Dense smoke is expected to begin clearing Saturday afternoon, but children, older adults and people with heart or lung conditions should remain cautious through the weekend.

Delaware residents are being urged to limit strenuous outdoor activity Friday as smoke from Canadian wildfires pushes fine-particle pollution into the unhealthy range across the First State.

The Delaware Department of Natural Resources and Environmental Control forecast a Code Red Air Quality Action Day for particulate matter Friday, July 17. The state projected a fine-particle Air Quality Index of 186, a level considered unhealthy for everyone.

The smoke is expected to begin gradually clearing Saturday afternoon and evening as winds shift and scattered thunderstorms help mix cleaner air into the region. However, dense smoke may remain trapped near the ground Saturday morning, keeping conditions unhealthy for sensitive groups during the first half of the day.

DNREC forecasts a PM2.5 index of 102 for Saturday, placing air quality in the Code Orange category, or unhealthy for sensitive groups. Conditions are expected to improve to moderate Sunday and Monday, although thin smoke and haze could remain over Delaware.

New Castle County is expected to experience the greatest impact from the wildfire smoke, particularly in Wilmington, Newark and Bear, where fine-particle pollution may remain concentrated near the ground. Kent County, including Dover and Smyrna, is expected to see a moderate impact. Conditions in Sussex County may range from light to moderate depending on wind direction, with Milford, Georgetown and Laurel likely to experience less severe smoke than northern Delaware.

Why the air is unhealthy

The primary concern is PM2.5, microscopic particles with diameters of 2.5 micrometers or smaller. The particles are produced when trees and other organic materials burn and can travel hundreds or thousands of miles from the original fire.

Because the particles are so small, they can enter the lungs and, in some cases, affect the cardiovascular system. The smoke also contains gases and other pollutants, but federal health officials consider fine-particle pollution the greatest immediate health concern during most wildfire-smoke events.

Light northerly winds carried the dense smoke into Delaware. A temperature inversion — a layer of warmer air above cooler surface air — also helped trap the pollution close to the ground, allowing smoke concentrations to build during the morning.

Saturday’s approaching warm front is expected to turn winds toward the south and southwest. Thunderstorms may also help disperse the smoke. A cold front Sunday could carry a thinner plume back into Delaware, while light winds Monday may allow some haze to linger.

Who should be most careful

Code Red means some members of the general public may experience health effects, while people in sensitive groups face a greater chance of more serious symptoms.

Those at higher risk include:

• Children and teenagers, particularly those with asthma.
• Adults 65 and older.
• People with asthma, chronic obstructive pulmonary disease or other lung conditions.
• People with heart disease, high blood pressure or diabetes.
• Pregnant women.
• Outdoor workers and people exercising or playing sports outside.
• People who do not have reliable access to filtered indoor air.

Children are more vulnerable because their lungs are still developing, they are often more active outdoors and they inhale more air relative to their body weight. Older adults are more likely to have existing heart or lung conditions that can be aggravated by smoke.

Symptoms to watch for

Wildfire smoke can cause burning or watery eyes, a runny nose, throat irritation, coughing, headaches and fatigue.

More concerning symptoms include wheezing, chest tightness, shortness of breath, an irregular heartbeat or becoming unusually winded during light activity. People with asthma may need their rescue inhalers more frequently, while those with heart disease may face an increased risk of serious cardiovascular problems.

Anyone experiencing severe chest pain, significant difficulty breathing, confusion, fainting or signs of a heart attack or stroke should seek immediate medical assistance.

How residents can reduce exposure

Residents can lower their exposure by moving exercise and other strenuous activities indoors, keeping windows and doors closed and running air conditioning on a recirculation setting.

Portable air cleaners or high-efficiency heating and cooling filters may help reduce smoke particles indoors. People who must spend extended periods outside may consider a properly fitted N95 respirator, although masks do not eliminate all exposure and are less effective when they do not seal tightly against the face.

Healthy adults are generally less likely to experience serious problems from a brief smoke event, but federal health officials advise everyone to reduce exposure when the air reaches Code Red.

TO GO BOX

• What: Delaware Code Red Air Quality Action Day for fine-particle pollution
• When: Friday, July 17, with Code Orange conditions expected Saturday morning
• Expected improvement: Smoke should begin dispersing Saturday afternoon and evening. Moderate air quality is forecast Sunday and Monday, although haze may linger.
• Who should take extra care: Children, older adults, pregnant women, outdoor workers and people with asthma, COPD, heart disease, high blood pressure or diabetes
• What to do: Limit strenuous outdoor activity, keep windows closed, use recirculated or filtered indoor air and check current conditions before exercising or working outside
• More information: Check DNREC’s Air Quality Forecast page or EPA’s AirNow service. Delaware health questions may be directed to the Division of Public Health at 302-744-4700.

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