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Black Carbon in the Maltese Islands: An overlook and a health impact assessment

This research presents one of the first insights into Black Carbon (BC), an unregulated pollutant of emerging concern in the Maltese Islands. BC is a component of fine particulate matter emitted from any form of fossil fuel combustion. The World Health Organisation and the European Commission are worried of this pollutant due to its apparent higher toxicity and hence can lead to more acute health impacts. In the Maltese Islands BC’s main and almost unique source is traffic exhaust. The two main aims of this work were to map the BC levels in different sites in the Maltese Islands and to estimate the mortality associated with the long-term exposure to this pollutant.

To measure BC around the Maltese Islands, a specific instrument (aethalometer) was deployed in a wide range of sites, from rural sites in Għarb, Gozo to suburban areas like Naxxar, to traffic sites in Msida and St. Paul’s Bay. Measurements were taken for a two-week period in each locality from January till June 2025. At select sites a traffic count was also carried out to identify the traffic profile and the variety of vehicles driving on our streets.

The results showed diurnal variations with expected strong morning peaks at all sites, associated with the heavy flow of morning traffic. Correlations with meteorological data collected simultaneously with the BC suggested that in most sites emissions were highly localised. The sampled average BC concentration in the Maltese Islands for all sites was 1.2 µg/m³, with the highest in St. Paul’s Bay at 3.6 µg/m³ while the lowest concentration of 0.3 µg/m³ was in Għarb. When compared to international studies, in the Maltese Islands the mean BC levels we recorded are similar to rural areas and less in suburban/urban background monitored in Europe. When it comes to traffic/urban areas, our levels are the same as similar environments in much bigger, major European cities.

A health impact assessment is a tool used to calculate the associated mortality from the long-term exposure to a pollutant. To date, when studying the impact of air quality pollutants, the main focus is on fine particulate matter (PM_2.5), nitrogen dioxide (NO₂) and ozone (O₃). Since BC is unregulated its health impact is not studied. As it is one of the more toxic components in PM_2.5, ignoring BC may lead to a drastic underestimation of the real health impact of PM_2.5. In the Maltese Islands BC accounts for about 2.2% of PM_2.5 in rural sites and up to 17.2% in traffic sites.

To the authors’ knowledge this BC-driven health impact assessment is the first one of its kind in Europe. It reveals that averaged out across the Maltese Islands, approximately 79 deaths per year (2% of the total deaths) may be attributable to the exposure to BC. Comparing the seven traffic sites considered with the six suburban/urban background sites, the difference is striking. The BC levels are double in trafficked streets and the estimated annual deaths due to BC in these areas are more than double compared to suburban/urban background settings.

In this seminar dissemination of the findings related to Black Carbon will be discussed in more detail in the context of the daily experience with constant traffic and the implications of the long-term exposure to this pollutant.

An introduction to this project will be given by Professor Noel Aquilina from the Department of Chemistry, an atmospheric chemist whose research revolves around understanding the exposure to various atmospheric pollutants through measurements and modelling.

Mr Benjamin Tabone Adami is an MSc student in the Department of Chemistry who carried out the fieldwork associated with this project around the Maltese Islands.