Air Pollution, Pollen, and Indoor Exposures in Allergic Conjunctivitis: A Systematic Review

Area of Science:

• Ophthalmology
• Environmental Health
• Immunology

Background:

• Environmental factors are recognized as key drivers of ocular surface inflammation.
• The combined impact of various environmental exposures on allergic conjunctivitis (AC) requires comprehensive synthesis.

Purpose of the Study:

• To systematically review and synthesize evidence linking air pollutants, aeroallergens, and indoor/occupational exposures to allergic conjunctivitis.
• To evaluate the contribution of environmental factors to the onset, exacerbation, and clinical burden of AC.

Main Methods:

• Systematic review adhering to PRISMA 2020 and AMSTAR-2 guidelines, registered in PROSPERO.
• Searched PubMed, Web of Science, and Scopus; data extraction and quality assessment using MINORS tool by two independent reviewers.
• Narrative synthesis of findings due to substantial heterogeneity across 29 included studies.

Main Results:

• Consistent associations found between air pollutants (particulate matter, NOx, SO2, CO, O3) and increased AC incidence/severity.
• Synergistic effects observed between pollen and air pollutants; indoor exposures linked to increased risk in children.
• Occupational settings showed exposure-response relationships; experimental studies identified mechanisms like epithelial barrier disruption and NF-κB/TSLP signaling.

Conclusions:

• Environmental exposures significantly contribute to the development and worsening of allergic conjunctivitis.
• Findings support the need for improved prevention strategies and personalized clinical management of AC.
• Further research into specific exposure-mechanism links can refine interventions for ocular surface inflammation.