Indoor Air Pollutants and Related Human Health Hazards

Almost all the products indoors are sources of harmful & toxic pollutants like Particulate matter (PM2.5 / PM10), Volatile Organic Compounds (VOCs), Carbon Dioxide, Formaldehyde, Carbon Monoxide, Ozone, Trichloroethylene, Benzene, Nitrogen Dioxide, etc.

Indoor Air Quality (IAQ) refers to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants. Understanding and controlling common pollutants indoors can help reduce your risk of indoor health concerns. Health effects from indoor air pollutants may be experienced soon after exposure or, possibly, years later.

The quality of air inside buildings affect the health, comfort, and performance of occupants and represented by

  • Concentrations of pollutants and
  • Thermal (Temperature & Relative Humidity) conditions
Indoor air pollution is ranked among the top 5 environmental health risks to the public by Environmental Protection Agency. In India, Indoor air pollution is one of the top 10 death, disease risk factors. It is invisible but no less a threat to our health.

A large part of household items in our homes as well offices are sources of Indoor Air Pollution.

Let us look at the main Indoor air pollutants, their sources in homes & offices and their harmful effects

1. Respirable Suspended Particulate matter (RSPM)

RSPM or PM (Particulate matter) is tiny pieces of extremely fine liquids & solids that get mixed in the air that we inhale. The smaller the PM, the more harmful it is; it then gets deeper into our lungs and even into our bloodstream and causes great damage to our body and system. The particulate matters are classified based on their size.

a. Coarse dust particles (PM10) are 2.5 to 10 micrometers in diameter. These tiny particles which are about 30 times smaller than the width of a hair on your head are small enough to get inhaled past our defensive nose hairs and into our lungs.

b. Fine particles (PM2.5) are 2.5 micrometers in diameter or smaller. While PM10’s story ends at the lungs, PM2.5 can pass from our lungs into our blood supply and be carried throughout our bodies thereby making them “the invisible killer”

Sources: Fine particles are produced from all types of combustion, including motor vehicles, power plants, residential wood burning, forest fires, agricultural burning, and some industrial processes. Indoor sources of fine particles include tobacco smoke, cooking (e.g., frying, sautéing, and broiling), burning candles or oil lamps, and operating fireplaces and fuel-burning space heaters (e.g., kerosene heaters).

Harmful Effects: Acute and chronic effects to the respiratory and cardiovascular systems with a variety of human health including Respiratory Illness, asthma, COPD, lung cancer

2. Volatile Organic Compounds (VOCs)

VOCs are emitted as gases from certain solids or liquids. VOCs include a variety of chemicals, some of which have short- and long-term adverse health effects. Concentrations of many VOCs are consistently higher indoors (up to 10 times more) than outdoors.

Sources include paints, varnishes and wax; all containing organic solvents, as do many cleaning, disinfecting, cosmetic and hobby products.

Harmful Effects: Eye, nose, and throat irritation, skin rashes, nausea, and can also damage the liver, kidney, and central nervous system. Other common symptoms include frequent headaches.

3. Carbon dioxide(CO2)


Carbon dioxide is a byproduct of combustion, as well as a result of the metabolic process in living organisms. This heavy, colorless gas is also formed in the decay or combustion of animal and plant matter. Carbon dioxide can reach high levels of concentration in poorly ventilated buildings and areas where room dividers restrict air low.

Harmful Effects: Headaches, dizziness, nausea, asphyxiation, and lethargic conditions.

4. Formaldehyde (CH2O)

Formaldehyde gas is colorless flammable and highly reactive at room temperature. Formaldehyde poses a great health threat because of the out-gassing that occurs in new products and persists for many years. Formaldehyde settles in small cavities within the products. Over time the harmful vapors are discharged into the air. Formaldehyde irritates the mucous membranes of human beings, and high concentrations are intolerable. The main purpose of mucus is to lubricate and shield the digestive tract and respiratory system of the body. Problems occur when the mucus membranes are not functioning properly due to outside pollutants.

Sources: It is a component in building materials, foam insulations, plywood, particle boards, concretes, plasters, building furnishings, carpets, furniture, draperies, plastics, adhesives, paper goods, grocery bags, facial tissues, towels, and milk cartons, household cleaners, disinfectants, automobile bodies, clothes, permanent-press, stiffening agents, wrinkle retardants, water repellents, fire retardants, cigarette smoke, fuels, natural gas, coal or kerosene, cosmetics, toothpaste, soaps, deodorants, food additives, and germicides and fungicides for plants and vegetables.

