What are outdoor air pollutants?

Outdoor air pollution is a complex mixture of several pollutants.In 1970, Congress passed the Clean Air Act that established national air pollutant standards for 6 criteria pollutants: ozone, respirable particulate matter (PM), sulfur compounds, lead, carbon monoxide (CO), and nitrogen dioxide (NO2). Since 1970, levels of these pollutants have been regularly measured.The most important of these outdoor air pollutants i

n the U.S. today are ozone, PM, and SO2.

How can my family be exposed to outdoor air pollutants?

Since almost all sources of outdoor air contains some pollutants, we are all probably exposed to some degree.  The main route of exposure to outdoor air pollutants is through breathing.  However, some of these substances can enter the local ecosystem through various ecological cycles and eventually become pollutants of water, soil, and plants.  Children may receive more exposure to these pollutants than adults because of their:

• Increased time outdoors
• Higher breathing rate
• Tendency to breathe by mouth

From 1990 to 1998, about 25% of U.S. children lived in a county that exceeded at least one national air quality standard during the year.[2]   In the paragraph below, we discuss exposure to ozone, particulate matter (PM), and sulfur dioxide (SO2).

Ozone

Ozone is formed from a chemical reaction between certain volatile organic compounds (VOCs) and vehicle exhaust emissions (nitrogen oxides) in the presence of sunlight and moisture.  The ozone layer high above the earth in the stratosphere helps to filter out ultraviolet light from the sun.  However, ground level ozone may have negative health effects.  The precursors of ozone are released into the environment from:

• Automobile exhaust
• Power plant emissions
• Gasoline vapor and solvents
• Some trees and plants

Exposure to ozone is highest on now, summer days from May to September. Ambient ozone levels peak during mid to late afternoon hours.

Ozone is the major component of urban smog.   In 1998, about 21% of children lived in counties that exceeded the national ozone standard. [2]

Respirable particle matter (PM)

Airborne PM are small particles resulting from incomplete combustion of various fuels as well as physical breakdown of rock, soil, and dust.  The components of particle matter are diverse and change from day to day.

The main factor determining how deeply PM penetrates the lungs is the size of the particle.  The nasal passages filter particles bigger than 10 micrograms.  However, children often breathe through their mouths and may bypass this filtering method.  Particles smaller than 5 micrograms (PM5) can easily get deep within the lungs.  There is increasing evidence that points to very fine particulate matter smaller than 2.5 micrograms (PM2.5) as the main health concern.

SO2

SO2 is a gas released from various industrial processes.  The main sources of airborne SO2 include:

• Coal-burning power plants
• Paper mills
• Smelters

Since 1993, there have been relatively few counties in the U.S. that have exceeded the national SO2 standard. [2]

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What are the health effects of outdoor air pollutants?

The health effects from outdoor air pollutants depend on a number of factors:

• The specific pollutant(s) involved
• Intensity of exposure
• Time course of exposure (minutes, days, years)
• The individual's health status

Children may suffer more health effects from outdoor pollutants than adults because:

• They have narrower airways than adults.  Irritation to the airways may cause a proportionately greater obstruction of airflow in children.
• Children may not stop their activities when their airways become partially obstructed. 

Often, people are exposed to several air pollutants at the same time.  The health effects from such mixtures are not well understood, but could produce synergistic effects. [5][10][14][33]  Synergism occurs when the combination of two or more substances causes a greater effect than the sum of each individual effect.

The health effects of each major outdoor air pollutant - ozone, particulate matter, and SO2 - will be discussed in terms of acute high-level and chronic low/moderate-level exposure:

Ozone

Acute effects

Ozone is considered one of the most important outdoor air pollutants.  The acute health effects from ozone exposure have been studied in both occupational and general environmental settings.  Acute exposure to ozone may cause:

• Coughing, irritation of nose and throat.
• Decreased lung function, which may last 1-2 days after exposure. [8][9][12-15]
• Worsening of asthma symptoms. [12][13]
• Increased emergency room visits for asthma. [40]
• Decreased exercise tolerance in individuals with heart disease. [36]
• Increased overall death rates in the population, especially among individuals with preexisting heart or lung disease. [3][19]

