Optimal reactive nitrogen control pathways identified for cost-effective PM_2.5 mitigation in Europe

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Public Health

Background:

• Excess reactive nitrogen (Nr), encompassing nitrogen oxides (NOx) and ammonia (NH3), is a major contributor to fine particulate matter (PM2.5) air pollution in Europe.
• This pollution poses significant challenges to public health across the continent.

Purpose of the Study:

• To identify optimal and cost-effective reactive nitrogen (Nr) control roadmaps for mitigating PM2.5 air pollution in Europe.
• To evaluate the mitigation efficiencies and implementation costs of different Nr control strategies.

Main Methods:

• Integration of emission estimations, air quality modeling, and exposure-mortality modeling.
• Inclusion of reactive nitrogen (Nr) control experiments and cost data analysis.
• Comparative assessment of ammonia (NH3) and nitrogen oxides (NOx) control effectiveness and cost-efficiency.

Main Results:

• Phasing out Nr emissions could reduce European PM2.5 by 2.3 ± 1.2 μg·m⁻³, aiding WHO guideline achievement and preventing nearly 100,000 premature deaths.
• Ammonia (NH3) controls show increasing efficiency with higher ambition, becoming more effective than NOx controls.
• NH3 controls are 5-11 times more cost-effective per unit of PM2.5 reduction than NOx controls, particularly up to 50% reduction.

Conclusions:

• Ammonia (NH3) control policies should be prioritized for cost-effective PM2.5 mitigation in Europe.
• Strategic Nr emission reductions offer substantial public health benefits by improving air quality.
• Optimal Nr control pathways involve a shift towards prioritizing ammonia (NH3) reduction strategies.