WHY WE SHOULD BE INTERESTED IN THE QUALITY OF OUR AIR?
The choice to follow through on more sustainable building methods and practices often clashes with economic, material and labor variables which are the forefront issues for most clients. I believe that if the implications that sustainable building had on human health and lifestyle were brought to the attention of mainstream Americana that it would be the ultimate deciding factor in the design of building systems.
COMPARATIVE STUDY OF AIRBORNE PARTICLES
In order to better understand how particulate matter that is found both naturally and man made begins to interact with the human respiratory system it is important to break down these pollutants by size. The diagram below breaks down micro items found from the environment, man made emissions, the human body, materials, and biological organisms.
- Volatile Organic Compounds [VOCs] are the smallest in scale and are comparable to the wavelength of X-rays
- Keep note of the Human Body items in blue to begin to understand how these particulates interact with various parts of the body
- The initials AC represent Activated Carbon, a filtration material which utilizes a wide variety of pore sizes and surface area to trap particles
Particulate matter cannot be seen by the naked eye, they can be soil or liquid forms. The coarse/ bigger particles are between 2.5 and 10 micrometers, these particles are called PM10. The fine/small particles are smaller than 2.5 micrometers and are called PM2.5. PM10 particles can stay suspended in the air for minutes or hours whereas PM2.5 particles can stay suspended for days to weeks. The lightness of the PM2.5 particles allows them to stay in the air longer and travel farther, up to hundreds of miles, than PM10 particles.
PM10 HEALTH EFFECTS
The coarse particles can be detrimental to human health and are classified as inhalable particles. Inhalability is the fraction of the suspended material in ambient air that actually enters the noise or mouth and deposits on the respiratory tract. It is a function of the particles aerodynamic size, flow rate, wind speed and direction [See the following equation].
I = 0.50 (1 + e ^(-0.06d)
for PM10, d= 10 um and I = 0.770
The health effects that come from inhaling these particles which include pollen, sand, silt and dust, just to name a few, range from minor to severe health effects. PM5 particles enter into the bronchial tubes and upper lungs, leading to more severe problems. These health implications include ENT irritation, headaches, dizziness, fatigue, asthma, and emphysema.
PM2.5 HEALTH EFFECTS
The adverse health effects of PM2.5 is more severe than PM10 and can lead to chronic and fatal incidents. The reason for this is that the smaller particles can enter the blood stream and respiratory system. Respirablity is the particles that are inhaled which enter the gas exchange region of the lungs. The equation for calculating respirability is a function of the cumulative log normal function [See following equation].
R= 1 [1-F(x)]
x= ln (d/4.25)/ ln 1.5
for PM2.5, d=2.5 and R = 0.83
The health effects that come from PM2.5 particles range from ENT irritation, coughing to more severe chronic bronchitis, heart strain, pneumonia, lung cancer, heart disease, vascular inflammation, atherosclerosis and heart attacks. PM0.5 is the most prevalent size which enters indoor air due to infiltration. Exceedances of the PM2.5 standard causes up to 15,000 premature deaths globally.
WHY IS THIS IMPORTANT
It is critical to bring to light how pollutants in the air impact the health of people. When making design decisions for building systems, the most important criteria is how material selection and proper ventilation strategies affects the individuals who are directly and indirectly engaged with the building. The rising rate of ailments in the American population, such as asthma, cannot be ignored or deemed less important than any other variable which affects building design decisions.
Essentially, in order to sell our ‘product’ of sustainable building systems, the problems that arise from poor case studies must be humanized. To draw parallels between building systems and an individual person is the first step towards allowing people to understand the issue and prioritize it as a critical issue in their lives. With proper understanding of the importance of good air quality we can then analyze just how to develop systems which improve the air quality of the built environment.