The Air Quality Index

In all of our Saharan Dust forecasts, to quickly surmise the possible impacts on the population, we use an index called the Air Quality Index (AQI). Through the end of June 2019, TTWC has been using the United States Environmental Protection Agency’s (EPA) Air Quality Calculator and standards to determine the type of air quality across Trinidad and Tobago.

What is the Air Quality Index (AQI)?

The AQI is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you.

The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air. The Air Quality Index is calculated using the five major air pollutants: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide.

For each of these pollutants, there are established national air quality standards to protect public health around the world. Generally, particulate matter, specifically PM2.5 and PM10 are the two pollutants that pose the greatest threat to human health in this country, as a result of Saharan Dust surges.

The national standard for Particulate Matter (PM) of diameter ≤2.5 µm (PM2.5) is 65 µg/m3 and PM of diameter ≤10 µm (PM10) is 75 µg/m3 for Trinidad and Tobago.

In Trinidad and Tobago, note that our largest driver in air quality change is surges of Saharan Dust year-round. However, other local features can determine air quality such as forest/bush fires, chemical fires, waste disposal fires and other effects from landfill areas, traffic congestion, and surface winds (or lack thereof).

While most ambient air quality monitoring stations across Trinidad and Tobago are generally placed in areas to avoid these localized effects, changes in air quality can be highly localized depending on surrounding features.

A good example of this is the ambient air quality monitoring station located at the WASA Beetham Waste Water Treatment Plant. This station ran by the Environmental Management Agency (EMA), is located directly downwind of the Beetham Landfill, which throughout the year has numerous fires. Beyond fires, chemicals and other air pollutants emanating from the landfill may be detected as unhealthy to even hazardous for that local area but depending on wind direction, does not mean that hazardous air quality would be occurring in the capital nearby, Port of Spain.

How does the AQI work?

Think of the AQI as a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern.

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 hazardous air quality.

An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EMA (T&T) and EPA (U.S) has set to protect public health.

AQI values below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is considered to be unhealthy-at first for certain sensitive groups of people, then for everyone as AQI values get higher.

Understanding the Air Quality Index

Air Quality Index Values, Levels of Health Concern and corresponding color
Air Quality Index Values, Levels of Health Concern and corresponding color

The purpose of the AQI is to help you understand what local air quality means to your health. To make it easier to understand, the AQI is divided into six categories:

  • Good” AQI is 0 to 50. Air quality is considered satisfactory, and air pollution poses little or no risk.
  • Moderate” AQI is 51 to 100. Air quality is acceptable; however, for some pollutants, there may be a moderate health concern for a very small number of people. For example, people who are unusually sensitive to ozone may experience respiratory symptoms.
  • Unhealthy for Sensitive Groups” AQI is 101 to 150. Although the general public is not likely to be affected at this AQI range, people with lung disease, older adults and children are at greater risk from exposure to ozone, whereas persons with heart and lung disease, older adults and children are at greater risk from the presence of particles in the air.
  • Unhealthy” AQI is 151 to 200. Everyone may begin to experience some adverse health effects, and members of the sensitive groups may experience more serious effects.
  • Very Unhealthy” AQI is 201 to 300. This would trigger a health alert signifying that everyone may experience more serious health effects.
  • Hazardous” AQI is greater than 300. This would trigger a health warning of emergency conditions. The entire population is more likely to be affected.

Based on the United States standards, which Trinidad and Tobago Weather Center has used through the end of June 2019, T&T has experienced widespread unhealthy and unhealthy for sensitive groups air quality levels two times this year, in March and in June. Both of these events were as a result of Saharan Dust outbreaks across the islands, increasing PM2.5 and PM10 concentrations.

However, the Trinidad and Tobago standards by the Environmental Management Agency (EMA) for PM2.5 and PM10 concentrations slightly differ from the United States Environmental Protection Agency (EPA). This means that air quality that would be considered unhealthy for the United States are only considered moderate for Trinidad and Tobago.

