Moulds are becoming an increasing source of indoor air pollution

Moulds are becoming an increasing source of indoor air pollution and may trigger asthma attacks in susceptible individuals. Andrew Kibble, Shalini Pooransingh and Patrick Saunders review the facts

In recent years, there has been widespread concern over the toxic mould, Stachybotrys chartarum (atras). This has been cited as a potential cause of human disease. What are the true health implications?

Fungi are simple organisms, possessing cells with nuclei and rigid cell walls but lacking chlorophyll. A key characteristic is the ability to produce spores, which can be air-, water-, or insect-borne. Typical fungi include mushrooms, yeasts, toadstools, rusts, moulds and mildews. Fungi are common in the environment, and human exposure is inevitable1).

Fungi produce a range of chemicals, called mycotoxins, which are thought to have developed as a chemical defence system2). Approximately 400 mycotoxins are known. Some affect humans and animals adversely, but some also have beneficial effects, such as penicillin.

Moulds are microscopic fungi and are commonly found indoors where there is excessive moisture. They typically grow on wood, paper, carpet and foods, but have been found on a variety of surfaces, particularly on organic substrates rich in cellulose. These include gypsum, jute, vinyl, and paper wall coverings. They have also been recovered in a variety of dust and lint samples and in tobacco3).

The 'toxic mould'
Several moulds, including species of Fusarium, Trichoderma, and Stachybotrys, have the potential to produce extremely potent mycotoxins. The species most frequently implicated as the 'toxic mould' is Stachybotrys, which belongs to the class of fungi called the deuteromycetes. The most common species is Stachybotrys chartarum (also known as S atras), which is greenish black in appearance and typically slimy or wet to the touch.

S chartarum prefers to grow on materials high in cellulose and low in nitrogen content. It thrives in places of high humidity and on materials that have become moist or waterlogged. It is not found on materials such as plastic, vinyl, or ceramic tiles. Constant moisture is required for growth and areas prone to excessive humidity or water damage are most likely to be affected. Stachybotrys is relatively slow growing both in nature and in the laboratory3).

Stachybotrys toxins
Mycotoxins are lipid-soluble and are readily absorbed by the intestinal lining, airways and skin4). Many are capable of producing illness and even death in animals and humans, and some have been used as biological warfare agents. The Assyrians are known to have poisoned enemy wells with rye ergot in the sixth century BC2).

Many species of mould, including Stachybotrys, produce mycotoxins called trichothecenes. When ingested, these mycotoxins can affect the gut and bone marrow and cause a medical condition called alimentary toxic aleukia. This is characterised by the absence or extremely decreased number of white blood cells in the circulating blood. This disease is thought to have affected thousands of people exposed to contaminated straw in Eastern Europe in the 1930s5).

S chartarum also produces a range of trichothecenes called satratoxins. These can inhibit protein synthesis and cause haemorrhaging2. These satratoxins are generally produced in greater quantities than other trichothecenes5.

Human exposure
The main routes of exposure to moulds include inhalation of airborne spores, direct contact, or ingestion of contaminated food. Stachybotrys colonies are typically wet and slimy, and it is therefore unusual for spores from active colonies to become airborne. However, there is increased risk of air dispersion when colonies die or become dehydrated, or if the colony is disturbed or damaged. The health effects of Stachybotrys can be allergic or toxic.

• Allergic effects: Many moulds, not just Stachybotrys, can potentially affect health, and all moulds should be treated the same when it comes to removal. Some people are sensitive to moulds and may experience nasal stuffiness, eye irritation and wheezing. More severe reactions can occur in those exposed to high levels of moulds in occupational settings, such as farmers working with mouldy hay6). Individuals with chronic respiratory disease may experience difficulty in breathing. Asthma attacks may be triggered, and asthmatics should avoid exposure to moulds. Individuals with reduced immunity may also be at increased risk for infection from moulds. There have been no reported cases of hypersensitivity lung inflammation caused by Stachybotrys3.

