to further warming. Managing mold plant infections may also require pesticides, whose production consumes and generates even more CO2 emissions. Research in 2022 found that climate change has also caused increases in aflatoxin, a chemical that is produced by a type of mold, and that it will likely continue to increase in the majority of US states that grow corn. This is likely to cause widespread damage to crops in the nation's Corn Belt.
There is another indirect relationship between mold spores and climate change. In nature, many molds are capable of decomposing woody plants, such as trees. Cellulose and lignin in these trees are the biological molecules most resistant to decomposition. Molds, however, use cellulose and lignin from woody plants as their source of energy and carbon, and they release CO2 in the process. Trees function as carbon sinks, retaining carbon for the duration of their lives and sequestering it from the atmosphere. As increases the amount of mold spores and, eventually, molds, the CO2 released by the decomposition of woody plants by those molds will also increase. Eliminating mold spores is impractical. Therefore, the only solution to keep molds under control is to control global warming.
Bibliography
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