Multi-pollutant exposure regimes and environmental inequalities in Europe: evidence from Bulgaria

Background

Air pollution is a major public health challenge in Europe, but evidence from Eastern Europe remains fragmented and mostly focused on single pollutants. This limits understanding of how pollutants co-occur and create unequal exposure across populations. Using Bulgaria as a case study, this research explores multi-pollutant exposure patterns and their spatial inequalities.

Methods

An ecological analysis was conducted using national air quality monitoring data for 2024. Station indicators included annual means, maximum concentrations and exceedances for particulate matter (PM10), nitrogen dioxide (NO2), sulfur dioxide (SO2) and ozone (O₃). Sites were classified as urban, industrial, rural/background or mixed. A rule-based method was used to identify multi-pollutant exposure profiles according to relative pollutant dominance. Continuous variables were summarized with means and standard deviations, and exposure gradients across environments were compared.

Results

Air pollution showed a clear unequal distribution. Urban areas had sustained exposure (PM10: 27.7 ± 2.8 µg/m³; 31.3 ± 14.6 exceedance days), compared with lower rural levels (10.1 ± 2.4 µg/m³; no exceedances). Nitrogen dioxide followed the same pattern (29.5 ± 5.4 vs 8.4 ± 4.6 µg/m³). Industrial sites recorded extreme sulfur dioxide peaks (mean maximum 882.7 ± 192.5 µg/m³), suggesting localized high-intensity emissions. Rural environments had the highest ozone exceedances (62.3 ± 57.2 days). Four exposure regimes were identified: urban traffic, industrial, rural/background and mixed.

Conclusions

Air pollution is not only unevenly distributed, but organized into distinct multi-pollutant regimes that create different environmental health risks. These findings suggest that environment-specific pollutant combinations may generate different population health risks and should be considered in environmental monitoring and public health planning.

Key messages

• Air pollution in Bulgaria follows distinct patterns: urban areas struggle with PM10 and NO2, industrial sites face extreme SO2 peaks, and rural regions deal with high ozone levels.

• Pollution is unequal and site-specific. Different environments create unique health risks, requiring targeted monitoring and public health planning instead of one-size-fits-all solutions.