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/)