How severe is PM2.5>900 in Beijing?

       

I am not surprised to see a picture which shows vividly how notorious Beijing’s air is. Last year I took a flight from Seattle to Beijing. Right before landing, I noticed that the sky was yellow and smoggy. When I went to the restroom, the worker there complained to me how he had to mop the floor and wipe the counter all day long to prevent the dust from smothering everything. 

        This time I am not surprised. What I saw in this picture is similar to that of last year. But this time, instead of giving it a casual glance, I stopped to think: how severely will this air pollution affect our health? 

       Some indexes by size have been used to classify particulates in the air. Unlike other parameters such as component and shape, size is a simple yet concrete standard, and is easy to measure. PM2.5 and PM10 (particulate matter with diameters of up to 2.5 micrometer and 10 micrometer, respectively) are two common categories. PM10 can enter the lung; PM2.5 can penetrate the air exchange membranes of the lung.

Some studies showed that PM2.5, once in the body, can induce oxidative stress and damage DNA. It has been associated with high risks of heart disease, cancer, and asthma. Even short-term exposure to high concentrations of PM2.5 can pose significant health risks. PM2.5 at 10 (10 microgram per cubic meter) or less is considered safe. PM2.5 at 75 or less is acceptable. Based on the news, some cities (not only Beijing) have detected PM2.5 at a concentration of over 900. That is more than 10 times of the acceptable level! 

        Needless to say, something must be done to curb this severe air pollution.