Health Effects Categories
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Visibility (miles)1
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NowCast Concentration2(μg/m3)
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Health Effect
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Cautionary Statement
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Hazardous
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Less Than 1.3
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Greater Than 250.4
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Serious aggravation of heart or lung disease and premature mortality in people with cardiopulmonary disease, older adults, and people of lower SES; serious risk of respiratory effects in general population.
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Everyone should avoid all physical activity outdoors; people with heart or lung disease, older adults, children, and people of lower SES should remain indoors and keep activity levels low.
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Very Unhealthy
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2.1 - 1.3
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150.5 - 250.4
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Significant aggravation of heart or lung disease and premature mortality in people with cardiopulmonary disease, older adults, and people of lower SES; significant increase in respiratory effects in general population.
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People with heart or lung disease, older adults, children, and people of lower SES should avoid all physical activity outdoors. Everyone else should avoid prolonged or heavy exertion.
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Unhealthy
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5.0 - 2.2
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55.5 - 150.4
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Increased aggravation of heart or lung disease and premature mortality in people with cardiopulmonary disease, older adults, and people of lower SES; increased respiratory effects in general population.
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People with heart or lung disease, older adults, children, and people of lower SES should avoid prolonged or heavy exertion; everyone else should reduce prolonged or heavy exertion.
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Unhealthy for Sensitive Groups
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8.7 - 5.1
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35.5 - 55.4
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Increasing likelihood of respiratory symptoms in sensitive individuals, aggravation of heart or lung disease and premature mortality in people with cardiopulmonary disease, older adults, and people of lower SES.
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People with heart or lung disease, older adults, children, and people of lower SES should reduce prolonged or heavy exertion.
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Moderate
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13.3 - 8.8+
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12.1 - 35.4
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Respiratory symptoms possible in unusually sensitive individuals, possible aggravation of heart or lung disease in people with cardiopulmonary disease and older adults.
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Unusually sensitive people should consider reducing prolonged or heavy exertion.
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Good
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More Than 13.4 +
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0.0 - 12.0
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None
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None
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Note: SES stands for Socioeconomic Status
- John Coefield, Cyra Cain, Montana Department of Environmental Quality empirical study (July 2000) presented at Fire, Smoke and Health Workshop, Seattle, WA, June 5 - 6, 2001.
- NowCast concentration breakpoints are based on EPA’s 24-hour average breakpoints. More information can be found in the Technical Assistance Document for the Reporting of Daily Air Quality – the Air Quality Index (AQI); EPA-454/B-13-001; December 2013