Ontario Ministry of Health Issues Report on
Health Effects of Mould Contamination in Buildings
& Guidelines for Mould in School Facilities

Some of the more important conclusions are given below:

Q1A: "What are the health effects of exposure to moulds?"

The Expert Panel said that there is strong evidence to support the relationship between the exposure to mould in buildings and many health effects. However, some of the health effects do not apply to exposures generally experienced in residential settings or at low levels, where the exposure is by inhalation. Some effects have only been reported in occupational settings where exposures may be much higher. Considering exposure in all settings, the possible health effects listed by the Expert Panel were:

1. Allergic and other immune-mediated mechanisms (e.g. asthma, hay-fever, and hypersensitivity pneumonitis)
   
   
2. Infectious diseases (e.g. illnesses in immuno-compromised individuals from normally non-pathogenic organisms such as Aspergillus species.)
   
   
3. Potential (toxic effects) from mycotoxins and volatile products:
   • Local and mucosal irritant effects (eye and throat irritation, skin rash)
   • Systemic effects (changes in lymphocytes and neurobehavioral and cognitive effects)
   • Pulmonary hemorrhage in infants
     
     
4. Potentially carcinogenic mechanisms. There is strong evidence of a carcinogenic effect in certain agricultural and industrial settings. However, there is no evidence that low-level exposure to fungi that would occur in residential and school facilities, has any relationship to cancer.

Q1B1: How convinced are you that the health effects as stated above are associated with mould or with environmental conditions (e.g. water damage or excess humidity) that might give rise to mould?

To quote the final report, "The Expert Panel agrees that there is evidence in the scientific literature which supports an association of several health effects, primarily symptoms, with unusual fungal growth in the indoor environment or with environmental conditions which are associated with fungal growth (e.g. humidity and conditions which promote fungal growth - "mould amplifiers")."

Q1B3: Within these circumstances, what constitutes a susceptible individual?

The determination of susceptibility can be specific to individual mould species and to the effects measured. Populations susceptible to one or more adverse health effects from mould and dampness may include:

1. Infants and children. Pulmonary hemorrhage / hemosiderosis associated with mould exposure and other home environment factors was reported only in infants. Respiratory symptoms such as cough associated with damp house were reported in children (as well as adults). Lymphocyte ratio changes were reported in children, although the clinical implications of this finding are uncertain.
   
   
2. Persons with specific diseases such as diabetes and immuno-suppression (e.g. organ transplant recipients, chemo-therapy patients, persons with AIDS) are more susceptible to infection with certain fungi such as Aspergillus species.
   
   
3. Atopic individuals. Some experts believe that allergic effects seen are simply due to IgE-mediated allergy. This would imply that only a minority of susceptible individuals exists. Atopy prevalence has been reported at about 15% of adults and 18% of teenagers. Others believe that the association is seen in non-allergic individuals, which implies that the general population may be at risk of allergic responses. Atopic children in particular are likely to be susceptible to the allergic effects of mould exposure. House dust mite-sensitized children may be more susceptible to airborne viable fungi or to mould allergens.
   
   
4. Pregnant women and the fetus. At the present time this concern is supported by animal studies only with ingested mycotoxins. Although adverse reproductive outcomes have been observed related to poisoning from ingested mycotoxin in (farm) animals, this experience does not allow extrapolation to pregnant women.
   
   
5. Institutionalized population such as the elderly and inmates of correctional facilities. This is a potential but unproven risk category except for the occurrence of AIDS and tuberculosis-related morbidity in inmates of correctional facilities.

Q4A: Clarify and comment on the dose-response relationship between mould exposure and adverse human health outcomes. Identify / comment on what happens in terms of outcomes at low doses or levels of exposure?

The Panel concluded that at the present time there is no valid model for quantifying the dose-response relationship of "mould exposure" and other adverse health events.

Currently, there are insufficient data to establish threshold levels of exposure to most fungal components, in order to differentiate acceptable from unacceptable. This means that it is not possible to determine a level at which intervention should occur to permit avoidance of all health effects.

In relation to allergic sensitization, it has been shown with other aeroallergens that there is a dose-response relationship between exposure levels and the risk of sensitization. But, once sensitized, the individual will respond to extremely low levels of exposure.

For irritant and toxic effects, the higher the level of exposure, the higher the probability of response.

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