The United Auto Workers and United Steelworkers of America asked the court to compel the U.S. Occupational Health and Safety Administration to lower the current standard, which is 5 milligrams of oil mist per cubic meter of airduring an eight-hour day.

Lawyers for the unions and the agency pleaded their cases and answered jurist questions in a hearing that lasted 45 minutes, according to Jeffrey L. Leiter, legal counsel for the Independent Lubricant Manufacturers Association. The court had previously denied a request by ILMA and other trade groups to join the suit as co-defendants, but it did accept friend-of-the-court briefs from them.

The unions contend that allowable levels of oil mist exposure cause a variety of health problems, including cancer, skin ailments and pulmonary diseases. OSHA says the scientific evidence on effects of oil mist is inconclusive, and that the agency has more important priorities.

Leiter said the judges generally raised two lines of question during the hearing. One asked under what conditions courts should interfere with an agencys prerogative to set its own agenda. The unions argued that OSHA has ignored the mist issue so egregiously that intervention is called for. The judges also probed the attorneys positions on interpretation of the scientific evidence regarding oil mist.

The court is expected to rule on the suit in six to eight weeks, Leiter said.