United States of America

Air Quality Index

Air Quality Index, USA

An air quality index is used by different agencies / countries to converse with the public about how polluted the air currently is or how polluted it could be.Different countries have their air quality indices, corresponding to different national air quality standards. The AQI of USA is EPA’s (Environmental Protection Agency) index for reporting air quality.
AQI, USA is based on the levels of five main pollutants regulated by the EPA::
  • Ground-level ozone
  • Particle pollution (also known as particulate matter, including PM2.5 and PM10)
  • Carbon monoxide
  • Sulfur dioxide
  • Nitrogen dioxide
For each of these pollutants, EPA has established national air quality standards to protect public health. Ground-level ozone and airborne particles (PM) are the two pollutants that pose a significant threat to human health in this country. Other pollutants include such as black carbon and volatile organic compounds (VOCs), both of which are formed from the incomplete combustion of both fossil fuels and organic matter.

Basics of AQI

A higher AQI value means higher air pollution levels and higher concern for effects on health. For example, an AQI value of 50 represents good air quality with little potential to affect public health, while an AQI value over 300 represents a hazardous factor that everyone may experience serious effect.
The USA AQI is divided into 6 categories. Each category points to a different level of health concern. It has a specific colour. The colour makes it easy to determine whether air quality is reaching unhealthy levels.
Air Quality Index (AQI) Values Levels of Health Concern Colors
0 - 50 Good
51 - 100 Moderate
101 - 150 Unhealthy for Sensitive Groups
151 - 200 Unhealthy
201 - 300 Very Unhealthy
301 - 500 Hazardous

Understanding Health concerns related to different Air Pollution levels

  • Good: Air quality is satisfactory and poses little or no health risk.
  • Moderate: Air quality is acceptable, but pollution in this range may cause a moderate health concern for a small number of individuals. People who are sensitive to ozone or particle pollution may experience respiratory symptoms.
  • Unhealthy for Sensitive Groups: Members of sensitive groups may experience health effects, but the general public is unlikely to be affected.
  • Unhealthy: Everyone may begin to experience health effects. Members of sensitive groups may expose to more serious health effects.
  • Very Unhealthy: It triggers a health alert, meaning everyone may experience more serious health effects.
  • Hazardous: Triggers health warnings of emergency conditions. The population is even more likely to be affected by serious health effects.

Five major pollutants

EPA, USA has established an AQI for five major air pollutants regulated by the Clean Air Act. These are:
  • i. Ground-level ozone
  • ii. Particulate matter (including PM2.5 and PM10)
  • iii. Carbon monoxide
  • iv. Sulfur dioxide
  • v. Nitrogen dioxide

Advisory for different AQI Levels

Some advice for different AQI levels are as below:
Air Pollution Level Advisory
Good None
Moderate & Unhealthy for Sensitive Groups Active children and adults, and people with respiratory disease, such as asthma, should limit prolonged outdoor exertion.
Unhealthy & Very Unhealthy Active children and adults, and people with respiratory disease, such as asthma, should avoid prolonged outdoor exertion; everyone else, especially children, should limit prolonged outdoor exertion.
Hazardous Everyone should avoid all outdoor exertion.

For Pollutant-Specific Sub-indices and guidance on the Air Quality Index (AQI) – click here.

AQI Calculation

The Index is based on measurement of pollutants – particulate matter (PM2.5 and PM10), Ozone (O3), Nitrogen Dioxide (NO2), Sulfur Dioxide (SO2) and Carbon Monoxide (CO) emissions. All measurements are based on hourly readings: For example, an AQI reported at 8AM means that the measurement was done from 7AM to 8AM.

Importance of AQI

The citizens play a vital role in improving the air quality of a nation. They should be informed about the local and global air pollution problems and the ways to reduce them.
Along with indexing the air quality, AQI also provides advice on how air quality can be improved. This index mainly considers the people sensitive towards air pollution and advises them ways to protect themselves from different health risks posed at various air quality levels.
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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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