Wednesday October 21 2015
Aeroplanes waiting for takeoff can release a great deal of carbon monoxide
"People who live within six miles [of an airport] have higher levels of asthma and heart problems," the Daily Mail reports after a US study has suggested exposure to carbon monoxide from planes may impact on health. This potential pollutant is thought to occur when planes are taxiing on busy runways.
Researchers used data to look at the link between exposure to daily pollutants and health in areas close to the 12 biggest airports in California. Health outcomes were measured using data for overnight hospital admissions and emergency visits from residents within 10km of these airports.
An association was found between higher levels of carbon monoxide and increased hospitalisation rates for respiratory conditions such as asthma, as well as heart-related issues.
But this study is not able to prove cause and effect, and there may be other factors at play, such as higher levels of urbanisation in areas near airports.
Still, these findings are in line with other research, which suggests increased pollution levels are associated with poorer health outcomes. The results are likely to add fuel to the debate about whether Heathrow or Gatwick airports should be expanded with a new runway.
Where did the story come from?
The study was carried out by researchers from Colombia University and the University of California, and was supported by the Robert Wood Johnson Foundation.
It was published in the peer-reviewed journal The Review of Economic Studies on an open access basis, so it can be downloaded free as a PDF.
This study has been reported accurately by the Daily Mail, but the paper does not note any of the study's limitations.
What kind of research was this?
This data analysis study aimed to assess the link between variations in airport congestion and health outcomes related to daily carbon monoxide exposure, particularly respiratory conditions.
While this type of study can draw links for further investigation, it can't prove pollution was responsible for the health outcomes. However, it is important to note pollution is a known risk factor for respiratory and heart-related conditions.
What did the research involve?
Air pollution and the link with respiratory and heart-related issues were investigated in the areas surrounding the 12 largest airports in California.
This study used a number of sources to obtain data for analysis for the period 2005-07. Airport traffic data was found in the Bureau of Transportation Statistics (BTS) Airline On-Time Performance Database, which contains flight information for passenger aircraft, such as departure and arrival times, and airports.
The measure of air traffic for 12 major airports in California consisted of:
- the time aeroplanes spend between leaving the gateway and taking off from the runway
- the time between landing and reaching the gate
Data for pollution around the airports was collected from the California Air Resource Board (CARB), which includes hourly and daily pollution readings.
The weather effects on health were controlled for in the analysis by using temperature, precipitation and wind data in distributing airport pollution from airports. Wind data was obtained from the National Climatic Data by the National Oceanic and Atmospheric Administration's (NOAA) hourly weather stations.
Health effects were measured using the California Emergency Department and Ambulatory Surgery data for emergency room visits, and inpatient discharge data for overnight hospital admissions. Daily admissions of all people with a diagnosis associated with respiratory illnesses were included.
Statistical modelling was performed to estimate a number of links, including:
- pollution levels and hospitalisation
- increased levels of airport traffic
- congestion and local measures of pollution
- health and air pollution
What were the basic results?
The study found a large proportion of local air pollution is caused by congestion from airports, and the average area of impact is a 10km radius, with levels of carbon monoxide fading with distance.
In terms of the link with health outcomes, admissions for respiratory problems and heart disease were strongly related to these pollution changes. A one standard deviation increase in area-specific pollution levels increased asthma counts by 17% of the baseline average.
It also increased admissions for respiratory problems, such as chronic obstructive pulmonary disease (COPD), by 17% and heart problems by 9%. Changes in pollution levels had a negative impact on the whole population, but greater effects were seen in children and the elderly.
How did the researchers interpret the results?
The researchers concluded that, "Daily variation in ground level airport congestion due to network delays significantly affects both local pollution levels, as well as local measures of health."
They also stated that, "A one standard deviation increase in daily pollution levels leads to an additional $540,000 in hospitalisation costs for respiratory and heart-related admissions for the six million individuals living within 10km (6.2 miles) of the airports in California.
"These health effects occur at levels of carbon monoxide exposure far below existing Environmental Protection Agency mandates, and our results suggest there may be sizeable morbidity benefits from lowering the existing CO standard."
This study aimed to assess the link between pollution from air traffic and health outcomes. Researchers used a number of data sources, finding an association between levels of carbon monoxide and hospitalisation rates for respiratory and heart-related issues.
Perhaps worryingly, these effects were observed at lower levels of carbon monoxide exposure than the allowed amounts found in Environmental Protection Agency mandates.
However, this study does have a number of limitations:
- Air traffic data was only from passenger aircrafts.
- The focus was only on the population within 10km of the airport. We don't know the levels of other pollution sources in the areas studied, or whether residents spend large amounts of time in other areas, either for work or study purposes, for example.
- The main sources of air pollution are traffic and industrial sources, such as factories.
These findings are in line with other research, however, which suggests increased pollution levels are associated with poorer health outcomes.
Air pollution is a known major risk factor for health, and ways to reduce levels should be investigated to reduce the burden of disease from stroke, heart disease, lung cancer, and both chronic and acute respiratory diseases, including asthma.
These findings might suggest policies may need to be reassessed worldwide to ensure the best possible health outcomes.