Health Officials Plan Inquiry of Gas in Subway : Red Line: Foul odor is blamed on hydrogen sulfide, about which some riders and workers have complained. There is no cause for worry, officials say.

The stench greeted passengers arriving Friday at the Civic Center subway station like hard-boiled eggs left too long in the sun.

“It’s unpleasant, to say the least,” said Bart Blakesley, who when asked his opinion was already discussing the aroma with a friend.

For months, transit officials have said that water leaks and incursions of a different, odorless gas into the Los Angeles subway were no cause for worry--although millions of dollars were spent during construction to keep the structures virtually sealed to gas.

But on Friday, two public health officials said they will take steps to examine the pervasiveness of the sulfur-smelling gas, called hydrogen sulfide, in the tunnels and stations of the 4.4-mile Red Line subway.

“This is an issue that I think needs to be looked into,” said Dr. James W. Stratton, a chief deputy director of the California Environmental Protection Agency in Sacramento.

The comments of Stratton and Dr. Paul J. Pananek, of the county Health Department’s toxics epidemiology unit, came after they learned during interviews with The Times that levels of hydrogen sulfide in the subway typically range from 5 parts per million to 8 parts per million.

Those quantities of hydrogen sulfide “are not uncommon” on any day, said Ralph de la Cruz, the Metropolitan Transportation Authority’s deputy executive officer for operations. Records obtained for Jan. 17, the day of the Northridge earthquake, show that hydrogen sulfide levels of 5 to 8 parts per million occurred at three different times--volumes that doctors say could cause headaches, nausea or malaise.

Federal health standards warn against human exposure to hydrogen sulfide, among the most toxic gases, at a level of 10 parts per million or greater for more than 10 minutes. According to the National Institute of Occupational Safety and Health, hydrogen sulfide at levels of at least 50 parts per million can cause serious eye injuries and, at 300 parts per million or greater, can cause death.

Pananek and Stratton said that hydrogen sulfide at the levels detected in the Los Angeles subway could make people temporarily sick but would not be life threatening.

“Symptoms of nausea or headaches or malaise would not be unexpected,” Stratton said. “At 5 (ppm) to 8 (ppm), it’s up in the range where further scrutiny is warranted.”

The most serious danger, the doctors said, would be if someone encountered a random pocket of the gas at a higher concentration.

“Fatalities from hydrogen sulfide are an ongoing, perennial problem,” said Pananek, referring to industrial accidents that occur when workers succumb to such pockets of gas, which is heavier than air and is typically concentrated at foot level.

Stratton and Pananek said they believe the MTA should, on an experimental basis, place gas sensors at the lowest levels of the tunnels and stations to see if the volumes detected differ from the levels found by the raised sensors being relied upon.

MTA officials confirmed that the sensors for hydrogen sulfide and methane gas are at the tops of the tunnels and stations. Methane is lighter than air and concentrates most heavily at the crown of a structure. As for the heavier-than-air hydrogen sulfide, MTA officials said the elevated sensors are still reliable because the turbulence caused by trains and fans mixes and raises the gas.

“Once mixed with air, hydrogen sulfide does not again separate from it, especially in the tunnel’s turbulent airflow,” said MTA spokesman Bill Heard, who along with De la Cruz said the agency has no reason to suspect a health risk.

De la Cruz said the MTA staff is reviewing the question of whether the same sensors can be relied upon to detect methane and hydrogen sulfide.

Franklin E. White, the MTA’s chief executive officer, said the matter has not been brought to his attention. “I’m confident my people will look at the situation and make sure our present arrangement is suitable,” White said.

The presence of hydrogen sulfide and methane were noted in reports prepared in advance of subway construction. De la Cruz said Friday that he believes the hydrogen sulfide is entering the subway through the many cracks in the tunnel and through breaches in a plastic gas and water barrier, installed at an extra cost of about $2 million a mile.

In addition to the health dangers hydrogen sulfide poses in air, the gas is extremely corrosive to cement and steel when contained in water. The potential effect of water on the durability of the $1.45-billion subway is expected to be addressed by a panel of three specialists appointed last fall by the MTA.

The panel, formed in response to a Times article reporting that numerous segments of the tunnels were built with concrete thinner than called for by design plans, is expected to announce its findings regarding the soundness of the structures within days. Investigations by the FBI and the inspector general’s office of the U.S. Department of Transportation also were launched.

Although the smell of sulfur was only faintly noticeable when the Downtown subway opened a year ago, the aroma over the past few months has become, for some, sickening.

“It gives you a headache,” a train operator said Friday. He is one of several people interviewed over the past months who have described symptoms that they believe are caused by the hydrogen sulfide. MTA officials said at least one train operator has filed a disability claim based on the smell.