• Toxic effects: Stachybotrys is thought to have been responsible for significant health problems in both animals and humans in Siberia in the 1930s. A large number of horses suffered from gastrointestinal haemorrhages and ulceration after ingesting barley, corn and wheat contaminated with Stachybotrys. Symptoms were also reported in farmers who were exposed through handling contaminated straw. Indeed, acute toxicity resulting from inhalation of the Stachybotrys mycotoxins in Siberia and other parts of the former Soviet Union in the 1930s led to this disease being termed stachybotryotoxicosis.

Possible inhalation exposure to mycotoxins from Stachybotrys has also been linked with acute pulmonary haemorrhage in infants: a number of reports of acute pulmonary bleeding in the USA have been thus linked4)&6).

Skin exposure to the Stachybotrys may cause problems, with dermatitis and inflammation being reported among people handling contaminated materials such as straw and mouldy horticulture pots3).

How common is Stachybotrys?
The most common species of indoor moulds are Cladosporium, Penicillium, Aspergillus, and Alternaria. Stachybotrys is typically found at low concentrations and is rarely the dominant fungus. There is little information on the relative occurrence of Stachybotrys. However, it is most prevalent in buildings which have sustained considerable water damage, for example through flooding or broken pipes, and on gypsum wallboards.

Detection and prevention
The presence of excess moisture and signs of water damage or ingress may indicate possible areas of mould growth. Materials that may provide an ideal growth medium, such as paper, cardboard or wood, should be identified. Indoor air sampling for mould spores is a common approach to confirming the presence of moulds, but this technique may be unreliable with Stachybotrys, since spores from active colonies do not become readily airborne.

Visual examination of the colony and its location may help identify Stachybotrys. However, care should be taken when inspecting any colony that resembles Stachybotrys. Samples of suspected colonies should only be taken by qualified contractors and sent to a microbiology laboratory for species confirmation.

Prevention involves avoiding water ingress and excessive humidity. Humidity levels should be kept below 50%. Areas likely to suffer from excessive humidity should be well ventilated.

Fungi are ubiquitous in the environment and human exposure is inevitable. The moulds that produce mycotoxins will be among those commonly growing in people's homes. There are a few case reports linking these toxic moulds with exceptional conditions such as pulmonary haemorrhage, but it is important to note that no causal relationship has been established. The common health concerns involving moulds include allergic reactions. Certain individuals, such as those with chronic respiratory disease, or those with reduced immunity, may be at increased risk.

Businesses should take a commonsense approach to mould prevention and treatment inside buildings. This involves good building maintenance, ventilation and cleaning regimes. The measures that are taken to prevent or treat common moulds will also deal with toxic moulds.

1) Page, E. and Trout, D. 1998: Mycotoxins and building related illness. J Occup Environ Med 40:761-763.

2) Etzel, R. 2002. Mycotoxins. JAMA. 287: 425. 3) Terr AI. 2001. Stachybotrys: relevance to human disease. Ann Allerg Asthma Im 87(6 Suppl 3):57-63. 4) Flappan, S. Portnoy, J. Jones, P. and Barnes, C. 1999. Infant pulmonary hemorrhage in a suburban home with water damage and mold (Stachybotrys atra). Environ Health Perspect 107:927-930. 5) Stachybotrys chartarum: The Toxic Indoor Mould. URL: 6) Centers for Disease Control and Prevention (CDC). 2000. Update: Pulmonary hemorrhage/hemosiderosis among infants – Cleveland, Ohio, 1993-1996. Morb Mortal Wkly Rep 49(09):180-184.

