Home is believed to be the safest and the healthiest place to live in. However, the environment inside the house can also affect one's health, especially the air we breathe in. Indoor air pollution (IAP) means the presence of unwanted substances in the indoor air at concentration toxic to health.
The World Health Organization (WHO) asserts the rule of 1000 which states that a pollutant released indoors is one thousand times more likely to reach people's lungs than a pollutant released outdoors.
The indoor air pollutants can be physical (dust, ash, and suspended particulate matter), Chemical (pesticides, insect repellents, carbon monoxide (CO), and nitric oxides (NO2) and biological (bacteria, fungi, microbial spores, and animal dander).
Principal sources of IAP include fuel combustion, building materials, bio-aerosols, and growing outdoor air pollution. The unclean fuels used for cooking such as wood, biomass, and kerosene are at the bottom of energy ladder which produce a range of health-damaging pollutants such as fine particles, CO, NO2, sulphur dioxide (SO2), and benzene remains a major public health concern in the developing countries.
Apart from sources, there are certain factors which contribute to Indoor air pollution such as poorly ventilated houses, overcrowding, presence of damp walls/roof, and poor housekeeping.
Cooking-related household air pollution: One of the major sources of household air pollution, especially in developing countries, is fuel used for cooking as well as heating practices.
Homes from developed countries and many houses in the developing world use electricity, natural gas, or clean LPG for cooking, whereas houses in rural communities and some houses of the developing world use biomass fuel for cooking.
Natural gas is primarily methane, whereas LPG is primarily propane or a mixture of propane and butane. Natural gas requires less air for combustion (an air-to-gas ratio of 10:1). LPG, on the other hand, requires more air for combustion (an air-to-gas ratio of 25:1), releasing almost three times the energy released by burning natural gas (93.2 MJ/m3 through LPG versus 38.7 MJ/m3 through natural gas). LPG is relatively denser than air, which is further denser than natural gas (1.52:1:0.55).
Gas leakage when using LPG therefore tends to settle in the household air at human levels, whereas leakage of natural gas ascends toward the ceiling, reducing health effects.
Burning of natural gas not only produces a variety of gases such as sulphur oxides, mercury compounds, and particulate matter but also leads to the production of nitrogen oxides, primarily nitrogen dioxide.
Biomass fuel includes wood, crop residue, animal dung and wood charcoal. Approximately, 3 billion people, or half the world’s population, use biomass for cooking or heating across the globe and burn about 2 million kilograms of biomass every day. China alone is responsible for 420,000 annual deaths due to indoor air pollution caused by the use of solid fuels.
These homes have very high levels of particulate matter and gaseous air pollutants such as carbon particles, iron, lead, cadmium, silica, phenols and free radicals, carbon monoxide (CO), nitrogen dioxide, sulphur dioxide, formaldehyde, hydrocarbon complexes, and other inorganic and organic substances which include polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds, and chlorinated dioxins.
Various studies have shown that, on average, the levels of particulate matter of less than 2.5 microns in mean aerodynamic diameter (PM) in such houses range from 500 to 1,500 µg/m3, which is very high as the permissible indoor level of PM according to the WHO ranges between 10 and 50 µg/m in a 24-hour mean value. High levels of CO, especially during the burning of charcoal, are also produced. However, burning of wood produces the least amounts of PM2and CO among the biomass fuels.
The method of cooking also has an impact on the levels of particulate matter released in the air. Stir frying, deep or shallow frying, charbroiling, roasting, and grilling have different emission levels of particulate matter.
The type of meat, the amount of fat in the meat, and the type of oil used for cooking also determine the emission levels. Meat charbroiling, for example, emits large quantities of particulate matter of 0.1 to 0.2 µm in mean aerodynamic diameter Meat frying and charbroiling contribute to about 21% of the particulate matter emitted.
Regular meat emits about 40 g of particulate matter per kilogram of meat when charbroiled, whereas lean meat emits about 7 g of particulate matter per kilogram of meat when charbroiled.
When subjected to frying, the same meat emits about 1 g of particulate matter per kilogram of meat. Oil used in cooking emits a significant amount of PAHs, which further add to the household air pollutants.
Smoking: Smoking tobacco in any form within the confines of a house is a major source of household air pollution. Globally, there are approximately 1.1 billion smokers, a number which is steadily on the rise.
Cigarette smoke contains 7,357 different chemical compounds such as benzene, CO, PAHs, heterocyclic amines, cyanide, formaldehyde, terpenoids, phenols, nicotine, and heavy metals. Burning of tobacco also emits considerable amounts of PM (burning one cigarette emits 7 to 23 mg of PM). Tobacco smoke could be first-hand, second-hand, or third-hand smoke.
A person who smokes within the confines of his house is exposed to the smoke himself (first-hand smoke). Other occupants of the house inhaling these fumes but not actually smoking are exposed to second-hand smoke. The particles emitted during smoking settle on the furnishings, hair, clothes, and the floor.
These particles remain suspended in the household air for quite a while even after the primary smoker has exited the premises. This constitutes third-hand smoke
Temperature control-related household air pollution: Temperature control may involve both heating and cooling of the household environment. Houses in some houses in developing countries use air conditioning for temperature and humidity control.
To ensure effective conditioning of the house, insulation material and drafting control are used extensively.
Preventing the temperature-controlled air from escaping the closed environment leads to poor ventilation in these houses and further causes accumulation of the particulate matter pollutants inside the house. Furthermore, inadequately cleaned air conditioning units are breeding grounds for various fungi and bacteria.
Opening windows is a form of natural ventilation. Ambient air pollutants containing copper, iron, potassium, nickel, silicon, vanadium, and zinc, with a particle size of between 2.5 and 10 microns, and ozone gas easily find their way into these houses through the natural ventilation, in turn contributing to household air pollution.
