Air Quality Alert: Common Indoor Pollutants Revealed

Indoor air pollution is a serious health concern, with the air inside a home potentially containing two to five times more pollutants than outdoor air. Common indoor air pollutants include excessive moisture, volatile organic compounds (VOCs), combustion products, radon, pesticides, dust particles, viruses, and bacteria. These pollutants can cause a range of health issues, from respiratory problems to cancer. Sources of indoor air pollution can vary, from building materials to tobacco smoke, and poor ventilation can further exacerbate the problem. Understanding the sources and health effects of indoor air pollutants is crucial for maintaining a healthy living environment.

Volatile organic compounds (VOCs) from rugs, plants, and tobacco smoke

Volatile organic compounds (VOCs) are a group of chemicals that are abundant in most indoor areas due to their presence in consumer products, building materials, and other mass-produced items. They are unique in that they vaporize at room temperature, which is why you can smell them after cleaning or painting a room. VOCs are not just a nuisance; they are also a health hazard. Overexposure to VOCs can cause dizziness, headaches, and memory impairment, and long-term effects may include liver, kidney, and central nervous system damage, and even cancer.

Rugs and carpets are a significant source of VOCs in the home. The glues used in carpeted walls and floors can release noxious gases, and the manufacturing process involves numerous chemicals that can pose health risks. One of the main sources of pollutants in carpets is styrene, which is used for carpet backings. Other sources include textile auxiliaries and polycyclic aromatic hydrocarbons.

Interestingly, certain houseplants can help to absorb VOCs and improve indoor air quality. The bamboo palm, for example, is effective at removing formaldehyde and benzene from the air, while also giving off water vapour and increasing humidity. The rubber plant is another option that can help remove formaldehyde.

Tobacco smoke is another common source of VOCs. Studies have found various harmful compounds in cigarette smoke, including acrylonitrile, furan, 1,3-butadiene, 2,5-dimethylfuran, vinyl chloride, and nitrobenzene. The World Health Organization (WHO) has recommended regulatory action on VOCs in tobacco smoke, and the Food and Drug Administration (FDA) has also taken steps to address this issue by publishing a list of harmful constituents and requiring the tobacco industry to report levels of certain compounds.

Radon from uranium in the soil or rock beneath homes

Radon is a colourless, odourless, and tasteless radioactive gas that is released from bedrock material and passes through the soil. Uranium, a chemical element that can be found in soil, water, and construction materials, decays and produces radon. Uranium is also present in all rocks and soils. As uranium naturally breaks down, it releases radon gas, which then enters homes through cracks in the floor, gaps in construction, windows, drains, or spaces around cables and pipes.

Radon is the second leading cause of lung cancer in the US, causing about 21,000 lung cancer deaths each year. It is responsible for one out of seven radon-related lung cancer deaths among people who have never smoked. Radon concentrations indoors tend to differ among countries and even individual buildings due to differences in climate, construction techniques, ventilation, and geology.

Radon levels are usually higher in basements, cellars, and living spaces in contact with the ground. However, radon can also be found in water, and radon in water can be released into the air during routine water use, such as showering or doing laundry. While epidemiological studies have not confirmed a connection between consuming drinking water containing radon and an increased risk of stomach cancer, radon released into the air and inhaled poses a significant health risk.

There are several ways to reduce radon concentrations in buildings. One method is to use a small fan connected to a PVC pipe system to reduce the pressure of the soil gas and vent the radon-rich air harmlessly into the atmosphere. Another approach is to prevent radon from entering the indoor environment through isolation and indoor air pressure manipulation. Additionally, corrective actions such as thermal retrofitting of existing buildings and ensuring proper ventilation can help decrease radon levels.

Excessive moisture, leading to mould, mildew, and dust mites

Excessive moisture is one of the most important and least recognised indoor pollutants, affecting both human health and the health of the building. Moisture problems arise when warm, moist air encounters a cool surface, such as a mirror, window, or the wall of a cooler space. Cooler air can hold less moisture, so the excess condenses in droplets on the surface.

Where there is moisture, mould, mildew, and dust mites often follow. These organisms thrive in humid environments, with mould and mildew growing on damp surfaces and dust mites feeding on skin flakes in household dust. Mould and mildew are types of fungi that grow and spread in moist, warm conditions. Mould typically appears as a thick, fuzzy growth and can come in various colours, while mildew usually presents as a powdery or downy surface that is white or grey and may darken over time.

