Tag Archives: Sick Building Syndrome

Air Quality TVOC (Total Volatile Organic Compound Theory) and Health Effects

It is a widely held belief in the environmental health sciences community that exposures to individual VOCs and SVOCs (Semi-Volatile Organic Compunds) in indoor environments ARE NOT the sole factor for health issues and symptoms so much as the COMBINATION of the chemicals in question. This is the basis for what indoor air quality scientists call “TVOC Theory”.

While exposures to VOCs tend to be at levels significantly lower (by two or more orders of magnitude) than safety precautions (PELs and TLVs) outlined by health advisory bodies such as the ACGIH and OSHA, it is believed that there is a synergistic (additive and multiplicative) effect caused by the combined chemical loading of the hundreds of different organic chemicals which may result in symptomology and even a condition known as Sick Building Syndrome. (SBS) This is what would be called in engineering parlance, a parametric (multiple factor) failure with no single chemical being solely responsible for illness.

TVOC Table for Environmental Illness Effects from Indoor Air Quality Issues

Dose Response Model Relationship between TVOC levels and Health Effects  (Toluene Equivalent) with 5 mg/m^3 and 25 mg/m^3 approximately equivalent to 1 ppmv and 5 ppmv toluene equivalent. Effect threshold for acute effects with exposure to sub-mixtures of 6-9 VOCs are less than 1.7 mg/m^3.

The biological mechanism for this phenomena is linked to the stimulation of the trigeminal nerve system which is also known as the “common chemical sense”. This system is one of two olfactory (smell) mechanisms by which humans respond to odor. The chemical sense organ consists of trigeminal nerves in the nasal cavity and eyes as well as the facial skin areas. Stimulation of these nerves produces irritation which includes burning, stinging and smarting. Other effects include changes in heart and respiratory rates, as well as coughing, sneezing and tearing up of the eyes.

TVOC theory is more an indicator of the risk of nonspecific sensory irritation to relatively unreactive VOCs as opposed to a generic indicator of the potential health risks of contaminated indoor air quality.

Total VOC Volatile Organic Compound Chart for Indoor Air Quality

TVOC Dose Symptom Relationship Log Chart

A log-linear relationship between symptom prevalence rates and concentrations of terpenes, n-alkanes (C8-C11) and butanols in problem buildings. ScanTech checks for TVOCs in the Dallas, Fort Worth, Houston and Austin metropolitan areas.

More information can be found in this European report:

TVOC Indoor Air Quality Investigations

New Homes and Carbon Dioxide Levels: The Overlooked Indoor Air Quality Health Hazard

One of the “mythologies” that I have heard from clients and real estate agents is something along the lines of “But the house is too new to have any air quality issues, isn’t it?” Actually, it is usually the opposite. Besides the fallacy that newer is necessarily better (how long do appliances last now compared to 30 years ago?) there are several reasons why air quality in a new home may be severely impaired compared to an older one.

  • The construction materials and potentially new furniture, carpet, linens, etc. are still outgassing (releasing chemical fumes) for weeks and months after the initial build.
  • All of the dust from construction has not necessarily been removed from the general air circulation with the finer, more dangerous fine and ultra-fine particulate matter known to stay suspended for weeks.
  • Unpacking of boxes and materials from the move can release contaminants that have now been imported into your home.
  • Houses in general are built more “tightly” than in the past with the aim of increased energy efficiency. As with any engineering design, there is almost always a trade-off or a compromise somewhere. In this case, you potentially cut down on the amount of fresh air and oxygen in exchange for saving money on your utility bill. This means increased CO2 (carbon dioxide levels) which is potentially hazardous to your health. Please note that I am not talking about carbon monoxide which is an entirely different gas.
  • There tends to be a synergistic relationship between CO2 levels and VOC (Volatile Organic Chemical) levels in a structure. Elevated carbon dioxide levels means that ventilation is inadequate, not just for human occupants but ALSO for proper outgassing of the chemical fumes discussed above. This is why levels of CO2 which exceed 1000 ppm (or 1%) is associated with Sick Building Syndrome. Normal outdoor atmospheric levels are 400 ppm.
  • Furthermore, chemoreceptors in the human body located in the aorta, carotid arteries and in the brain respond to increased CO2 levels by INCREASING the breathing rate. This means that consequently more chemicals and dust enter the lungs and bloodstream.
  • Excess levels of CO2 can rapidly build up, particularly in an enclosed space such as a smaller room with the door shut and no air circulation. This can begin manifesting as physical symptoms as described in the illustration below.
Carbon Dioxide Toxicity impact on Indoor Air Quality

Symptoms of Carbon Dioxide Toxicity

TRUE STORY – I investigated a very new home (less than a year old) in which I was called out because the 23 year old healthy son passed out unconscious and non-responsive. When checked out at the hospital, they could find nothing wrong. When I arrived and began testing, I found something very wrong as my carbon dioxide meter began alarming immediately and climbed to very high levels even inside of an open hallway on the second floor. The family had been complaining of fatigue and headaches within a week of moving in.

The official medical terminology for carbon dioxide toxicity / poisoning is known as “hypercampnia”. Please note that this is an entirely different issue from CARBON MONOXIDE poisoning which is discussed in a blog post here:

Carbon Monoxide Safety Levels and Indoor Air Quality