Drive down just about any main street in Anytown, USA, and you will notice those unsightly dark streaks running down the roofs and siding of houses. You also might notice that those streaks are more than just dark-colored but often include a vast array of greens, browns, yellows, and the like. They extend beyond the roof to encompass the northerly sides of buildings and cling to gutters and window frames. It’s so widespread you could call it an epidemic. If you are experiencing respiratory problems, this seemingly insignificant microorganism could be to blame.
Primary Colonizer Science
Microorganisms (such as bacteria) are often the primary colonizers of newly created environments. They colonize what initially appear to be inhospitable substrates such as bare rock, glacier surfaces, and even the exterior of the International Space Station.
The next microorganisms to arrive are the Lichens, organisms formed from a symbiotic relationship between fungi and algae. Well, our roofs and building exteriors could be called inhospitable substrates, and these extremophile bacteria are colonizing them at alarming rates.
Recent studies have shown that mold and fungi aren’t just surviving — they’re thriving — in extreme environments, including outer space, landfills, and dark, oxygen-deprived areas. This includes species such as Pestalotiopsis microspora, Aspergillus terreus, and Engyodontium album, which can survive without sunlight or oxygen. These extremophile fungi highlight just how resilient and potentially invasive mold organisms can be, colonizing not only rooftops but also crawlspaces, insulation, and areas homeowners may never think to inspect.
Asphalt Shingles
Asphalt shingles are a type of roof shingle that uses asphalt for waterproofing purposes. An American invention first used in 1903, asphalt shingles have been used in roofing projects all over the globe for over a century. It is relatively inexpensive, easy to install, and available in many colors. Making asphalt shingles the go-to roofing material for many homes.
Unfortunately, changes in the asphalt mix are attracting primary colonizing bacteria, the most prevalent being Gloeocapsa magma, which gained notoriety in the Southeast in the 1990s for the dark-stained roofs it causes. C. magma has since spread throughout the United States and Canada. It’s probably in your neighborhood, and you didn’t even give it a second thought. But if your family is having odd respiratory issues, you might want to pay closer attention to this cyanobacteria.
What is Gloeocapsa Magma?
It is a cyanobacteria that originates in fresh water and relies on photosynthesis for energy. As the bacteria drifts from local water sources and starts to colonize your roof, it initially looks like algae in part due to its greenish-blue color.
It can thrive anywhere on your asphalt shingle roof, but it tends to favor north-facing sides of your home that hold moisture a little longer. But it isn’t the only airborne algae or cyanobacteria found. There are dozens and dozens of these microorganisms that have been shown to induce allergens or produce toxins (Genitsaris, 2011).
Is It Dangerous?
Gloeocapsa magma is a particularly aggressive fungus that can wreak havoc with your roof as it eats away at the calcium carbonate (CaCO3) in the limestone filler used to weigh your asphalt roof shingles down. It also can join with fungus to create Lichens, tougher organisms than algae alone. All combined, they will be unsightly, reduce the value of your home, and shorten the life expectancy of the roof,
And while C. magma eats your roof; it will cause the shingles to weaken and start to break down into small dust-like granules. Most experts within the subject area conclude the bacteria to be harmful if left untreated, as the growth holds moisture within shingles, causing premature aging, rotting, and/or granule loss.
As the bacteria goes through its life cycle it too will die and start to breakdown casting off secondary metabolites like Cyanotoxins. When on your home, Cyanotoxins saturate the resulting roof dust much the same way it collects along the shorelines of lakes, ponds and rivers. There it can work its way into the bio-burden of the home or impact occupants entering and exiting the home.
Health Effects from Cyanotoxin Exposure
While the research regarding C. magma on your roof is scant, exposure to cyanotoxins has been well-established around algal blooms and red tide. Adverse health effects may range from a mild skin rash to serious illness or, in rare circumstances, death. Acute illnesses caused by short-term exposure to cyanobacteria and cyanotoxins during recreational activities include hay fever-like symptoms, skin rashes, and respiratory and gastrointestinal distress. And yes, your dog is susceptible too.
Mold That Eats Plastic?
