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Department of the Environment Reminds Residents to Take Steps in Response to Air Quality Alerts Hottest weather of the year brings “Code Orange” forecast to most of Maryland

BALTIMORE, MD (July 17, 2013) – With some of the hottest weather of the summer increasing the potential for bad air quality, the Maryland Department of the Environment reminds residents to take steps to protect their health and the air we breathe.

The air quality forecast for today through Friday for metropolitan Baltimore, the Maryland portion of metropolitan Washington and Maryland’s Eastern Shore is “Code Orange.” A Code Orange forecast indicates that air quality is likely to be unhealthy for sensitive groups such as children, the elderly and adults with respiratory and heart ailments. Those groups should limit time outside.

To protect the air – and, in turn, everyone’s health – on bad air days you should: avoid or reduce driving (use public transportation, carpool or telework); reduce car idling; refuel your car after dusk; use a propane grill instead of charcoal; avoid mowing the lawn or use an electric mower; and delay painting and avoid using aerosol products.   

So far in 2013, there have been three Code Orange Days and no Code Red days in the Baltimore region. In the Maryland portion of the metropolitan Washington region, there has been one Code Orange day and no Code Red days. Clean Air Partners’ Air Quality Action Guide includes an explanation of air quality ratings, from Code Green for good air quality to Code Purple for very unhealthy air.

The quality of the air across Maryland continues to show measurable signs of improvement, the Maryland Department of the Environment's review of preliminary monitoring results from 2012 shows. Hot weather is a significant factor in the formation of the pollutant ground-level ozone, but the ratio of bad air days to temperature has declined over the years in Maryland.

For air quality forecasts and information on air quality, go to MDE’s website or to, where you can sign up to receive emailed air quality alerts. Clean Air Partners also offers a free smart phone app to receive air quality forecasts. You can also call MDE’s air quality hotline at 410-537-3247.

More Information

Air pollution levels typically peak during the summer, when air can stagnate and the sun reacts with chemical compounds to form ground-level ozone. Health effects associated with ozone include decreased lung function, asthma attacks, and eye irritation.

MDE collects air quality readings hourly at 24 sites across Maryland. The readings are for levels of such pollutants as ground-level ozone, fine particles, carbon monoxide and sulfur dioxide, along with oxides of nitrogen, compounds that when warmed by the sun can create ozone. The readings are given a numerical value, with ranges that indicate levels of health concern. MDE provides current readings for a map that is displayed online.

MDE meteorologists combine their knowledge of how pollutants react to weather with the predicted weather for upcoming days to develop air quality forecasts.

Preliminary results of 2012 air quality monitoring data show continued improvements in our State’s air quality thanks to decades of sustained efforts and the continued strong support of Maryland’s air quality programs by Governor Martin O’Malley. With Maryland’s implementation of the Healthy Air Act, the Clean Cars Act, the Regional Greenhouse Gas Initiative, energy conservation and renewable energy goals, the scientific evidence shows that Maryland has effective controls in place to address the air pollution generated in-State. However, the science also demonstrates clearly that Maryland cannot fully meet air quality standards that protect public health unless air pollution generated outside of our State’s borders is controlled. Research indicates that states upwind of Maryland are responsible for as much as 70 percent of Maryland’s current air quality problem. Therefore, reducing emissions in upwind states is the key to solving our air quality problems.

Studies have indicated that climate change, if unaddressed, could result in increased ozone and fine particle levels, increasing adverse health effects. Governor O'Malley will release his final Greenhouse Gas Reduction Plan July 25, which includes implementation of policies to mitigate these harmful air quality issues.

Core Facts
  • Air quality ratings are based on ground-level ozone levels.

  • Code Green is for good air quality. Enjoy the great outdoors.

  • Code Yellow is for moderate air quality. Some pollution can pose a health risk to the highly sensitive.

  • Code Orange is for unhealthy for sensitive groups. Pollution levels are harmful to children, the elderly and anyone with respiratory or heart conditions. They should limit outdoor activities.

