An Adjustment Factor for Air Quality Standards for Pollutant Gases at Different Altitudes: A Tool for Sustainable Environmental Policy and Health Protection

Air density and pressure above the Earth’s surface in the tropospheric region depend on altitude relative to sea level. When a given amount of pollutant gas enters the atmosphere at sea level, it produces a contaminated air mixture; if the same amount of pollutant gas enters the atmosphere at a location situated at higher altitude, atmospheric pollution certainly also occurs. However, the relative compositions are not the same in both cases due to the greater air density present at sea level compared to the air density at higher altitude. Current regulatory frameworks, including the National Ambient Air Quality Standards (NAAQS) of the United States Environmental Protection Agency and the Air Quality Guidelines (AQG) of the World Health Organization, establish constant numerical values for air quality standards uniformly applicable at all geographic locations, regardless of altitude, resulting in inadequate health protection for millions of people. To address this critical gap, a universal adjustment factor for atmospheric pollutant gas concentrations at different altitudes has been derived from first principles of atmospheric physics; this factor is f=e−0.000115 h, where h is expressed in meters, assuming air at constant temperature given that small temperature variations do not substantially influence atmospheric density and pressure or pollutant concentrations at different altitudes. The factor was systematically applied to the NAAQS and WHO AQG, demonstrating that for altitudes of 3500 m, representative of cities such as Cusco, Peru, the adjusted standards are approximately 67% of the nominal values established at sea level, preserving the gaseous pollutant–air proportionality. Experimental measurements of atmospheric density in six Peruvian cities distributed along an altitudinal gradient of 0–3826 m validated the theoretical model with relative deviations less than 5%, confirming the physical consistency of the derived factor. The importance of this research lies in adequately regulating air quality standards related to public health and the environment, supporting the implementation of equitable environmental policies aligned with the United Nations (UN) 2030 Sustainable Development Goals, and establishing that the constant values defined at sea level must be adjusted according to the aforementioned factor when geographic altitude is considered.