Indoor Air Quality: 3 Common Sources Of Pollution

Indoor air pollution is a serious threat to human health, causing millions of deaths each year. There are many sources of indoor air pollution, including outdoor air pollution, building materials, and human activities. Three possible sources of indoor air pollution are:

1. Inefficient and polluting fuels and technologies: The use of polluting fuels and stoves for cooking and heating can lead to elevated levels of fine particulate matter and carbon monoxide, which can have harmful effects on human health.

2. Biological pollutants: Sources of indoor biological pollutants include plants, people, and animals. Building materials that support the growth of biological pollutants, such as mold and dust mites, can also contribute to indoor air pollution.

3. Household products: Certain household products, such as paints, furnishings, air fresheners, and cleaning agents, can release chemicals and pollutants that affect indoor air quality.

Tobacco smoke and other human activities

Human activities, including tobacco smoking, are major contributors to indoor air pollution, which poses serious health risks. Tobacco smoke contains over 4,000 compounds, more than 40 of which are known to cause cancer in humans or animals, and many of which are strong irritants. The World Health Organization has identified tobacco smoking as one of the leading causes of death worldwide. Smokers are at a higher risk of developing a wide range of illnesses, many of which are life-threatening. Inhaling tobacco smoke, whether through active or passive smoking, has been linked to tuberculosis (TB). Research shows that smokers have an increased risk of TB infection, disease progression, and mortality compared to non-smokers.

Furthermore, cigarette smoking is a significant risk factor for cardiovascular disease (CVD). Exposure to tobacco smoke and air pollution contributes to the development of CVD through various mechanisms. Fine particles in smoke can enter the bloodstream, causing premature death in individuals with heart and lung conditions. Even short-term exposure to elevated levels of particulate matter in the air, such as PM2.5, is associated with an increased risk of heart attack and stroke. Passive smoking, where non-smokers are exposed to tobacco smoke in their environment, also poses significant health risks. It has been linked to an increased risk of fetal coronary artery disease and myocardial infarction, with passive smokers having a higher number of risk factors compared to active smokers.

Other human activities that contribute to indoor air pollution include the use of fireplaces and wood stoves for heating. Inefficient combustion in these sources can result in the release of smoke and particle pollutants, such as carbon monoxide and hydrocarbons, into the indoor environment. Burning activities, such as trash burning, can also release cancer-causing pollutants and high levels of particulate matter. Additionally, human activities related to cleaning and sanitation can introduce pollutants into indoor spaces. Cleaning agents, pesticides, and household cleaners can contribute to indoor air pollution and negatively impact air quality.

To mitigate the effects of indoor air pollution from human activities, it is important to implement control strategies. These can include improving ventilation, using air purifiers or filters, and reducing the use of fireplaces or wood stoves. It is also crucial to address the root cause by promoting smoking cessation and encouraging the adoption of cleaner alternatives for heating and waste management practices. By taking these measures, the health risks associated with indoor air pollution from tobacco smoke and other human activities can be significantly reduced.

Inefficient fuels and technologies

The use of inefficient fuels and technologies has significant health impacts. The pollutants produced can cause short-term health issues such as burning eyes, coughing, and nose and throat irritation. More seriously, long-term exposure to indoor air pollution from these sources has been linked to an increased risk of pneumonia in children, as well as chronic obstructive pulmonary disease, lung cancer, stroke, and cardiovascular disease in adults. The WHO estimates that household air pollution leads to approximately 3.2 million deaths per year, including over 237,000 children under the age of five.

Women and children are particularly vulnerable to the health effects of inefficient fuels and technologies as they typically spend the most time near the domestic hearth and are often responsible for household chores such as cooking and collecting firewood. The use of polluting fuels and inefficient devices also requires significant time for cooking, fuel gathering, and preparation, further increasing the exposure to harmful pollutants for those involved in these tasks.

To address the negative health impacts of inefficient fuels and technologies, the WHO has developed guidelines for indoor air quality and household fuel combustion. These guidelines provide health-based recommendations on the types of fuels and technologies that protect health, such as improved biomass stoves, and the adoption of cleaner-burning fuels like biogas, electricity, ethanol, liquefied petroleum gas (LPG), and natural gas. Additionally, the transition to cleaner and more modern stoves and fuels can significantly reduce harmful emissions and personal exposure to household air pollutants.

Furthermore, the use of inefficient fuels and technologies has climate and environmental implications. Greenhouse gas emissions from non-renewable cooking fuels contribute about 2% of global carbon dioxide emissions, similar to the amount produced by aviation or shipping globally. Each biomass stove emits an estimated 2-6 tons of CO2 annually, but improved biomass stoves can reduce these emissions by up to 80%, and clean-fuel stoves can achieve reductions of over 95%.

