Indoor Air Quality: 4 Major Sources Of Pollution

Indoor air pollution (IAP) is a serious threat to human health, causing millions of deaths each year. The four major sources of indoor air pollution are poor ventilation, biological pollutants, human activities, and building materials. Poor ventilation can cause excess moisture buildup, leading to mold growth, which releases toxins into the air, causing mild allergies and severe respiratory issues. Biological pollutants include plants, people, animals, and viruses, which can trigger allergic reactions and cause illnesses. Human activities such as smoking, cooking, and burning solid fuels release harmful particles and chemicals into the air, while building materials and furniture can emit volatile organic compounds (VOCs) and other toxic chemicals. These sources of indoor air pollution can have detrimental effects on human health, including respiratory diseases, heart disease, and cancer.

Poor ventilation

The impact of poor ventilation on indoor air quality is far-reaching. When there is inadequate ventilation, pollutants from various sources can accumulate to unhealthy levels. These sources include cleaning products, off-gassing from furniture or building materials, and outdoor contaminants drawn indoors. In addition, poor ventilation can cause excess moisture buildup, promoting mould growth and creating an uncomfortable, damp environment. Mould releases toxins that can trigger mild allergies and severe respiratory issues such as asthma.

Furthermore, poor ventilation can lead to high levels of volatile organic compounds (VOCs), carbon monoxide (CO), carbon dioxide (CO2), and fine particulate matter (PM2.5) indoors. These pollutants have been linked to a range of health issues, including respiratory problems, headaches, dizziness, eye irritation, and even heart disease. The presence of high CO and CO2 concentrations can also result in nausea and, in extreme cases, death.

To address poor ventilation, it is essential to ensure adequate air exchange between indoor and outdoor spaces. This can be achieved through natural ventilation, such as opening windows, or mechanical ventilation, including fans and exhaust systems. Investing in heating, ventilation, and air conditioning (HVAC) systems can significantly improve indoor air quality. However, it is crucial to properly maintain these systems, as contaminated HVAC units can spread pollutants throughout a building.

Additionally, duct sealing and regular maintenance of HVAC systems are important to minimise the spread of pollutants. Dehumidification is also key in controlling indoor humidity, as high humidity can spur mould growth and create an environment conducive to indoor contaminants. By implementing these measures, it is possible to enhance indoor air quality and create a safer, more comfortable living or working environment.

Biological contaminants

One of the key sources of biological contaminants is inadequate ventilation, which allows pollutants from various sources, such as cleaning products, off-gassing furniture, and building materials, to accumulate indoors. Poor ventilation can also cause excess moisture buildup, leading to the growth of mould and mildew, which release toxic compounds. Contaminated central air handling systems and humidifiers can become breeding grounds for mould, mildew, and other biological contaminants, distributing them throughout a building.

To minimize the growth of biological contaminants, it is important to control the relative humidity level, typically maintaining a range of 30-50% in indoor spaces. This includes properly ventilating and maintaining air circulation equipment, addressing water leaks, and preventing moisture buildup, especially in areas like basements, attics, and crawl spaces.

Additionally, biological contaminants can be introduced by household pets, such as through animal dander and cat saliva, as well as pests like cockroaches and mice. Pollen, which originates from plants, can also be carried indoors, triggering allergic reactions in susceptible individuals.

The presence of biological contaminants in indoor environments can lead to various health issues, including allergic reactions, infectious illnesses, and toxic effects. Allergic reactions may develop over time with repeated exposure to specific biological allergens, and can result in symptoms such as sneezing, watery eyes, coughing, and shortness of breath. Infectious illnesses transmitted through the air include influenza, measles, and chickenpox. Furthermore, exposure to toxins released by moulds and mildews can lead to diseases like humidifier fever and hypersensitivity pneumonitis.

Human activities

Combustion activities, such as cooking and fossil fuel combustion, are a major source of indoor air pollution. The use of polluting fuels and stoves for cooking, such as solid fuels, kerosene, and unprocessed coal, releases harmful pollutants into indoor environments. Incomplete combustion of these fuels generates particulate matter and other pollutants that inflame airways and lungs, impair immune responses, and reduce oxygen-carrying capacity in the blood. Inefficient stove combustion also emits black carbon (sooty particles) and methane, which are powerful short-lived climate pollutants. Gas stoves and heaters contribute to higher levels of nitrogen oxides, which are associated with combustion sources.

