WASHINGTON (Reuters) - Air quality in the Arkansas neighborhood where an Exxon Mobil Corp pipeline leaked thousands of barrels of Canadian crude has improved but was still unhealthy where workers were cleaning it up, the company and the U.S. environment regulator said on Thursday.
Readings of air quality "are below levels likely to cause health effects for the general population with the exception of the cleanup areas where the emergency responders are directly working," the Environmental Protection Agency said.
"As cleanup continues, contaminant levels continue to decrease," it said.
Exxon has been digging out oil-soaked lawns and replacing them with fresh sod in the neighborhood in Mayflower, Arkansas, where the government estimated up to 5,000 barrels of Canadian crude leaked on Friday.
The Pegasus line, which can transport more than 90,000 barrels per day of Canadian crude to Texas from Illinois, remained shut with no estimate of when it would restart.
Exxon said its data showed levels of benzene, a component of crude linked to cancer, had fallen in days following the leak.
On Sunday benzene had been detected 10 times in the area where workers are cleaning up the crude, with the highest concentration recorded at 0.8 parts per million. By Tuesday, benzene was detected three times in the work area with the highest level at 0.3 ppm.
Monitors detected that instances of volatile organic compounds (VOCs), which are linked to ear and throat irritation and kidney and liver damage, had also fallen. Exxon data detected VOCs 43 times on Sunday. By Tuesday that had fallen to 35 instances.
Twenty-two homes were evacuated by authorities after the leak and residents had not returned by Thursday.
Workers cleaning up the spill were using breathing equipment where necessary, the EPA said.
Residents in the area surrounding the spill had complained of a strong asphalt odor in the days after the leak. That odor has died down considerably since Monday, residents said on Thursday.