Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, HETA 2000-0410-2891, 2002 Aug; :1-39
On August 28, 2000, the National Institute for Occupational Safety and Health (NIOSH) received a confidential request for a health hazard evaluation (HHE) at STN Cushion Company (STN) in Thomasville, North Carolina. The request was submitted by employees concerned about health effects potentially associated with 1-bromopropane (1-BP, also called n-propyl bromide) and 2-bromopropane (2-BP, also called isopropyl bromide) exposures during the spray application of an adhesive. The employees' concerns centered around neuropathy (abnormal nerve function), weakness and numbness in the lower extremities, dizziness, and headaches. Site visits were conducted in November 2000 (exposure monitoring and informal [confidential] employee interviews), April 2001 (ventilation assessment), and July-August 2001 (medical evaluation and repeat exposure and ventilation evaluations). After April 2001, STN improved the local ventilation in the area of concern based on recommendations made by the NIOSH ventilation engineer. During both exposure assessments, employees were monitored for full-shift 1-BP and 2-BP inhalation exposure. Short-term (15-minute) and ceiling (5-minute) 1-BP and 2-BP inhalation exposure measurements were also collected from the adhesive sprayers (Sprayers). Area air sampling for 1-BP and 2-BP was conducted also. The ventilation assessments included an evaluation of local exhaust ventilation at the workstations (consisting of spray tables and spray booths). The medical survey, consisting of a questionnaire, a complete blood count, start-of-week and end-of -week urine analysis for bromine, and a battery of neurobehavioral tests, was performed on all employees within the facility who were willing to participate. Additionally, a reproductive study was performed which included all eligible female employees who were willing to participate. The purpose of the medical survey was: 1) to assess whether hematological (blood), neurobehavioral (postural stability and psychomotor ability), and reproductive effects might be associated with 1-BP exposure; 2) to assess whether health effects reported on the questionnaire were associated with 1-BP exposure; and 3) to evaluate urinary bromine levels at the start and end of the week and compare these results to airborne 1-BP levels (to see if urinary bromine concentration can be used as a biomarker of exposure). The "exposed" population consisted primarily of those employees who worked in the Fabrication area performing spraying activities. The comparison ("less exposed") population consisted of all other employees who worked in the facility. At the first site visit the mean (average) airborne 1-BP exposure for the Sprayers was 65.9 parts per million (ppm) (range 41.3 to 143.0 ppm). The mean full-shift airborne 2-BP exposure for Sprayers was 0.66 ppm (range 0.33 to 1.35 ppm). At the second site visit, the mean concentration of 1-BP for the Sprayers increased from the first (16.6 ppm) to the third (23.3 ppm) day of sampling, but was lower than the concentration found during the first site visit. Two individual spray booths (Stations #6 and #11) did, however, yield a 3-day average exposure above a recommended level of 25 ppm. The initial ventilation assessment revealed that all of the workstations had exhaust flow rates which were lower than recommended values. Enclosure of spray tables led to improved ventilation at each of the workstations; however, factors were identified which would lead to further improvement in ventilation effectiveness. Of the 84 individuals employed at STN at the time of the survey, 32 (38%) volunteered to participate in the medical survey. The symptoms most often reported from all participants included: headache (reported by 48%), trouble falling asleep or staying asleep (reported by 28%), dizziness or feeling "off balance" (reported by 25%), and blurred vision (reported by 24%). Two of the symptoms in the questionnaire, blurred vision and dizziness or feeling "off-balance," were significantly more common among the exposed versus the comparison groups. Of the exposed employees, five of six reporting blurry vision and four of six reporting dizziness noted symptom improvement during time away from the work environment. All of the results for blood indices were within the normal value ranges provided by the testing laboratory; however, because of the small number of blood specimens available for analysis, a statistical determination regarding the blood tests and their relationship to 1-BP exposure could not be made. The start-of-week and end-of-week urine bromine concentrations for the exposed group were both significantly higher than the corresponding values for the comparison group. We found no significant elevation in urine bromine level in the end-of-week urine samples compared to the start-of-week urine samples - in other words, we did not detect an increase in urine bromine from the first urine sample (start-of-week) to the second urine sample (end-of-week). Urinary bromine concentrations were highly correlated to the airborne concentration of 1-BP, and it was concluded that urinary bromine may be a good indicator of 1-BP exposure. A total of 30 participants participated in the neurobehavioral testing. We found no differences in the Postural Stability test results between employees in the exposed and comparison groups. Of the 16 Psychomotor Ability parameters tested, 3 demonstrated a statistically significant difference between the exposed and comparison groups. Specifically, we found indications of increased tremor in the right hand of participants in the exposed group. Although we cannot determine the cause of the tremor observed by our testing, we believe that this unilateral tremor is likely due to muscle fatigue (a known cause of the type of tremor observed), as 1-BP exposure, if sufficient to cause tremor, would likely cause bilateral tremor (tremor on both sides) due to a potential mechanism involving the central nervous system. And lastly, we collected insufficient data among exposed workers in the reproductive evaluation part of the survey to be able to make any comparisons between exposed and comparison workers in that portion of the HHE. Although we found the Sprayers at STN to have greater exposure to 1-BP than other employees, we are unable to determine if these exposures constitute a health hazard. By enclosing the spray booths in the Fabrication area, STN has dramatically reduced Sprayers' exposures to 1-BP and 2-BP. Because of symptoms consistent with excessive solvent exposure reported among the exposed workers, concerns raised in other studies, and the lack of definitive information, efforts should continue to minimize 1-BP and 2-BP exposures. Recommendations are provided in this report to assist in this, and include improving the ventilation of spray booths #6 and #11 as well as improving personal protective equipment use.