Causes & Sources of IAQ Prblems

Causes and Sources
of
Indoor Air Pollutants

Causes of Indoor Air Pollutants

Indoor air pollutants that release pollutants (such as gases and particulates) into the ambient air are the major sources of IAQ problems. Improper ventilation or deficiencies in the ventilation system employed is another main source of the Indoor air pollutants. The deficiency in ventilation system degrades the indoor air quality by reducing the dilution of the indoor air pollutants and by also not allowing the polluted indoor air outside the house.

Indoor air quality problems arise due to the following causes:

· Pollutant sources

· Deficiencies in ventilation system

· Outdoor air pollution

· Overcrowding

· High temperature and

· High humidity

Air pollutants and ventilation both play a very important part in determining indoor air quality. The pollutants come from a variety of sources as indicated in Table 5, and emission from these sources may be weak or strong. The situation can be regarded as a contest between the pollutants and the ventilation system. If a source is weak and the ventilation system is performing as designed, air quality will be good; however, if a strong source is present, then the ventilation system may be operating at the maximum efficiency but still the air quality may be bad. Other factors that aggravate this situation are temperature, humidity and microbiological contamination. A brief description of general categories of major indoor air quality problems is as follows.

Inadequate Ventilation

In the context of air quality, this can be defined as insufficient air to remove pollutants that are degrading the quality of air.

Causes of inadequate ventilation include:

· Early shutdown and late startup of ventilation system

· Insufficient fresh air (outdoor) entering the ventilation system

· Poor air distribution by the ventilation system with in the building

· Limited air mixing in occupied areas

· Clogged filters

The first two causes are often a direct result of overzealous energy saving procedures. The remaining causes can be due to:

     Poor designing and incorrect installing of components
   Operating the system differently from its design
   Incorrect balance
   Component malfunction
   Occupant intervention
   Lack of maintenance etc

Temperature and Humidity extremes

These factors can affect the emission rates of some pollutants, such as formaldehyde. However, the way the extremes affect occupant perceptions is probably more important. High humidity and high temperature cause people to feel lethargic and want more air movement. Low humidity induces coughing, dry throat and dry eyes. These are all symptoms of the "sick-building syndrome" mentioned above, and are thus usually blamed on poor air quality. An additional problem with low humidity is that it accentuates the sense of smell.

Other Physical Stressors

Noise from the mechanical systems or glare from lights can cause headaches and fatigue. Again, these are symptoms of the "sick building syndrome" and may be blamed on the air.

Sources of Indoor Air pollution

There may be many sources of the air pollution indoors in any home. Some of the indoor air pollutant sources include:

    Building materials
    Combustion sources (gas stoves, kerosene stoves, smoking etc.)
   Asbestos as insulation
   Overcrowding
   Outside sources (e.g. pesticides, radon, outdoor pollution etc.)
   Household products and Personal care products
   Hobbies (such as welding, soldering etc.)
   Central heating and cooling devices
   Humidification devices

Building Materials

The main pollutants released due to the building materials are Formaldehyde, Asbestos and to a lesser extent Radon.

Formaldehyde

Formaldehyde is a colorless, organic chemical. It is used in an amazing range of products - everything from lipstick and shampoo to kitchen cabinets and carpeting because it is an excellent preservative and bonding agent.

Formaldehyde, a main pollutant is released from building materials. Building materials like pressed wood products (hardwood plywood wall paneling, particleboard, fiberboard) and furniture made with these pressed wood products. Urea-formaldehyde foam insulation (UFFI) a widely used insulation material is one of the major sources of formaldehyde.

Exposure to formaldehyde vapors can cause eye, nose and throat irritation, coughing, skin rashes, headaches, dizziness, nausea, vomiting and nosebleeds. It is suspected of being carcinogenic to animals and the US EPA ranks it to be a carcinogen to humans.

Radon:

Radon is a colorless, odorless and noble radioactive gas that is formed by natural decay of radium. Radon releases isotopes after decay, which is of primary concern.

Radon a major pollutant can be released due to the building materials. Granite, clay, bricks, marble and sandstone etc. are the major sources of radon in the building materials.

Radon has no immediate effect on an individual but it is carcinogenic. Cancer deaths in the US due to radon per year are estimated to be around 7,000 to 30,000 (US EPA). Smokers are at high risk due to radon induced lung cancer.
(For more Info. click here)

Combustion Sources

The main pollutants released due to the combustion sources (such as wood-burning stoves, fire places, furnaces and tobacco products) are Formaldehyde, Inorganic gaseous pollutants (such as CO,CO2,NOx) and Respirable suspended particulates etc.

