جودة الهواء في Darwin

How bad is the air quality in Darwin Australia?

Darwin, the capital of Australia’s Northern Territory state, is home to the majority of residents within the otherwise sparsely populated state. Located on the northern coast of Australia close to Indonesia, Darwin experiences a tropical monsoon climate, with an established dry season (from May to October) and a wet season (November to April). During the wet season, spectacular thunderstorms are common, and Darwin’s region can be vulnerable to cyclones. Like the rest of Australia, Darwin generally experiences relatively healthy air quality most of the year round, in comparison to global locations. However, as in the rest of the country, Darwin is also vulnerable to experience short-term air pollution spikes from extreme events such as bushfires and dust storms, which can significantly affect air quality for short periods of time.

The main pollutants of concern within Darwin are particulate matter (PM): this describes tiny airborne particles measuring less than 2.5 or 10 micrometers in diameter, abbreviated to PM2.5 and PM10 respectively. This is for two main reasons: firstly, these pollutants are the most affected by local emission sources such as smoke from nearby and distant burning of vegetation during the dry season, which can significantly increase air pollution levels.¹ Secondly, PM is a particularly hazardous pollutant to human health. These particles’ tiny size enables them to travel deep into the human system when inhaled, entering the lungs and in the case of PM2.5, moving beyond into the bloodstream, causing a range of health effects.

How does Darwin’s air quality compare to other cities?

According to Northern Territory’s Environment Protection Authority (EPA)’s records, Darwin averaged a PM2.5 concentration during 2019 of 9 μg/m³, which exceeds Australia’s national air quality standard for PM2.5, which is a guideline of less than 8 μg/m³.² However, this achieves the World Health Organisation (WHO)’s slightly less strict annual PM2.5 target of 10 μg/m³. Australia’s standards, called the National Environment Protection (Ambient Air Quality) Measure (Air NEPM), are among the strictest in the world for PM2.5 pollution; both stricter than the WHO’s guideline (10 μg/m³), the USA’s annual target (below 12 μg/m³), and the European Union’s annual target (25 μg/m³). For context, this annual rating for Darwin’s particle pollution ranks it as less polluted than other state capitals Canberra’s air quality (15 μg/m³) and Sydney’s particle pollution (10.1 μg/m³), but more polluted than the air quality in Brisbane during 2019 (8.1 μg/m³), according to IQAir’s 2019 World Air Quality Report.³

What are the main sources of Darwin air pollution?

Within Australia, key sources of air pollution include emissions from motor vehicles, industry, wood heating and power generation, in addition to natural sources such as wildfires and dust storms. Within Darwin, however, smoke from seasonal fires during the dry season from April to November dominate changing air pollution levels, causing significantly higher levels of pollution to be recorded.⁴

What are the health effects of air pollution in Darwin?

Exposure to air pollution can cause a range of short- and long-term effects to human health. Short-term effects can include aggravation of existing conditions such as asthma, as well as the irriration of eyes, nose and throat. Long-term effects can include a higher risk of developing cardiovascular and respiratory disease, such as lung cancer, chronic pulmonary obstructive disease (COPD), and premature mortality. Even at relatively low concentrations such as found in Darwin, air pollution can cause notable health impacts; the World Health Organisation emphasises that there is no known “safe” limit below which no health impacts can be observed from air pollution, particularly particulate matter.⁵

It is interesting to note that the health impacts of air pollution in the Darwin area may vary both by pollution source, and population bracket. For example, two studies examined the health impacts of the Darwin region’s most significant air pollution source, the planned burning of vegetation which most often occurs during the dry season. One study found that while higher levels of vegetation smoke in Darwin (particularly PM10) correlated with increased hospital admissions for respiratory conditions, these impacts were strongest among indigenous people.⁴ Secondly, another study found that while elevated levels of vegetation smoke (PM2.5 and PM10) from planned burning among the Australian monsoon tropics correlated with increased aggravation of asthma symptom among people with asthma, there was a lower correlation with more extreme symptoms of asthma, such as attacks, increased hospitalisations and time missed from school or work. This may be linked to how planned or prescribed burns typically result in a lower level of air pollution overall, than the more extreme air pollution often generated by uncontrolled wildfires.⁶

What is Darwin doing about air pollution?

The Northern Territory EPA is responsible for monitoring air quality across key locations of concern within the state, and accordingly, runs a network of air quality monitors concentrated around the Darwin area. As of December 2020, these include 4 monitoring stations, located at Palmerston, Winnellie, Stokes Hill and one beyond Darwin, in Katherine. The stations monitor a range of key pollutants, including carbon monoxide (CO), nitrogen dioxide (NO₂), ozone (O₃), sulfur dioxide (SO₂), and particulate matter (PM2.5 and PM10). The EPA is responsible to try to ensure that air quality levels do not exceed the Australian NEPM standards, which are designed to limit the health hazard to people from air pollutants, based on scientific evidence.

Does Darwin use an air quality index?

The Northern Territory EPA communicates its air quality data to the public using Australia’s broader air quality index system. A Darwin air quality index is therefore calculated for each pollutant monitored at a given site, and expressed as a percentage of that pollutant’s respective NEPM standard. A Darwin AQI of 100 therefore represents a pollutant level equivalent to the maximum amount allowed under the NEPM standard, and an AQI of 200 indicates a twofold exceedance. At locations where multiple pollutants are measured, the pollutant with the highest AQI will determine that location’s overall AQI level. The Darwin AQI scale is colour-coded into categories, from 0-33 indicating “Very Good” air quality (green), up to 201+ indicating “Severe” air quality (red), with accompanying health advisories. By displaying air pollution levels in this way, the Northern Territory EPA strives to quickly convey air quality levels in a simplified scale so that Darwinians can quickly respond to air pollution when necessary.

+ Article resources

[1] Northern Territory EPA. “Air Quality”. Northern Territory EPA website, November 26, 2020.
[2] Northern Territory EPA. “Reports: Yearly Dialog”. Northern Territory EPA website, n.d.
[3] IQAir. “2019 World Air Quality Report”. IQAir website, March 18, 2020.
[4] Ivan C Hanigan et al. “Vegetation fire smoke, indigenous status and cardio-respiratory hospital admissions in Darwin, Australia 1996-2005: a time series study”. Environmental Health 7, August 5, 2008. DOI: 10.1186/1476-069X-7-42
[5] World Health Organisation. “Ambient (outdoor) air pollution”. WHO website, May 2, 2018.
[6] Dr Fay H Johnston et al. “Vegetation fires, particulate air pollution and asthma: A panel study in the Australian monsoon tropics”. International Journal of Environmental Health Research (16)6: 391-404. December 12, 2006. DOI: 10.1080/09603120601093642