How much do potentially cancer-causing air pollutants vary between Greek cities and between summer and winter?

Details

This observational environmental sampling study examined how particle-bound polycyclic aromatic hydrocarbons (PAHs) varied across space and time and assessed their carcinogenic potential in six contrasting urban environments in Greece. Researchers collected and analyzed 305 filter samples.

Sampling covered urban-background and traffic locations in Athens, Ioannina and Heraklion, a rural location in Xanthi, and near-port locations in Piraeus and Volos.

The analysis considered both the sum of the 16 U.S. EPA priority PAHs and the sum of six EU-proposed PAHs. Average summer concentrations varied moderately across locations, at 0.4–2.2 ng m−3, independently of each site's population. The highest values were observed in Piraeus and Volos, areas affected by port and industrial activities.

Winter levels were significantly higher and more spatially variable than summer levels. Seasonal increases ranged from 7-fold in Piraeus to 98-fold in Ioannina, indicating a large impact from PAH emissions associated with residential wood burning.

Benzo(a)pyrene (BaP) is an IARC Group 1 carcinogen and the only PAH regulated by the EU. Its winter/summer concentration ratios were 24–33 in Athens, Volos, Heraklion and Xanthi; 60 in Piraeus; and 480 in Ioannina, which experiences severe wood-burning pollution events.

During the cold period, organic carbon (OC) and BaP were very strongly correlated at all urban sites (r² > 0.8), with stable BaP/OC slopes of 0.09–0.14 × 10−3. This highlights the potential use of OC as a proxy for estimating BaP under winter conditions.

The authors describe this as the first exploration of PAH contrasts across space and time at this scale in the Eastern Mediterranean. The findings offer insights into emission sources and the atmospheric conditions controlling PAHs, and reveal large differences in exposure risks among cities that raise the issue of environmental injustice at the national level.