A public inquiry into a second runway at Stansted Airport began on Wednesday, beginning months of evidence presented for and against the proposal.
People who live near airports are worried about pollution
The current emphasis on climate change means that many environmental campaigners will focus on the additional carbon dioxide which the runway may generate.
However, local residents still have concerns about the impact of the airport on their quality of life - and even directly on their health.
Stansted's semi-rural location in North Essex is one of the key factors behind the government's decision to back plans for an extra runway here.
Supporters of Stansted's expansion say that means a minimal amount of people would be affected by any increase in air pollution.
When an aircraft is taxiing or taking off, it produces a 'plume' of gases, including some, such as nitrogen dioxide, which can be harmful.
They can irritate the lungs, making respiratory illnesses more severe.
Depending on the wind conditions, this can drift for some distance away from the airport at ground level, and campaigners claim that tests in residential streets up to a few miles downwind from Heathrow Airport often fail World Health Organisation standards.
However, Department for Transport testing of pollutant levels at the boundaries of Heathrow show greatly reduced levels of harmful gases, and some experts say that the problem is 'manageable', and shouldn't prevent the expansion of the airport in future.
Compared with an extra runway at Heathrow, Stansted expansion supporters say that only 30, rather than 30,000 people would be subjected to illegally high levels of air pollution.
However, others believe that only tells part of the story.
Nic Ferriday, from the Aviation Environment Federation, said: "There is plenty of medical evidence that high nitrogen dioxide and ozone levels can harm your health - and legal limits have been set.
"But although only 30 people will probably go over the legal limit in terms of air pollution at Stansted, a lot more will suffer an increase, and it won't do them any good."
Noise is a much bigger concern for campaigners. Any increase in take-offs and landings from Stansted would have an impact on an estimated 14,000 people living locally.
In addition, it's much easier for researchers to identify and measure aircraft noise.
Nic Ferriday said: "We know that noise not only causes annoyance and affects quality of life, but it can cause health problems, such as stress.
"The idea that aircraft noise can cause learning deficits in children is also well-established, and the World Health Organisation has produced noise limits."
Studies in West London carried out by University of London scientists, published in the Lancet medical journal suggested, that living close by an airport meant an average noise level of 60 to 70 decibels a day, compared with the London average of 50 to 60.
Reading age in children exposed to large amounts of aircraft noise was delayed by up to two months for every extra five decibels of noise at their school, researchers said.
Professor Stephen Stansfeld, who led the project, said: "Schools exposed to high levels of aircraft noise are not healthy educational environments."
John Stewart, from HACAN, which campaigned against the building of a fifth terminal at Heathrow, echoed this: "There is clear evidence that aircraft noise is harmful to the health and learning of children. Several studies support this."
Chris Goater, from the Airport Operators Association, said that reducing noise pollution and improving air quality were important tasks for the industry.
"We have seen air quality improve dramatically in recent years, primarily as a result of the introduction of more modern, cleaner aircraft, but we recognise that there are still issues to resolve and it is clearly a huge priority for us.
"In addition, new aircraft are significantly less noisy than older ones, and the noise contour has reduced, although in some cases the frequency of flights within that contour has increased, so some people may not be experiencing the benefits of quieter aircraft."