The science behind the story.

Health

1. 1
   World Health Organization — Ambient (outdoor) air quality and health

   99% of the world's population lived where WHO guideline levels were not met (2019). Ambient and household air pollution together are associated with 6.7 million premature deaths a year. Health effects include stroke, heart disease, lung cancer, COPD and respiratory infections.
2. 2
   World Health Organization — Household air pollution and health

   An estimated 2.9 million deaths a year (2021); around 2.1 billion people cook with open fires or inefficient stoves.
3. 3
   World Health Organization — Tobacco, fact sheet

   Tobacco kills more than 7 million people each year, including more than a million non-smokers exposed to second-hand smoke.
4. 4
   IPCRG / WHO webinar — Access to asthma and COPD care

   Global Burden of Disease 2019: 262 million people with asthma and 212 million with COPD.

Medicine

1. 5
   Global Market Insights — Inhalation Drug Delivery Market

   Global market estimated at USD 46.5 billion in 2025. A commercial forecast; other analysts define the market differently.
2. 6
   Drug Development & Delivery — FDA approval of inhaled insulin (Afrezza)

   Peak insulin levels are reached within 12–15 minutes of inhalation.

Climate & nature

1. 7
   Carbon Brief — How human-caused aerosols are “masking” global warming

   Based on IPCC AR6: sulphate aerosols offset about 0.5 °C of warming (range 0.1–0.9 °C).
2. 8
   NASA — CALIPSO observes Saharan dust crossing the Atlantic

   Satellite data 2007–2013: about 27.7 million tonnes of Saharan dust settle over the Amazon basin each year.
3. 11
   Lelieveld et al. (2015), Nature — The contribution of outdoor air pollution sources to premature mortality on a global scale

   In Europe, the eastern USA, Russia and East Asia, agricultural emissions make the largest relative contribution to PM2.5.

Cities, industry & everyday life

1. 9
   Packaging Journal — FEA European aerosol production

   3.46 billion aerosol cans produced in the EU in 2024.
2. 10
   World Health Organization — Updated terminology for pathogens that transmit through the air (2024)

   Introduces “infectious respiratory particles” and “transmission through the air”.
3. 12
   European Environmental Bureau — Cutting the dead wood out to clear Europe's air

   Domestic heating with wood and coal emits about half of all PM2.5 and black carbon in the EU.
4. 13
   OECD (2020) — Non-exhaust particulate emissions from road transport

   Wear from brakes, tyres and road surfaces will soon overtake exhaust as the leading source of fine particles from road traffic — electric vehicles included.
5. 14
   UK Health and Safety Executive — Isocyanates campaign

   Vehicle spray painters are around 80 times more likely to develop occupational asthma than the average UK worker.

General background

Particle size ranges, deposition in the airways and lung anatomy (airway branching, ~480 million alveoli, 50–100 m² surface) follow standard aerosol-science and respiratory-physiology textbooks. Sizes are typical ranges; real particles vary.