Chronic effects

The health effects from chronic ozone exposure have been studied in both occupational and general environmental settings.  The health effects from chronic exposure is not as well-established as the effects from acute exposure.  Chronic ozone exposure may cause:
• Decreased performance on lung function tests. [4][11]
• Impaired lung growth in children. [41]
• Increased absenteeism from school due to illness. [6]
• Increased prevalence of allergic rhinitis, asthma symptoms, and asthma. [7]
• Increased risk of lung cancer in non-smokers. [16][32] 
• Increased risk of developing asthma. [24][27] 

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Particulate Matter (PM)

Acute effects

The health effects from acute PM exposure have been studied mostly in general environmental settings.  Acute exposure to PM may cause:

• Coughing and wheezing
• Decreased performance on lung function tests. [11][15]
• Increased hospital admissions in individuals with preexisting heart and lung disease. [18]
• Increased emergency room visits for asthma. [40]
• Increased overall death rates in the population, especially among individuals with preexisting heart or lung disease. [3][11][17]

Chronic effects

Chronic exposure may cause:

• Decreased lung function performance in otherwise healthy individuals [11][22]
• Worsening of respiratory symptoms in individuals with asthma [26][29]
• Increased risk of emergency room visits for pneumonia [23]
• Increased risk of lung cancer in non-smokers [16][32]

SO2

Acute effects

• Coughing and wheezing
• Decreased performance on lung function tests [42]
• Increased hospital admissions in individuals with preexisting heart and lung disease [18][37]

Chronic effects

• Decreased lung function performance in nonsmoking individuals [30]
• Increased risk of lung cancer in non-smokers [32]
• Increased risk of emergency room visits for asthma [38]
• One human study has suggested-  that suspended sulfates may increase risk for developing new-onset asthma. [31]

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Is there a test to see if my family has been exposed to excessive outdoor air pollutants?

The EPA provides a daily Air Quality Index (AQI) that helps individuals understand the relationship between local air quality and their health.  This information is updated yearly.The AQI is divided into 4 scales:  good, moderate, unhealthy for sensitive groups, and unhealthy.

This advice is appropriate for most people.   However, there is some evidence that even healthy individuals can experience health effects at pollutant levels classified as "good" or "moderate." [15]   At-risk individuals may be well-advised to view these air quality scales cautiously.

"Good" refers to air quality that poses little health risks over the long and short term.This corresponds to an AQI of 0-50.

"Moderate" air quality (AQI 51-100) poses a modest health risk for some at-risk individuals.

Air quality that is "unhealthy for sensitive groups" (AQI 100-150) poses a health risk to susceptible individuals like children, but most people will likely not be affected.

At "unhealthy" levels (AQI>150), most people will experience some health effects while at-risk individuals may suffer serious health effects.  Also, local radio stations, television broadcasts, and newspapers may provide recent information on air quality.

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What can I do to limit my family’s exposure to outdoor air pollutants?

Restrict the amount of time that children spend outdoors during periods of poor air quality, especially if they are engaging in strenuous exercise.

Since ozone levels are highest in mid to late afternoon on hot days, reschedule your child’s outdoor activities to either morning or evening hours. This is especially important if your child is sensitive to outdoor air pollutants.

Check with local radio stations, television broadcasts, and newspapers for information on local air quality.  Also, check your state government’s website for current information on local air quality.  Georgia citizens can access this information on the Georgia Dept. of Natural Resources, Environmental Protection Division, Air Protection Branch web site: www.air.dnr.state.ga.us. 

The American Academy of Pediatrics does not recommend using dust masks for protection against outdoor air pollution. "Not only do poor fit and uncertain compliance limit any potential benefits, but most simple dust masks do not ... filter out harmful VOCs or ozone." [1]

If a family member has asthma or other respiratory conditions that may be affected by outdoor air pollution, make sure they receive proper medical care for their condition. If they are using the right medications properly, they are less likely to suffer health effects from outdoor air pollutants. 

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Resources

American Academy of Pediatrics. Ambient Air Pollution: Health Hazards to Children. Pediatrics 2004, 114(6): 1699-1707.

References

[1] Etzel R, Balk, S. Handbook of Pediatric Environmental Health. Outdoor Air Pollutants. American Academy of Pediatrics Committee on Environmental Health Affairs 1999:181-191.

[2] US EPA.America’s Children and the Environment: A First View of Available Measures. Washington D.C. 2000.

