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Air Quality

Burning and smoke


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Using visibility to estimate health effects

Mt washington

DEQ monitors air pollution throughout the state to ensure that air quality standards are being met. Because wildfires often occur in remote areas, and the smoke impacts are transitory, monitoring wildfire smoke levels is often difficult. Given the highly visible nature of wildfire smoke, it is possible to make visual estimates of smoke levels. Generally the worse the visibility, the worse the smoke. The table below shows this relationship and how to estimate potential health effects.

Visibility range Health category Health effects Cautionary statements
15 miles and up Good None None
8 to 14 miles Moderate Possibility of aggravation of heart or lung disease among persons with cardiopulmonary disease and the elderly. None
3 to 7 miles Unhealthy for sensitive groups Increasing likelihood of respiratory symptoms in sensitive individuals, aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly. People with respiratory or heart disease, the elderly and children should limit prolonged exertion.
1½ to 2½ miles Unhealthy Increased aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly; increased respiratory effects in general population. People with respiratory or heart disease, the elderly and children should avoid prolonged exertion; everyone else should limit prolonged exertion.
1 mile Very unhealthy Significant aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly; significant increase in respiratory effects in general population. People with respiratory or heart disease, the elderly and children should avoid any outdoor activity; everyone else should avoid prolonged exertion.
Less than ½ mile Hazardous Serious aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly; serious risk of respiratory effects in general population. Everyone should avoid any outdoor exertion; people with respiratory or heart disease, the elderly and children should remain indoors.

Source: Guideline For Reporting of Daily Air Quality – Air Quality Index (AQI), EPA-454/R-99-010, July 1999, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards.

The procedure for making this observation is:

  1. Face away from the sun
  2. Determine the limit of your visual range by looking for targets at known distances (miles).
  3. Visual range is that point at which even high contrast objects totally disappear.
  4. Use the values above to determine the local forest fire smoke category.
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For more information about Air Quality call 503-229-5359 or email.

Oregon Department of Environmental Quality
Headquarters: 811 SW Sixth Ave., Portland, OR 97204-1390
Phone: 503-229-5696 or toll free in Oregon 1-800-452-4011
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