In particular, houses that are close to traffic-heavy roads, which are populated with vehicles using diesel as fuel, tend to have a higher load of household air pollutants. Diesel exhaust particles can settle on the pollen of roadside trees and consequently find their way into an open household.
Carbon particles, soot, diesel exhaust-laden pollen, and organic particulate matter are therefore found to be in very high concentrations in these houses which use natural ventilation.
Insecticides and pest control: The use of chemical repellents the most widely and commonly used repellent is the mosquito coil.
A standard mosquito coil is made up of 0.1% of the active repellent pyrethroids, whereas the remaining 99.9% contains binders, resins, and flammable material such as coal dust and coconut husks.
Twelve million such coils are sold every year in the world. The coil is ignited and allowed to smoulder for 6 to 7 hours. Ideally, the coil is meant to be lit and smouldered in a room with windows and doors closed to get the most desired effect. Studies have shown that burning of one such coil emits particulate matter equivalent to burning 100.
When the mosquito coil is burnt with doors and windows closed. Improving ventilation by opening the windows but retaining closed doors reduced the pollutant levels markedly but remained at 500 times and twice the limits permissible by the WHO.
Only when both the doors and the windows are kept open the pollutant levels drop down to the safety limits. However, this defeats the use of the mosquito coil to control the mosquito menace.
Other forms of mosquito repellents such as vaporizers, sprays, ointments, and medicated papers do not produce as much particulate matter but produce gaseous air pollutants that are irritants to the airway mucosa.
Perfumes, deodorants, and cleaning agents: Poorly ventilated homes tend to accumulate kitchen odours as well as concentrate the household air pollutants.
This warrants the use of perfumes and scents to improve the level of hygiene in the house. Improved hygiene involves the use of cleaning agents, perfumes and deodorants, scented candles, and so on to make the house more cosy and comfortable. Air fresheners, laundry products, personal care products, and cleaning agents, multiple studies have been done to identify the volatile organic compounds released by them. Interestingly, these studies identified 156 different volatile organic compounds, of which the US Food and Drug Administration classified at least 42 as toxic or hazardous.
Building material: Paints and varnishes used in houses emit significant amounts of volatile organic compounds, increasing the burden of household air pollutants.
Particulate board furniture is also responsible for emission similar to that of volatile organic compounds largely because they are held together by adhesives that emit volatile organic compounds.
Insulation material used in buildings has also been implicated in the emission of volatile organic compounds. Asbestos used in sheets in the construction of houses leaves the finished houses with fine asbestos dust particles. Similarly, silicon particles are found in abundance in houses made of bricks and cement. Improvements in technology have led to digitalization in houses.
Every household today has hi-tech electronic gadgets such as computers, tablets, iPads, printers, and mobile phones. These have been implicated in increased levels of ozone in the houses. Polybrominated diphenyl ethers (PDBEs) are used as fire retardants in foam-containing furniture and electronics. These emit PentaPDBEs and DecaPDBEs in minute quantities which contribute to household air pollutants.
Faulty plumbing, alone or coupled with weather conditions, has led to an increasing incidence of indoor wall dampness. These walls form an ideal environment for the growth of fungi such as Alternaria, Aspergillus, Cladosporium, and Penicillium along with fungi, damp mouldy walls are also a breeding ground for several species of Gram-positive and Gram-negative bacteria which include Streptococcus, Micrococcus, Staphylococcus, Mycobacterium, Nocardia, and Streptomyces Budding spores of these fungi, microbial particulates, volatile organic compounds, mycotoxins, and endotoxins of the bacteria contribute a great deal to household air pollution.
Indoor air pollution is a key contributor to the global burden of lung diseases.
In developing countries, the problem of IAP far outweighs the outdoor air pollution. India is one of the ten low- and middle-income countries where IAP is responsible for a total of more than 1.5 million deaths a year.
The Global Burden of Diseases, 2015 reports household IAP as the fourth leading cause of attributable Disability Adjusted Life Years in India.
There is convincing evidence of the adverse effects of IAP on human health. These effects may be short term or long term.
Symptoms such as suffocation, burning eyes, and headaches pose as short-term problems. The long-term health effects though are influenced by the time of exposure result in premature deaths from non-communicable diseases.
The women and under-five children face a greater impact due to IAP as they stay indoors most of the time. In our society , women are in charge of cooking and are exposed more. Small particulate matter and other pollutants in indoor smoke inflame the airways and lungs, impairing immune response, and reducing the oxygen-carrying capacity of the blood leading to adverse consequences.
And, the children in the first few years of their lives are exposed to indoor smoke when their airways are still developing thereby making them vulnerable and susceptible to respiratory tract infections. The use of kerosene as fuel has been found to be significantly associated with cough, bronchitis, and other chest illnesses. IAP as a health problem and its deleterious effects are much neglected in the developing countries.
There is a need to evaluate not only the presence of IAP but also whether the houses are well-ventilated or not, in which our women and children spend most of their time.
Almost all types of indoor air pollutants, especially cooking fuel and housing conditions, are preventable, and IAP can be minimized. Majority of the households used kerosene as fuel and smoke from neighboring houses, streets entered their houses which lead further to IAP followed by overcrowding and ill-ventilation which is accentuating the problem further.
IAP and its detrimental effects are preventable. The urban poor should be provided with better housing conditions. The policy-makers should promote the use of clean fuel (LPG) as it is cost-effective and beneficial. The members of households who smoke indoors should be made aware and encouraged to quit smoking, at least indoors as it affects the health of their wives and children.
Women should be educated and made aware of the deleterious effects of IAP on their own health and also of their children so that they can raise healthy children.