Mould in homes is a frequent concern and often associated with cultural issues related to the aesthetics of mould and musty odours. However, beyond aesthetics, mould is associated with respiratory illnesses, particularly asthma. However, public concern has now shifted towards more serious impacts on health, with some individuals linking mould exposure, particularly “black mould”, to serious conditions such as potentially fatal lung disease in children.
The most prominent mould connected to these considerations is Stachybotrys chartarum, also referred to as black mould. S. chartarum can be seen on damp walls and ceilings with its dark colour. In 1990, it received extensive media attention following several cases in the United States involving infant deaths which had been linked to haemorrhagic lung disease (bleeding occurring in the lungs). The initial assumption was that mycotoxins produced by this fungus were involved in these cases of lung disease.
Mycotoxins are toxic compounds produced by certain species of fungi to protect themselves. Mycotoxins are not only produced in damp buildings but also other contaminated food items such as cereals, dried fruit, nuts, and spices. Mycotoxins can be associated with a wide range of health effects from acute poisoning (often associated with food consumption) to chronic (long-term) health conditions (such as cancer, immune suppression). The World Health Organization and the Food and Agriculture Organization evaluated these dangers through a joint committee called JECFA, which facilitates the development of international food safety standards.
The toxic compounds S. chartarum can produce are roridin and satratoxin. These toxins can inhibit protein synthesis. It is known that toxicity associated with high degrees of these substances can produce tissue necrosis. Tested in laboratory animals, lethal doses of S. chartarum can lead to lung bleeding. However, scaling this result to real-world exposures in humans is complicated.
One reason it is challenging to translate laboratory settings to actual S. chartarum exposure situations is that it does not rapidly disperse spores into the home environment. Spores produced by S. chartarum tend to coalesce or group together in a slime mass. It is unlikely to find large quantities of spores being released into the environment. Additionally, the first research linking black mould to infant lung disease has been found to have significant methodological problems. For example, the doses of spore exposure were not calculated correctly, and after recalculating the dose exposures, the links to lung disease disappeared.
The American Academy of Allergy, Asthma and Immunology states that there is currently no credible evidence to suggest that the mycotoxins produced by black mould are contributing to significant health problems. Mould is still, nevertheless, a health hazard; just not in the ways we may assume.
Moulds are significant allergens. Mould exposure may exacerbate asthma, which contributes to sinusitis or, in rare instances, may induce hypersensitivity pneumonitis. Individuals with weakened immune systems may face an increased risk of infections due to mould exposure. The allergic and immune responses are the central rationale for experts’ recommendations to remove mould and dampness from residences.
In conclusion, while mould (particularly in wet environments) can provoke a range of allergic reactions and respiratory symptoms, questions surrounding the potentially dangerous and toxic effects of black mould are unsubstantiated by current scientific evidence. Good ventilation, vigilance around moisture, and prompt cleanup are likely the most effective responses against potential health effects.
For more detailed insights into Stachybotrys chartarum (black mould), including its classification, characteristics, and associated health risks, you can explore our in-depth profile here.
References: Musgrave I. Is black mould really as bad for us as we think? A toxicologist explains. The Conversation. Published June 5, 2025. https://theconversation.com/is-black-mould-really-as-bad-for-us-as-we-think-a-toxicologist-explains-258173
