NIOSH Evaluates Helicopter, Vehicle Exhaust Exposures at a Hospital
A hospital should consider efforts to reduce the chances for helicopter and other vehicle exhaust to enter its ventilation systems, NIOSH recommends in a recently published health hazard evaluation (HHE) report. Agency staff evaluated the acute care hospital following a confidential request from employees who were concerned that exhaust entering the building could be contributing to cases of a rare cancer among individuals working in a particular section of the hospital. The report notes that three employees of the hospital were diagnosed with primary mediastinal B-cell lymphoma (PMBCL), “a rare, fast-growing subtype of … the most common type of non-Hodgkin lymphoma in the United States,” in recent years—one in 2023 and two in 2024. Three diagnoses are more than expected based on national cancer data, which indicates around two to three cases of PMBCL out of a million people in the general population are to be expected per year, the report explains. While NIOSH did not have enough information to draw conclusions regarding the causes of cancer among the three affected employees, the agency’s report urges the hospital to consider engineering controls to address potential carcinogenic exposures stemming from exhaust in the building’s heating, ventilation, and air-conditioning systems.
NIOSH investigators found a variety of evidence showing that helicopter exhaust could enter the hospital’s HVAC systems. For example, due to the location of the helipad, helicopters arrived and departed within 100 to 300 feet of outdoor air intakes and some of the building’s entrances, and employees complained of odors shortly after the arrival or departure of helicopters. Air monitoring conducted by NIOSH to measure levels of airborne particulates “showed that the number of airborne particles increased and peaked within minutes after a helicopter landed on the helipad before decreasing to background levels within 20 minutes,” according to the report. Air monitoring results also showed an increase in the number of airborne particles after a helicopter departed, though the change was less pronounced. The report notes that the type of air filters installed in the outdoor air intakes—filters with activated carbon and potassium permanganate—may not be fully effective in removing odors of helicopter exhaust “because of limited contact time between the air stream and the filter.”
Additional potential sources of exhaust include loading dock doors that NIOSH staff noted were left open when no trucks were present. The doors were equipped with air curtains that were not in use, so outdoor air containing exhaust from trucks and helicopters could potentially enter the building and move to other areas of the hospital that way, the report explains.
NIOSH recommends that the hospital consider ways to increase the distance between the helipad and the building’s outdoor air intakes and explore strategies such as air filters and minimizing helicopter idling time to reduce the effects of exhaust on indoor air quality. In the loading dock area, the agency recommends the hospital keep the doors closed when the loading dock is not in use and ensure that the air curtains are used when the doors are open.
“Engineering controls that reduce the potential for helicopter exhaust to enter the ventilation systems, along with continued communication with employees, are expected to be the most effective strategies for addressing these concerns and promoting the continued health and safety of employees at the workplace,” the report concludes.
Further findings from NIOSH’s evaluation and details on the agency’s recommendations can be found in the full HHE report (PDF).