Houses: Silent Air Polluters In Our Midst

Household air pollution is a significant issue, causing 3.2 million premature deaths annually, according to the World Health Organization. The burning of polluting fuels, such as wood, animal dung, charcoal, and kerosene, in inefficient stoves or open fires, is a major contributor to indoor air pollution. Additionally, indoor air pollution is caused by tobacco smoke, combustion products, volatile organic compounds, bioaerosols, pesticides, and inadequate ventilation. Outdoor pollutants can also enter homes through open doors, windows, pets, and clothing, impacting indoor air quality. The accumulation of contaminants from various sources inside a house can lead to poor indoor air quality, causing adverse health effects such as respiratory infections, asthma, and cardiovascular diseases.

Tobacco smoke and second-hand smoke

Second-hand tobacco smoke, a mixture of the smoke from tobacco products and the smoke exhaled by a smoker, contains more than 7,000 substances. It can cause serious health issues, including lung cancer, cardiovascular disease, low birth weight, and other diseases. It is a leading cause of preventable disease, disability, and premature death, especially among non-smoking adults and children. There is no known safe level of exposure to second-hand smoke, and it can linger in a room for hours.

To reduce exposure to second-hand smoke, it is essential to prohibit smoking inside or near homes, buildings, and vehicles. While ventilation, filtration, and air cleaning techniques can help reduce indoor smoke, they do not eliminate it. Residents in multi-unit dwellings, such as apartments, often face the challenge of second-hand smoke infiltration from neighbouring units, which can be addressed through smokefree housing policies and legal options.

To maintain good indoor air quality, proper ventilation and the elimination of contaminant sources are crucial. Mechanical fans and air-to-air heat exchangers can be used to supply fresh outdoor air and reduce the concentration of indoor pollutants. Additionally, homeowners can install fans that directly supply outdoor air to the HVAC system, although this may increase operating costs.

Poor ventilation

Indoor air quality is often compromised by the accumulation of contaminants from various sources, such as emissions from fireplaces, stoves, cigarettes, cleaning products, building materials, and stored chemicals. Inadequate ventilation leads to a buildup of these pollutants, resulting in poor air quality. The National Institute for Occupational Safety and Health identified inadequate ventilation as the primary problem in more than half of its workplace indoor air investigations.

Several factors can contribute to poor ventilation. Firstly, weatherizing homes by adding insulation and caulking can reduce air circulation and trap contaminants inside. This phenomenon is known as "tight building syndrome" or "sick building syndrome," and it can lead to various health issues for occupants. Secondly, the use of air conditioning for temperature and humidity control can also result in poor ventilation. Preventing temperature-controlled air from escaping leads to a reduction in air exchange, causing a buildup of particulate matter pollutants. Additionally, inadequately cleaned air conditioning units can become breeding grounds for fungi and bacteria, further contaminating the indoor air.

In warmer climates, heating, ventilation, and air conditioning (HVAC) systems can pull warm, humid air inside, creating indoor humidity problems unless the system also dehumidifies the air. Inadequate ventilation in these systems can contribute to the spread of pollutants throughout the home. Contaminants may include mold in duct lining, bacteria on coils or filters, and the distribution of pollutants from one area to another within the home.

To improve indoor air quality and address poor ventilation, it is essential to increase ventilation and air circulation. This can be achieved through the use of exhaust fans in bathrooms and kitchens, ceiling fans, and opening windows when safe to do so. Additionally, regular maintenance and duct sealing of HVAC systems can help minimize the spread of pollutants.

Household products and chemicals

Tobacco smoke is another critical indoor air pollutant, containing over 7,000 chemicals, with at least 70 known to be carcinogenic. Secondhand smoke exposure is a significant concern, causing about 7,300 lung cancer deaths each year in non-smoking adults in the United States alone. The combustion of tobacco also releases carbon monoxide, acrolein, formaldehyde, hydrogen cyanide, and respirable particles, leading to adverse health effects.

Cleaning products and chemicals are also significant contributors to indoor air pollution. These products release toxic fumes, which, when inhaled, have been linked to respiratory infections, asthma, and cancer. Many of these chemicals are volatile organic compounds (VOCs) that evaporate at room temperature, causing short- and long-term health issues such as headaches, nausea, and damage to vital organs like the liver, kidneys, and central nervous system.

