SMOG SEASON 2009

What Can We Expect?

Read what Georgia Conservancy board member and Georgia Institute of Technology senior research scientist Dr. Michael Chang has to say.

Why more smog alerts in the summer? There are two pollutants that factor into smog alerts: ground-level ozone and particle pollution, and for various reasons we tend to see higher concentrations of these pollutants in the atmosphere during the period May through September, the “smog season.” First, here in the sultry South, our collective energy use – in our homes, businesses, and vehicles – is highest in the summer months. That energy mostly comes from burning coal, natural gas, and gasoline all of which emit pollution and pollution precursors (that is, ingredients that are needed to make pollution). But that uptick in seasonal emissions isn’t the only thing. And after three decades of controls to reduce those emissions, it may not even be the main reason why we see more smog alerts in the summer.

 Perhaps the biggest reason is the weather itself. In the summertime, the different weather systems that buffet our region slow down. The “lazy-hazy-days of summer” is more than just an old saying. In the hot months, we tend to see long periods between the arrival of fronts and other weather systems that would otherwise change out our polluted air mass with fresh air. Within these stagnant air masses, pollutants accumulate day after day and sometimes week after week. During one particularly hot, dry, and windless stretch in 1999, Atlanta experienced 36 code orange, red, or purple days in a row. But stagnant air isn’t the only weather feature that puts us on smog watch during the summer. Bright sunshine, heat, and humidity also contribute. All the ozone and some of the particle pollution that we see is not emitted directly from tailpipes and smokestacks. It is instead “manufactured” in the atmosphere from ingredients (pollutant precursors) that we put there and ingredients that nature puts there. This manufacturing process is a chemical process that is powered by solar energy. Light itself initiates a series of photochemical reactions that can create ozone and particle pollution (though a larger fraction of particle pollution is still emitted directly into the atmosphere, the secondary formation of particles in the atmosphere is quite significant). With the sun at its zenith and days are long, no doubt pollution production goes into overdrive. Heat further contributes to the chemical reactions by making everything cook a little faster, and humidity provides water which is also important to much of the chemistry and physics of pollution formation. But wait, that’s not all. Summer is also the peak growing season when trees, crops, and other vegetation are in full leaf. In season, the emissions of hydrocarbons from natural sources – though wonderful and the source of “fresh smelling” air - when combined with the human-made ingredients in this chemical recipe, generate smog.  

So, as the weather drives us to turn on the air conditioner or hit the road, as it creates those long, slow, sunny summer days, and as the verdant land springs into life, pollution and those pesky smog alerts will rise in intensity and frequency. This isn’t to say that weather and nature are the cause of our smog, but it does mean that we have to be cognizant of it. We have to design how we live to fit where we live. We can build cities in earthquake prone areas, but we better build them with the understanding that the ground will periodically shake. So too we can build cities in smog prone areas (for example, Georgia), but we better build them in ways that don’t exasperate the ability of our atmosphere to provide clean air.  

Michael Chang, Ph.D., is Deputy Director of the Brook Byers Institute for Sustainable Systems at Georgia Tech.  He joined the Georgia Conservancy’s board of trustees in 2005.

AIR QUALITY 101

What Is Air Pollution?
Air pollution is a variety of substances and gases in our air that pose risks to health.  Important air pollutants include ozone, nitrogen oxides (NOx), sulfur dioxide (SO2), particulate matter (PM), volatile organic compounds (VOCs), toxic substances such as mercury and some naturally occurring substances such as pollen. Read more.

What is Smog or Ozone?
Smog is another term for ground level ozone, which is formed when nitrogen oxide (NOx) combines with volatile organic compounds (VOCs) in the presence of sunlight. NOx are a by-product of fossil fuel combustion (oil, natural gas, coal) and so come from cars and trucks, power plants, and industrial processes. 

What is Soot or Particulate Matter?
Particle pollution, or particulate matter (PM), is a mixture of solids and liquid droplets that vary in size. PM includes aerosols and fine solids, such as dust. These particles can get trapped in the lungs and cause pulmonary and circulatory problems, as well as trigger asthma attacks.  High levels of PM has also been linked to Sudden Infant Death Syndrome (SIDS) and slow lung function growth in children.  Read More about how exposure to particulate matter exacerbates respiratory and cardiovascular diseases.

What is Mercury?
Methylmercury (MeHg) is a developmental neurotoxin that interferes with brain development. Human exposure results principally from consumption of fish and other seafood contaminated by mercury. Significant amounts of mercury are emitted from Georgia’s coal-fired power plants.  Read about a new rule in Georgia that requires tighter controls for mercury emissions.

Health Effects of Bad Air
Exposure to many pollutants in the air can result in a range of adverse health effects from shortness of breath and coughing to heart attacks and lung cancer.

Medical Perspectives on Air Pollution

Read Scientific and Medical Expert Perspectives on Smog and Health

Read about a major study in California showing that air pollution is not just a problem for children and adults with asthma.  Children in polluted areas developed asthma at higher rates and had slower lung function growth than children in less polluted areas.

Read the latest Report on Childhood Asthma from the Centers for Disease Control and Prevention (CDC).

Protecting Children from Air Pollution

In 2007, Mothers & Others for Clean Air united a group of air quality, public health and medical experts to update public health guidelines that outline appropriate levels of outdoor activity on smog alert days. This document serves as the basis for educating schools, athletic directors, pediatricians and other health professionals, day care centers, other child care providers and the general public on the appropriate precautions to take when air quality is poor.

Mothers & Others for Clean Air thanks Kaiser Permanente for its generous support in making possible the production and distribution of thousands of guidance documents for Georgia Schools and Georgia Families.

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Read About Childhood Asthma
Find Resources About Sending Your Child Back-to-School with Asthma

Fact Sheets

Climate Change and Health

Health Effects of Bad Air

Particulate Matter 101

Personal Action to Reduce Air Pollution

Safer and Healthier School Buses

What is Air Pollution?

Additional Information

Clean Air Act in Plain English

Physicians for Social Responsibility

More information on air pollution and health

American Lung Association

Outdoor Air Quality

Indoor Air Quality

Georgia Agency responsible for monitoring ambient air quality

The Georgia Environmental Protection Division (EPD), Air Protection Branch

National Collaborative Work Group on Green Cleaning and Chemical Policy Reform in Schools