  • Code Red is for unhealthy. Pollution levels are harmful to all. Sensitive groups should avoid outdoor activities, and others should limit outdoor exertion.

  • Code Purple is for very unhealthy. Pollution levels are very unhealthy for everyone. Avoid any physical activity outdoors.

  • Ozone and fine particles are Maryland’s biggest air quality issues. Both pollutants are created from fuel-burning sources such as vehicles, electric utilities and industrial boilers. These pollutants can irritate the respiratory system causing coughing, throat irritation and chest pains. They are also linked to premature death.

  • Monitoring stations in Garrett and Washington Counties and Baltimore City recorded ozone levels that met health standards. In the summer of 2012, the temperature topped 90 degrees on 46 days at Baltimore-Washington International Thurgood Marshall Airport, and the health standard for ground-level ozone was exceeded on 29 days in Maryland. In comparison, in 1995 the temperature topped 90 degrees on 51 days -- and the ozone standard was exceeded on 71 days. Hot weather is a significant factor in the formation of ground-level ozone, but the ratio of bad air days to temperature has declined over the years in Maryland.

  • Pollution from neighboring states is the top contributor to Maryland’s continuing ground-level ozone problem. As much as 70 percent of Maryland’s air pollution comes from upwind states.

  • Addressing air pollutants from neighboring states is a priority for Maryland. Maryland is urging the EPA to adopt federal rules to reduce emissions from these states. Maryland is also working with other Mid-Atlantic and Northeast states to use selected provisions in the federal Clean Air Act to legally compel reductions in upwind contributing states.

  • Air pollution accounts for about a third of the nitrogen pollution affecting Maryland waterways, including the Chesapeake Bay. Reductions in nitrogen oxide emissions due to the Healthy Air Act have reduced the amount of nitrogen pollution to the Bay by an estimated 300,000 pounds a year.


  • Ozone is a gas that occurs in two layers of the atmosphere. Nitrogen oxide is emitted when fossil fuels are burned. Nitrogen oxide combines with volatile organic compounds to form ground-level ozone when cooked by the sun.

  • When ozone is up very high in the atmosphere it is considered “good” as it protects us from the sun’s ultra-violet rays, however when ozone occurs near ground-level it becomes harmful to human health and our environment.

  • Particle pollution (also called particulate matter or PM) is the term for a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke are large or dark enough to be seen with the naked eye. Others are so small that they can not be seen by the naked eye.

  • Sulfur dioxide is produced by the burning of fossil fuels containing sulfur compounds. It is the most significant contributor to the problem of fine particles, which creates haze that decreases visibility and is linked to premature death and heart and lung problems.

  • Preliminary 2012 monitoring results are subject to quality review and possible corrections, though any corrections made to preliminary results in recent years have not been significant.

  • MDE's air monitoring results are viewed in relation to health-based standards for air quality as established by the EPA.

What You Can Do

  • Conserve energy by turning off lights and appliances when you leave a room.

  • Use energy-efficient appliances such as refrigerators, air conditioners, heat pumps and furnaces.

  • Reduce, Reuse, Recycle – this also conserves energy and reduces emissions.

  • When possible, walk, bike or use public transportation to get around town.

  • Avoid letting your car idle – this will reduce toxins and other pollutants from being released into the air.

  • Get regular engine tune ups and car maintenance checkups.

  • Carpool or use public transit to get to work.

  • Shop with reusable bags instead of using paper or plastic.

  • Plant trees in locations around your home to provide shade in the summer.

  • Follow air quality forecasts and plan your outdoor activity as appropriate. Put off mowing the lawn or painting and reduce driving on bad air days.


 “Breathing clean air is something most of us take for granted. But if you have respiratory concerns such as asthma, poor air quality is something that can’t be ignored. We all make choices everyday that can help reduce air pollution.”

--Robert M. Summers, Secretary, Maryland Department of the Environment

Additional Information

Samantha Kappalman

Jay Apperson


MDE Mission
Our mission is to protect and restore the quality of Maryland's air, water and land resources, while fostering smart growth, a thriving and sustainable economy and healthy communities.