How Much Mold Exposure Is Harmful (The Real Answer)


I bet there’s a 90% chance everyone has experienced mold in one way or another.

Yes, even that a piece of moldy bread in your kitchen pantry counts as mold exposure.

Whether you lived in a home with that had a leak which caused mold growth, work in an office where mold was a problem.

Mold is everywhere, and it’s a part of our natural environment.

I think that sometimes people forget that.

Mold becomes an issue when it starts to grow in your home because of a moisture problem.

When this happens, it can cause allergic reactions. And, it can slowly deteriorate the indoor air quality and damage the structure of your home.

I have had many experiences with mold both professionally and personally.

So I take it very seriously when I hear about individuals with legitimate mold complaints.

I remember an incident that happened to a new home my fiancé and I bought in Florida.

Generally, no one would think that a brand new home would have a mold problem.  But I will tell you this, any home, old or brand new can have a mold infestation.

The issue started in our master bedroom closet.


Occasionally I would see a small patch of greyish formation about 2-3 inches in diameter on the closet ceiling.

At the time, I really didn’t think much of it.

Because it was a brand new home that passed building inspections. After inspecting the drywall, I found that it was dry and there were no visible signs of water damage.

So, I cleaned the growth and summed it up to a humidity issue that developed when the closet door remained closed for long periods.

To help solve the humidity issue, I made sure the closet door stayed open allowing airflow in the closet.

Every now and then after it rained, the growth would come back in the same spot.  This usually happens a couple days after it rained.

This went on for about 8 months.

Finally, I decided to take a look in the attic to see if there were any signs of a leak.

But I couldn’t locate one. I saw no stains, discolorations, mold growth, or other signs of water intrusion over the closet.

Finally, the problem really reared its ugly head.

One night while I was working out of town, I received a frantic call from my fiancé at about 2 am. “There is water pouring out of the light fixture in the closet.”

I told her to turn off the breaker to the closet light for safety reasons and place a container under the light fixture to stop the water from spreading all over the second floor.

That morning, I reached out to the builder of the home, our homeowner’s insurance company, and the HOA to let them know about the incident.

Within a couple hours, the insurance company sent a water restoration company to find the cause and dry out the building to prevent mold growth.

The inspectors remained in the attic for about an hour when they finally found the source of the roof leak.

Below is the actual picture from the inspection.

The leak was above the dormer section of the roof. In general, a dormer is a small roof built on top of another roof.


This made it hard to find the leak because they had to remove a small section of the roof to get access and then to crawl up into the dormer.

The area would leak a little each time rain would fall. But because of the heavy rain that week the water poured into the attic then seeped into the closet ceiling.

What caused the leak?

The contractor failed to add metal flashing in a critical location to stop water from getting the attic (pictures below).

how to remove mold from attic plywood

The wet ceiling in the closet and the damp drywall and insulation in the attic below.

wet insulation in attic

We were fortunate that the mold growth didn’t spread into the living area.  Mostly is was contained in the attic.

The contractor ended up removing an 8-foot x 8-foot section of the roof as well as the drywall.

A dry out chamber was used to remove moisture from the wall sections, carpet, baseboards, and the flooring on the second floor.

Even now when it rains I check the area to make sure there are no leaks.

So, when you see a small amount of mold on wall or ceiling, make sure you look into the cause.

If you are unable to do it yourself, get a professional to look at the problem.

The last thing you want to do is take a chance and end up with costly repairs.

The Various Level Of Mold Exposure To Humans

How much mold is ideal and what amount is significant enough to cause health problems?

The simple answer is, there is no defined amount that is considered safe or unsafe.

The U.S Environmental Protection Agency and the Centers for Disease Control and Prevention (CDC) have no published guidelines that tell us how much mold is good vs. how much is bad.

Why is this the case?

Mainly because each person body reacts to mold exposure in a different way.

Some individuals can develop allergic reactions like shortness of breath, itchy and watery eyes, and other hay fever-like symptoms with short mold exposure.

While other individuals may show no signs of an allergic reaction, this makes it difficult or nearly impossible to establish any form of exposure guideline.

If you look at a common contaminant in older homes like Lead, we know that it can affect all kids the same way.

It can cause problems with brain development, learning disabilities, and many other health issues. When you get exposed to X amount of lead, you will have Y reaction.

This is not the case with mold exposure.

No one can say without a doubt that, if you are exposed to 10 spores of a certain mold (or a specific concentration of mycotoxin), you will get a sinus infection or something like that.

How mold can affect you is entirely different than how it will impact another individual.

It really depends on your health.

That is if you have pre-existing problems, your age, the strength of your immune system, the type of mold and mycotoxin it produces, and your body’s response – biological response to mold exposure.

Individuals who spend too much time in moldy environments will often complain of respiratory problems, headaches, and other physical symptoms.

Lets Look At An Example

John is a healthy 30-year-old construction worker is good health with no respiratory problems and a robust immune system.

And, Mary, is a 30-year-old high school teacher, recovering from treatment that has weakened her immune system causing her to become sick easily.