[3] Hoek G, Brunekreef B, et al. Daily mortality and air pollution in the Netherlands. Journal of the Air & Waste Management Association 2000; 50(8):1380-1389.

[4] Kopp M, Bohnet W, et al. Effects of ambient ozone on lung function in children over a two-summer period. European Respiratory Journal 2000;16(5):893-900.

[5] Kleinman M, Bufalino C, et al. Toxicity of chemical components of ambient fine particulate matter (PM 2.5) inhaled by aged rats. Journal of Applied Toxicology 2000;20(5):357-364.

[6] Gilliland F, Berhane K, et al. The effects of ambient air pollution on school absenteeism due to respiratory illnesses. Epidemiology 2001;12(1):43-54.

[7] Ramadour M. Burel C, et al. Prevalence of asthma and rhinitis in relation to long-term exposure to gaseous air pollutants. Allergy 2000;55(12):1163-1169.

[8] Foster W, Brown R, et al. Bronchial reactivity of healthy subjects: 18-20 h postexposure to ozone. Journal of Applied Physiology 2000;89(5):1804-1810.

[9] Dormans J, van Bree L, et al. Interspecies differences in time course of pulmonary toxicity following repeated exposure to ozone. Inhalation Toxicology 1999;11(4):309-329.

[10] Paige R, Wong V, Plopper C.Long-term exposure to ozone increases acute pulmonary centriacinar injury by 1-nitronaphthalene: II. Quantitative histopathology. Journal of Pharmacology & Experimental Therapeutics 2000;295(3):942-950.

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[11] Gold D, Damokosh A, et al. Particulate and ozone pollutant effects on the respiratory function of children in southwest Mexico City.Epidemiology 1999;10(1):8-16.

[12] Scannell C, Chen L, et al.: Greater ozone-induced inflammatory responses in subjects with asthma. AmericanJournal of Respiratory CriticalCare Medicine 1996, 154: 2–9.

[13] Balmes J, Aris R, et al. Airway inflammation and responsiveness to ozone in normal and asthmatic subjects. Researchon Respiratory Health EffectsInstitute 1997, 78: 1–37.

[14] Jorres R, Nowak D, et al. The effect of ozone exposure on allergen responsiveness in subjects with asthma or rhinitis. AmericanJournal of Respiratory CriticalCare Medicine 1996, 153: 56–64.

[15] Korrick S, Neas L, et al.: Effects of ozone and other pollutants on the pulmonary function of adult hikers. Environmental Health Perspectives 1998, 106: 93–99.

[16] Beeson W, Abbey D, Knutsen S. Long-term concentrations of ambient air pollutants and incident lung cancer in California adults: results from the AHSMOG study.Adventist Health Study on Smog. Environmental Health Perspectives 1998;106(12):813-23.

[17] Samet J,Dominici F, et al.Fine Particulate Air Pollution and Mortality in 20 U.S. Cities, 1987-1994. New England Journal of Medicine 2000; 343(24):1742-1749.

[18] Zanobetti A, Schwartz J, Dockery D. Airborne particles are a risk factor for hospital admissions for heart and lung disease. Environmental Health Perspectives 2000;108(11):1071-1077.

[19] Spix C, Anderson H, et al. Short-term effects of air pollution on hospital admissions of respiratory diseases in Europe: a quantitative summary of APHEA study results. Air Pollution and Health: a European Approach.Archives of Environmental Health 1998;53(1):54-64.

[20] Simpson R, Denison L, et al. Effects of ambient particle pollution on daily mortality in Melbourne, 1991-1996. Journal of Exposure Analysis & Environmental Epidemiology 2000;10(5):488-496.

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[21] Ostro B, Broadwin R, Lipsett M. Coarse and fine particles and daily mortality in the Coachella Valley, California: a follow-up study. Journal of Exposure Analysis & Environmental Epidemiology 2000;10(5):412-419.

[22] James Gauderman W, McConnell R, et al. Association between air pollution and lung function growth in southern california children. American Journal of Respiratory & Critical Care Medicine 2000;162(4):1383-1390.

[23] Ilabaca M, Olaeta I, et al. Association between levels of fine particulate and emergency visits for pneumonia and other respiratory illnesses among children in Santiago, Chile.Journal of the Air & Waste Management Association 1999;49:154-63.

[24] McDonnell W, Abbey D, et al. Long-term ambient ozone concentration and the incidence of asthma in nonsmoking adults: the AHSMOG Study. Environmental Research 1999;80(1):110-21.

