On January 23, 1998, the National Institute for Occupational Safety and Health (NIOSH) received a confidential employee request for a health hazard evaluation (HHE) at Exempla Health Care Facility/St. Joseph's Hospital in Denver, Colorado. The request stated that hospital employees experienced facial flushing, rhinitis, sneezing, itching and watery eyes, and fainting while at work. According to the request, the exposure thought to cause the employees' health problems was latex protein from powdered natural rubber latex (NRL) gloves. The NIOSH investigation consisted of concurrent medical and industrial hygiene evaluations during the weeks of July 13-16, 1998, and August 3-6, 1998. Additional medical evaluations were completed November 9-13, 1998. The medical evaluation included a self-administered questionnaire and blood tests for total IgE and latex-specific IgE. The industrial hygiene evaluation consisted of air, surface, and bulk dust sampling to evaluate the presence of latex proteins within the hospital environment. The overall prevalence of latex sensitization (defined by the presence of latex-specific IgE) was 10.5% (56/531). There was no statistically significant difference in the prevalence of latex sensitization between employees who wear latex gloves (10.6% or 28/264) and those who do not wear latex gloves (10.6% or 27/255) (p=1.0). There was also no statistically significant difference in the prevalence of latex sensitization between employees who reported current latex glove use or having worn at least one pair of latex gloves per day at another job or in training (i.e., ever having occupational latex glove use), with a prevalence of 11.0%, and those who reported never having occupational latex glove use, with a prevalence of 8.9% (p=0.5). Reporting of work-related hand dermatitis was more common among those who currently wore latex gloves (23.4%) than among those who did not (4.9%) (p < 0.01), as were rhinoconjunctivitis (16.3% and 7.9%, respectively, p < 0.01) and hand urticaria (9.9% and 2.1%, respectively, p < 0.01). There was no significant difference by latex glove use in the reporting of work-related asthma or general urticaria. There was no statistically significant association between any of these symptom complexes and latex sensitization, although hand urticaria and hand dermatitis were more prevalent in those who were sensitized. Atopy (history of allergic rhinitis, asthma, or atopic dermatitis) was significantly associated with latex sensitization; 83.6% of those with latex sensitization were atopic, compared to 58.2% of those who were not sensitized (p<0.05). Twenty-seven percent of those with latex sensitization reported no Type I allergic symptoms, i.e., urticaria, rhinoconjunctivitis, or asthma, either at work or home, while sixty-three percent reported no work-related Type I symptoms. A total of 23 area air samples for NRL allergen were collected in clinical (16) and non-clinical (7) areas of the hospital. Five of the seven samples collected in the non-clinical areas had no detectable NRL protein. One sample, collected in inpatient admitting, had a concentration between the limit of detection (LOD) and the limit of quantitation (LOQ), that is, a trace concentration. One sample, collected in the medical records area, had a quantifiable concentration, 0.26 nanograms per cubic meter (ng/m3). Sixteen air samples were collected in clinical areas of the hospital. Nine of sixteen samples (from a variety of clinical areas) had NRL protein concentrations ranging from 0.41 to 3.33 (ng/m3). Four samples contained trace concentrations, and three samples had no detectable NRL protein. v Nineteen surface dust samples were collected from ceiling tiles and air handling unit (AHU) plenums. Ten samples were collected from clinical areas and nine from non-clinical areas. In the non-clinical areas, no NRL was detected in seven of the samples, one had a trace amount, and one sample from an AHU serving the inpatient admitting had 368 nanograms of NRL per 100 square centimeters (ng/100 cm2). In the clinical areas, 7 of 10 surface dust samples had no detectable NRL protein. One sample collected from the back of a ceiling tile in the labor and delivery (L&D) suite 242 had 118 ng/100 cm2, and two surface samples collected inside AHUs contained 1,022 and 3,952 ng/100 cm2. Two filter dust samples were collected from AHUs serving non-clinical areas of the hospital; neither had detectable NRL protein. Five samples of filter dust collected from AHUs serving clinical areas of the hospital had NRL protein concentrations ranging from 4,433 ng/gram of dust (ng/gm), from an AHU which serves the emergency department (ED), to 83,682 ng/gm, from an AHU which serves the labor and delivery areas. We found that levels of airborne, surface, and filter dust latex proteins were higher in the work areas of the employees who were not sensitized to latex than those who were sensitized, although these differences were not statistically significant. We found that neither current nor past occupational use of latex gloves was associated with latex sensitization in this study population. Latex glove use, however, was associated with reporting of work related rhinoconjunctivitis, hand urticaria, and hand dermatitis. Airborne natural rubber latex protein levels were very low, but there was a significant amount of latex protein on filters in the ventilation system. Exposure to filter dust could present risks to individuals who change AHU filters (e.g., maintenance workers), or to other workers if NRL proteins were to be released into the hospital environment. Recommendations include the use of nonlatex gloves for those who do not encounter infectious materials, and the use of low-protein, powder-free latex gloves for those who do encounter infectious materials; education for employees about latex allergy; and re-assessment of prevention strategies if a worker is diagnosed with latex allergy.