Airplane Cabin Air May Be Unhealthy

By Cat Lazaroff

WASHINGTON, DC, December 11, 2001 (ENS) - Holiday travelers may run into unhealthy air while in the air, suggests a new report by the National Research Council. The researchers conclude that air in airplane cabins sometimes fails to meet federal health standards, and urge the Federal Aviation Administration to investigate whether regulations governing the air quality are adequate to protect public health.

More than a decade after the Federal Aviation Administration (FAA) banned smoking on all domestic airline flights, passengers and cabin crew still frequently complain that the air on planes is unpleasant and may be unhealthy. The air is a mixture of outside and recirculated air, similar to that in many homes and offices.

But the proximity of passengers to one another, the need for cabin pressurization, low humidity, and potential exposure to common chemical and biological contaminants - all in an enclosed structure - makes the cabin environment unique.

The invisible air filling airline cabins may contain hidden toxins, a new study suggests (Photo courtesy Neales Aircraft Interiors Ltd)

The committee that wrote the report noted that the number of air passengers worldwide has nearly quadrupled in the last 30 years to about 1.5 billion a year. Along with this increase, the number of older and younger passengers has gone up, including children, infants, and people with preexisting medical conditions.

Because few data have been collected regarding the health effects on passengers and crew of unhealthy cabin air, it is difficult to prove that poor air quality on planes causes adverse health effects, the report says. But some evidence suggests that environmental factors inside commercial aircraft may be responsible for particular health complaints among passengers and crew.

Ozone pollution may cause respiratory problems and decreased oxygen pressure may present a health risk for people with certain pre-existing conditions, such as cardiac and respiratory diseases, the NRC notes. Although the FAA requires that ozone concentrations be maintained within specified limits, studies indicate that ozone levels on some flights may exceed FAA and U.S. Environmental Protection Agency standards.

Elevated ozone concentrations at ground level have been associated with decreased lung function, airway irritation, exacerbation of asthma, and impairment of the immune system. The NRC committee said the FAA should take steps to ensure that its current regulation for ozone - which limits average concentrations to less than 0.1 parts per million above 27,000 feet, and less than 0.25 parts per million above 32,000 feet - is met on all flights.

Aircraft should be either equipped to prevent ozone from entering the cabin or prohibited from flying at altitudes where high ozone concentrations are likely to occur, the report says. To ensure compliance, the FAA should monitor flights to verify that ozone controls are working properly.

The committee was also concerned about adverse health effects that may result from what is known as the reduced partial pressure of oxygen. At cruising altitudes, oxygen pressure in the atmosphere is too low to support human life, so the cabin must be pressurized. Current FAA regulations require that cabin air pressure must be no lower than the air pressure that naturally occurs at 8,000 feet.

Medical experts do not know whether that regulation is enough to protect all passengers and crew from reduced partial pressure of oxygen, which typically does not cause problems for healthy people, but could pose risks for those who have conditions that may reduce oxygen circulation through the bloodstream. People with pulmonary or cardiac disease, for example, might experience symptoms such as headache, lightheadedness, dizziness, fatigue and numbness.

The National Research Council suggests that the FAA may need to adopt new measures to insure the safety of airline passengers (Photo courtesy NASA)

Low ventilation rates in buildings have been linked to increases in health problems and sick leave. On airplanes, the spread of infectious agents such as the viruses which cause the common cold appear to be caused by the high density of people, rather than inadequate ventilation, the committee concluded.

An aircraft's environmental control system can be a source of contamination during abnormal operations when engine oil, hydraulic fluids, or de-icing solutions enter the cabin through the air supply system in what is called "bleed air." These toxic substances have not been monitored enough to assess their potential health risks, the committee said.

But many crews and passengers have reported incidents of smoke or odors within cabins. The committee said FAA should study the need for and feasibility of installing equipment to remove vapors and particles from air supplied by the environmental control system on all flights.

Two other environmental factors that may contribute to passenger and crew complaints about air quality are low relative humidity and pesticide use. Low relative humidity occurs on almost all flights and might cause some temporary discomfort, such as drying of the eyes, nose and skin. Exposure to pesticides that are routinely sprayed on some international flights can cause skin irritation and are reported to be toxic to the nervous system.

Reiterating a recommendation made in a 1986 Research Council report on cabin air quality, the committee called for a regulation requiring the removal of passengers from an aircraft within 30 minutes after the ventilation system fails or is turned off on the ground. Air conditioning also should be required to be kept on continuously during warm weather, the report says.

Cabin crews should be trained to recognize and respond to asthma attacks and other serious allergic reactions that can be triggered by the presence of airborne allergens in the cabin, the committee said.

The report was sponsored by the Federal Aviation Administration.