Article by CAP team June 2023 ©

When looking at your favourite air quality app you are usually shown an icon and a value from a scale that looks something like the image below.

Have you ever wondered what it all means or have you even questioned if the index and number ranges used by the app are applicable in South Africa?

What is Ambient Air Monitoring?

Is the methodical, long-term assessment of air pollutant levels by detecting and measuring the quantity and type of specific pollutants in the surrounding air. Most air pollution regulatory agencies use beta attenuation monitoring to detect particulate matter, with strict calibration and management protocols.

Some air pollutants are found almost everywhere and are considered harmful to humans if their concentration in the ambient air exceeds certain levels. Each country sets its own air quality standards and limits for each of these pollutants. These standards usually include all the criteria pollutants sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3), lead (Pb), and particulate matter (PM).

Why do we monitor Ambient Air?

The monitoring of ambient air is a crucial element of a successful implementation of an air quality management system and helps: –

  • determine the level and extent of air pollution;
  • make real-time ambient air quality data to the public in a timely manner;
  • support the implementation of air quality standards and objectives;
  • assess the efficacy of local and national emission control strategies and objectives;
  • provide information about air quality trends;
  • provide data to be used in the development of reliable air quality models; and
  • support research, such as the health effects of high levels of air pollution.

What is an Air Quality Standard?

An ambient air quality standard (AAQS) is a limit set on the concentration of a particular pollutant in the air. An air quality standard may indicate a limit such as the level of pollutant X shall not exceed Y. The standard may set a target such as by the year 2030 the level of pollutant X shall not exceed more than amount Y. In some cases, the air quality standards will include both.

These standards are usually codified in legislation and are both legally binding and enforceable. These standards are established to protect the health of the people, especially the most vulnerable, such as the young and old and those with pre-existing medical conditions.

A common objective of these standards is to improve air quality, to protect human health and the environment as it is generally accepted that air pollution: –

  • is responsible for premature death and chronic sicknesses: and
  • has negative impacts on ecosystems and biodiversity.

Is there a Single Standard?

Unfortunately, no, just as air quality varies depending on where you are in the world, so do the air quality standards. When trying to compare various international standards with our national standard you will notice that they contain a mix of units and averages. For example, the US prefers setting standards in part per million (ppm) while the EU states values in µg/m3 (micrograms per cubic metre of air). Some of the limits are set as an average over 1, 8, or 24 hours. This variability makes their comparison more difficult.

Some of the most comprehensive standards and guidelines are those issued by the World Health Organization [1] (WHO), European Environment Agency [2] (EEA) and the U.S. Environmental Protection Agency [3] (EPA). The WHO air quality standards are not legally binding but rather serve as a guide for those countries that choose to adopt them. Both the EEA and EPA standards are currently under review, we anticipate that they will be brought closer in line with the WHO guidelines.

Given the variability in national and international standards, we cannot help but wonder: What limits are truly safe for humans? According to epidemiological research, there is no safe level at which health effects do not occur.

South African

Standards 2012


Guidelines 2021

Annual limit 20 µg/m3  5 µg/m3 4 times WHO
24-hour limit  40 µg/m3 25 µg/m3 1.6 times WHO

What is An Air Quality Index?

The Air Quality Index, or AQI, is a scale that some government agencies use to communicate the levels of air pollution to the public. These governments believe that AQI scales make reporting easier by having easy-to-understand ranges like 0 to 50 and 50 to 100. The US AQI scale, for example, has six colour-coded levels of concern ranging from 0 to 500 AQI values. The values in the index range correspond to different health concerns. A high AQI value indicates a higher level of air pollution and associated health risks.

There are many different AQI scales and ranges of numbers, [4] [5] [6] which can make things even more confusing. The AQI scales are calculated using conversion formulas and have no correlation to the South African air quality standards or other government scales.

Often popular apps, that you rely on for your AQI reports, do not specify which AQI scale or data they are using. Some of these apps also rely on satellite data. While the IHME [7] satellite data represented a major leap in understanding global air pollution exposure, the methodology has its limitations. In some countries, the PM2.5 exposure levels appear to be skewed. For example, some cities have it is possible to have very high levels of pollution, but the average for the country is relatively low. These low averages could result from several factors including the fact that pollution in some areas may be highly variable seasonally and spatially and that satellites only measure day-time data, so there are some clear differences in daytime and night-time pollution levels.

The two PM2.5 AQI scales below are very different and because of the ranges used, CAP believe that the South African AQI scale under-reports the true picture of air quality in the country. The SA AQI scale is misleading and shows no correlation to legislated limits. The legislated PM2.5 24-hour limit is 40 µg/m3, but the scale indicates green for good from Level 1 to Level 3 or 0 to 103 µg/m3 where 103 µg/m3 equates to ± 2.6 times the SA legislated limit and ± 5.15 times the WHO Guideline limit. How can this be considered Green for Good?