Additionally, the use of fireplaces, stoves, and newer building materials can introduce contaminants into indoor air. Emissions from these sources can include combustion products, volatile organic compounds (including formaldehyde), and bioaerosols. Poor ventilation exacerbates the problem by trapping contaminants indoors, leading to "tight building syndrome" or "sick building syndrome."

Furthermore, certain household activities and products can indirectly contribute to indoor air pollution. For example, inadequate cleaning of air conditioning units can provide breeding grounds for fungi and bacteria, while open windows can allow outdoor air pollutants and allergens to enter the home. Even pets can be a source of indoor air pollution through the shedding of pet dander, which can be found in their fur, skin, and saliva.

Incomplete combustion of solid fuels

Household air pollution is a serious issue, with 4.3 million people dying annually due to its effects. The incomplete combustion of solid fuels is a significant contributor to this problem. This occurs when there is insufficient oxygen for the fuel to burn completely, leading to the formation of harmful compounds and particulate matter.

The incomplete combustion of solid fuels, such as wood, charcoal, coal, and kerosene, releases pollutants that negatively impact human health and the environment. These pollutants include carbon monoxide (CO), particulate matter (PM), unburned hydrocarbons (UHCs), sulfur dioxide (SO2), and nitrogen oxides (NOx). Carbon monoxide, a toxic gas, can cause CO poisoning with symptoms like headaches, dizziness, and even death in high concentrations. Particulate matter, a mixture of solid particles and liquid droplets, can cause respiratory issues and heart attacks. Fine particulate matter, with a diameter of 2.5 micrometers or less, is especially harmful as it can reach the lungs and bloodstream.

The use of biomass fuels, such as livestock dung cakes, wood, and crop residues, for cooking, heating, and lighting, is common in many parts of the world. In rural Tibet, for example, more than 54% of energy sources are from biomass fuels. The moisture content of these fuels, combined with local climate conditions like low air pressure and oxygen content, leads to incomplete combustion, producing harmful pollutants.

Houses with inadequate ventilation can exacerbate the problem of indoor air pollution caused by incomplete combustion. In cold regions like the Tibetan Plateau, homes are often kept closed and unventilated to conserve warmth, leading to a rapid increase in pollutant concentrations. Similarly, insulation and caulking practices in weatherized homes can reduce air circulation and trap contaminants, contributing to "tight building syndrome" or "sick building syndrome."

The health impacts of exposure to indoor air pollution from incomplete combustion of solid fuels are significant. In 2019, household air pollution accounted for an estimated 86 million healthy life years lost, with the highest burden on women in low- and middle-income countries. It is linked to cardiovascular and pulmonary diseases, lower respiratory infections in children, lung cancer, and other adverse health outcomes.

Inefficient stoves

Wood-burning stoves, for example, have been recognized by air quality regulators and officials as a public health and environmental concern. The burning of wood releases black carbon (sooty particles) and methane, which are powerful short-lived climate pollutants (SLCPs). These emissions contribute to both indoor and outdoor air pollution, affecting not only the users of wood stoves but also their neighbors and the surrounding community.

Gas stoves are another major source of indoor air pollution, with research suggesting that gas cooking produces twice as much PM2.5, a deadly air pollutant, compared to electric cooking. Gas stoves also release nitrogen oxides (NOx), including nitrogen oxide (NO) and nitrogen dioxide (NO2), carbon monoxide (CO), and formaldehyde. These pollutants pose serious health risks, especially for children, with studies linking nitrogen dioxide pollution to childhood asthma.

The incomplete combustion of solid fuels and kerosene in inefficient stoves has severe health consequences. Particulate matter and other pollutants released into the air can inflame airways and lungs, impair immune response, and reduce blood oxygen levels. Exposure to household air pollution is associated with an increased risk of cardiovascular and respiratory diseases, with an estimated 4.3 million deaths attributed to it annually.

To reduce the impact of inefficient stoves on air pollution and health, transitioning to cleaner energy sources and technologies is essential. This includes adopting electric stoves, induction stoves, or other electric kitchen appliances such as slow cookers, pressure cookers, or rice cookers. Additionally, proper ventilation and the use of air purifiers can help improve indoor air quality by reducing the concentration of pollutants in the air.

Frequently asked questions