The RAC Air Health Monitor’s hourly real-time data reflects the current Western Australian Air Quality Index (WA AQIs) and incorporates each of the World Health Organisation (WHO) Air Quality Guidelines (WHO AQGs) for each pollutant —  so that the community can see clearly how air quality is changing hour by hour, and year by year, in line with national and international standards.

Here is what the RAC Air Health Monitor colour classifications mean and background on why RAC chose to use these AQI classification categories:

Category PM2.5 (ug/m3) PM10 (ug/m3) NO2 (ppb)
Good (better than WHO threshold) 0-4 0-14 0-9
Moderate (not ideal, but better than WHO 24-hr average threshold) 5-14 15-44 10-24

Unhealthy for sensitive groups (worse than WHO threshold)

15-24 45-49 25-79
Unhealthy 25-49 50-99 80-119
Very unhealthy 50-99 100-199 120-179
Hazardous 100-299 200-599 180-239
Extreme 300+ 600+ 240+

RAC began reviewing the WA AQI categories as part of the RAC Air Health Monitor development, in comparison to the WHO recommended guideline thresholds — the WHO AQGs.

The WHO releases guideline values which set annual averages and 24-hour averages for Particulate Matter 2.5 (PM2.5), Particulate Matter 10 (PM10), Nitrogen Dioxide (NO2) and also Sulfur Dioxide (SO2) and Ozone (O3). The guideline value averages, set a level that nations should be aiming to not exceed over the set timeframe, so it made sense to include these values as category thresholds.

In WA, we utilise the WA AQI to measure air quality. Across the globe, we commonly assign different colours to classify and communicate air quality levels.

We identified that the WA AQI the category labels did not reflect the realities of what was occurring. This is particularly so in the ‘good’ category, the broad category ranges did not lend themselves well to displaying and helping people to understand changes in localised air quality — a lot of the smaller but still important changes that occur would not have shown up. The ‘good’ category also does not reflect the WHO recommended thresholds. Further, the upper categories make the air sound cleaner and healthier than it may be.

We looked to both the WHO and the WHO AQG recommendations around air quality, to guide the RAC Air Health Monitor scale.

The WHO emphasises that there is no ‘safe’ or ‘risk free’ level of air pollution. So, it’s important to understand what’s happening even when the air quality is ‘good’. We have categorised the lower levels reflected in the ‘good’ category to show greater differentiation and utilised the readily accepted WHO AQGs for this purpose.

We also altered the category labels — leaving the category numbers as defined by the State Government — to be more reflective of the impact on peoples health.

The RAC Air Health Monitor aims to make localised air quality available to everyone and aim to do so in a way that is valuable, easy to view and understand, and with the ability to respond. We have created the RAC Air Health Monitor map with a greater range of categories, reflecting smaller changes.

In Australia, the State Environment Ministers agree to a level for ‘acceptable’ air pollution categories through the National Clean Air Agreement (219KB). The State Environment Ministers then implement versions of those levels in the relevant States through air quality indexes (AQI).

The table below shows a side-by-side comparison of the WA AQI classification categories with the adapted RAC Air Health Monitor classifications:

Current RAC Indicators (based on WHO) Current WA Air Quality Indicators
PM2.5 (ug/m3) PM10 (ug/m3) NO2 (ppb) PM2.5 (ug/m3) PM10 (ug/m3) NO2 (ppb)
0-4 0-14 0-9 Good
(better than WHO threshold)
5-14 15-44 10-24 Moderate
(not ideal, but better than WHO 24-hr average threshold)
Good 0-25 0-50 0-80
15-24 45-49 25-79 Unhealthy for sensitive groups
(worse than WHO threshold)
25-49 50-99 80-119 Unhealthy Fair 25-50 50-100 80-120
50-99 100-199 120-179 Very unhealthy Poor 50-100 100-200 120-180
100-299 200-599 180-239 Hazardous Very poor 100-300 200-600 180-240
300+ 600+ 240+ Extreme Extremely poor 300+ 600+ 240+