Tom Morton, Townsquare Media

Midwest School second-grade student Marco O'Brien on Monday shyly but succinctly described how his school's travails -- shut down in May because of very high levels of carbon dioxide and benzene -- have affected him.

"I don't like to wake up early in the morning and be on the bus," the 12-year-old told the Natrona County School District board of trustees about having to commute to Casper.

Despite the sleepy inconvenience, the district had to shut down the school May 26.

The Casper-Natrona County Health Department on Monday reported the Agency for Toxic Substances and Disease Registry, a division of the U.S. Centers for Disease Control and Prevention, completed a formal review of the air sampling it conducted on June 16 and 17,

"ATSDR concluded that the air quality events that occurred in Midwest School in May 2016 constituted an urgent health hazard and that school officials and others who determined that the school needed to be evacuated were right in doing so," the report said.

The most serious findings from testing on May 26 were very high levels of carbon dioxide, areas of the school that were deficient in oxygen, and one classroom that had a level of benzene 200 times more than ATSDR guidelines.

Short-term effects of inhaling benzene include drowsiness, tremors, unconsciousness and death. Long-term exposure can cause anemia, cancer and leukemia, the report said.

Air quality varied from day to day. The air quality on the June testing dates was much better than on May 25, according to the report.

The health department reported the Salt Creek Oil Field owner Fleur de Lis Energy, LLC, has been monitoring the school's air quality during the summer,

FDL has not found any abnormal CO2 levels since it tested the area on June 6 and 17.

FDL has sealed an old well next to the school. It has conducted a comprehensive evaluation of every well bore drilled within a half-mile of the school, has looked for other sources of gas, and has retained an environmental consulting company to advise it about soil remediation.

The health department interviewed 139 staff and students and turned the results of those surveys to epidemiologists at the Wyoming Department of Health. Evaluating those surveys will take several weeks.

Department Director Kelly Weidenbach said it has recommended the school district implement these programs: develop an indoor air quality mitigation and monitoring plans, conduct another round of air quality sampling, place CO2 monitors in the school, and develop a response plan if or when other air quality problems occur.

In June, FDL installed a vapor extraction system in the school, which has been effective in improving the indoor air quality, Weidenbach said.

"The big concern is the benzene that was found in the school," she said. "The ATSDR did some calculations and found that the increased risk of cancer is very low. It is not zero, but it is very, very low. We are not expecting any increase in cancer in staff and students at the school."

But the school's closure will continue to cause problems for Marco O'Brien and dozens of other Midwest School Pre-K through eighth grade students who need to be on the bus by about 6:30 a.m. to ride to Casper and attend classes at Westwood Elementary School.

Likewise, ninth through 12th grade students ride a bus to attend classes at the new Roosevelt/P.I.C. (Pathways Innovation Center) School.

Parents also voiced their frustrations with the closure, such as Justin Marken who wanted to know if the district would allow Midwest School to host its homecoming game on its own field.

Board Chairman Kevin Christopherson said he'll look into that.

Meanwhile, Christopher said the health department, federal and state agencies must deal with the safety issues.

The school will be closed through this semester, but that doesn't mean it will reopen after that, Christopherson said.

Nor does it mean, contrary to rumors, the district is considering closing Midwest School permanently, he said.

"We're not even thinking about it," Christopherson said. "Right now we are all looking how to get in there and make it a viable school again as soon as possible."