Air quality in Honolulu

Is Honolulu a city with polluted air?

Honolulu is a city located in Hawaii, a state comprised entirely of islands and situated some 2000 miles away from the mainland USA in the Pacific Ocean. It is both the largest city of the state, as well as the capital, being home to over 337,000 inhabitants, as of 2010.

In regards to its air pollution levels, Honolulu has come in with some significantly clean air quality readings over the past few years and continues to do so in more current times, with readings taken in mid-2021 also showing very good levels of air quality (with the following figures shown in US AQI, or the United States air quality index). These readings are aggregated from the main pollutants found in the air, both in Honolulu and worldwide, with ones such as nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), carbon monoxide (CO) and the two main forms of fine particles, PM2.5 and PM10 being used to calculate the overall US AQI reading.

Out of the two forms of particulate matter, PM2.5 is the far more dangerous of the two, being a pollutant that is comprised of a variety of different materials that include metals, sulfates, dust and other ultrafine particles such as silica or soot.

Due to the highly clean nature of Honolulu, breathing the air in the city would carry with it significantly fewer health consequences or risks of adverse health issues from developing. However, it is important to know the damaging effects of pollution, when and how they can occur, along with certain procedures that can be undertaken in order to reduce the damaging effects, should such pollution elevations occur. As such, the variety of health issues that may present themselves when individuals are exposed to the various pollutants in the air will be discussed in more detail in the following questions.

Regarding some of the air quality readings taken in late June of 2021, a US AQI reading of only 13 was taken. This placed Honolulu into the 'good' rating bracket for the particular day and time in which it was taken, one of the best air quality ratings brackets when going by US AQI standards. It requires a reading of anywhere between 0 to 50 to be classified as such and is color-coded as green, which is used on the air quality maps, graphs and forecasts present on the page, as well as throughout the IQAir website.

It represents a level of air quality in which both the general public and those with failing immune systems or pre-existing health conditions (particularly of the cardiac or pulmonary variety) would be free to go about their daily activities without any worry of respiratory distress or aggravation occurring. The air would also be significantly free from smoke, haze and many other damaging particles that can permeate the atmosphere in more polluted cities and states throughout the world.

At the time when the above-mentioned US AQI reading of 13 was taken, the PM2.5 concentration in the air was found to not be in excess of the World Health Organization's (WHO's) exposure recommendation. Other readings of US AQI that were taken over the course of June were all ones that remained in the 'good' rating bracket, coming in with other numbers such as 16, 18, and a high of 21, showing that the air quality remained consistently clean throughout the month of July.

However, on a somewhat less positive note is that whilst Honolulu and Hawaii as a whole maintains some of the best air quality not only in the United States but throughout the whole world, Honolulu may be a risk of being negatively affected due to changes in climate and increasing heat levels. These changes have been shown to have had a small impact on the level of ozone present throughout Hawaii over the last few years. But as it currently stands the air quality still remains as some of the best in the world.

Over the course of 2020, Honolulu came in with a PM2.5 reading of only 3.8 μg/m³, an extremely low reading that placed it well within the WHO's target goal for the best quality of air at 10 μg/m³ or less, with the closest to 0 being the most optimal. This reading placed it in 4702^nd place out of all cities ranked worldwide, placing it in the upper echelons of the cleanest cities on the global circuit.

What causes air pollution in Honolulu?

Whilst Honolulu maintains a great level of air quality throughout the year, there are still sources of pollution present that cause elevations in the US AQI and PM2.5 reading, however minor they may be. Of note is that any level of pollution exposure has the chance to cause adverse effects, and as such during certain periods of time, adverse meteorological conditions such as lack of rain (which can tamp down larger particles found in the air) as well as lower wind speed can lead to build-ups in air pollution, particularly in certain areas such as roads that see a high volume of traffic, as well as near industrial sites, power plants or factories.

The combination of such events occurring can lead to temporary rises in air pollution, with one of the main contributing sources being fumes and emissions given off by vehicles. A large number of cars and motorbikes would be in use on the roads, all of which would give off various chemical compounds and fine particles.

Many of the primary pollutants given off by vehicles (primary pollutants being ones that are released directly from a singular source such as a motor or a fire) such as gases, chemical compounds and the various oxides of nitrogen (NOx) can be converted into ozone when exposed to high enough levels of solar radiation, which would be found in abundance in Hawaii, particularly during the hotter months of the year.

The creation of this secondary pollutant is another contributing factor, and one that is of significant concern throughout Hawaii as well as the rest of the world, with many of the more densely populated cities having large build-ups of smog (as it is more well known as when it accumulates in large amounts) permeating the air, being a visible fixture in some cities throughout the world, particularly in areas that see a large volume of vehicles passing through them.

