TULSA, Okla. (AP) -- Tulsans were urged to car pool to work or ride the bus for 50 cents Thursday as temperatures in the upper 90s for the fourth straight day prompted the year's first ozone alert.
The Oklahoma Department of Environmental Quality issued the alert Wednesday, the same day medical authorities issued heat alerts in Oklahoma City and northeastern Oklahoma in effect for Thursday.
Ground-level ozone, a respiratory irritant, forms on sunny, still days when volatile organic compounds from gasoline-powered engines and nitrogen oxides from industrial activities bake.
Authorities say Tulsans should not refuel their cars until after the sun goes down, not mow their lawns and avoid outdoor cooking or burning to reduce the prevalence of such compounds in the air.
Tulsa had its first ozone alert on July 2 last year and a total of eight for the year. July and August are typically the worst months for the gas, which can exacerbate asthma and other respiratory problems.
The city narrowly escaped being put on the federal government's "Dirty Air List" this year after flirting with the ozone standard for years. The list means restrictions on emissions, tighter regulations on industry and costly changes in fuel and fueling equipment for the area.
The Tulsa Emergency Medical Services Authority issued a heat alert for Thursday after fielding calls from five patients for heat-related emergencies. All were taken to the hospital.
By early afternoon, Tulsa EMSA had already treated three patients for heat-related problems, making it likely the threshold of five for another heat alert for Friday would be passed, spokeswoman Tina Wells said.
The Oklahoma City EMSA also issued an alert after receiving a dozen heat-related calls in a 25-hour period ending Wednesday, said Jennifer James, EMSA spokeswoman.
The National Weather Service did not issue a heat alert even though temperatures reached the upper 90s in both cities Wednesday and were forecast to do so again Thursday and Friday.
The weather service usually reserves alerts for when the heat index, the combination of temperature and humidity, reaches above 105 degrees, the service said.
EMSA officials recommended citizens stay in air-conditioned areas when possible and drinking plenty of water and avoiding coffee, soft drinks and alcohol. Those working or staying active outdoors should take frequent breaks.
While the heat has caused some health problems, no Oklahomans have died so far this summer from high temperatures, said Ray Blakeney, spokesman for the state Medical Examiner's Office.
"It's only been hot for three days," he said.