According to The World Economic Forum and Reuters, certain mold and fungi species are now known to digest plastic, including the kinds found in landfills. These fungi, such as Pestalotiopsis microspora, have enzymes that break down plastic polymers like polyurethane. Even more astounding, they can do this in complete darkness and without oxygen. That means they can survive in landfills — or sealed, dark home environments like behind walls, inside vents, or deep inside insulation.
These fungi don’t just consume plastic — they convert it into edible biomass. This adaptation may offer a potential breakthrough in addressing plastic waste, but it also reveals something important about your home: mold doesn’t need light or fresh air to grow. If conditions are right (moisture, organic material, warmth), it will find a way — and thrive in ways we’re only just beginning to understand.
🚫 If mold can digest plastic in a landfill, imagine what it can do to your home if left unchecked.
How Fungi Are Breaking Down Plastic—Even in the Dark
- Fungi and Plastic Degradation: Certain fungi, including some found in soil and landfills, possess enzymes that can break down the chemical bonds in plastic polymers.
- Enzymatic Action: These enzymes, like hydrolases, hydrolyze (break down) plastic polymers into smaller, soluble units (monomers).
- Biodegradation: The fungi then use these monomers as a source of carbon and energy, effectively consuming the plastic and converting it into biomass.
- Examples: Aspergillus terreus and Engyodontium album have shown the ability to degrade plastic in as little as 140 days, even in the dark and without oxygen, making them suitable for landfill conditions. Pestalotiopsis microspora is another fungus that can degrade polyurethane, a common plastic, even in anaerobic (oxygen-free) environments.
- Landfill Applications: The ability of these fungi to break down plastic in the absence of light and oxygen makes them promising candidates for treating plastic waste in landfills.
What Do I Do Now?
There is currently no cure to eradicate roof algae, only better management, where roof replacement is the best choice. While the research on the topic regarding the dangers of rooftop fungus, algae, and lichens is scant, experts do agree that fungus should be remediated and waterborne cyanobacteria should be avoided. It’s best to play it safe and get rid of it if you have it. Or reach out to the Indoor Air Quality (IAQ) experts at GreenWorks if you suspect your IAQ has been compromised.
Tips from the Pros
References
Asphalt Roofing Manufacturers Association (ARMA). (2017, 05 10). History of Alphalt Roofing and Algae Discoloration of Roofs. Retrieved from Asphalt Roofing: https://www.asphaltroofing.org/algae-discoloration-of-roofs/
Environmental Protection Agency. (2023, 07 13). Health Effects from Cyanotoxins. Retrieved from Cyanobacterial HABs: https://www.epa.gov/cyanohabs/health-effects-cyanotoxins
Environmental Protection Agency. (2023, 07 11). Learn about Cyanobacteria and Cyanotoxins. Retrieved from Cyanobacterial HABs: https://www.epa.gov/cyanohabs/learn-about-cyanobacteria-and-cyanotoxins
European Space Agency. (2005, 08 11). Lichen Survives in Space. Retrieved from European Space Agency Science & Exploration: https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Lichen_survives_in_spaceGenitsaris, S. (2011). Airborne Algae and Cyanobacteria: Occurance and Related Health Effects. Frontiers in Bioscience, 772 – 787.
World Economic Forum. (2023, June 7). The plastic-eating mushroom that could help fight pollution. Retrieved from: https://www.weforum.org/agenda/2023/06/plastic-eating-mushroom-fungi-environment/
Earth.org. (2023, March 1). Plastic-Eating Mushroom of the Amazon and Ecuador’s Development Dilemma. Retrieved from: https://earth.org/plastic-eating-mushroom-of-the-amazon-and-ecuadors-development-dilemma/
Lamycosphere. (2023). Plastic-Eating Mushrooms: A Natural Solution to the Pollution Crisis. Retrieved from: https://lamycosphere.com/en-int/blogs/the-future-is-fungi/plastic-eating-mushrooms-a-natural-solution-to-the-pollution-crisis
National Institutes of Health (NIH). (2022, November 23). How Superworms Make Styrofoam Into a Healthy Meal. Retrieved from: https://www.ncbi.nlm.nih.gov/search/research-news/16509/
Reuters. (2023, May). Fungus found that turns plastic into food — even in complete darkness.
Published on: Feb 27, 2024
Updated on: July 1, 2025
