What is an emission inventory and what data does it typically include?

• A. A compilation of pollutant emissions by source and sector, including amounts, locations, time periods, and pollutant species.
• B. A forecast of pollutant concentrations by city.
• C. A list of air quality standards by country.
• D. A schedule of emission permits and compliance dates.

Answer: (A)

An emission inventory is a systematic record of pollutant releases, organized by source and sector, and typically tied to location and time. It captures how much of each pollutant is emitted, where the emissions come from (for example, transportation, industry, energy, or agriculture), when they occur (annual, monthly, or daily), and in what form or species (NOx, SO2, PM, VOCs, greenhouse gases, etc.). This structured data lets us quantify total emissions, compare contributions from different sectors, track trends over time, and feed models that predict air quality or assess the impact of control measures.

Other options describe outputs or concepts that are not inventories: forecasting pollutant concentrations, listing air quality standards, or scheduling permits and compliance dates. These serve different purposes and do not constitute a catalog of actual emissions by source, location, time, and pollutant.