A groundbreaking new study has confirmed what environmental advocates have long argued: low-emission zones (LEZs) in major cities significantly improve air quality, benefit surrounding areas, and may lead to positive health outcomes. The comprehensive research, conducted by a team from the University of Antwerp and published in Environment International, provides compelling evidence that LEZs implemented in Antwerp and Brussels have successfully reduced harmful air pollutants and narrowed air quality disparities between socioeconomic groups.

Belgian LEZs Outperform Control Cities in Air Quality Improvement

Researchers evaluated the impact of low-emission zones in Antwerp (implemented in 2017) and Brussels (2018) by comparing air pollution levels with seventeen control cities across Belgium where no such restrictions were introduced. Using high-resolution air quality maps and administrative health data from over 420,000 individuals, the study tracked changes in pollutant concentrations and health outcomes between 2014 and 2023.

The findings reveal that while both LEZ and non-LEZ cities experienced overall air quality improvements during the study period, cities with low-emission zones saw significantly faster reductions in all measured pollutants. This effect was particularly pronounced for nitrogen dioxide (NO₂) and black carbon (BC), two pollutants strongly associated with vehicle emissions.

"With the introduction of the LEZ, all pollutant concentrations declined significantly more rapidly in both Antwerp and Brussels and adjacent areas compared to other Belgian cities," the researchers noted in their report.

In Brussels, NO₂ concentrations dropped from 29.44 µg/m³ in 2017 (the year before LEZ implementation) to 18.53 µg/m³ in 2022. Comparatively, control cities in Wallonia started with lower NO₂ levels in 2017 (26.10 µg/m³) but ended with higher concentrations in 2022 (19.21 µg/m³). Similar patterns emerged for black carbon and particulate matter, confirming the LEZs' effectiveness in accelerating air quality improvements.

Benefits Extend Beyond City Boundaries

One of the study's most surprising discoveries was the significant positive "spillover effect" detected in areas surrounding the LEZs. The research found air quality improvements extended up to 5 kilometers beyond the LEZ boundaries, challenging concerns that such zones merely redirect pollution to neighboring areas.

"Our findings suggest strong positive spatial spillover effects of up to 5 km from the implementation of both the Antwerp and Brussels LEZ," the research team explained.

This spillover effect contradicts some previous studies suggesting that traffic restrictions might simply redistribute pollution. Instead, the Belgian experience indicates that LEZs may be influencing broader behavioral changes in transportation patterns and vehicle fleet composition across metropolitan areas.

Narrowing the Gap: Socioeconomic Air Quality Disparities Decrease

The study also examined how LEZs affected air quality disparities between socioeconomic groups, focusing particularly on Brussels where sufficient neighborhood diversity existed for statistical analysis. Using the Belgian Indices of Multiple Deprivation (BIMD), researchers categorized neighborhoods from most deprived (Decile 1) to least deprived (Decile ≥5).

Their analysis revealed that while more deprived neighborhoods consistently experienced higher pollution levels both before and after LEZ implementation, the disparity between socioeconomic groups narrowed over time. For critical pollutants like black carbon and nitrogen dioxide, disadvantaged neighborhoods saw faster improvements in air quality compared to more affluent areas.

"For BC, there is a consistently stronger decline with each increase in socioeconomic deprivation. For NO₂, the least deprived neighbourhoods declined less rapidly compared to other neighbourhoods," the researchers reported.

This narrowing of environmental inequality represents a significant environmental justice achievement, as disadvantaged communities often bear disproportionate pollution burdens while having fewer resources to mitigate health impacts.

Health Impacts: Positive Signals for Diabetes Management

While the study tracked multiple health outcomes, including respiratory conditions, cardiovascular disease, and mental health indicators, the most notable finding related to diabetes. The researchers observed a less steep increase in chronic use of anti-diabetic medications among residents of Brussels compared to control cities after LEZ implementation.

"For Brussels, the chronic use of anti-diabetics medication shows a significant difference in pre-post slope change suggesting a less steep increase in Brussels versus the control cities, by 0.11% annually," the study notes.

This finding aligns with previous research linking air pollution exposure to increased diabetes risk. The European Environment Agency estimates that for NO₂, the highest health impact is due to diabetes mellitus, with 314,574 disability-adjusted life years (DALYs) attributed to this connection—substantially higher than impacts on stroke (204,723 DALYs) and asthma (115,425 DALYs).

The researchers suggest that the significant reductions in NO₂ achieved in both Antwerp and Brussels LEZs may be contributing to this positive diabetes outcome, though they note that longer follow-up periods will be needed to confirm effects on other health conditions.

Policy Implications as Europe Tightens Air Quality Standards

The study's timing is particularly relevant as the European Union prepares to implement stricter air quality standards by 2030. Under Directive 2024/2881 on Ambient Air Quality and Cleaner Air for Europe, which entered into force in December 2024, member states must achieve new limits more closely aligned with World Health Organization recommendations.

By 2030, EU countries will need to respect an annual average concentration of 10 µg/m³ for PM2.5 and 20 µg/m³ for NO₂—targets that may be challenging to meet without significant policy interventions like LEZs.

"With the decision to postpone (in the Brussels-Capital region) or to not tighten the LEZ (in Flanders), the regions increase the risk of failing to comply with the new 2030 requirements," the researchers warn.

The study's authors emphasize that multiple integrated strategies will be needed to reach these targets, including improved public transportation, promotion of active mobility modes like walking and cycling, increased urban green spaces, and targeted social-ecological policies that address both environmental and social objectives simultaneously.

A Model for Other Cities

As LEZs continue to expand across Europe, with 320 already in force as of 2022, the Belgian experience offers valuable lessons for other cities considering similar measures. The documented benefits in air quality, the positive spillover effects, and the narrowing of socioeconomic disparities present a compelling case for urban pollution control policies.

The study also underscores the importance of robust monitoring systems and consistent regulation enforcement. The researchers note that while the LEZs were initially controversial—with implementation timelines in some Belgian regions postponed or abandoned—the evidence strongly supports their effectiveness as a public health intervention.

For policymakers and urban planners worldwide, this comprehensive evaluation provides data-driven support for implementing and strengthening low-emission zones as part of broader strategies to improve urban air quality and protect public health.

The full research can be read here.