Particulate matter is a term for solids in the atmosphere. The smaller the particle, the more lethal it is to humans. The smallest of these particles are classified PM2.5 because they are less than 2.5 micrometers in diameter. They are dangerous because they can lodge deep inside lung your tissue.

In the United States, the EPA mandates no more than an average of 15 micrograms per million over a period of three years. According to the World Health Organization, safe daily levels are those with measurements under 25 micrograms per square meter.

What does this have to do with art?

The man on the left is the Chinese artist Ai Weiwei. Yesterday he posted a picture of himself in a gas mask with a fog grey sky behind him. It was succinct commentary on conditions in Beijing. Remember, WHO considers 25 micrograms per square meter safe. Now consider this: Last weekend, Beijing’s atmospheric pollution shattered all records. The official measurement was 600 micrograms per square meter.  According to Reuters it was much worse — 900 micrograms.

If a society can’t provide a habitable environment, then it fails at the most basic level. When conditions become inhospitable, it falls on the people to change them. This applies even in totalitarian societies. Caution be damned if the atmosphere is killing you. Yet now we find the usually defiant Weiwei in a display of reserved acceptance. He’s not trying to change conditions; he’s just blocking them out.

Should he wear the bottoms of his trousers rolled?