Inorganic Gaseous Pollutants

The major combustion products are CO₂, CO, NO₂, NO and SO₂along with formaldehyde, hydrocarbons and respirable particles.

The main sources of Inorganic gaseous pollutants are the combustion appliances like wood-burning stoves, fireplaces, furnaces, space heaters and tobacco products. The heaters are mainly divided as Unvented and Vented space heaters. Further, they are classified based on the type of fuel used as kerosene or gas heaters of each kind.

Kerosene heaters are further classified into convective, radiant, convective / radiant, two stage and wickless depending on the design of the burner used in the heaters. The emission rates of NO₂, CO and SO₂ were higher from old radiant heater than from the new one. CO was released from the heaters with blue flame. Emission rate of CO₂ depends on the type of fuel used. The average emission rates from a vented gas heater were higher to that of unvented gas heater.

Wood-burning stoves, fireplaces and furnaces release NO, NO₂, CO, CO₂, SO₂, respirable particles and HCHO (formaldehyde).

CO mixes with hemoglobin and myoglobin in blood to form carboxyhemoglobin and CO-myoglobin, which reduce the transformation of oxygen to the tissues effecting the brain, muscles and myocardium.

At high concentration NO₂is known to cause lung cancer. Both NO and NO₂ active species combine with other air pollutants forming carcinogenic chemicals.

High SO₂concentration (in the range of 0.25 to 0.50 ppm) causes bronchoconstriction.

Respirable Particulates

Fine solid particles, mist, smoke, dust, fibers, fumes and aerosols are collectively called as particulates. Respirable suspended particulates include ETS, Asbestos and other fibers.

ETS

Secondhand Smoke also known as environmental tobacco Smoke (ETS) is the smoke coming out from the burning end of a cigarette, cigar or pipe and the smoke exhaled by the smokers.

ETS is a mixture of over 4,000 compounds, of which over 40 are considered to be carcinogenic (Group A carcinogen in humans by the US EPA) to humans and animals. Passive smokers (non-smokers) are people who are exposed to the smoke by the combustion of tobacco products by the smokers.

ETS causes various heath problems like respiratory irritation like cough, excess phlegm, and wheeze. It is suspected to be a carcinogen. ETS is particularly harmful to young children and infants whose parents smoke in their presence. Based on survey conducted by the US EPA there are approximately 3,000 lung cancer deaths (EPA publication viz. EPA-43-F-93-003) each year in nonsmoking adults and impairs the respiratory health of hundreds of thousands of children. According to a study by the American lung Association (ALA) there are about 37,000 heart disease deaths in non-smokers each year. (for more Info. Click Here)

EPA estimates that about 150,000 to 300,000 passive smokers have lower respiratory infections mainly children and infants below the age of 18 months resulting in 7,500 to 15,000 hospitalizations each year.

ETS has health effects in children like increased risk of lower respiratory tract infections, such as bronchitis and pneumonia, and ear infections, build-up of fluid in the middle ear, increased severity and frequency of asthma episodes, decreased lung function etc.

EPA also estimates that about 200,000 to 1000,000 asthmatic children have worsened their condition due to this Secondhand Smoke (SS). Exposure to SS or ETS causes eye, nose, and throat irritation. It can affect the cardiovascular system and some studies have linked exposure to secondhand smoke with the onset of chest pain irrespective of the age group (but more in children). For more information about the EPA publications on ETS Click Here.

Asbestos

Asbestos is a mineral fiber widely used in variety of building materials and as an insulating material and also as a fire-retardant.

There are many varieties of asbestos used for various purposes they are:

· Chrysotile or White asbestos

Most common asbestos mineral, made from fibrous variety of the mineral serpentine, a sheet silicate mineral. It is recognized by its long, wavy, flexible fibers.

Crocidolite: Made from fibrous variety of Riebeckite, a mineral in the Amphibole group. Crocidolite is purple, and the fibers are short and rigid.

Amosite: Made from Amphibole (Cummingtonite-Grunerite series), amosite has short, rigid, tan or whitish colored fibers. Actinolite: Actinolite is a relatively common mineral in some metamorphic rocks. Actinolite is composed of microscopically fibrous crystals (asbestos) and is called byssolite. It is usually green or white with a vitreous luster. (Click Here)