Cleaning activities, including the use of household cleaning products and agents, contribute to indoor air pollution. These products can release gases and particles into the indoor environment, and certain chemicals within them can be harmful to human health.

Construction or renovation activities can introduce indoor air pollutants through the use of certain building materials. Off-gassing from furniture or building materials, for example, can accumulate to unhealthy levels in poorly ventilated spaces.

The operation of electronic machines, such as machine operation and residential hobbies, can also generate indoor air pollution. These activities can release particles and pollutants into the air, impacting indoor air quality.

In addition to these specific activities, human daily activities more broadly can cause indoor air pollution through the discharge of waste gases, tobacco smoke, pesticides, solvents, particulates, dust, mould, fibres, and allergens. Humans also create favourable conditions for the development of pollutants such as mould, fungus, pollen, spores, bacteria, viruses, and insects.

Building materials

To mitigate the impact of building materials on indoor air quality, it is essential to prioritize the use of sustainable, non-toxic, and air-purifying construction materials. Low-emitting materials, such as those with low VOC content, can significantly reduce indoor air pollution. Building certification systems like LEED and WELL recognize the importance of this by awarding points for the use of low-VOC construction materials and placing a strong emphasis on improving indoor air quality.

Furthermore, proper ventilation plays a crucial role in maintaining healthy indoor air. In new buildings, extra ventilation is necessary to remove the higher emissions associated with new construction materials. Smart ventilation systems equipped with air quality sensors can enhance indoor air quality by increasing airflow when higher concentrations of pollutants are detected. Additionally, indoor plants are recommended as they absorb harmful substances as part of their metabolism, although flowering plants may cause irritation and allergies in sensitive individuals.

The quality of the building envelope and insulation also impact indoor air quality. In cold climates, improving airtightness and insulation can reduce the risk of mould buildup, enhance energy efficiency, and improve thermal comfort. Conversely, in warmer climates, ventilation and dehumidification are vital to removing stale air and clearing condensation, thereby reducing the potential for mould growth.

By implementing sustainable design practices, using low-emitting construction materials, and incorporating effective ventilation strategies, it is possible to minimize the impact of building materials on indoor air pollution and create healthier indoor environments for occupants.

Outdoor particles

Vehicle exhaust emissions are a significant contributor to outdoor particle pollution, particularly in urban areas with high traffic density. These emissions release a complex mixture of pollutants, including particulate matter (PM), nitrogen oxides, carbon monoxide, and volatile organic compounds (VOCs). The particulate matter emitted by vehicles can be further categorized into different fractions based on particle size, with PM2.5 being the most concerning due to its ability to penetrate deep into the respiratory tract.

The combustion of fuels, such as gasoline, diesel, oil, and wood, is another major source of outdoor particles. This includes emissions from industrial processes, power generation, and residential heating and cooking. Like vehicle emissions, the combustion of these fuels releases a range of pollutants, including particulate matter, nitrogen oxides, and carbon monoxide. In addition, the burning of wood and other biomass fuels can release organic compounds and toxic chemicals, further contributing to outdoor air pollution.

Industrial emissions from factories, power plants, and manufacturing facilities also release a plethora of pollutants into the atmosphere. These emissions can include particulate matter, toxic metals, and hazardous chemicals released during industrial processes. In addition, certain industries may emit specific pollutants, such as sulfur dioxide from smelters and refineries or chlorine from chemical manufacturing.

Natural sources, such as wildfires, volcanic eruptions, and dust storms, also contribute to outdoor particle pollution. Wildfires, in particular, can release massive amounts of particulate matter, carbon monoxide, and other toxic chemicals into the atmosphere. These particles and pollutants can travel long distances and affect air quality in regions far from the source. Additionally, dust storms in arid and semi-arid regions can generate large amounts of mineral dust, which remains suspended in the air and contributes to reduced air quality.

To address outdoor particle pollution, global organizations such as the World Health Organization (WHO) have developed guidelines and targets to reduce air pollutant concentrations. These guidelines provide recommendations for managing particulate matter, such as black carbon and ultrafine particles. Additionally, implementing policies that support cleaner transportation, energy-efficient practices, improved industrial processes, and better waste management can significantly reduce outdoor air pollution and its associated health risks.

Frequently asked questions