Air Pollution
Monitoring & Management
in China
Brief introduction to particulate materials
“Particulate matter,” also called particle pollution or PM, is by definition a “complex mixture of extremely small particles and liquid droplets which is made up of a number of components including acids, organic chemicals, metals and soil or dust particles” (EPA). The smaller the size of particles is, the more potential harm they may bring to human health since the volume of particles inhaled increases as their diameter decreases.
Current universal recognized standard, which is originated in the U.S. and has been widely accepted by many countries including China, regards particles whose diameter are equal or less than 10 micrometers as noticeable pollutants, because of their capacity to pass through both throat and nose and even enter the lungs. The inhaled particles will affect functions of hearts and lungs and therefore cause serious health damage to human body.
The U.S. Environmental Protection Agency has categorized particle pollution into two groups: “inhalable coarse particles” whose diameter falls in the range from 2.5mm to 10mm, and “fine particles” that are 2.5mm in diameter and smaller. It was the ladder one – fine articles or PM2.5 - that
played a crucial rule in China’s hazardous pollution last winter. PM2.5 can be found generally in smoke and haze that directly resulted from automobiles gases, forest fires and industrial emissions.
How small is it?
In order to understand the actual size of the particle pollutants, let’s compare it to human hair – about whose size that everyone has direct sense. Averagely, human hair is approximate 70mm in diameter, which makes it nearly 30 times larger than a fine particle!
What makes it up?
There are various shapes and sizes as well as components of fine particles. For those referred to as primary particles, they usually come directly from single source such as construction sites, unpaved roads and smokestacks. In contrast, the so-called secondary particles are the results of complicated reactions of different chemicals and conditions. For instance, emissions from a power plant are compounds of several kinds of dioxides derived from different stages of the reactions. Automobile gas and most of the industrial off-gas are of this kind, contributing to an overwhelming proportion of the whole particle pollution.
How harmful can it be?
Particle pollution, due to its extremely small size, has easier access than other air pollutants to human bodies, both organs such as lungs and circulations like bloodstream. It’s been firmly verified by numerous scientific researches that exposure to high volume of particles pollution leads to various of health problems, especially malfunctions of hearts and lungs and increasingly burst of respiratory-related diseases such as asthma. What’s worse, children and seniors turn out to be the most vulnerable groups in face of particle pollution.
In terms of environmental damage, particles are the main cause of haze. It severely reduces the visibility, exactly what had happened in our China case where the impaired visibility prevented people from seeing buildings only 500 yards away. In addition, the particles may acidize water resources, breaks nutrient balance of the soil and even brings fatal damages to sensitive crops and plants. The entire ecosystem is put at stake if particles sustained for a long period of time.