The U.S. Environmental Protection Agency Promulgates New Standards For Fine Particles

Abstract

On July 18, 1997, EPA promulgated new standards for fine particles, with PM_2.5 as the indicator (15μg/m³, annual average; 65μg/m³, 24-hour average). EPA also retained the existing levels of the PM₁₀ standards (50μg/m³, annual average; 150μg/m³, 24-hour average) to pro-. tect against exposure to coarse particles. This decision was based on an extensive review of the scientific information regarding effects of PM. The upper 50% cut point of 10μm was chosen because it provides a measure of thoracic particles (i.e., those particles entering the lung). The 50% cut point 2.5μm was chosen to divide thoracic particles into fine and course particles because of their differences in sources, composition, and properties (chemical, physical, and biological). The time required for determining compliance or noncompliance with the revised PM standards is such that the next periodic review of the PM standards (required every 5 years) will take place before new particle control measures will be required. Monitoring requirements for determining compliance and research needed for the next review have been identified by EPA. Research needs include improved measurement techniques for finemode particles.