Note: There has been, and will continue to be some discrepancy between published air quality index values from the EMA and TTWC in the short term based on different AQI calculations between the T&T and US methods. However, we’re aiming to bridge this gap in the near future. In the interim, we’ll be focusing on the impacts of Saharan Dust Outbreaks.

Good Air Quality

Good Air Quality

AQI – 0 to 50

What does this mean for you?

At this level, air quality is considered satisfactory, and air pollution poses little or no risk to public health. It’s a great day to be active outside.

Who needs to be concerned?

No one.

What should you do?

Sensitive Groups: Sensitive groups, children and the elderly do not need special protection.

Air purification: It is recommended to run an air purifier in auto-mode, so it automatically reacts to changes in air quality.

Ventilation: It is good for ventilation.

Masks: No masks are needed.

Outdoor Activity: Very suitable for outdoor exercise and activities.  

Moderate Air Quality

Moderate Air Quality

AQI – 51 to 100

What does this mean for you?

Air quality is acceptable; however, for some pollutants, there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.

Who needs to be concerned?

Unusually sensitive people: Consider reducing prolonged or heavy exertion. Watch for symptoms such as coughing or shortness of breath. These are signs to take it easier.

Everyone else: It’s a good day to be active outside.

What should you do?

Sensitive Groups: Sensitive groups such as those with respiratory ailments, children and the elderly are advised to reduce outdoor physical exertion, and reduce the time of their stay outdoors, especially in areas with heavy traffic.

Air purification: At this level, the air is slightly polluted. It is recommended to turn on your air purifier, running at a low level, at a minimum.

Ventilation: Please close windows, as the air is slightly polluted.

Masks: Wearing a mask during outdoor activity is recommended, particularly in areas with heavy traffic.

Outdoor Activity: It is recommended to stay indoors and avoid outdoor exercise.

Unhealthy for Sensitive Groups

Unhealthy for Sensitive Groups Air Quality

AQI – 101 to 150

What does this mean for you?

Members of sensitive groups may experience health effects. The general public is not likely to be affected. There is the increasing likelihood of respiratory symptoms in sensitive individuals, aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease & the elderly.

Who needs to be concerned?

Sensitive groups include people with heart or lung disease, older adults, children, and teenagers.

What should you do?

Sensitive groups: Reduce prolonged or heavy exertion. It’s OK to be active outside, but take more breaks and do less intense activities. Watch for symptoms such as coughing or shortness of breath.

People with asthma should follow their asthma action plans and keep quick-relief medicine handy.

If you have heart disease: Symptoms such as palpitations, shortness of breath, or unusual fatigue may indicate a serious problem. If you have any of these, contact your health care provider.

Air purification: At this level, the air is polluted. Turn on your air purifier, running at a high level.

Ventilation: Please close doors windows, as the air is polluted.

Masks: Wearing a mask during outdoor activity is recommended, particularly in areas with heavy traffic.

Outdoor Activity: It is recommended to stay indoors and avoid outdoor exercise.

Unhealthy Air Quality

Unhealthy Air Quality

AQI – 151 to 200

What does this mean for you?

Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.

There is increased aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly; increased respiratory effects in general population. Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.

Who needs to be concerned?

Everyone.

What should you do?

Sensitive groups: Avoid prolonged or heavy exertion. Move activities indoors or reschedule to a time when the air quality is better.

Everyone else: Reduce prolonged or heavy exertion. Take more breaks during all outdoor activities.

Air purification: At this level, the air is highly polluted. Turn on your air purifier, running at a high level.

Ventilation: Please close all doors and windows. Ventilation is not recommended.

Masks: Wearing a mask during outdoor activity is recommended, particularly in areas with heavy traffic.

Outdoor Activity: It is recommended to stay indoors and avoid outdoor exercise.

