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 2011-0128-3166, 2013 Feb; :1-26
NIOSH received a request for technical assistance from OSHA to evaluate employee health effects after a chlorine gas release in a poultry processing plant in Arkansas. On the morning of June 27, 2011, human error resulted in the mixing of an acidic solution of Fresh FX, an antimicrobial used in poultry processing, with a sodium hypochlorite solution. This mixing of chemicals caused a release of chlorine gas into the plant. About 600 employees who were at work at the time of the release were evacuated. We made three site visits to evaluate the employees who were at work on the morning of the release. Five hundred forty-five employees participated in part or all of our evaluation. Of those who participated in our evaluation, 195 reported seeking medical care, 152 reported being hospitalized, and the company reported that 5 were admitted to intensive care units immediately after the incident. On our first site visit in June 2011, we spoke with an employee involved in the chlorine release and the managers about what led to the event. We administered questionnaires about medical history and symptoms in the days following the incident to employees in Spanish, English, and Marshallese. On the second site visit in November 2011, we evaluated participants for symptoms of asthma (because a single high level exposure to an irritant like chlorine can cause a type of asthma called RADS) and PTSD approximately 4 months after the release. On our third site visit in January 2012, we did spirometry and methacholine challenge tests on participants who reported asthma symptoms at the second site visit, but had no history of asthma prior to the release. Five hundred twenty-three participants were present at the first site visit and at work on the morning of the chlorine release. An additional 22 were later identified as present the morning of the chlorine release but not during the first site visit. Of the 545 participants, 60% were female, 17% primarily spoke English, 68% primarily spoke Spanish, 12% primarily spoke Marshallese, and 3% spoke other languages. Eleven percent of participants were current smokers, and 6% reported a history of asthma. Strength of chlorine odor was used as a surrogate for intensity of exposure. Of the 542 participants who responded to the question of whether or not they smelled chlorine, 29% reported not smelling chlorine, and 22% reported a light odor, 7% a moderate odor, and 42% a strong odor. Of the 523 participants who were present at the first visit, 213 (41%) reported a strong chlorine odor. Their most commonly reported symptoms within 24 hours of the chlorine release were burning throat, headache, burning eyes, and cough. Headache, burning throat, and cough were the most common symptoms reported 3-5 days post-release by those reporting a strong chlorine odor. Two hundred forty-five participants (47%) present at the first site visit reported lower respiratory tract symptoms (cough, shortness of breath, chest tightness, or wheeze). These 245 plus 22 additional participants who had not yet returned to work at the time of our first site visit were asked to complete the asthma symptoms questionnaire during the second site visit. Of the 240 who did so, 116 (48%) had one or more asthma symptoms in the 2 weeks prior to that site visit. Overall, 106 (22%) of 493 participants at the second site visit reported symptoms consistent with PTSD approximately 4 months after the release. The prevalence of PTSD symptoms increased with increasing strength of reported chlorine odor (from 4% among those who reported not smelling chlorine to 37% among those reporting a strong odor of chlorine, P<0.01). At the third site visit we did spirometry on 101 subjects who reported asthma symptoms at the second site visit and had no history of asthma prior to the release. Methacholine challenge testing was done on 78 participants with a forced expiratory volume at 1 second at or above 70% (this means they did not have significant obstruction) and no medical contraindications for testing. Three had borderline bronchial hyperreactivity, two had mild bronchial hyperreactivity, and one had moderate to severe bronchial hyperreactivity. Mild, moderate, and severe bronchial hyperreactivity are consistent with RADS, or asthma. The unintentional release of chlorine gas at this plant posed a serious health hazard to employees. Three employees developed RADS, and more than 100 developed symptoms of PTSD.