With a new year comes a new opportunity to protect our health and our lungs. Even though California’s climate is milder than most other states, people generally spend more time indoors during the winter as temperatures cool and the state experiences more rain. This can compromise our lungs in two ways.  

First, when we go outside, we’re breathing cold, arid winter air which can irritate our respiratory passages. Second, when it’s cold outside, we keep our windows and doors closed, which limits air circulation.  Surprisingly, this can cause indoor air to become more polluted than the outdoors.    

Winter air is dry because cold air naturally holds much less moisture.

When this cold, dry air enters our warm homes and is heated further, its capacity to hold water increases, but the actual moisture content stays the same, drastically lowering the relative humidity. Heating systems that warm the air, but don't add humidity, exacerbate the dryness and pull moisture from our skin and sinuses. 

Low humidity also removes the protective moisture from respiratory passages, triggering irritation that often causes airways to constrict. Our bodies compensate by generating extra mucus that's thicker than normal, which clogs airways, further impeding breathing. This can lead to persistent coughs, shortness of breath, difficulty getting enough air, and chest discomfort—particularly for those with existing lung conditions like chronic obstructive pulmonary disease (COPD) or asthma.

Sealing our homes from the cold air outside leads to a dramatic drop in air circulation inside which traps airborne irritants inside. These often include indoor allergens, such as dust mites living in fabrics and carpeting, mold spores, and for those with pets, animal dander. Other irritants include combustion particles from smoke (whether from tobacco or cannabis, fireplaces, or wood burning stoves), cooking with oils that have a low smoke point (such as olive oil), fragrances from scented candles, incense, and certain air fresheners, and fumes from furniture, cleaning products, paints, and new carpeting.  Exposure to these substances can make it difficult to breathe for all, but especially when they aggravate breathing conditions like asthma and allergies.

Winter is also the peak season for respiratory illnesses such as colds, the flu, COVID-19, and pneumonia, due to the dry air that pulls moisture from your body, creating ideal conditions for viruses to survive longer. When we gather with others indoors with the windows shut, we increase the chance that we’ll breathe in air from someone already infected.  

Shorter days with less sunlight cause our bodies to get less vitamin D and melatonin, both of which help us fight illnesses.  The frigid air may also compromise our bodies’ immune defenses, also reducing our ability to ward off infections.  

This all may sound like getting sick is unavoidable.  But we can take steps to safeguard our lungs and prevent everyone in our household from getting sick.

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