PM2.5 — Fine particulate matter

Fine particles are the pollutant with the clearest long-term health evidence behind it, and the one where Malta’s own number is usually unremarkable while the yearly average still matters.

Measured at 5 of the 5 monitoring stations in Malta and Gozo · averaged over hourly · µg/m³

What it is

Airborne particles smaller than 2.5 micrometres across — roughly thirty times finer than a human hair. They stay suspended for hours and are small enough to be breathed deep into the lungs.

PM2.5 means any airborne particle smaller than 2.5 micrometres across. That is a size class rather than a substance: a PM2.5 measurement counts sulphate from a ship’s funnel, soot from a diesel engine, and a fragment of Saharan clay in the same figure, because what the instrument weighs is mass per cubic metre, not chemistry.

The size is the reason it is regulated separately from PM10. Particles this fine are not caught by the nose and throat. They reach the smallest airways and the gas-exchange surfaces of the lung, and the smallest of them cross into the bloodstream. A coarse dust particle makes you cough; a fine one does not announce itself at all.

They also stay airborne for hours to days, which is why a fine-particle episode is regional rather than local. A PM2.5 figure at a background station tends to describe the air mass sitting over the islands, not the street the monitor stands on.

Where it comes from

Vehicle exhaust and brake wear, construction and quarrying dust, domestic and agricultural burning, and shipping. Saharan dust reaching Malta lifts levels for short spells.

Locally, the dominant contributors are combustion and wear: vehicle exhaust, brake and tyre wear, construction and quarrying, domestic and agricultural burning, and shipping. Combustion sources matter more for PM2.5 than for PM10 — burning makes fine particles, while grinding and abrasion make coarse ones.

A substantial share of what is measured in Malta was not emitted in Malta. Fine particles travel, so continental European pollution and Saharan dust both register here. This is the normal condition for a small island in the central Mediterranean rather than an exceptional event.

PM2.5 in Malta and Gozo

Two features make Malta unusual for PM2.5. The first is that there is no large distance between any monitor and the sea, so the air arriving at a station has often spent hours over water rather than over land, and it brings whatever the air mass was carrying.

The second is dust. A Saharan intrusion raises PM10 far more than PM2.5, because desert dust is predominantly coarse — but it raises both. During an episode the fine-particle figure can sit well above its usual range while remaining a much smaller number than the coarse one, and attributing all of that rise to local traffic would be wrong.

This is also why the yearly average is the figure to watch rather than any single hour. The long-term health evidence for fine particles is built on annual exposure, and an hourly reading in the Good band tells you nothing about whether the annual mean is where it should be.

Health effects

Short-lived rises are associated with irritated airways, coughing and worsening asthma. Sustained long-term exposure is associated with heart and lung conditions. At the levels usually recorded in Malta most people notice nothing.

For short exposures, raised fine particles are associated with irritated airways, coughing, and worse asthma control. Most people in Malta will notice nothing at the levels usually recorded, and that is an honest statement rather than a reassuring one: the absence of a symptom is not evidence of an absence of effect.

The long-term evidence is where PM2.5 earns its attention. Sustained exposure is associated with cardiovascular and respiratory disease. The WHO’s annual guideline is far stricter than the EU’s legally binding limit, and the gap between those two numbers is a policy gap, not a measurement disagreement.

Who is most affected

These are the groups for whom PM2.5 specifically is most relevant, in rough order. The ordering is a matter of which mechanism this pollutant acts through, not a ranking of how much anyone matters.

People with asthma
People with lung conditions
People with heart conditions
Older adults
Children

maqua.app provides general environmental information and does not replace medical advice or official emergency guidance.

How a PM2.5 reading becomes a band

The fine-particle scale is the tightest of the five. Good ends at 5 µg/m³ against 15 for PM10, so any figure at the top of PM10’s Good band is already Fair as PM2.5. The bands are not comparable across pollutants: 20 µg/m³ is Fair as PM10 and Moderate as PM2.5, which are genuinely different statements about the same air.

Because the index takes the worst pollutant at a station, a modest fine-particle number is often what sets the band on a day when nothing else is elevated.

These are the European Air Quality Index bands for PM2.5 alone. Each band is an inclusive range of whole µg/m³: a concentration is rounded to the nearest whole number first, then matched. A station takes the band of its worst pollutant, so a single figure here does not by itself decide what the station reports.

Index bands for PM2.5, in µg/m³
Band	PM2.5 (µg/m³)
Good	1–5
Fair	6–15
Moderate	16–50
Poor	51–90
Very poor	91–140
Extremely poor	141–800

Source: European Air Quality Index (EEA), verified 2026-07-26.

Legal limits and health guidelines

The index is a communication scale. It is not the law, and it is not the World Health Organization's advice — all three describe PM2.5 and none of them is a translation of the others.

EU limit values — legally binding

25 µg/m³ — Calendar year: This limit is an average over a longer period, so no single hourly reading can establish anything about it. Directive 2008/50/EC Annex XIV.

WHO guidelines — health guidance, not law

15 µg/m³ — 24 hours: A health-based guideline rather than a legal threshold. Nobody is in breach of a WHO guideline; it describes where the evidence suggests harm begins. WHO 2021.
5 µg/m³ — Annual: A health-based guideline rather than a legal threshold. Nobody is in breach of a WHO guideline; it describes where the evidence suggests harm begins. WHO 2021.

A single hourly reading above any of these figures is not a breach of a limit, and this site will never describe one as such. Most are averages over 24 hours or a calendar year, and several permit a fixed number of exceedances before the limit is breached at all. Directive (EU) 2024/2881 tightens several of them from 1 January 2030; the figures above are the ones in force today.

Where PM2.5 is measured

Not every station measures every pollutant, and the ones that do are not interchangeable — a Traffic site is deliberately placed where exposure is highest, a Background site deliberately is not, so they answer different questions rather than competing to answer the same one.

Attard, Malta — Background, Urban: Sited away from single sources to represent general exposure in the area. 86 m above sea level. See the current PM2.5 reading.
Għarb, Gozo — Background, Rural-Regional: Sited away from single sources to represent general exposure in the area. 114 m above sea level. See the current PM2.5 reading.
Msida, Malta — Traffic, Urban: Sited beside a busy road, so it records the higher end of local exposure. 2 m above sea level. See the current PM2.5 reading.
St Paul's Bay, Malta — Traffic, Urban: Sited beside a busy road, so it records the higher end of local exposure. 7 m above sea level. See the current PM2.5 reading.
Żejtun, Malta — Background, Urban: Sited away from single sources to represent general exposure in the area. 56 m above sea level. See the current PM2.5 reading.