World Health Organization on health risks of indoor mold

In 2009, the World Health Organization published a position paper about the dangers of indoor dampness and mold. At over two hundred pages, this summary is inaccessible for all but the most committed reader. 


To begin to bridge this gap, I will list seven notable quotes from the article and a brief description of its meaning in everday English. 


1.     “Microbial pollution is a key element of indoor air pollution.”

A hazard of indoor dampness is it hyper-charges the growth of microbes. Dampness increases the levels of mold and bacteria on damp surfaces. With time, these microbial elements rise into the air with spores, cell fragments, toxins, and other harmful compounds.

2.     “Indoor air pollution—such as from dampness and mold, chemicals and other biological agents—is a major cause of morbidity and mortality worldwide.”

Bad indoor air is dangerous. It causes a range of illnesses and even death. Indoor air pollution involves a range of contaminants beyond microbial pollution to also include chemicals such as toxic fumes known as volatile organic compounds and toxic gases such as carbon monoxide.

3.     “People are often exposed to multiple agents simultaneously and there are complexities in accurately estimating exposure.”

Estimating how bad the air is from a single test is bound to offer a partial view of the true state of the indoor air. To give one example, a mold air sample will capture some intact spores. But it will not describe mold fragments, bacteria, or volatile organic compounds that may be also contaminating the air.

4.     “Dampness is therefore a reliable risk indicator.”

The WHO defines dampness as any visible, measurable, or perceived outcome of excess moisture that causes mold, leaks, material degradation, mold odor, or directly measured excess moisture. Simply put, the presence of any single one of these factors involves potential risk to human health:

·      active leaks

·      moisture detection

·      signs of past water damage to materials

·      visible mold

·      musty smells

·      and increased mold on commercial testing.

5.     “Toxicological evidence obtained in vivo and in vitro supports these findings, showing the occurrence of diverse inflammatory and toxic responses after exposure to microorganisms isolated from damp buildings, including their spores, metabolites, and components.”

This statement highlights that there is a body of scientific evidence demonstrating harm from exposure to mold and bacteria growing in damp buildings. Notably, it’s not just the living, intact spores that cause harm. Unlike in infection, cell fragments and metabolites are sufficient to cause inflammatory and toxic injury. Mold does not have be alive to be a hazard.

6.     “Many of the health effects may result from recurrent activation of immune defense, leading to exaggerated immune responses and prolonged production of inflammatory mediators.”

Breathing in contaminated air causes massive inflammation. Inflammatory injuries range from allergic responses to autoimmune problems to immune suppression. The immune system influences the entire body, a fact that accounts for the widespread nature of symptoms that can damage virtually every organ system in the body.

7.     “Such health effects as fatigue, headache, and difficulties in concentration indicate that microbes or other agents present in damp buildings have neurological effects.”

Bad air is bad for your brain. While infection, allergy, and toxic responses are most widely known, neurological symptoms are overlooked and dismissed. For many, however, brain injury is the most devastating effect of prolonged respiratory exposure to contaminated water-damaged buildings.