NFL monitoring air quality in California

As air quality index levels rise in California, the San Francisco 49ers are hopeful their game against the Arizona Cardinals on Sunday will be played at Levi's Stadium, a league spokesman told ESPN's Nick Wagoner.

Wild fires in the area and a heat wave have created air quality concerns.

The Niners practiced under "apocalpytic" skies on Wednesday, head coach Kyle Shanahan said. However, the air quality index was at 69, well under the 200 threshold allowed by the league. On Friday, that number climbed to above 150.

"We would have (altered the schedule) if it got to 200, but it didn't," Shanahan said. "If it happens Sunday, my understanding is if it gets to 200, that's when the NFL will start really discussing what to do with the game ... Hopefully it won't get there, hopefully it will be safe, but we've got to see what the wind does."

Cardinals head coach Kliff Kingsbury said Arizona is "definitely monitoring the situation."

Even air quality levels at 150 could prove problematic for people with health concerns. San Francisco running back Tevin Coleman was held out of practice Friday because of a pre-existing sickle cell trait condition.

"Just taking a precautionary decision to help him for Sunday," Shanahan said. "I know when it is up to 150 that's when it can affect people with different conditions, so that's something that Tevin, it will be a personal decision when he gets there. It's not just an automatic no ... that's stuff you have got to discuss with the doctor and be comfortable with."