Dangerously high pollution levels have Chile's capital on the brink of issuing an environmental emergency, the first such time the measure is to be implemented in 16 years.

"Tomorrow Environmental Emergency" Santiago regional governor Claudio Orrego tweeted Sunday, after three days at pre-emergency levels.

The emergency status -- the highest-level alert allowed -- is earned when the air quality index, considered good at 0-50, reaches hazardous levels as it tops 500.

Orrego's move means that 40 percent of vehicles must stay off the roads, while 3,000 factories and other businesses must shut down in the capital area of 6.7 million.

Student sports will be put on hold for now, and public bus-only lanes will be opened on local roads under the measures.

The extremely high pollution has hit just as Chile hosts the Copa America, with the capital one of the main venues.

The regional federation does not allow matches to be cancelled because of air quality.