In May 1998, the National Institute for Occupational Safety and Health (NIOSH) received a confidential request for a health hazard evaluation (HHE) at the Mueller Company facility in Chattanooga, Tennessee. The HHE requesters expressed concern over exposures to formaldehyde, phenol, xylene, isocyanates, toluene, naphthalene, carbon monoxide, trimethyl benzene, cumene, lead, and silica in the Pepset, No- Bake, shell core, green sand, and iron pouring areas; silica and iron dust in the cleaning room, shell core, green sand, and machining areas; oil mist from hydraulic tanks; and asbestos from the concrete plant floors. The HHE request listed respiratory symptoms and possibly increased cancer rates as health concerns. On March 31-April 1, 1999, NIOSH investigators conducted a walk-through survey, reviewed material safety data sheets and environmental sampling data, and interviewed 22 employees about the work environment and possible work-related health effects. Employer records were examined to determine the number of cancer cases among employees. On August 8-9, 2000, environmental monitoring was conducted for phenol, volatile organic compounds, Stoddard solvent, formaldehyde, toluene, cumene, ammonia, trimethyl benzene isomers, 4,4'-diphenylmethane diisocyanate (MDI), and hexamethylenetetramine (HMTA). Formaldehyde was detected at low levels in some air samples. MDI and HMTA were detected at low concentrations. Phenol, Stoddard solvent, toluene, cumene, ammonia, and trimethyl benzene isomers were detected at levels below current occupational exposure limits. Smoke released from the shell core ovens was found to move through the employees' breathing zones before being exhausted through the canopy hood. Twenty-one (4.4% of the 475 production workers) were interviewed. Among those interviewed, most employees who had prolonged exposure to emissions from the Pepset and No-Bake coremaking/molding operations reported transient respiratory irritation. The workers who worked in these areas on a regular basis generally did not report persistent respiratory illnesses that they associated with their workplace exposures. Review of the medical records of six employees who reported work-related respiratory illnesses found that some workers had worsening of pre-existing chronic respiratory conditions, although the cause of this was not determined. Information concerning cancer diagnosed among Mueller Co. employees did not reveal an unusual number or pattern of cancers; however, it is not possible to determine the cause of the cancers that developed among the employees. All of the substances sampled in the employees' personal breathing zones had concentrations below the occupational exposure limits. The 16 identified cancer cases were of 10 different types, and there was not enough information available to determine if the cancers resulted from workplace exposures. Among the small number of employees interviewed, most who had long term exposures to emissions in the Pepset and No-Bake coremaking/molding areas reported temporary respiratory irritation. Recommendations are provided for additional monitoring for MDI, formaldehyde, and phenol, use of gloves, reporting of health symptoms to medical personnel, and local exhaust ventilation in the shell core area.