Whom do you think exposure to a mycotoxin producing mold will affect more?

If you guessed Mary, you would be right.

If both John and Mary went into a water damaged building that has mold, Mary would most likely have a reaction to even small amounts of mold spores.

In comparison, John may have little or no response when placed in the  same environment.

This was just to show you how mold can affect people differently.  It depends on the mold, dose-response relationship.

How long a person is exposed to the mold (allergen), your health, and multiple other factors.

So, what levels of mold is considered bad for your health?  It depends on the individual.

But it’s safe to say that, if you live in an environment where there is mold growing all over the walls, there is a strong musty odor, you have a metallic taste in your mouth will run the risk of getting a mold-related illness.

This would be an example of an unhealthy level of mold exposure for anyone.

Mold Poisoning and Infection Symptoms in Humans

Can exposure to molds make me sick?

This is a common question that only your medical provider can answer.

But in general, exposure to some molds, not all, has been linked to allergic reactions, hay fever-like symptoms, and other forms of irritation.

How mold can affect you depends on your health and other factors like

the type of molds and the toxin/mycotoxin it produces, how much mold (spores) you were exposed to, how long you were exposed, and your biological response.

Most illnesses caused by mold exposure affects the respiratory system.

This should be no surprise because respiratory organs are exposed to the natural environment, and that’s where mold is found.

Furthermore, because the respiratory system continually takes in the air, it is the perfect way for mold spores to enter your body.

One person may display no ill effects while another can have severe reactions from the same exposure.

Prolonged exposure to high levels of molds can become unhealthy for anyone.

The most common complaints regarding mold exposure include a runny nose, scratchy throat, hay fever-like symptoms and coughing.

Individuals with asthma, the elderly, infants, individuals with chronic respiratory conditions, allergies, and individuals with weakened immune systems are more susceptible to the effects of exposure to some molds.

Here are some things to look out for if you were in or, live in a building where mold is a problem.

  • Nasal congestion,
  • Itchy and watery eyes,
  • Sneezing,
  • Stuffy or a runny nose,
  • Scratchy or a sore throat,
  • Throat clearing,
  • A persistent cough
  • Chronic sinus infections
  • Chronic fatigue
  • Shortness of Breath

Symptoms of fungal infection caused by Aspergillus Fumigatus include

  • Wheezing
  • Short of breath
  • A chronic cough

Signs of Aspergilloma sometimes referred to as the “fungus ball” includes:

  • A cough
  • Coughing up blood
  • Shortness of breath

Invasive aspergillosis will mainly affect people with weak immune systems who are already sick and have other underlying health conditions.

The symptoms of an Aspergillus infection can be difficult to diagnose due to preexisting health conditions, but the symptoms of aspergillosis affecting an individual’s lungs include the following:

  • Some Fever
  • Chest pain
  • Coughing
  • A cough that produces blood
  • Shortness of breath

I think we can all agree that, in general, that mold can be a hazard and you can get exposed at home, work, or outside.

But sometimes the fear and worry about mold can create unnecessary concerns.

And some people are quick to point the finger at mold for a wide variety of health problems.

Sometimes, even when they have no mold problems or visible growth in the home.

When To See A Doctor For Mold Exposure

When To See A Doctor For Mold Exposure

Remember, mold is everywhere and there is not much we can do about it.

It’s a part of our natural environment and it’s here to stay.

Sometimes we can get exposed to some mycotoxin producing molds that can cause some health effects.

Some people with the weak immune system, infants, and those with allergies are at high risk of getting the mold-related illness.

“If you suffer from persistent or unexplained coughing, hay fever-like symptoms, or other respiratory problems and you think you were or live in a home with severe water damage; it may be time to give your doctor a ring.”

You should always speak with your doctor if you have ailments that could be caused by exposure to mold toxins.

If you have any of these ailments after accidentally ingesting or inhaling large amounts of mold, you should see your doctor as soon as possible:

  • Shortness of breath,
  • Development of rashes,
  • A persistent headache
  • Sinus infections,
  • Chest pain
  • Fever
  • Persistent coughing
  • Abdominal pain,
  • Nausea, diarrhea, appetite changes
  • Allergic reactions
  • Blurred vision
  • Coughing up blood – aspergillosis

If these symptoms last for a couple days, or they get worse and don’t respond to common over the counter medication; you should schedule an appointment with your doctor to get it checked out.

It’s important that you let your medical provider know that the symptoms could be caused by mold exposure.

When Do You Need To Get Emergency Medical Treatment?

IMPORTANT NOTE: Anyone experiencing severe symptoms should speak with their primary doctor because sometimes the symptoms may not be related to mold exposure.

Most of the time, health issues caused by mold exposure don’t classify as a medical emergency.

However sometimes this is not the case.

If you have trouble breathing or feel like your suffocating after inhaling mold spores, you should seek medical attention immediately.

Also, if your asthma flares up and doesn’t respond to your medication or get worse, get medical attention as soon as possible.

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