Autumn brings cooler temperatures and seasonal delights, but it also introduces unique air quality challenges. From allergens to wildfire smoke, these fall-specific concerns can affect everyone, especially those with seasonal allergies.

How is the air in autumn?

Autumn is a transitional season marked by fluctuating weather conditions that can significantly impact air quality. As temperatures drop, humidity levels shift, and winds increase, which can stir up allergens, pollutants, and particulates.

These factors make autumn a particularly volatile air quality season—fall air quality today could easily change tomorrow.

Fall air quality can also vary locally. In some locales, fall often sees a continuation of summer's wildfire activity, and with that comes wildfire smoke. In other locations, cool, damp weather typical of autumn can promote the growth of mould, particularly on outdoor surfaces like fallen leaves and decaying vegetation, further affecting air quality.

Fall seasonal allergies are allergic responses, typically, to one or more of the following:

1. ragweed and flower allergens
2. dust mites
3. wildfires
4. scented candles and holiday decorations
5. pumpkin mould

Read on for a deeper look at these top 5 fall air quality concerns and learn how to breathe cleaner air throughout the season.

1. Ragweed, flowers and pollen

Ragweed

Ragweed is the main allergen that aggravates people with fall seasonal allergies (1). Ragweed is native to North America and is an invasive species in Europe.

When the body encounters ragweed pollen, it treats the allergen as a threat. The body’s immune system creates a reaction – the chemical histamine – that enters the bloodstream. This reaction can be helpful in fighting harmful invaders, like parasites.

However, when histamines are created in reaction to an allergen like ragweed, they result in a non-helpful allergic reaction. Ragweed pollen allergy symptoms are similar to common pollen reactions, including:

• sneezing
• runny nose or congestion
• headache
• eye and throat irritation
• aggravated symptoms for people with asthma

Climate change is impacting ragweed habitat, creating worsening conditions for people with ragweed pollen allergies. A 2015 study published in Nature Climate Change anticipates that concentrations of airborne ragweed pollen in Europe will be around four times higher than current estimates by 2050 (2).

Two-thirds of the anticipated ragweed pollen concentration increase can be attributed to projected climate and land-use changes in northern and eastern Europe, as well as an increase in production in currently established areas of southern Europe. All hope is not lost; despite these expected increases in overall pollen, there are steps that can be taken to alleviate allergy symptoms.

On heavy ragweed pollen days, consider staying indoors when possible. There are other ways to prevent symptoms as well, such as:

• washing bedding with soap and hot water
• keeping windows and doors closed
• removing shoes before entering a home
• vacuuming regularly

Flowers

Decorative fall flowers can also be a problem for people with allergies. Apart from ragweed, one of the most common problematic autumn flowers is the Chrysanthemum, which can spread pollen. A 2002 study published in Allergy surveyed and tested Dutch greenhouse workers to find out whether nasal inflammations, or rhinitis, were work-related symptoms (3). The study found that about 57 percent of symptoms were work-related, and that about 20 percent of workers were affected by flowers in the Chrysanthemum family.

Tip: Certain brightly colored flowers, like roses, produce less airborne pollen, because they are able to attract birds and bees more directly without needing to release pollen (4).

Some other tips for reducing pollen count include:

• Avoid planting near windows and sitting areas.
• Garden after it rains or in the late afternoon. Don’t overwater the garden, as this may result in unintentional mould growth.

But ragweed and pollen aren’t the only fall culprits. Let’s look at another common element, dust mites, becomes particularly problematic in autumn.

2. Dust mites

Autumn is a time of year that’s particularly favorable for dust mites. Dust mite allergens tend to peak between May and October, the dust mite’s breeding season (5). Like ragweed, inhaled dust mite bodies and waste can cause an allergic reaction in the body.

Measuring only 250 microns in diameter, dust mites are commonly found in many parts of the home, including (6) (7):

• bedding
• carpets
• curtains
• upholstered furniture
• dirty air ducts

You can manage dust mite allergens by keeping humidity below 50 percent, cleaning and replacing mattresses and pillows, and installing a whole-house air purifier into an existing HVAC system. There are even more dust mite control strategies for pet owners to consider like keeping pets out of the bedroom and purchasing washable pet toys.

3. Wildfires

Human-created climate change is creating global conditions for longer, more intense wildfire and brush fire seasons. Summer wildfires now commonly continue well into autumn and even winter, especially if heatwaves and dry conditions persist in a region.

Wildfires don’t just pose a threat to the local community. Wildfire smoke contains many pollutants, including:

• ultrafine particles
• PM2.5
• PM10
• carbon monoxide
• carbon dioxide
• nitrogen oxides
• volatile organic compounds (VOCs)

When wildfire smoke affects air quality, avoid going outdoors and close doors and windows. If going outdoors is unavoidable, wearing a pollution mask can be an effective means of managing airborne pollutant inhalation.

4. Scented candles and holiday decorations

Fun holiday decorations can liven up a living space. But some decorations can also pose indoor pollutant concerns.

Polyethylene vinyl acetate (PEVA) plastic, sometimes used to make holiday decorations, has been positioned as an alternative to polyvinyl chloride (PVC) because it is chlorine-free. However, a 2014 study published in the Journal of Toxicological Sciences found that both PVC and PEVA VOCs off-gassing were harmful to freshwater worms, and therefore, PEVA is not a safe alternative to PVC (8).

Another potential source of indoor air pollutants in the fall can be scented candles. Some scented candles Some scented candles can be a source of VOCs, including formaldehyde. A 2013 study published in Environmental Science and Pollution Research noted the presence of several aldehyde emissions –including formaldehyde – in scented candles, as opposed to non-scented candles (9) (10).

Try to avoid holiday decorations made of either PVC or PEVA plastics. Instead of lighting scented candles, consider making a potpourri out of dried berries, flower, fruit rinds, spices, wood chips and essential oils.

5. Mouldy pumpkins

Pumpkins are often used as decorations for both Halloween and Thanksgiving. But as they grow older and mould develops, old pumpkins pose a health hazard (11).

Moulds can reproduce wherever there is moisture, including in old pumpkins and jack-o-lanterns. Allergenic moulds can trigger an allergic reaction in some people. Rotting pumpkins can grow several common moulds, including species of Caldosporium, Penicillium, Aspergillus, and Alternaria – all four of which are considered allergenic moulds.

Some species of Aspergillus can be pathogenic, meaning that they can cause an infection in a healthy human. A few species of Aspergillus and Penicillium moulds are toxigenic; they can create chemical metabolic byproducts called mycotoxins. Mycotoxins can result in a toxic response in people.

When pumpkins or jack-o-lanterns begin to show signs of rot, be sure to throw them out promptly.

Conclusion

Though certain allergens and airborne pollutants may be more pressing in autumn, it’s possible to reduce their impact and take back control over one’s quality of life any time of year.

When autumn begins, that’s the perfect time to change the air filters in your HVAC and air purifiers. Over time, filtration can become clogged with particles and pollutants. Changing older filters offers many benefits, including:

• increasing equipment efficiency
• lowering energy costs
• extending the life of your air cleaning technology

Monitoring your indoor and outdoor air quality will help in identifying issues before they affect quality of life. When air quality is degraded, running an air purifier will help create a safe space in the home for easier breathing and cleaner air. For better air directly affecting personal breathing space, a desk or car air purifier can also be beneficial.

Just as autumn brings its unique charm, it also presents unique air quality challenges. By staying proactive, you can ensure that this fall, the air you breathe is as crisp and clean as the season itself.