Hazardous moulds

hazardous moulds-respiratory irritation

From the amazingly large group of fungi there are perhaps 30-40 species commonly found indoors. The term “hazardous moulds” is a relative one because each and one of us is susceptible to mould to a different degree. Some of us can be exposed to very large concentration of moulds spores without experiencing ill effects but some less fortunate ones will be strongly affected. From all the species regularly found in our homes some are particularly important due to the fact they are known to cause harm.


Penicillium mould is usually one of the first one to appear if our home suffers from condensation or a damp problem. Penicillium is mainly considered to be hazardous mould because it can spread extremely quickly, colonise large surface areas and most importantly produce vast amounts of irritating spores. There is only a small risk of health damage from penicillium mould in normal situations but like with any other moulds it can pose a serious threat in hospital environment.

Aspergillus mould similarly to penicillium can spread rapidly across water damaged surfaces. It produces vast amount of mould spores very similar to those of penicillium. Aspergillus as hazardous mould is well known to everybody because it causes disease called aspergillosis. The level of hazard this mould poses to a human largely depends on the state of one’s immune system.

Alternaria mould is a mould with worldwide distribution which produces relatively large and characteristic spores and therefore is easily identified by competent microbiologist. It can quickly colonised damp surfaces and cause respiratory irritation. Alternaria mould produces several mycotoxins but they are not as well known as those from other species. Human infections are known but are largely confined to hospital patients with severely reduced immunity.

Cladosporium mould is possibly the most wide spread and most abundant mould in the worlds. It does not produce large amount of mycotoxins but the spores can be found almost everywhere and at all times. It is considered to be hazardous mould mainly through the production of very large number of irritating spores. Exposure to Cladosporium spores in large quantities usually results in allergic reaction.

Mucor mould is not as well known as the other common species and cannot be identified just from mould spore samples. Culturing or DNA analysis are usually required to identify this mould. It has been reported to cause infection in a limited number of otherwise healthy individuals. The primary route of infection was through open wounds. It is considered to be a hazardous mould in hospital environment.

Fusarium is a well know hazardous mould for it production of very potent mycotoxins. It is causing great deal of damage to agricultural animals in third world countries where control measures are not as well developed as in the western world. Presence of Fusarium mould in the indoor environment always signifies a serious health hazards and thorough investigation and decontamination should be carried out on areas contaminated by this fungus.

Stachybotrys mould is possibly one of the most infamous hazardous moulds described in the literature. It is not as hazardous as some other species but has been widely reported which has contributed to its recognition as “The Black Toxic Mould “. It does not produce large amounts of spores and the fact that the spores develop in slimy balls makes it harder to spread around. Its main hazard potential lays in the production of very potent mycotoxins which can cause serious health problems. Chronic, long term exposure to this mould and its toxins is considered as the main hazard and its presence indoors always indicated potentially serious water damage

Chaetomium mould is considered to be an indicator of water damage in properties. It has been linked to several serious health conditions affecting neurological system.

Other slightly less common hazardous moulds are:
Trichoderma  and others