On September 20, 2004, the National Institute for Occupational Safety and Health (NIOSH) received a health hazard evaluation (HHE) request from the International Brotherhood of Teamsters, Local 769. The union asked NIOSH to evaluate employee chemical exposures during sewage sludge de-watering activities at the Regional Sludge Facility in Vero Beach, Florida. Some employees reported health complaints such as cardiomyopathy, liver and neurological disorders. NIOSH investigators conducted a site visit, collecting personal breathing zone (PBZ) and general area air samples for hydrogen sulfide (H2S), other sulfur-containing compounds, and VOCs. The ventilation system used to control odors emanating from the sludge de-watering process was evaluated, and confidential medical interviews with current and past employees were conducted. Concentrations of sulfur-containing compounds (including dimethyl sulfide and hydrogen sulfide), as well as VOCs were extremely low or not detectable and were below occupational exposure limits. The odor control system in the sludge de-watering area appeared adequate. However, the ventilation system in the adjacent office consisted of a surface-mounted air conditioner/heater that recirculated the room air. This may have drawn odors from the de-watering process into the office through open doors. Confidential medical interviews and a review of incident reports were conducted to gather information on the health status of de-watering plant employees. Plant employees reported symptoms such as fatigue, headache, diarrhea, vomiting, shortness of breath, and chest tightness. The HHE request indicated that some employees had cardiomyopathy, liver and neurological disorders. Only one of the concerns, cardiomyopathy, had been reportedly diagnosed as work-related by the employee's treating physician. Our investigation and subsequent review of current scientific and medical literature do not support an association between the reported liver and neurological disorders with this particular work environment. NIOSH investigators conclude that no health hazard existed at this facility since the air contaminants measured on the days of our survey did not exceed any occupational exposure limits. However, the composition of the sludge constantly changes, so the type and concentration of potential airborne contaminants the sludge de-watering process emits do not remain constant. The result is a dynamic work environment with potential health hazards that may change from day to day. Improving office ventilation (see Recommendations section) should reduce the infiltration of airborne contaminants.