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Most people spend as much as 90 per cent of their time indoors. They ingest almost three to four liters of water and one kg of food daily but inhale almost 15 liters of air each day. Therefore, maintaining a superior Indoor Air Quality (IAQ) in occupied spaces can translate to occupant health and safety, greater productivity and reduced healthcare costs.

Indoor air is often more polluted than outdoor air (albeit with different pollutants). Research has shown that indoor air in buildings can be two to five times—and occasionally up to 100 times—more contaminated than outdoor air. In fact, indoor air is often a greater health hazard than the corresponding outdoor setting, although this has not changed the common understanding of air pollution.

Indoor air pollution consistently ranks among the top five environmental risks to public health. US Occupational Safety and Health Administration (OSHA) estimates that 30 per cent of workers in nonindustrial buildings—including offices, schools and hospitals—are exposed to poor indoor air quality.

The World Health Organisation (WHO) estimates that 4.3 million people in 2012 lost their lives due to indoor air pollution. Estimates from the WHO and others suggest that between 30 and 150 times more people are killed due to indoor air pollution than global warming.

Air tight buildings made for higher energy efficiency – if not provided with sufficient ventilation – lead to a common problem viz. build-up of carbon dioxide and various pollutants. This leads to ‘sick building syndrome,’ the term introduced in 1980s to describe the increasingly common maladies caused by improperly designed and ventilated buildings. By 1984, a WHO Committee reported that “up to 30 per cent of new and remodeled buildings worldwide may be the subject of excessive complaints related to indoor air quality. Since that time, consciousness increased on this subject mainly in the developed countries and standards were introduced.

What is Indoor Air Quality?

IAQ is one of the most important areas of Indoor Environmental Quality (IEQ), particularly, in terms of the impact of a building on the health of occupants. IEQ encompasses more than air quality, including thermal comfort, visual comfort and acoustical quality.

IAQ deals with the content of interior air that could affect health and comfort of building occupants. It refers to the presence or absence of air pollutants in buildings. There are many different types of pollutants that can affect indoor air, and they come from a wide range of sources.

According to the US Environmental Protection Agency (EPA) and National Institute of Occupational Safety and Health (NIOSH), the three key elements that contribute to the quality of the air people breathe when they are inside include:

• Introduction and distribution of adequate ventilation air
• Control of airborne contaminants
• Maintenance of acceptable temperature and relative humidity.

How does Indoor Air Pollution Impact us?

Poor IAQ leads to a variety of health risks that have significant costs for the people affected directly, as well as for their family members, employers and society at large. Despite the fact that IAQ can have an immense impact on health and general quality of life, it is generally an unregulated field.

The Environmental Protection Agency notes that occupants may experience adverse health effects from indoor air pollutants soon after exposure – or years later. Health conditions associated with poor IAQ can be categorised as either building related illness (BRI) or sick building syndrome (SBS).

 Building Related Illness (BRI)

As defined by the World Trade Center Resource Guide, BRI includes specific, identified maladies attributed to an identified material, product or system in a home or building. Examples include Legionnaire’s Disease, hypersensitivity pneumonitis, humidifier fever and asthma-like symptoms in non-asthmatic individuals. Approximately 25 per cent of the ailments associated with indoor air quality can be identified specifically and are attributed to BRI.

Sick Building Syndrome (SBS)

SBS refers to a general set of symptoms that affect building occupants during the time they spend in the building and that diminish or go away during periods when they leave the building. SBS cannot be traced to specific pollutants or sources within the building, and it typically is multi-factorial, or caused by a number of factors combined with or worsened by inadequate ventilation. About 75 per cent of building-related health cases are classified as SBS. Common SBS symptoms include headaches, nose, eye and throat irritation, a dry cough, dry skin irritation, dizziness or nausea, difficulty concentrating and fatigue.

SBS and BRI are frequently confused with each other. BRI usually entails a specific diagnosis of a set of symptoms caused by a specific environmental factor, one that has developed into an illness that persists whether that factor is present or not. SBS refers to more general symptoms of malaise or discomfort, which are temporary and limited to time spent in the building. Conversely, BRI is often associated with a longer recovery time than SBS symptoms.

Particulate matter is the prime villain. The most lethal are the smallest particles (also known as PM2.5, for particulate matter smaller than 2.5 microns in diameter, about one-third the diameter of a red blood cell), which are produced by combustion and household activities like cooking. These specks can get deep into the lungs, tarring the airways and weathering the heart, disrupting its ability to beat properly. Many studies have linked exposure to PM2.5 with heart attacks, cardiac arrhythmias, strokes, chronic obstructive pulmonary disease, worsened symptoms of asthma and an increased risk of respiratory illness.

Worldwide, particulate matter contributes to about 800,000 premature deaths each year, according to the WHO, making it the 13th leading cause of death worldwide. Other pollutants also cause major problems, especially indoors—radon, a gas produced naturally in the Earth, is the second leading cause of lung cancer in the US, and additional gases like carbon monoxide and volatile organic compounds (VOCs) cause innumerable health effects.

What are Indoor Air Pollutants and Where do They Come from?

There are many potential sources that lead to poor indoor air pollution with the most common being mold, radon, second hand tobacco smoke, smoke from burning wood, gas furnaces and various allergens. Volatile Organic Compounds (VOCs), formaldehyde, pesticides, lead and asbestos are also common sources of air pollution. Some of these items are naturally occurring, some are man-made and some depend on chemical reactions to occur under the right conditions.

What are the Strategies to Control Indoor Air Pollution?

Even though the factors that affect quality of indoor environment are numerous, the good news is that most indoor environmental problems can be prevented or corrected. Achieving better IAQ in buildings requires proper application of science and technology. It calls for an optimum combination of proper buildings materials, effective ventilation systems design and indoor pollutant control mechanism.

Indoor air quality crosses economic status, race and ethnicity. Poor indoor air quality can be present at work, home, school or vehicles. Hence, this is a subject that needs to be addressed carefully for our present as well as future well-being.