Very Unhealthy Air Quality

Very Unhealthy Air Quality

AQI – 201 to 300

What does this mean for you?

Health alert: everyone may experience more serious health effects.

There will be a significant aggravation of heart or lung disease & premature mortality in persons with cardiopulmonary disease and the elderly. A significant increase in respiratory effects in general population is expected.

Who needs to be concerned?

Everyone.

What should you do?

Sensitive groups: Avoid all physical activity outdoors. Move activities indoors or reschedule to a time when air quality is better.

Everyone else: Avoid prolonged or heavy exertion. Consider moving activities indoors or rescheduling to a time when air quality is better.

Air purification: At this level, the air is very polluted. Turn on your air purifier, running at a high level.

Ventilation: Please close all doors and windows. Ventilation is not recommended.

Masks: The air is very polluted. Concentrations of one or many pollutants are high. Masks are necessary for any outdoor activity, especially in areas with heavy traffic.

Outdoor Activity: It is recommended to stay indoors and avoid outdoor exercise.

Hazardous Air Quality

Hazardous Air Quality

AQI – 301 – 500

What does this mean for you?

Health warnings of emergency conditions. The entire population is more likely to be affected.

There will be a serious aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly. In addition, there will be a serious risk of respiratory effects in general population.

Who needs to be concerned?

Everyone.

What should you do?

EveryoneAvoid all physical activity outdoors.

Sensitive groups: Remain indoors and keep activity levels low. Follow tips for keeping particle levels low indoors.

Air purification: At this level, the air is hazardous. Turn on your air purifier, running at a high level.

Ventilation: Please close all doors and windows. Ventilation is not recommended.

Masks: The air is hazardous to public health. Concentrations of one or many pollutants are high. Masks are necessary for any outdoor activity, especially in areas with heavy traffic.

Outdoor Activity: It is recommended to stay indoors and avoid outdoor exercise.

Particle Pollution (Saharan Dust)

Particle pollution comes from many different types of sources. Fine particles (2.5 micrometers in diameter and smaller) include power plants, industrial processes, vehicle tailpipes, woodstoves, and wildfires.

Coarse particles (between 2.5 and 10 micrometers) come from crushing and grinding operations, road dust, and some agricultural operations.

Both of these particles are transported across from the Saharan Desert, the Atlantic Ocean to our shores year-round as Saharan Dust, bringing a myriad of problems to those included in sensitive groups. In addition, landfill and bush fires also contribute to this particulate pollution across Trinidad and Tobago.

Particle pollution is linked to a number of health problems, including coughing, wheezing, reduced lung function, asthma attacks, heart attacks, and strokes. It also is linked to an early death. (EPA)

Should I Be Concerned?

While it’s always smart to pay attention to air quality where you live, some people may be at greater risk from particle pollution. They include:

  • People with cardiovascular disease (diseases of the heart and blood vessels)
  • People with lung disease, including asthma and COPD
  • Children and teenagers
  • Older adults
  • Research indicates that obesity or diabetes may increase risk.
  • New or expectant mothers may also want to take precautions to protect the health of their babies.

How can I protect myself?

Use Saharan Dust AQI forecasts to plan outdoor activities. On days when the AQI forecast is unhealthy, take simple steps to reduce your exposure:

  • Choose a less-strenuous activity.
  • Shorten your outdoor activities.
  • Reschedule activities.
  • Spend less time near busy roads.

When particle levels are high outdoors, they can be high indoors – unless the building has a good filtration system.

Keep particles lower indoors:

Saharan Dust Precautions
Saharan Dust Precautions

Can I help reduce particle pollution?

Yes! Here are a few tips.

  • Drive less: carpool, use public transportation, bike or walk.
  • Choose ENERGY STAR appliances.
  • Set air conditioning controls higher in warmer weather and lower in cooler weather.
  • Don’t burn leaves, garbage, plastic or rubber.
  • Keep the car, boat and other engines tuned.
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