Building materials and furnishings

One of the most common indoor air pollutants associated with building materials is formaldehyde. Formaldehyde is often found in plywood, blockboard, flooring products, and other pressed-wood products. These materials can emit formaldehyde and other volatile organic compounds (VOCs) into the indoor air, particularly as they age. Other sources of formaldehyde include wallpaper, paints, adhesives, and furniture made from wood-based materials. The use of several products containing formaldehyde simultaneously can result in the mixing of different chemical fumes, further deteriorating indoor air quality.

In addition to formaldehyde, building materials and furnishings can release other toxic chemicals, such as benzene, toluene, ethylbenzene, xylene, and styrene. These chemicals are known as VOCs and have been linked to adverse health effects. Older building materials, such as tiles, insulation, drywall, and paint, may also contain asbestos or lead. Disturbing or removing these materials without proper precautions can release asbestos fibers and lead dust, endangering the occupants' health.

To mitigate the impact of building materials and furnishings on indoor air quality, several strategies can be employed. Designers and builders should prioritize the selection of low-VOC and least toxic materials, such as water-based adhesives and coatings. It is recommended to air out building materials and carpets for at least 72 hours before installation, ensuring proper ventilation during this process. Flush-out techniques can also be utilized, where large amounts of outdoor air are forced through a newly constructed building for a period of time to remove pollutant emissions from building materials and finishes before occupancy. Additionally, encapsulation techniques can be applied to pressed-wood products containing formaldehyde to reduce the amount of pollutants emitted into the air.

Biological pollutants

Biological contaminants include bacteria, mould, mildew, viruses, animal dander, cat saliva, house dust, mites, cockroaches, and pollen. Many of these contaminants are transmitted by people and animals, such as viruses, while others like pollen originate from plants. Bacteria can be carried by people, animals, and soil and plant debris. Household pets are sources of saliva and animal dander.

Mould and mildew release disease-causing toxins and can grow in damp conditions, on water-damaged materials, or wet surfaces. They can also grow in home heating and cooling systems, humidifiers, and large building ventilation systems. Contaminated central air handling systems can become breeding grounds for mould, mildew, and other biological contaminants, which can then be distributed throughout a home.

House dust mites, one of the most powerful biological allergens, grow in damp, warm environments. They can also be stirred up into the air when vacuuming, increasing airborne levels. Other sources of biological pollutants include pest droppings or body parts, and the urine of rats and mice, which can become airborne when dry.

Outdoor air pollution

One of the main sources of outdoor air pollution is the burning of polluting fuels. The widespread use of polluting fuels and stoves for cooking has led the WHO to issue guidelines for indoor air quality, recommending clean fuels and technologies such as solar, electricity, biogas, liquefied petroleum gas (LPG), natural gas, alcohol fuels, and biomass stoves that meet specific emission targets. The use of inefficient and polluting fuels and technologies in and around the home releases a range of harmful pollutants, including small particles that penetrate deep into the lungs and enter the bloodstream. Poorly ventilated dwellings with indoor stoves can have levels of fine particles up to 100 times higher than acceptable. This is particularly detrimental to women and children, who typically spend the most time near the domestic hearth and are at higher risk of exposure.

Another significant contributor to outdoor air pollution is tobacco smoke. Tobacco smoke contains over 7,000 chemicals, with at least 70 known to be carcinogenic. It is estimated that tobacco smoke causes ten times more air pollution than diesel car exhaust, making it one of the most severe indoor air pollution sources. Exposure to secondhand smoke, also known as environmental tobacco smoke (ETS), is often referred to as passive smoking and can lead to serious health issues, especially in children.

Additionally, outdoor air pollution can be influenced by human daily activities such as cooking, cleaning, and the use of certain products. For example, the chemicals in many conventional cleaning products can pollute indoor air and release toxic fumes that are harmful when inhaled. These chemicals have been linked to respiratory infections, asthma, and cancer. Similarly, combustion sources and cooking activities contribute to carbon dioxide (CO2), sulfur dioxide (SO2), carbon monoxide (CO), nitrogen dioxide (NO2), and particulate matter (PM).

The effects of outdoor air pollution on indoor air quality can be mitigated through proper ventilation and the adoption of cleaner fuels and technologies. Improving ventilation by bringing in outdoor air can help dilute indoor emissions and carry indoor pollutants out of the immediate environment. Additionally, the use of clean fuels and technologies, as recommended by the WHO, can significantly reduce the presence of harmful pollutants in both outdoor and indoor spaces.

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