Dr Jackson Kung'u- Mold Specialist

Helping People Resolve Mold Problems

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How Toxic is the Mould?

I have a question regarding mould. Thank you first off for someone that is passionate about what you love to do; its great how much you share about all that you know. I’ve been contacted by a young lady that needs information. She lives in Vancouver, BC in a rancher home built in the late 80’s, or early 90’s and she is having mould problems. She just discovered on a window sill, a yellow golfball-sized fungus, that has orange dots on it. When she touched it to clean, it burst and had green goo inside. She has had a persistent cough for several months now and when she talked to the landlord about the fungus, plus black staining in the bathroom, he threatened to evict them, as he just told them that he will paint over it and not to bother him again.

The Mould Stachybotrys
The Mould Stachybotrys is know to be toxic (toxigenic)

Question: Just how much should they be concerned and/or how toxic is the mould? She is an employee of mine and she had approached me as of today of the incident(s). I thank you in advance for your time.

Answer: It’s hard to tell the type of mould and whether it’s toxigenic or not from the description only. However, all moulds are potentially a health hazard and should be removed (not painted over). The source of moisture that is promoting mould growth should be identified and corrected otherwise mould will continue growing. As for your employee, the best thing to do if the landlord is not willing to remove the mould is to move out or to seek help/advice from the public health department who may compel the landlord to remove the mould. Before reporting to any authority she should be sure that the mould is growing due to the landlord’s negligence and not her own lifestyle.

Black Mould

Question:  My tenants are saying that there is black mould in my rental townhouse. I’ve replaced fixtures in the bathrooms, stopped leaks and spent thousands of dollars but they are still bringing in the local public health inspector.

I’m allergic to black mould myself and have been in while damaged drywall was being removed. I handled it myself with no ill effects and observed the joist cavities being treated with mould inhibiting sprays and ‘killex’.

Should I be worried that my tenants are still pursuing this investigation? I’ve taken every remedial step I can think of and the only stuff I saw was dried up and the rest looked like shower mildew to me. All the discoloration spots on the bathroom ceiling stuff came off with a cleaner called BAM and the paint was unaffected once the ceiling was wiped down.

Answer: Shower mildew is actually mould though it may not be what people call black mould (Stachybotrys chartarum). I would suggest you hire a qualified professional such as an industrial hygienist who is experienced in indoor microbial contamination. This person should be able to assess the extent of contamination, possibly determine the underlying cause, and then advise on the most appropriate level of remediation. They may also be able to advise you whether the tenants’ lifestyle could be contributing to mould growth. For instance, if they don’t switch the fan on (if there is one) when showering or bathing, then there will be mould growth due to condensation on the walls and the ceiling.

If you have further questions regarding black mould, please contact us at 905-290-9101.

Mould Growth

Dampness and mould growth are recognised as major problems affecting a
significant proportion of houses in the North America. Apart from health problems associated with dampness and mould growth, wood decay is also significant problem.

Mould growth in houses is unsightly. But most important, there is considerable evidence to support the view that mouldy housing has a detrimental effect on the health of occupants residing in such environments. This is a cause for concern, considering that many individuals spend most of their time indoors especially during winter. Respiratory problems and allergic reactions are the common health problems associated with mould. Generally, indoor moulds affect people through inhalation of airborne spores. High levels of airborne spores may occur due to growth of mould on walls and furnishings.

Requirements For Mould Growth
Requirements for mould growth in buildings include:

  • nutrients: found in the materials which make up or are deposited on indoor surfaces
  • oxygen. Like most other living things, common indoor moulds require air (oxygen) for growth.
  • suitable temperature (around 25 degrees Celcius)
  • moisture: the relative humidity (RH) at a surface is the best indicator of moisture available for mould growth.

In most cases, mould growth in homes is caused by condensation. Condensation in buildings occurs where moist air meets a cold surface. For example if air meets cold water pipes, window glasses or other cold surfaces and is cooled below its dew point temperature, the vapour close to the surface becomes saturated and excess vapour turns to liquid.

There are two types of condensation:

  • Surface condensation. Surface condensation occurs at the surface of the material.
  • Interstitial condensation. Interstitial condensation occurs inside a material. If vapour passes through porous building materials and the dew point temperature occurs within that material then the vapour will condense. Interstitial condensation is responsible for mould growth in building envelopes.

The major factors influencing condensation in buildings include:

  • Moisture production from sources inside the building. Moisture sources include respiration, cooking, washing and drying of clothes.
  • Air and structural temperatures
  • Ventilation. Proper ventilation helps to reduce condensation. 

Contact Information

Dr. Jackson Kung'u, PhD.
Phone: 905-290-9101
Fax: 905-290-0499