Harmful Effects: Since mucus coats the throat and mouth, if the mucous membranes are clogged the body will experience difficulty with swallowing and dry mouth. Other problems occur in breathing passages. Some of the problems associated with formaldehyde include respiratory problems, headaches, dizziness, nosebleeds, shortness of breath, coughing, wheezing, and chronic respiratory disease, digestive tract problems, vomiting, irritation to the eyes (burning), skin (pain and rash), memory lapse and depression.

5. Carbon Monoxide (CO)

Carbon monoxide is an extremely toxic gas. It is colorless and odorless. It is emitted by motor vehicles, heating and cooking appliances, and cigarette smoke.

Harmful Effects: This gas hinders the body’s ability to move oxygen throughout the system since it connects to hemoglobin more forcefully than oxygen. Since carbon monoxide limits oxygen to the body, it causes headaches, lethargic conditions, blurred vision, lack of oxygen to the brain, and abnormalities in the heart.

6. Ozone (O3)

Ozone is a widespread outdoor air pollutant. It reacts with VOC and Nox to form a chemical reaction affecting indoor air quality. It can also cause photochemical reactions from outdoor sources entering the room through natural/mechanical ventilation and infiltrates from cracks in the building envelope system.

Sources: Indoor sources are from ozone emission devices like photocopying, air purifying, disinfecting devices, etc.

Harmful Effects: Exposure to Ozone leads to respiratory problems, impaired lung function, local or systemic inflammation, cardiovascular disease, and cancer in human beings.

7. Trichloroethylene

Another toxic pollutant lurking indoors is trichloroethylene. This chemical should be used only with proper ventilation. Trichloroethylene is used as a solvent for many products. For example, it is a solvent used to remove grease, floor wax, resin, varnish, lacquer, paint and rubber. It is also added to or present in many products such as inks, paints, oils, varnishes, adhesives, lacquers, dry cleaning compounds, and shoe polish.

Harmful Effects: Modest exposure to trichloroethylene can cause humans to experience a drunken (alcoholic) state. In higher concentrations humans experience a narcotic condition from trichloroethylene. Heavy exposure may cause the heart to twitch because the individual muscle fibers cease to work together with perfect correlation. This results in very swift irregular contractions of the muscle fibers of the heart. The muscles of the heart then become unable to synchronize the rhythm necessary between the heartbeat and the pulse. In heavy exposures, death may occur.

8. Benzene

Benzene is created during the manufacturing process or added to many manufactured products. Benzene is used in the manufacturing of medicinal chemicals, gasoline, plastic, dyes, linoleum, rubber, artificial leather, detergents, varnishes, and inks. It is also highly concentrated in tobacco smoke, a serious pollutant in many homes.

Harmful Effects: Although benzene is clear and colorless, it is highly flammable in liquid form. In humans, ingestion or inhalation of benzene can cause severe difficulties. Benzene attacks the mucous membranes; therefore, it breaks down the natural protection of the digestive tract and respiratory system. This breakdown can cause restlessness, depression, and in severe cases convulsions or death. Benzene irritates the skin and eyes and may cause chromosome damage and leukemia. Skin that comes into contact with benzene may burn, blister, and become painfully dry. Exposure to benzene may cause the eyes to burn and itch. High levels of benzene can cause damage to body organs and various respiratory diseases. Intermittent exposure and low levels of benzene can cause headaches, nervousness, leukemia, loss of red blood cell, and bone marrow deterioration.

9. Nitrogen Dioxide

Nitrogen Dioxide is created during the manufacturing process or added to many manufactured products. Benzene is used in the manufacturing of medicinal chemicals, gasoline, plastic, dyes, linoleum, rubber, artificial leather, detergents, varnishes, and inks. It is also highly concentrated in tobacco smoke, a serious pollutant in many homes.

Sources: Scientists from the Harvard School of Public Health found that nitrogen dioxide is significantly concentrated in homes with gas stoves.

Harmful Effects: Exposure to nitrogen dioxide can cause short-term and long-term injury to the bronchial airways. It may produce eye irritation and affect sensory perception, primarily hindering the eye’s ability to adjust to the darkness. It is believed nitrogen dioxide concentration causes limited lung growth, colds and bronchitis in children. Studies also indicate that exposure increases upper respiratory infection and in extreme cases, may cause chronic bronchitis.

10. Pb (Lead)

Lead is a natural element, recognized as a harmful environmental pollutant. It is found in lead-based paint, plumbing pipes, consumer products, food and occupational hazards, toys. It mostly routes to us through consumption and inhalation.

Harmful Effects: It severely affects brain development, nervous system disorder, anemia to children, early birth of a baby with the certain disorder at the integral development of baby, reproductive problems, cardiovascular effects, decreased kidney function for adults.

