‘Unhealthy Air Quality for Sensitive Groups’ – What Does That Mean?

It can be startling to see the phrase “unhealthy air quality for sensitive groups” in your weather app, but this small nugget of knowledge could actually save a life. This air quality notice refers to “code orange” days, or days when the pollution level in the area outside your door may be risky for young children, the elderly, and people who already have health issues.

What Causes Unhealthy Air Quality?

Numerous factors, including emissions from close-by companies and fossil-fuel powered power plants, wildfires, and seasonal pollen, can result in unhealthy air. Air quality can be impacted by the weather.2 For instance, high pressure systems, which are linked to sinking air, promote the buildup of pollutants close to the surface of the earth where they are inhaled more frequently. Since colder, denser air can trap pollutants at lower levels, thermal inversions—cold air near the surface and warmer air above—have a similar impact during the winter. And as seen in June 2020 when dust from Africa’s Sahara Desert was transported nearly 5,000 miles to the U.S. Gulf of Mexico, winds can contribute to the long-distance spread of pollution.

Polluted air is bad for everyone, but it can be especially bad for kids, the elderly, those who work outside or are physically active, people with heart disease, lung diseases including asthma, emphysema, and bronchitis, and people with diabetes.4

Particle pollution can cause inflammation of the airways and lungs in those with respiratory illnesses, making it difficult for them to breathe as deeply as they should and causing symptoms such as coughing, wheezing, exhaustion, and shortness of breath.istances

Children are at increased risk from air pollution primarily because they spend prolonged periods of time outdoors. What’s more, much of this time is spent playing sports or games, meaning children are not only exposed to unhealthy air for longer periods of time than adults, but also at higher rates. (The more strenuous the activity, the more air intake is required, thus the more unhealthy air that is breathed in.) Since kids’ lungs are still developing, high levels of pollutant exposure can go so far as to cause irreversible damage, including decreased lung-function growth.¹ The fact that about 1 in 14 children (7%) have asthma also puts youth at increased risk

In addition to being more likely to have a pre-existing condition, older persons (those 65 and over) are also more vulnerable to environmental dangers since ageing weakens their bodies’ resistance to stimuli from the outside world.

Heart disease and air pollution have a more nuanced relationship. People with cardiovascular disease are more at risk from the extremely small pollution particles known as PM2.5 because they can enter the circulation and irritate blood vessels. Consequently, blood arteries may burst, leading to a heart attack or stroke.

The Air Quality Index

For many, air quality alerts such as “unhealthy for sensitive groups” is their introduction to the fact that air quality forecasts even exist. Just as the National Weather Service (NWS) is responsible for monitoring weather conditions and hazards across the United States, the U.S. Environmental Protection Agency (EPA) monitors and reports on air quality each day. It also issues air quality forecasts for up to six days ahead. The EPA does this via the Air Quality Index (AQI).

Data on pollutant concentrations are used to produce AQI values, which range from 0 to 500. If there are many pollutants present on a particular day, the AQI for that day is based on the pollutant that poses the greatest concern.

AQI readings under 100 are generally regarded as excellent, whereas readings over 100 indicate poor air quality.

Measurement of Major Air Pollutants by AQI
Ground-level ozone, carbon monoxide, sulphur dioxide, nitrogen dioxide, and two types of particle pollution (inhalable solid and liquid specks, which are smaller in size than the width of a human hair), are the five main pollutants that the AQI measures.

There are other types of pollution, but the AQI only reports on these five. Another typical air pollutant that is subject to regulation under the Clean Air Act is lead (Pb), however due to the lengthy time it takes to collect and analyse lead samples, lead is not included in the AQI. Additionally, between 1980 and 2014, lead emissions decreased by 98% as a result of the elimination of lead from petrol (as in leaded vs. unleaded gas). Because of this, lead isn’t now thought of as

Ozone (O3)

Ozone is one of the most common pollutants found in the United States. It’s also the primary source of smog. When it lives roughly six miles above the surface in Earth’s stratosphere, it protects life on earth from the sun’s harmful ultraviolet radiation. However, when ozone exists at ground levels where it can be breathed in, it’s considered harmful to human health and can trigger asthma attacks or even cause asthma to develop. Unlike other pollutants, ozone isn’t emitted directly into the air; it’s created when nitrogen oxides (NO_x) and volatile organic compounds (VOCs), such as those from vehicle exhaust, chemically react in the presence of heat and sunlight.

Carbon Monoxide (CO)

Carbon monoxide is a colorless, odorless gas that’s released through burning. (Kerosene heaters and gas stoves are two well-known sources of indoor carbon monoxide.) Carbon monoxide can lower the amount of oxygen that can be carried in the bloodstream to vital organs like the heart and brain. As a result, exposure to high levels of it can cause dizziness, unconsciousness, and even death.

Sulfur Dioxide (SO2)

The largest source of sulfur dioxide gas in the atmosphere is the burning of fossil fuels by power plants and other industrial facilities. Asthma sufferers are particularly sensitive to it. Alongside nitrogen oxide, it plays a significant role in forming acid rain

Nitrogen Dioxide (NO2)

Nitrogen dioxide is a gas that primarily enters the air from the burning of fuel, which is why its primary sources include vehicle emissions, fossil-fuel-based power plants, and commercial manufacturing. When breathed in, it irritates the body’s airways and can aggravate or even cause respiratory disease. When nitrogen dioxide reacts with sulfur dioxide and water molecules in the atmosphere, it forms acid rain.

Good (Green)

A green level (AQI values up to 50) signifies good air quality. These are the best days to be active outdoors, since air pollution poses little to no risk. 

Moderate (Yellow)

A yellow level (AQI values of 51-100) means that air quality is OK for the general public. Sensitive groups, however, may face an elevated health risk and should take caution while outdoors. 

What to Do When the Air Quality Is Unhealthy

When the air quality is unhealthy, the best way to reduce exposure to particle pollution is to reduce time spent outdoors or avoid going outdoors altogether.

The following tips can help limit your pollutant exposure even further.

• Keep your vehicle’s ventilation setting on “recirculate,” especially when driving on busy roads.
• If you need to refuel your vehicle, wait until after dark to pump gas. It’ll discourage additional gas emissions from mixing with sunlight and heat to create ground-level ozone.
• Avoid using gas-powered lawn mowers.

• Don’t burn leaves, garbage, or use wood stoves or fireplaces; doing so will contribute to the elevated air pollution levels in your area.
• Reduce the intensity of any outdoor activities; the more strenuous the activity, the more air intake you’ll require, and the more unhealthy air you’ll breathe in.
• Keep prescribed medications on hand in case any symptoms are triggered.
• Keep your home’s windows and doors closed.
• Use High Efficiency Particulate Air (HEPA) filters and air purifiers in your home; they help keep indoor particle levels low by trapping over 99% of pollutants 0.3 microns in size.¹⁷  
• Wear a mask/respirator that’s capable of filtering very small particles.