OxyFile #170

Exerpted from a paper by:
Richard Olcerst Phd., CIH, CHCM, CSP
Brujos Scientific Inc.
Industrial Hygeine and Toxicology
505 Drury Lane
Baltimore Maryland, 21229



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.