AQI vs µg/m3

The use of micrograms for air quality data makes things a lot simpler as it directly correlates to the South African ambient air quality standards. The CAP monitors and real-time air quality map use micrograms.

The CAP/AirGradient Live Real-Time Air Quality Map uses the US AQI colour coding but what we believe is more important is the numbers shown on the map, they should read 5 or less and not peak above 20.

The EPA provides a useful tool which can be used to convert AQI to Concentration and vice versa, see AQI Calculator Concentration, The tool will help find the colour and corresponding health recommendations.

Do our air quality standards need to be reviewed?

The South African annual average PM2.5 limit is 20 µg/m3 which is four times the WHO standard.

Science is constantly advancing and what we believed was safe for human health, ten or twenty years ago, is no longer considered safe today.

Our national and local standards should be regularly reviewed. Experts agree that it is the finer PM2.5 particles that are most dangerous, as they are capable of penetrating deep into the respiratory tract and causing severe health damage. It should be noted that the South African government last published amended PM2.5 values in 2012 [8].

Most national air quality standards do not include some extremely toxic pollutants. Many experts believe that Volatile Organic Compounds (VOCs) should be included. VOCs are gases emitted into the air by products or processes. Some are very harmful and may cause cancer. They can also react with other gases to form other air pollutants once they are released into the air.

Another major problem relates to the way the limits are measured and reported. The ambient air quality standards specify methods that must be used to measure and report air quality. These methodologies mandate expensive equipment that is complicated and immobile. The problem with such equipment is that most governments can afford only a handful of monitoring stations.

Governments must investigate alternative methods of measuring air quality. Advances in technology have made high-quality equipment less expensive and often more accurate and mobile. Why then are governments not installing and maintaining more monitors?

Is our air quality being monitored?

Poor air quality is not always visible or obvious and if you live near a high-traffic road or freeway, industrial facility, or where there is constant biomass burning, your air quality is most likely to be worse than your neighbours’ just a few hundred metres away.

People living in the vicinity of a functioning monitoring station can rely on the air quality that is reported, but what about those people who live 10 or 20 km or more away from the nearest station?

The iLembe district claims it has 3 monitors, but both the Ballito and Mandeni monitors have not functioned for years and the KwaDukuza unit does not monitor PM2.5.

How does iLembe compare with its neighbours? Durban [9] and Richards Bay [10] have monitoring stations but there are no functioning stations in the iLembe district. The table below shows the number of stations, monitors per person and how many were functioning at the time of writing this article.

Total # of



per monitor




per monitor

Durban 12  269,000 2 1,614,002 25%
Richards Bay* 8 8,588 1  68,701 88%
iLembe 1 669,748 0  669,748 0%

* Richards Bay private network – Durban and iLembe monitors are maintained by local and national governments.

Addressing the Problem

The iLembe district has no functioning air quality monitors and the people district have a legislated right to know what they are exposed to!

The CAP co-founders asked themselves do we wait for someone else to sort out the problem or do we become part of the solution?

CAP decided that part of the solution is to “Own the Problem”. Taking inspiration from the words of Nobel laureate Wangari Maathai’s “You cannot protect the environment unless you empower people, you inform them, and you help them understand that these resources are their own, that they must protect them.” CAP setup a community science initiative to install and manage an independent network of air quality monitors in KwaDukuza.

CAP’s first monitor, situated near Shakaskraal, KwaDukuza, and in operation since March 2023, has already shown that the area averaged over 40 micrograms per 24 hours for five days in April and May. The maximum allowed according to the national air quality standards is four days. How many more exceedance days will it record in the next 10 months?

The installation of low-cost monitors will help fill the air quality monitoring gaps and help those people with health sensitivities. CAP’s independent air quality network will use near-reference monitors augmented by low-cost monitors and will focus on recording and analysing PM2.5 data.

Help expand the independent network and support our work by donating via our donation page or using the Zapper QR code below.

Communities Against Pollution is a registered Non-Profit Company, CIPC No. 2022/445204/08, and is a registered Public Benefit Organisation SARS No. 930076101.

[1] WHO global air quality guidelines 2021 Air Quality Guidelines

[2] EU Ambient Air Quality Directives (AAQDs) Air Quality Directive 2008/50/EC

[3] US EPA criteria pollutant limits US EPA – NAAQS Table

[4] India AQI Indian AQI Scale

[5] US AQI AQI Basics

[6] China AQI China Air Quality

[7] pg. v The World Bank’s The Little Green Data Book 2015

[8] South African NEMAQA – National Ambient Air Quality Standard for PM2.5

[9] Durban on SAAQS SAAQIS (

[10] Richards Bay Clean Air Association RBCAA Air Quality Index

1% Environmental Partner