Andrew Kibble, Shalini Pooransingh and Patrick Saunders are members of the Chemical Hazard Management and Research Centre (CHMRC), University of Birmingham,


Karl Nann gives a US update

When handled improperly, mould can cause serious problems and result in costly claims. US insurers have attempted to exclude or limit mould coverage under homeowners' property and general liability policies to help lessen expenses. Last year, in Texas, mould insurance claims generated $853m in losses, up from $151m in 2000. The cost of claims is also increasing dramatically. In 2001, the average pay out on a mould claim was approximately $2,800. In 2002, that figure nearly tripled to $8,000. At least one large insurer in Texas decided not to renew homeowner policies, citing a $1.3bn loss in the state over the last two years.

The cost of claims can be somewhat contained only when the claims are handled properly. The most significant factor in control is not the quantity of water involved but the time that the material has been exposed to the water or moisture. If spores land on a moist area where favourable temperatures and nutrients exist, they can multiply, building a colony. Mould grows by digesting the organic substance it lands upon. Such substances include drywall, carpeting/under-padding, panelling, ceiling tiles, insulation, paint, wallpaper, draperies, doors, drains and upholstery.

A mould colony does not need light to feed its growth. It can thrive on the lack of ventilation that might be caused by the improper use of humidifiers, HVAC systems, ventilators, etc. These factors all lend themselves to the colonies growing out of sight behind walls, ductwork, ceilings and sub-floors.

It is fundamental to recognise that any time water penetrates a building there is the potential for a mould problem. Generally, organic materials can develop mould if they remain wet for 24 to 48 hours. Experts say that a proper drying out process, which includes repairing or eliminating the source of the water, thoroughly drying all wet materials, and removing moisture from the air, must get under way within that critical 24-48 hour period in order to mitigate problems.

A skilled insurer will know how to handle mould claims properly and will be able to react immediately. This reduces claims costs and helps prevent further complications. If a claim is handled insufficiently, serious structural and health problems can occur. Improper handling of claims has led to a reported 10,000 current lawsuits involving mould issues in the US.

Retaining experienced and professional adjusters and contractors is critical to both the remedial process and the gathering of information to protect all parties. If a contractor or adjuster is not able to get to the site quickly, instructions must be given to policyholders to assist in the drying out process. This education will allow for better resolutions and lower claims costs.

Mould will continue to plague the insurance industry for years to come. As we learn more about these claims and how to handle them properly, the costs will hopefully decrease. Until that time, insurers will continue to pay dearly for the restoration of mould-infected buildings.

Karl Nann is director of property services, Crawford & Company, E-mail:

The views expressed in this article are solely those of Karl Nann and are not those, nor intended to be those, of Crawford & Company.

UK businesses could face liability claims arising from toxic mould, warns solicitors Davies Arnold Cooper's product liability group. In a recent bulletin produced by the group's partners, they point out that, under the UK Control of Substances Hazardous to Health Regulations 1999 (COSHH), an employer will be liable if he exposes any employees to any substance hazardous to health, unless he has made a suitable and sufficient assessment of risks created to the health of those employees, and of the steps that need to be taken to meet the requirements of the regulations.

Employers such as property managers and contractors also need to be aware of mould litigation, say the partners. In the US, claims have included allegations of injurious exposure to toxic mould by tenants and home owners. In Canada, one of the most important developing cases in the public sphere is a $2bn group action launched against the Dufferin Peel Catholic District School Board in Toronto. Mould exposure is alleged to have occurred while children were in temporary portable classrooms. During the past three years there have been more than 9,000 documented cases in the US and Canada involving toxic mould.

The bulletin states that lessons to be learnt include the necessity for swift action once flooding/damage has occurred, or the mould is detected, including instructing a restoration contractor to dry the property and to seal the rooms to prevent spores contaminating the building further.

It concludes that, given the volume of claims in the US in recent years, insurers, landlords and employers must take note of their potential exposure to property damage and employer's liability toxic mould claims. And, with the increased frequency and severity of flooding in the UK, coupled with lack of public spending on flood defences, it suggests that it will only be a matter of time before mould litigation spreads across the UK.