Wildfire smoke and Saharan dust intrusions

How trans-boundary events drive short-term PM2.5 spikes across Europe and how the EEA handles attribution.

Two big trans-boundary events shape European PM2.5

European air quality is increasingly shaped by two natural-but-anthropogenically-amplified phenomena: wildfire smoke from the Mediterranean and boreal regions, and Saharan dust intrusions from North Africa. Both drive short-term spikes in PM2.5 and PM10 that can dominate the annual mean if the year contains a large episode.

Wildfire smoke

Mediterranean wildfires have grown in frequency and severity since the 2000s, driven by hotter, drier summers under climate change combined with rural depopulation that allows fuel to accumulate. Major wildfire seasons (2017, 2021, 2022, 2023) have produced multi-day PM2.5 events of 100–500 µg/m³ across Greece, Turkey, southern Italy, Portugal, Spain, and southern France. The smoke is dominated by PM2.5 (combustion-derived ultrafine carbon and organic compounds) and also carries elevated CO and ozone precursors. Beyond the Mediterranean, smoke from Scandinavian and Russian boreal fires occasionally reaches central Europe; in 2010 and 2020 episodes the smoke plume crossed all of central Europe to the UK.

Saharan dust

Saharan dust intrusions ("calima" events) push large quantities of coarse mineral dust northwards across the Mediterranean roughly 10–40 times a year. Heavy events deposit visible dust across southern Spain, Sicily, Sardinia, southern Greece, and Cyprus, and occasionally reach central France, the Alps, and even southern UK. Dust events are dominated by PM10 (the coarse fraction) — typical PM10 spikes of 80–200 µg/m³ for 1–4 days. The PM2.5 fraction during dust events is more modest because the mineral particles are mostly larger than 2.5 µm.

How the EEA handles attribution

Article 20 of Directive 2008/50/EC allows member states to subtract contributions from "natural sources" — including Saharan dust and wildfire smoke — before assessing compliance with limit values. Each member state must report the methodology used for the subtraction. The EEA dataset publishes both gross and attribution-adjusted figures. PlainAirQuality uses the gross figures (no source subtraction) because they reflect actual human exposure regardless of attribution.

What this means for personal exposure

During a wildfire smoke or Saharan dust episode, the recommendation in most member-state advisories is the same: minimize outdoor activity, especially for vulnerable groups (children, older adults, people with cardiopulmonary disease); keep windows closed; run an HVAC system with a high-efficiency particulate filter (HEPA / MERV-13+) if available; consider an N95-equivalent respirator if outdoor activity is unavoidable. Real-time alerts are published by national agencies — Defra (UK), AEMET / Ministry for Ecological Transition (Spain), Anses (France), DPC / ISPRA (Italy), Hellenic Civil Protection (Greece), and others.

Source: European Environment Agency Air Quality e-Reporting Database, Dataflow E1a (validated annual).

Source: World Health Organization Global Air Quality Guidelines (2021 update).

Sources: European Environment Agency Air Quality e-Reporting; WHO Global Air Quality Guidelines 2021; EU Directive 2008/50/EC and the revised Directive (EU) 2024/2881; Copernicus Atmosphere Monitoring Service.