what are the health effects of breathing ozone?
TRANSCRIPT
Feroza Daroowalla, MD, MPHDivision of Pulmonary Medicine
Stony Brook UniversityThese slides were derived from the EPA website
What is ozone?Ozone is a highly reactive gas molecule made
up of three oxygen atoms Ozone occurs naturally in the stratosphere
(upper atmosphere) In the lower atmosphere, ozone is formed
primarily from photochemical reactions of man-made air pollutants
=Tropospheric ozone or "ambient" or "ground-level" ozone
What is asthma?Asthma is a chronic inflammatory
disease of the airways that causes recurrent episodes of wheezing, breathlessness, chest tightness, and cough
Background InformationThe prevalence of asthma has doubled in the
U.S. in the last 20 yearsMore than 20 million Americans report
having asthmaRates are higher among children under 17,
minorities, and inner-city populations 10 million patient visits and more than
470,000 hospital admissions annually
Effects on human healthBreathing in ground level ozone damages the
respiratory tractRespiratory symptoms Decreases in lung function Inflammation of airways
What are the symptoms of ozone exposureCoughing Throat irritation Pain, burning, or discomfort in the chest
when taking a deep breath Chest tightness, wheezing, or shortness of
breath
What effects does ozone have at the cellular level? Ozone does not get scrubbed out in the upper
respiratory tractReaches the lower respiratory tract and
dissolves in the thin layer of fluid lining the airways of the lung
Then ozone reacts rapidly with a number of biomoleculesThis results in free radicals and other oxidant
speciesThese react with epithelial cells, immune cells,
and with nerve receptors in the airway wall
How does ozone act in the lungInjury and inflammatory response result in :
An increase in small airway obstruction A decrease in the barrier function of the airway
epithelium An increase in airway reactivity
After a period of weeks following a single exposure, the airway appears to return to the pre-exposure state
Does response vary among individuals?
There is large variation in the response among individuals
Some people may experience no symptoms or lung function changes while the most responsive individual may experience a 50% drop in lung function and have severe coughing, shortness of breath, or pain on deep inspiration.
Which populations are susceptible to ozone damageOne factor that explains variability is age,
young adults (teens to thirties) are more responsive than older adults (fifties to eighties)
data do not suggest that children are more responsive than young adults
Children may have more response if they are more exposed (spend more time outside)
People with asthma are the most responsive group
How does ozone affect people with asthma?
Increased frequency of asthma attacks Increased use of health care services
A worsening of underlying asthma status, increasing the likelihood of an asthma attack or requiring more treatment
Studies indicate a relationship between ambient ozone concentration and medication use among children and ER visits and hospital admissions for asthma
How quickly do ozone-induced respiratory symptoms resolve in individuals without asthma? They should begin to improve immediately
upon cessation or reduction of exposure and should have disappeared completely within 24 to 48 hours after the exposure ends
What are the effects of recurrent or long-term exposure to ozone?One of the major unanswered questions
whether repeated episodes of damage and repair due to years of short-term ozone exposures result in health effects
Some early evidence that long-term ozone exposure may result in new asthma suggest that young children may be especially
susceptible to effects of ozone on lung developmentPrudent to avoid repeated short-term exposures,
particularly in young children, until more is known
How much is too muchMore potential for effect with longer time active
outdoors and with more strenuous activity Human exposure studies indicate that:
levels above 0.12 ppm, heavy outdoor exertion for 1 to 3 hours can increase risk
levels between 0.08 and 0.12 ppm, moderate outdoor exertion for 4 to 8 hours can increase risk
Moderate exertion = climbing stairs, tennis or baseball, simple garden or construction work, and light jogging, cycling
Heavy exertion = playing basketball or soccer, chopping wood, heavy manual labor, and vigorous running, cycling
What is the Air Quality Index?The Air Quality Index tells the public how clean
or polluted the air isThe AQI uses a scale from 0 to 500The higher the AQI value, the greater the level
of pollution and the greater the health concernAQI values below 100 are generally considered
to be satisfactoryThe AQI is divided into six categories that
correspond to different levels of health concern.
When AQI values are above 100, air quality is considered to be unhealthy, at first for members of susceptible populations, then for everyone as AQI values get higher
How can you reduce exposure to ozone? What is moderate exertion for one person
may be heavy exertion for anotherCutting back on the level and duration of
exertion when ozone levels are high will help
The times of poorest air quality are typically in the afternoon and early evening for most locations
InformationInformation about the health effects of ozone
may be found on the AIRNow Web site in the Publications section (http://airnow.gov/index.cfm?action=static.publications) and the Your Health section (http://airnow.gov/index.cfm?action=static.health). (http://www.epa.gov/ncepihom/)