Mould and mildew release disease-causing toxins, which can lead to respiratory issues and allergic reactions. Some types of mould produce mycotoxins, which can pose serious health risks when inhaled or ingested. Allergic reactions to mould are common and can cause symptoms such as sneezing, a runny nose, irritated eyes, and skin rashes. Mould exposure can also irritate the eyes, skin, nose, throat, and lungs of both allergic and non-allergic individuals.

Dust mites, composed of roughly 75% water, require high humidity to survive. They absorb water vapour from the air and are more prevalent in homes with higher humidity levels and constant warmth. Dust mites are often found in areas where skin cells accumulate, such as bedding, mattresses, and upholstered furniture. Like mould, dust mites can cause respiratory issues and allergic reactions.

To prevent and control excessive moisture, it is crucial to maintain optimal humidity levels in the home. The recommended relative humidity (RH) level is between 30% and 50%. When the RH level rises above 50-60%, it provides enough moisture for mould and mildew to flourish. Regular use of a dehumidifier can help control humidity levels and inhibit the growth of mould and dust mites. Additionally, it is important to address moisture sources, such as leaky pipes, dripping faucets, and condensation due to poor insulation or ventilation.

Carbon monoxide from gas-fired appliances and wood-burning stoves

Carbon monoxide is a highly poisonous, colourless, odourless, and tasteless gas with a similar density to air. It is produced by gas-fired appliances and wood-burning stoves when natural gas does not burn completely. Gas-fired appliances, including furnaces, water heaters, ranges, and some dryers, produce carbon monoxide when they are not vented properly to the outside or when the air pressure is negative enough to cause backdrafting, allowing combustion pollutants to enter the house.

Stoves that burn natural gas emit carbon monoxide, but in small amounts. However, if you smell rotten eggs, it is a sign of a leak, and you should take immediate action, such as opening windows, calling the gas company, and leaving the house. Leaving a gas stove on or using the gas oven to heat a home is a leading cause of carbon monoxide poisoning.

Wood-burning stoves are a popular way to heat homes, but they can also produce carbon monoxide. The process of wood burning creates a highly flammable substance called creosote, which can release carbon monoxide and cause chimney fires if not cleaned regularly. It is crucial to maintain a wood-burning stove and its flue system properly, removing ash and debris from the stove's interior and scheduling annual professional inspections and cleanings to reduce the risk of carbon monoxide build-up.

To prevent carbon monoxide poisoning from gas-fired appliances and wood-burning stoves, it is essential to install carbon monoxide alarms on each level of the home and near sleeping areas. These alarms detect the presence of carbon monoxide and provide early warning. Additionally, proper ventilation is critical to maintaining air pressure balance and avoiding gas spillages that can lead to carbon monoxide poisoning.

Furthermore, using the correct fuel type is essential for safe wood-burning. Burning seasoned hardwood that has been properly dried reduces smoke and the risk of carbon monoxide emissions. It is important not to burn treated or painted wood, as these materials can release toxic chemicals, including carbon monoxide.

Biological pollutants, including pollen, bacteria, viruses, and pet dander

Biological pollutants are contaminants that include bacteria, moulds, mildew, viruses, animal dander, pollen, and more. They are known to affect human health, causing allergic reactions and even neurological symptoms like headaches, fatigue, and forgetfulness.

Bacteria, one of the most common biological pollutants, can be found in both indoor and outdoor environments. Indoor air contamination by bacteria can have adverse effects on the respiratory system, especially for those with allergies or respiratory diseases. Legionella spp., for example, are bacteria that thrive in man-made water systems, including air conditioning systems.

Viruses are another significant biological pollutant. They are transmitted by people and animals, and their presence in indoor air can lead to the spread of infectious illnesses such as influenza, measles, and chickenpox.

Pollen, originating from plants, is a well-known biological contaminant that triggers allergic reactions, including allergic rhinitis and asthma.

Animal dander, or pet dander, refers to dried skin cells from pets. While pet hair can contribute to the issue, dander is the primary concern as these skin cells are so light that they can float in the air before settling on various surfaces. Pet dander is a common source of indoor air pollution and can trigger allergies.

To mitigate the presence of biological pollutants, it is essential to maintain proper ventilation and use air purifiers or filters. Source control is also crucial, such as removing or reducing the presence of pets or plants that contribute to the issue. By controlling the relative humidity in a home, the growth of certain biological contaminants can be minimised.

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