Cathay Pacific announces program to assure customers of cabin safety
When passengers perceive the cabin of an airliner as an incubator of deadly disease, they won’t fly. The drop-off in bookings from passengers fearful of a lethal lung disease has prompted the airline at the epicenter of the potential global pandemic to take aggressive action to reassure its customers.
Cabin health is just as much an issue of air safety as engine reliability and maintaining adequate separation among aircraft. Furthermore, there is a widespread public perception that cabin air and the close confines of a modern jetliner can facilitate the spread of disease. Even “potable” water carried aboard an airliner can harbor organisms of gastric distress. Anecdotal reports of catching a cold or suffering a short-term case of diarrhea contribute to the public’s perception that flying involves the risk of getting sick, not to mention the added risk of suffering a fatal embolism from deep vein thrombosis (DVT), an occasional byproduct of sitting in one position for hours on end.
Hong Kong-based Cathay Pacific announced last week the most comprehensive program yet seen by any airline to combat customer apprehensions about contracting sudden acute respiratory syndrome (SARS) during a flight. SARS is a deadly new form of pneumonia. Hong Kong is the locus of the SARS epidemic. Cases also have been concentrated in a number of other Asian locales: China’s Guangdong Province, Singapore and Vietnam. Because of the ease and speed with which people can travel internationally, SARS has the potential to be spread globally by infected passengers who can board in one of the Pacific rim countries, and debark a half-day later in the United States or Canada.
Similar concerns have been expressed about the speed with which multidrug-resistant tuberculosis (MDR-TB) can be spread across continents by air travel (see ASW, Jan. 3).
The fear of acquiring the disease by simply sitting next to an infected person has caused a plummet in international air travel. There is no doubt that SARS is spreading. Two data points, 24 hours apart last week, suggest that the disease may be far from contained. On April 7, the count was 2,671 SARS cases worldwide and 98 dead. On April 8, the count was 2,722 reported cases globally and 106 deaths, for a two percent and eight percent increase, respectively, in one day. Assuming a two percent rate of increase, the number of cases doubles in 35 days. The SARS counts, according to media reports, may be significantly under-reported.
Perception is reality
Even though there is no documented case of SARS being transmitted from an infected passenger to another in flight, the received wisdom is that SARS is spread through droplet transmission (e.g., coughing, sneezing). Since air travel packs people closely together, there is a widespread perception that the seating density involved in air travel and the recirculated cabin air presents a greater risk of infection than being on the ground.
When it comes to any fear of flying, passenger perception is reality. And it is for this reason that load factors have fallen and flights are being cancelled wholesale.
As a matter of customer assurance, if not customer care, Cathay has mounted a broad-front campaign to ensure the health of its passengers (and to reassure its aircrews with a series of proactive technical memoranda). The action agenda includes everything from denied boarding of passengers manifesting SARS symptoms to complete disinfection of the airplane should a case occur in flight. The Cathay campaign is similar but more detailed than the approach taken at some other airlines. Both carriers are stressing to aircrews and other employees the importance of hand washing.
“Frequent hand washing is the single most important thing airline staff can do,” said Judith Murawski, an industrial hygienist with the Association of Flight Attendants (AFA).
Issues to consider
Whether Cathay and other carriers need to take even further measures is a matter of discussion. Farrol Kahn, director of the UK-based Aviation Health Institute, believes filters should be replaced more frequently and cabin cleaning should be done immediately after a case of exposure. He believes that HEPA (high efficiency particulate air) filters should be replaced immediately on aircraft with suspect SARS. Kahn added that without more aggressive action, “I am afraid that this could become a pandemic if it spreads.”
Over the long term, it may be possible to wipe out virtually all bacteria and their much smaller viral cousins from the cabin air. The issues run the gamut from the efficacy of face masks to improved air system designs in airliners:
Interpersonal infection. SARS does not appear to be readily transmitted from person-to-person, according to Bob Valente, vice president of global operations for MedAire. The Tempe, Ariz., based company provides in-flight medical guidance to client airlines. Common colds can be passed from one person to another at a rate of about five percent, and SARS appears to be transmitted at a lower rate, he said.
“There are no confirmed cases of transmission aboard aircraft,” he declared.
Meanwhile, his company is “taking a retroactive look back to November to see if there are any trends.” Valente said his company received 23 calls in March – an average of about one per day – on suspected SARS-suffering passengers. Those calls were either from boarding gates or from airborne aircraft. Of those, none was a confirmed SARS infection. Nonetheless, the concern seems to be mounting. So far this month MedAire is receiving an average of two to three SARS-related calls per day, Valente said.
Face masks. One pilot suggested putting kits on aircraft with enough surgical masks for all passengers and crew:
“In the event of a suspected SARS case on the aircraft, the passengers would at least feel they have some protection. Let’s face it, SARS is now a quarantinable disease. If suspected on board, the aircraft and all the passengers will be quarantined, at least temporarily. If passengers had masks, they would at least feel like something was being done, and [they] probably would not feel so helpless.”
