I wonder whether I can hold my breath for 2 more months.

According to SEPA, the Chinese government environmental agency, today's Air Pollution Index is 253, a 4B rating.

Let's see what the good folk at SEPA have to say about such a rating:

4B, 251-300, Moderate-heavy polluted. The symptoms of the cardiac and lung disease patients aggravate remarkably, and the exercise endurance drop lower. The healthy crowds popularly appear some symptoms. The aged, cardiac and lung disease patients should stay indoors and reduce physical activities.

Let's look over at our friends at the US EPA. They calculate API on the same 0-500 scale as SEPA. What do they have to say about a 253 score?

Now, while the scale used is the same, it's normalized differently. 100 is set as the baseline, acceptable level of a pollutant. It took some digging to try to match these scales, since standards are recorded in different units and different time scales in different places. I settled on the National Ambient Air Quality Standards (NAAQS) for EPA data, and Environmental Air Quality Standard (GB3095-1996) (word document, in Chinese) for SEPA. Here's my comparison:

Ozone:
EPA used to use a 1-hour averaging measurement, with the normal level set at 0.235mg/m3. In 2005 the EPA revoked the 1-hour measurement in favor of a more meaningful 8-hour average, and lowered the acceptable level to 0.176mg/m3 averaged over the 8 hours.

SEPA uses a 1-hour averaging measurement, with the normal level set at .2mg/m3. So while their standard is lower then the EPA's old 1-hour standard, it's generally considered an inadequate measure.

Particulate Matter (PM):

The EPA measures two kinds of particulates, PM10 and PM2.5. PM10 is 10 microns across or less, and PM2.5 is 2.5 microns across or less. Allowable levels are .15mg/m3 and .035mg/m3 respectively.

SEPA also measures PM10, and has an identical allowable level, but does not measure PM2.5.

PM10 is about 1/4 the diameter of a grain of salt. It's small dust, basically. It gets into your lungs and inflames them, clogging things up. You cough and hack, but my impression is that your body flushes it out. PM2.5 is considered more dangerous- it goes into your blood stream, relatively unfiltered by your respiratory tract. So while the PM10 standards are the same here, PM2.5 is ignored in China.

Carbon monoxide (CO):

Carbon monoxide affects the respiratory, cardiovascular, and central nervous systems. The EPA allows 40mg/m3 an hour, and SEPA only allows 10mg/m3 an hour. This seems like a much more stringent standard, but more on that later.

NO2 and SO2-

This is harder to compare. EPA uses an annual average of .1mg/m3 for NOx, all nitrous oxides, and SEPA uses a .12mg/m3 limit of NO2 per day. So the timeframe is different, as are the exact pollutants allowed. It's normal for the hour number to be higher than the day which is higher than the year, the idea being that your body can take a quick shock more than prolonged exposure.

Similarly, SEPA uses .15mg/m3 a day for SO2, where the EPA uses .364mg/m3 a day for SOx. This to me seems to be the one category where SEPA's standards are stricter.

Conclusions-

The allowable levels seem to be slightly lower for pollutants in China. Here's the kicker, though: While SEPA has these standards, their monitoring center only measures SO2, NO2, and PM. So their stricter CO standards don't seem to factor in, and apparently neither does their O3 limit. This seems significant to me. Only as I was walking into my apartment today did I identify the smell- ozone. So after a bunch more reading, including the formulas for pollution index calculation, I still don't know how comparable the numbers are. Let's stretch and say they correlate perfectly, and read what the EPA has to say about a pollution index of 253:

Very Unhealthy 201-300 Health alert: everyone may experience more serious health effects.

Particulate Matter: People with heart or lung disease, older adults, and children should avoid all physical activity outdoors. Everyone else should avoid prolonged or heavy exertion.

Ozone: Active children and adults, and people with respiratory disease, such as asthma, should avoid all outdoor exertion; everyone else, especially children, should limit outdoor exertion.

In other words, hold your breaths. I'm looking forward to moving somewhere the sun isn't a red disk in a sleet-grey sky.