Particles less than 2.5 micrometers in diameter are called "fine" particles. These particles, approximately 1/30 the average width of a human hair, can lodge deeply into the lungs. Sources of fine particles include all types of combustion, including power plants, motor vehicles and residential wood burning.
China is suffering the world’s heaviest PM2.5 pollution. This is the direct result of an over reliance on coal. In 2009 China burned nearly half of the worl's coal, and coal accounts for nearly 70% of China's energy mix.
PM2.5 vs. Visibility
- 5-10km: No special protection required.
- 3-5km: Reduce outdoor activities.
- 2-3km: Reduce outdoor activities, especially for respiratory patients; wear a mask outdoors; stop outdoor physical exercise.
- Less than 2km: Avoid all outdoor activities, especially for respiratory patients; however if outside wear a mask.
PM2.5 is readily inhalable and penetrates deep into the lungs. PM2.5 allow for many chemicals harmful to human health to be carried into our internal organs, causing a wide range of illnesses and mortality, including cancer (especially lung cancer), stroke and damage to unborn children. They have a strong association with most types of respiratory illnesses, heart disease and even mortality.
PM2.5 is attached to various types of pollutants such as heavy metal and PAHs, causing placental blood toxicity that leads to direct harm to fetus, intrauterine growth retardation and low birth weight of babies, especially when PM2.5 exposure happens in the first month of pregnancy.
PM2.5 causes cardiotoxicity and also causes severe irritation to the autonomic nervous system, which regulates the activity of the heart muscle.
PM2.5 causes blood toxicity, blood coagulation abnormalities and can trigger heart disease.
The soluble part of PM2.5 directly enters the bloodstream and the insoluble part accumulates at the alveolus of the lungs, causing inflammation.
Air conditioners: When using air conditioners set the button on inner circulation.
Masks: Wearing N95 masks will provide effective protection against PM2.5 but ensure you are wearing the mask correctly with a tight seal around the face. N95 masks can be purchased in pharmacies and can be used multiple times. Only when it's hard to breathe while wearing, should you dispose of it and buy a new one.
Reduce activity: Try to stay indoors during the most polluted hours of a day, which is normally from dawn till dusk. Do less physical activities outdoors.
One strap paper masks and ordinary surgical masks has no effect on PM2.5 prevention.
While wearing the N95 mask ensure there is a tight seal around the face. Deeply inhale and exhale to test whether the mask is air-tight.
(1) Dai Haixia, et al, Health effects of PM2.5, Foreign Medical Sciences (Section of Hygiene), 2001, Vol 28, No. 5
(2) Mao Yushi, et al, The Truth Cost of Coal, Coal Industry Press, 2008