This course of action is based on the presumed effectiveness of the masks. The thin ones worn most often will catch coughed or sneezed droplets, but they may only be useful in protecting the wearer for 3-5 minutes. By this time, the moisture in one’s exhaled breath saturates the mask and turns it into a receiving conduit for droplet borne or airborne viruses. This information was mentioned fleetingly at the beginning of the SARS outbreak but does not appear to have been mentioned in more recent advisories – perhaps because widespread mask wearing might actually help to spread the disease. As one source pointed out, look closely at most recommendations, which suggest only that “anyone who believes they may have been infected should wear a mask.”
Air supply. Kahn said, “We’d really like to go back to 100 percent fresh air to reduce the likelihood of cross-infection.” He is calling for a return to the air standards of 1960s and 1970s-era jets, most of which featured 100 percent fresh air, although the Boeing B747-100 featured a mix of 26 percent recirculated air. Virtually all of the jets entering service in the 1980s, 1990s and today feature about 50 percent-recirculated air (see ASW, Sept. 23, 2002).
The AFA’s Murawski took a somewhat different tack. “If the recirculated air is filtered properly, it can help,” she said. However, she added, the HEPA filters advertised as contributing to healthy cabin air work most effectively against the SARS virus when it is contained in small droplets or is floating in clusters through the air. Viruses travelling singly can slip through even a HEPA filter, she said. In this case, she added, “you run the risk of recirculating pathogens.”
Dr. Martin Hocking, an expert on cabin air quality at Canada’s University of Victoria, said the rate of air exchange, such as the once every three to five minutes advertised by Cathay Pacific, is not the best measure of airflow. Rather, he suggested, “aircraft operators should provide a minimum of at least 15 ft3/minute per passenger of outside air at all times, whether or not some of the air is recycled.”
As Hocking has shown before in this publication, an airflow exchange rate of three to five times per minute equates to a flow of about 10 ft3/minute per person (see ASW, Sept. 23, 2002). That rate is considerably below the 15 ft3/minute per person recommended by the American Society of Heating, Refrigerating and Air- conditioning Engineers (ASHRAE) as the minimum for enclosed spaces in buildings. Hocking estimates that this rate of outside airflow can be done at a cost of about 18 cents per passenger per hour, or about $1.44 for a 10-hour flight.
“An expander turbine operated on the exhaust air to compress a part of the outside air intake could help to decrease the energy costs,” he suggested, adding, “so could recirculation of the relatively pristine flight deck.”
Bug-free air. Hocking also pointed out that the vaunted HEPA filters might not prevent contagion from a viral-borne disease like SARS. The filters will efficiently remove bacteria, which lie in the 0.5-15 micron (�m) diameter range. Viruses, however, are much smaller, varying in size from 0.003-0.05 �m. “They are much more difficult to trap,” Hocking said. He urged priority be given to maintaining a minimum airflow of 15 ft3/minute per passenger.
A Cathay Pacific official said the HEPA filters are 99.9 percent effective at trapping 0.003 �m particles, thereby capturing droplets “which are the life support systems for viruses.” The official added, “Viruses that are too small to be trapped by the filter pore size become stuck onto the filter material through Brownian movement. This makes them oscillate, rather than traveling in a straight line. Hence, the risk of airborne spread of viruses is minimized.”
As for the airflow rate, the Cathay official said, “Our cabin airflow is managed to its optimal condition to avoid turbulent airflow that might increase the distribution of a virus droplet aerosol.”
Hocking noted that ultra low particle air filters (ULPA) are available, which perform better against viral particles than HEPA filters. They are more expensive, but wider use could bring the cost down.
Other sources say various methods have yet to be exploited to kill all bacteria and viruses as they pass through the plenum of the air conditioning systems. Intense ultraviolet light and air circulating at a rate of about 60ft3/passenger per minute would virtually stop the spread of disease according to one source. Ozone, introduced at the beginning of the plenum and eliminated at the back end, also would kill all organisms. The ozone approach could be done for “pennies per ticketed passenger,” this source said. He added, “In tests we ran, 100 percent of the ozone decayed in the plenum, with pure oxygen mixed into the outflow.”
Hocking agrees that both concepts are viable, and at low cost. More particularly, he believes ultraviolet light produced by a 50-watt mercury arc lamp in the 253.7 nanometer wavelength – which is lethal to microorganisms – would do the job. Given the low power of the light, Hocking estimates this air sterilizing technology would cost about 2.5 cents per passenger for a 10-hour flight. Costs to modify the aircraft are not included, he hastened to add.
The point coming through, though, is that modest improvements to cabin ventilation systems could put pathogens at peril, not passengers.
>> Murawski, e-mail [email protected]; Hocking, e-mail [email protected]; Kahn, e-mail [email protected] <<