During the COVID-19 lockdown, road traffic dropped sharply, many businesses shut down, and millions stayed indoors. But did we really breathe healthier air? As experts in air quality monitoring, we analyze outdoor and indoor pollution trends from this period, drawing on data from certified associations like AASQAs.
Lockdown: Cleaner Outdoor Air?
In China, strict measures drastically cut outdoor air pollution, especially nitrogen dioxide (NO2), by halting most heavy industry factories. In France, gains were more modest.
Pollutant Shifts During Lockdown
Data from Approved Air Quality Monitoring Associations (AASQAs) reveal clear benefits: transport-related pollutants fell. Nitrogen dioxide (NO2) levels near major roads dropped 30-60%. Some PM10 fine particle concentrations decreased by up to 30%.
Away from roads, changes were less pronounced. AASQAs attribute this to:
- Weather conditions: Recent sunny weather and rising temperatures fueled fine particle formation from gases and nitrogen oxides. Light winds caused pollutant stagnation, creating a spring pollution episode despite lower traffic.
- Increased wood heating in March, even with milder evenings, in certain regions.
- Rising agricultural pollutants from spreading, including ammonium nitrate (NH4NO3) and ammonia (NH3).
Pollution's Health Toll
High pollution exposure poses serious risks to respiratory health and beyond.
Respiratory Risks
Polluting particles inflame airways, weakening defenses against pathogens like viruses. Pollution may worsen COVID-19 outcomes. A 2003 Environmental Health study in China found an 84% higher SARS mortality risk in polluted areas.
Respiratory allergies intensify with chemical pollutants. See our article: Indoor and Outdoor Pollution: Differences and Risks.
Long-term, pollution contributes to asthma and COPD.
Broader Health Impacts
Particles affect blood vessels and the heart, raising risks for diabetes, hypertension, and cancers. The IARC classifies outdoor air pollution as a "certain carcinogen."
Lockdown: Heightened Indoor Pollution Exposure
We spend 80% of our time indoors—more during lockdown. Homes trap concentrated pollutants.
Common Indoor Pollutants
Key sources include:
- Tobacco: Over 4,000 chemicals, 50+ carcinogens (Tabac-info-service). Passive smoking affects all; residues linger in fabrics. INPES reports 5,000 annual passive smoking deaths in France.
- Combustion from incense, scented candles, or deodorizing sprays releases gases and particles. ADEME advises moderation and ventilation; INPES suggests avoidance.
- Radon: Odorless radioactive gas from soil, highest in Auvergne, Limousin, Franche-Comté, Corsica. Check IRSN maps for your area.
- Carbon monoxide (CO): From faulty boilers; 5,000 annual poisonings (INPES).
- Sulfur dioxide (SO2) from coal/fuel oil combustion.
- Solvents like formaldehyde from paints, parquet, chipboard.
- Phthalates from plastics and PVC.
- Household products emitting volatiles.
- Allergens from pets, dust mites, cockroaches, pollen. Read our respiratory allergy guide.
- Mold in damp areas like bathrooms or walls.
Combating Indoor Pollution
COVID-19 spreads via droplets, not outdoor air. Standard anti-pollution steps apply:
- Keep vents and VMC clear.
- Ventilate 20+ minutes daily, morning/evening, even during peaks—indoor levels are 15x higher.
- No indoor smoking; quitting aids COVID-19 resilience (Tabac-info-service).
- Clean regularly with damp cloths/HEPA vacuums; use steam cleaners, vinegar, soda.
- Wash linens at 60°C; dry indoors; use dehumidifiers.
- Rinse hair nightly to remove pollen.
Lockdown offers a chance to build lasting healthy habits against indoor pollution.