[25] Abbey D, Burchette R, et al. Long-term particulate and other air pollutants and lung function in nonsmokers. American Journal of Respiratory & Critical Care Medicine 1998;158(1):289-98.

[26] Abbey D, Petersen F, et al. Long-term ambient concentrations of total suspended particulates, ozone, and sulfur dioxide and respiratory symptoms in a nonsmoking population. Archives of Environmental Health 1993;48(1):33-46.

[27] Greer J, Abbey D, Burchette R. Asthma related to occupational and ambient air pollutants in nonsmokers. Journal of Occupational Medicine 1993;35(9):909-15.

[28] Abbey D, Mills P, et al. Long-term ambient concentrations of total suspended particulates and oxidants as related to incidence of chronic disease in California Seventh-Day Adventists. Environmental Health Perspectives 1997;94:43-50

[29] Pekkanen J, Timonen K, et al. Effects of ultrafine and fine particles in urban air on peak expiratory flow among children with asthmatic symptoms. EnvironmentalResearch 1997, 74: 24–33.

[30] Wang B, Peng Z, et al. Particulate matter, sulfur dioxide, and pulmonary function in never-smoking adults in Chongqing, China. International Journal of Occupational & Environmental Health 1999;5(1):14-9.

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[31] Abbey D, Petersen F, et al. Chronic respiratory disease associated with long term ambient concentrations of sulfates and other air pollutants. Journal of Exposure Analysis & Environmental Epidemiology 1993; 3 (supplement 1): 99-115.

[32] Abbey D, Nishino N, et al. Long-term inhalable particles and other air pollutants related to mortality in nonsmokers. American Journal of Respiratory & Critical Care Medicine 1999;159(2):373-82.

[33] Strand V, Rak S, et al.Nitrogen dioxide exposure enhances asthmatic reaction to inhaled allergen in subjects with asthma. American Journal of Respiratory Critical Care Medicine 1997, 155: 881–887.

[34] Linaker C, Coggon D, et al. Personal exposure to nitrogen dioxide and risk of airflow obstruction in asthmatic children with upper respiratory infection. Thorax 2000;55(11):930-933.

[35] Shima M. Adachi M. Effect of outdoor and indoor nitrogen dioxide on respiratory symptoms in schoolchildren. International Journal of Epidemiology 2000;29(5):862-870.

[36] Superko H, Adams W, Daly P. Effects of ozone inhalation during exercise in selected patients with heart disease. American Journal of Medicine 1984;77(3):463-70.

[37] Atkinson R, Bremner S, et al. Short-term associations between emergency hospital admissions for respiratory and cardiovascular disease and outdoor air pollution in London. Archives of Environmental Health 1999;54(6):398-411.

[38] Sunyer J. Spix C, et al. Urban air pollution and emergency admissions for asthma in four European cities: the APHEA Project. Thorax 1997;52(9):760-5.

[39] Linaker C, Coggon D, Personal exposure to nitrogen dioxide and risk of airflow obstruction in asthmatic children with upper respiratory infection. Thorax 2000; 55(11):930-933.

[40] Tolbert P, Mulholland J, et al. Air quality and pediatric emergency room visits for asthma in Atlanta, Georgia, USA. American Journal of Epidemiology 2000; 151(8):798-810.

[41] Frischer T. Studnicka M, et al. Lung function growth and ambient ozone: a three-year population study in school children. American Journal of Respiratory & Critical Care Medicine 1999;160(2):390-6.

[42] Asgari M,DuBois A, et al. Association of ambient air quality with children's lung function in urban and rural Iran. Archives of Environmental Health 1998;53(3):222-30.

[43] Georgia Conservancy: Health Effects of Bad Air: www.georgiaconservancy.org/AirQuality/AQ_Health_Effects_Of_Bad_Air.asp

[44] Georgia's Clean Air Force: Your Resource for Georgia's Vehicle Inspection and Maintenance: www.cleanairforce.com

[45] The Clean Air Campaign: www.cleanaircampaign.com

[46] Georgia and Atlanta Air Quality Data: www.air.dnr.state.ga.us/amp/index.php

[47] Georgia Department of Transportation – Office of Planning – Air Quality Branch: www.dot.state.ga.us/DOT/plan-prog/planning/aq/

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