Articles, Definitions, and Q & A

What is PM2.5 and Particulate Matter?

Particulate matter, also known as particulate pollution, is a complex mixture of microscopic solid particles and liquid droplets. The composition can change depending on time, weather, and location, but it can include smoke, pollen, metal, dust, and sulfates and nitrates from industrial factories, power plants, and auto-mobiles.

PM2.5 refers specifically to fine particle pollution, those less than 2.5 microns in diameter or smaller ( which is less than 1/30th the diameter of human hair), and can be inhaled through breathing into our lungs where they can become trapped. Exposure to PM2.5 has been linked in health studies to cause premature death due to heart and lung disease1, and studies have also indicated that these particles can aggravate the conditions of those already suffering from cardiovascular and repository problems such as congestive heart failure, coronary artery disease, lung cancer, emphysema, and asthma as well, and cause health problems in younger children and older adults2.

More Information:

1 Dangerous Breathing - PM2.5: Measuring the human health and economic impacts on China's largest cities (In Chinese)

English summary of above Dangerous Breathing report

2 Seasonal Variation of Chemical Species Associated with Short-term Mortality Effects of PM2.5 in Xi’an, A Central City in China. American Journal of Epidemiology. 2012. 175(6): 556-566

More information can be found at the following links: special report - PM2.5: Invisible Killer

Beijing Municipal Environmental Monitoring Center (In Chinese)

Chinese Ministry of Environmental Protection (In Chinese)

Beijing Air Pollution: Real-time Air Quality Index (AQI)

What are V.O.C.s?

V.O.C stands for Volatile Organic Compound. They include any organic chemical which has high vapour pressure at room temperature, causing a large number of molecules to evaporate into the air. Some V.O.Cs can cause long term health problems for humans, and others can harm the environment. They can especially be a problem in indoor environments. Sources of V.O.C's include paint and paint coatings, cleaning products, tobacco smoke, car exhaust, and factory production.

What is HEPA?

HEPA stands for High Efficiency Particulate Air, and is a specific standard for air filters. HEPA air filters much remove at least 99.97% of particles that have a size of 0.3 microns. Don't be fooled: some products may market themselves as HEPA-like or HEPA style, but do not meet the exacting standards of true HEPA filtration.

What are microns?

Microns, or micrometers, are a unit of measurement, that can be used to measure the diameter of particles in the air.