PM10 — Coarse particulate matter

Coarse particles are the pollutant Malta’s geography affects most: sea salt and Saharan dust both land in this figure, which is why a high PM10 hour here often has nothing to do with traffic.

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

What it is

Airborne particles up to 10 micrometres across, including road dust, pollen and sea salt. The nose and throat filter out more of these than of finer particles.

PM10 counts every airborne particle up to 10 micrometres across — which includes all of PM2.5, since a fine particle is also smaller than 10 micrometres. The two figures are not independent, and PM10 is always the larger of the two at the same station and hour.

The useful distinction is the coarse fraction: the part between 2.5 and 10 micrometres. That is the mechanically generated material — crushed, ground, abraded or lifted by wind — and it behaves differently from combustion particles. It is heavier, so it settles out within hours and kilometres rather than days and hundreds of kilometres.

The nose and throat filter out much more of this size range than of fine particles, which is why coarse-particle effects are mostly upper-airway irritation rather than deep lung damage.

Where it comes from

Road and construction dust, quarrying, agriculture and sea spray, together with long-range Saharan dust episodes, which are a recurring feature of the Maltese climate.

Road and construction dust, quarrying, agriculture and sea spray are the standing local contributors, and all of them are mechanical rather than combustion processes. Resuspension matters too: particles already on the ground get lifted again by wind and passing vehicles, so a dry windy day can raise PM10 without any new emission at all.

Sea salt is a genuine and unavoidable component on a small island. It is a natural source, it is not a pollutant in the usual sense, and it is nonetheless counted — the instrument weighs particles, and it cannot be asked to exclude the ones that came off a wave.

PM10 in Malta and Gozo

Saharan dust is the single most important thing to understand about PM10 in Malta. Dust lifted from North Africa recurs over the central Mediterranean through the year, and during an intrusion the coarse-particle figure can rise far above anything local traffic produces. The islands sit directly on the corridor between the Sahara and southern Europe, so this is a feature of the Maltese climate rather than an anomaly.

Because dust arrives as a regional air mass, an intrusion raises PM10 at every station at once, including rural Għarb on Gozo. That is the signature worth learning: when the coarse figure is elevated at the background stations as much as at the traffic ones, the cause is almost certainly not the road outside.

The practical consequence is that a high PM10 hour in Malta is ambiguous on its own. The same number can mean a dust episode, a windy day over a dry landscape, or genuinely dirty local air, and distinguishing them needs the pattern across stations rather than one reading.

Health effects

Raised levels can irritate the eyes, nose and throat and can aggravate asthma or bronchitis. Effects are usually short-lived and ease as levels fall.

Raised coarse particles can irritate the eyes, nose and throat, and can aggravate asthma or bronchitis. The effects are typically short-lived and ease as levels fall, which matches the fact that a dust episode is a matter of a day or two rather than a season.

During a dust intrusion the sensible response is the ordinary one for a bad-air day: less strenuous outdoor exertion, particularly for people with asthma, and keeping windows shut on the windward side. None of that requires knowing the number to a microgram.

Who is most affected

These are the groups for whom PM10 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
Children
Older adults
People who work outdoors

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

How a PM10 reading becomes a band

The PM10 scale is much wider than the fine-particle one — Good ends at 15 µg/m³ and the Moderate band runs to 120 — because coarse-particle concentrations are routinely higher and the health evidence per microgram is weaker. The top of the scale reaches 1,200, which exists for dust events rather than for anything a city produces.

Comparing a PM10 figure against a PM2.5 band, or against the limit for a different averaging period, is the most common way to misread this pollutant.

These are the European Air Quality Index bands for PM10 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 PM10, in µg/m³
Band	PM10 (µg/m³)
Good	1–15
Fair	16–45
Moderate	46–120
Poor	121–195
Very poor	196–270
Extremely poor	271–1200

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 PM10 and none of them is a translation of the others.

EU limit values — legally binding

50 µg/m³ — 24 hours: Up to 35 exceedances are permitted per calendar year before the limit is breached. This limit is an average over a longer period, so no single hourly reading can establish anything about it. Directive 2008/50/EC Annex XI.
40 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 XI.

WHO guidelines — health guidance, not law

45 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.
15 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 PM10 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 PM10 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 PM10 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 PM10 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 PM10 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 PM10 reading.