11. Outdoor Air pollutants

Pollutants causing indoor air pollution can also originate from outside sources such as radon, ozone, sulfur dioxide, pesticides, and outdoor air pollution. These pollutants enter our home through natural/mechanical ventilation and also infiltrate from cracks in the building envelope system.

Harmful Effects: Inhalation of such pollutants lead to respiratory problems, lung disease, aggravates existing heart disease, asthma, irritation of nose and throat, cardiovascular disease, and cancer in human beings. 

Some health issues like irritation of the eyes, nose, and throat, headaches, dizziness, and fatigue can be due to single-time exposure and they are usually short-term and treatable. Some health issues may show up years after continuous exposure. These issues include respiratory diseases, heart disease, and cancer. Thus we need to have a better understanding of air inside our homes.
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Know Your Home Air

Gas heating systems, leaking chimneys, fire places emits carbon monoxide, nitrogen dioxide and other harmful pollutants. Plastics and common household cleaners, paints, paint thinner often placed under the kitchen sink, release Volatile Organic Compounds (VOCs), when used and stored. Overheating of non-stick cookware releases toxic fumes. Pesticides we use in and around the home also release various chemical and semi-volatile compounds.


Harmful effects
Carbon monoxide causes headache, dizziness and fatigue. These often cause eye, nose, and throat irritation, nausea, and can also damage the liver, kidney, and central nervous system. Fine particles are produced during all kinds of combustion which lead to acute and chronic effects to respiratory and cardiovascular systems.

Pet dander and hair, carpet, rugs, upholstery furniture are main source of dust mites, fungus, and bacteria. A dirty filter of air conditioners acts as a reservoir for dirt, dust and other airborne contaminants that are continuously circulated back into your breathing air. Secondhand smoke from cigarettes, other tobacco products and mosquito coil emits VOC’s and formaldehyde and various particulate matters. CO2 released from our lungs is exhaled in the air which pollutes the air if the place is too crowded or there is less ventilation.


Harmful effects
All these can trigger coughing, nosebleeds, shortness of breath, dry mouth, vomiting,
digestive tract problems, depression, allergy and asthma attacks, and other respiratory illness.

Shower, faucets and other water sources are main cause of humidity and mold. Bathroom cleaners and personal care products like toothpaste, soaps, facial tissues, detergent, fabric softeners, air fresheners, deodorizers, hair sprays, disinfectants, are full of VOC’s and chemicals which emits harmful pollutants.


Harmful effects
Mold can cause allergic reactions, asthma and other respiratory ailments. VOC’s and toxic chemicals released in the bathroom can causes eye, nose, and throat irritation, nausea and respiratory problems. All these products release harmful pollutants while they are used also when they are stored.

A bedroom contains many sources of indoor air pollution. Mattress, pillow and blankets, soft toys, are the reservoirs of dust mites, fungi and bacteria. Furniture, carpets, paints and beauty product like hairspray, nail polishes, perfumes, deodorants etc off gas VOC, formaldehyde and toxic gases into the air.


Harmful effects
These pollutants make the air unhealthy which leads to allergy, asthma attacks, dizziness, headache, fatigue and other respiratory ailments.

Second-hand smoke
Second hand Smoke is a mixture of the smoke given off by the burning of tobacco products, such as cigarettes, cigars or pipes and the smoke exhaled by smokers. Secondhand smoke is also called environmental tobacco smoke (ETS). Passive smoking can lead to coughing, excess phlegm, and chest discomfort. NCI (National Cancer Institute) also notes that spontaneous abortion (miscarriage), cervical cancer, sudden infant death syndrome, low birth weight, nasal sinus cancer, decreased lung function, exacerbation of cystic fibrosis, and negative cognitive and behavioral effects in children have been linked to ETS. Secondhand smoke exposure commonly occurs indoors, particularly in homes and cars. Secondhand smoke can move between rooms of a home and between apartment units.

Guest Bathroom

Central heating and cooling systems and humidification devices
The air filter in your HVAC system is the front line of defense against poor indoor air quality. A typical central heating and cooling system circulates over 1,000 cubic feet per minute of air through the filter. This means the entire air volume in your house passes through the filter multiple times every day. A dirty filter, however, can actually make indoor air quality worse by acting as a reservoir for dirt, dust and other airborne contaminants that are continuously circulated back into your breathing air. In addition to driving up your utility bill, a clogged air filter will allow all that dust and debris that should be filtered out to be re-circulated back into your home. This can cause chronic allergies and especially be dangerous for people with asthma or other respiratory conditions.

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