Exerpted from a paper by: Richard Olcerst Phd., CIH, CHCM, CSP Brujos Scientific Inc. Industrial Hygeine and Toxicology 505 Drury Lane Baltimore Maryland, 21229 301-566-1177 OZONE MONOGRAPH: TOXICITY AND EVALUATION INTRODUCTION Ozone is one of the most important components in our environment. It is generated from the interaction of ultraviolet radiation from solar sources with atmospheric oxygen, during lightning discharges and from reaction of nitrogen dioxide, sunlight and hydrocarbons of both natural and man made origin. While ozone is proportionally a minor atmospheric component, its strong oxidizing potential is responsible for a variety of effects. Uncontrolled and in extremely high levels it can cause damage to crops, building materials, pigments, fabrics and textiles as well as cause adverse human health effects. Controlled and in moderate concentration ozone is a useful tool both in industry and in medicine being used to control undesirable organic substances and microorganisms. Ozone is considered as in normal concentration below 80 ppb, in high concentration over 100 ppb and in extremely high concentration when over 500 ppb. Exposure to ozone at high and extremely highs can produce a variety of pulmonary function changes such as decrements in physiological lung function parameters, gas exchange, mucociliary particle clearance and airway permeability. This monograph provides the results of a comprehensive review of the technical and scientific literature regarding the effects of ozone exposure upon human health. The review of over 4500 abstracts, found no references for clinically observable lung function changes at less than 80 parts per billion after short term acute exposures. In 1971, after careful study and deliberation, the Environmental Protection Agency enacted the Clean Air Act. This regulation established National Ambient Air Quality Standards aimed at protecting what was then considered the most sensitive subgroup in the general population, those who suffer from heart and lung maladies, from the harmful effects of air pollutants. The initial concentration established for ozone was 80 parts per billion (ppb). This was a concentration that should not be exceeded for as long as one hour during any day of the year. It was the goal of the Clean Air Act to control fixed and mobile emission sources to be in compliance with the NAAQS. In 1978, the Environmental Protection Agency relaxed the NAAQS to its present value of 120 parts per billion (equivalent to 235 micrograms/cubic meter of air) because of the absence of data on adverse health effects observed at normal and lower concentrations. (1) Over the years, improvements in instrumentation and technology and refinements of experimental and clinical technique have enabled researchers to discern increasingly smaller and more subtle lung function changes.