| Abbreviation | Definition |
|---|---|
| APTB | Air Polution Technology Branch of the EPA |
| AQAP | Air Quality Action Plan |
| AQHI | Air Quality Health Index |
| AQI | Air Quality Index |
| AQIA | Air Quality Impact Assessment |
| AQMD | Air Quality Management District |
| AQMG | Air Quality Model Guideline |
| AQMG | Air Quality Modeling Group |
| AQS | Air Quality Subsystem |
| AR | Agricultural Residues |
| ARA | Aggregate Resources Act |
| ARBCA | Alabama Risk-Based Corrective Action (Alabama Department of Environmental Management) |
| ARC | Advanced Recycling Center |
| ARCUS | Arctic Research Consortium of the United States |
| ARD | Agricultural research for development |
| AREA | Association for Research and Environmental Aid |
| ARET | Accelerated Reduction And Elimination Of Toxics |
| ARFOR | Area Forecast |
| ARPA | Amazon Region Protected Areas |
| ARRA | Asphalt Recycling and Reclaiming Association |