A Metro committee approved plans yesterday to remove hazardous metallic dust, including lead particles, from subway stations and tunnels.
The plans, expected to be endorsed soon by the transit authority's board of directors, have been under consideration since 1979, when a D.C. government study found "quite high" concentrations of metal dust in many rail stations.
Under the authority's new plans, a consultant would be hired to design special equipment to remove dust and other debris. The tunnel and station cleaners are expected to be built within the next two years at a cost estimated at $800,000.
The 1979 study found that particulate levels, including lead, exceeded federal standards set by the Environmental Protection Agency for ambient, or outdoor, air but did not violate less stringent limits established by the Occupational Safety and Health Administration.
Herbert T. Wood, a District health official who oversaw the 1979 study, said yesterday that the dust concentrations may pose a long-term health problem, but do not appear to represent an immediate hazard. Metro officials said recent studies indicated no significant change in dust concentrations.
Dust has also been blamed for several smoldering fires in the rail system, including a 1981 incident in an exhaust-fan room at the Judiciary Square station. Severe build-ups of dust on lighting fixtures and emergency signs in tunnels also have caused concern.
"In the event of an emergency, the decreased illumination could impede evacuation of passengers," said a Metro report released yesterday.
In addition, officials said, the dust mars the rail system's appearance and causes some electronic equipment to malfunction. Metro now has no tunnel-cleaning equipment, officials said. The authority's station cleaner was described as obsolete.
Lead concentrations are not caused by the subway system, officials said. Instead, the lead is mainly a byproduct of car exhausts, which get into the rail system through ventilation shafts and station entrances. Much of the dust has been identified as iron oxide, resulting from wear and tear on train wheels and tracks.