Health hazard evaluation report: HETA-2003-0346-2969, Salvation Army Harbor Light Center, St. Louis, Missouri.
On August 20, 2003, the National Institute for Occupational Safety and Health (NIOSH) received a request for technical assistance concerning a tuberculosis (TB) outbreak at the Salvation Army Harbor Light Center in St. Louis, Missouri. The request was made by the Division of Tuberculosis Elimination (DTBE), National Center for HIV, STD and TB Prevention (NCHSTP), which was investigating the outbreak at the request of the Missouri Department of Health and Senior Services (MO DHSS). Between February 2001 and August 2003, MO DHSS had identified a total of 19 cases of active TB linked to the Harbor Light shelter. NIOSH investigators made five visits to the Salvation Army Harbor Light Center between September 2003 and October 2004. Thorough inspections of the shelter air-handling units (AHUs) were conducted, and ventilation air flow rates were monitored. Tracer gas studies were conducted to calculate air exchange rates and describe air flow patterns. This work revealed that the majority of the AHUs at the shelter were in poor repair and in need of cleaning and maintenance. Following our recommendations, the shelter improved the overall cleanliness of the AHUs and has instituted regular maintenance procedures. The filters in all AHUs were upgraded to MERV 11 filters from the original MERV 7 filters. Despite some AHU improvements in providing more outside air to the clients inside, some areas of the shelter are still not consistently capable of meeting the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommendations for outside air supply. Ultraviolet germicidal irradiation (UVGI) fixtures were installed in all of the highest-risk areas of the shelter to help kill or inactivate airborne Mycobacterium tuberculosis. We continue to recommend that all areas of the shelter should be brought into compliance with applicable ASHRAE recommendations for outside air supply. Thorough testing and balancing of the AHUs, along with the proper establishment of setpoints for each AHU, should be completed and documented. Detailed operations and maintenance plans should also be developed to keep the ventilation systems and UVGI fixtures operating properly. Preexisting conditions (prior to September 2003) relating primarily to inadequate fresh air supply and suboptimal filtration of air in the shelter's ventilation systems could have contributed to airborne M. tuberculosis transmission that resulted in the TB outbreak of 2001-2003.