/**
 * US EPA Air Quality Index computation.
 *
 * Piecewise-linear interpolation over per-pollutant breakpoints. Returns the
 * worst sub-AQI across the provided pollutants (EPA rule: overall AQI is the
 * maximum of the individual pollutant AQIs).
 *
 * Inputs are all in µg/m³; gas pollutants (O3, NO2, CO) are converted to the
 * volumetric units the EPA breakpoints are defined in (ppb for O3/NO2, ppm
 * for CO) using the standard 25°C, 1 atm factors.
 *
 * PM2.5 breakpoints use the EPA 2024 revision (lowered Good/Moderate bands).
 */
export interface AqiInputs {
    pm25?: number;
    pm10?: number;
    o3?: number;
    no2?: number;
    co?: number;
}
export type Pollutant = 'pm25' | 'pm10' | 'o3' | 'no2' | 'co';
export interface AqiResult {
    aqi: number;
    category: string;
    dominantPollutant: Pollutant;
    /** Pollutants (by key) whose value exceeds the WHO 2021 24-hr guideline. Sorted. */
    whoExceedances: Pollutant[];
}
export declare function aqiCategory(aqi: number): string;
export declare function computeUsAqi(inputs: AqiInputs): AqiResult;