Heavier freight vehicles such as trucks and lorries would also be in use, for the transportation of goods for both import and export. These often utilize diesel as their main fuel source, which can give off its own variety of pollution when combusted, typically being a considerably dirtier fuel source than other alternatives.

Furthermore, all vehicles can give off many tons of microscopic rubber particles over the course of time, coming from the wear and tear inflicted on tire treads. Much of this builds up in the soil, bodies of water, as well as lingering in the atmosphere. When it enters into the environment, it can cause damage to human health when inhaled, as well as entering into various ecosystems, causing further damage as it makes its way up the food chain.

Other sources of air pollution would be emissions from power plants, with the state of Hawaii relying heavily on oil, coal and other fossil fuels. The combustion of these materials leads to further pollutive output, with many chemicals being found in the smoke given off by such places. Some of these pollutants are ones included in the US AQI aggregate, as was mentioned above, as well as a variety of others such as black carbon, volatile organic compounds (VOCs), mercury, lead and cadmium, along with dioxins, furans and polycyclic aromatic hydrocarbons.

Construction sites, road repairs and any activity that disturbs a large amount of earth can also contribute to elevated pollution levels, with construction sites often giving out heavy metals and other pollutive byproducts from the use of heavy machinery. These are a number of the main polluting sources that would be present in Honolulu, although as of yet they have failed to put a significant dent into the cleanliness of the overall air quality reading.

However, as mentioned before, as with any city in the world, sudden elevations in air pollution can occur, causing respiratory irritation to those with pollution sensitivity, as well as the general public if the levels rise high enough.

As such, pollution levels and forecasts can be monitored during spells of higher pollution, particularly for those who have health conditions or for those who want to keep their pollution exposure to a minimum. For the most accurate and up-to-date readings, forecasts can be followed hourly either through this page or the AirVisual app.

What health issues can arise from pollution exposure in Honolulu?

Some health issues that may appear during periods of higher pollution levels would be ones such as dry coughs, chest pain and respiratory infections. Due to the extremely small size of PM2.5, it can penetrate deep into the tissue of the lungs and cause inflammation, irritation and scarring, which can reduce the lung's full capacity to take in oxygen.

Furthermore, when damage has been sustained to the lungs or respiratory tract, affected individuals become more susceptible to instances of chronic obstructive pulmonary disease (COPD), an umbrella term that contains within it a number of ailments such as asthma, bronchitis, emphysema and pneumonia. When those with pre-existing conditions, the elderly, or anyone with a poor overall level of health are affected, such conditions may worsen to the point where medical intervention is required.

Once again with PM2.5’s ultrafine size, it can enter into the bloodstream via the alveoli in the lungs. Once inside the bloodstream, fine particles can wreak havoc throughout the body, destroying blood vessels and causing health issues such as ischemic heart disease, heart attacks, arrhythmias, strokes, and death.

Other less serious conditions may include skin problems, with acne, atopic dermatitis, eczema and psoriasis all presenting themselves amongst certain individuals, particularly those with excessive sensitivity towards fine particles or chemicals.

Has Honolulu’s air quality improved over the last few years?

Observing the PM2.5 yearly averages taken over the course of the last few years, one can see that the overall reading has remained fairly constant, with mild improvements shown only for the number to rise back up ever so slightly. The difference is almost somewhat negligible, although any changes in air cleanliness are important when recording a city or state's transformation over time, regarding whether an improvement is slowly set as a trend over the years.

The respective readings from 2017 through to 2020 were 4 μg/m³, 3.9 μg/m³, 3.6 μg/m³ and 3.8 μg/m³. This shows a very slight improvement from 2017 by only 0.2 units, and as such, Honolulu will most likely follow the trend of staying within similar levels of air pollution in the coming years.

When does the air quality see improvements in Honolulu?

Observing the PM2.5 readings over the course of 2020, it can be seen that for all the individual months, whilst they all maintained a great level of air quality, there were certain months that were cleaner than the others by marginal amounts. March through to May had had the best levels of air quality, coming in with readings of 3.3 μg/m³, 3.3 μg/m³ again in April and 3.5 μg/m³ in May.

This put both March and April as the cleanest months of the year, a time in which the air would be even freer from smoke, haze and other contaminating elements. Regarding the more polluted months of the year, they were, in relative terms, January and February, along with October and December. Their respective readings were 4.1 μg/m³, 4.3 μg/m³, 4.2 μg/m³ and once again 4.2 μg/m³. This put February in the most polluted spot out of all of Honolulu’s months of 2020.

PM2.5 readings differ from the US AQI ones in that they are taken in micrograms per cubic meter. As touched on previously, the size of PM2.5 or 2.5 microns and below, puts it at roughly 30 times smaller than that of a human hair. As such, reducing or minimizing exposure to it is of constant importance, even in a city as clean as Honolulu.