Ever wonder about those clouds planes leave in the sky? About what effect they have on the environment and, more importantly, our health?

Rod McKinnon of Moncton wants to know, and he's looking to the government for answers.

Just like cars, planes release exhaust. Because they fly at high altitudes, the cold temperature causes the exhaust to turn into water vapour and crystallize. These clusters of crystals resemble thin clouds, known as contrails.

But McKinnon believes there's more to these contrails, especially the ones that persist for long periods of time. He calls them 'chemtrails.'

"They don't disappear," he said. "I've seen planes leave contrails and then I notice them disappear. The chemical sprays do not disappear; they form clouds and we don't know what effect they have on our Earth or our people when it comes down in rain."

McKinnon isn't alone in his queries.

Citizens and scientists across North America have been studying 'chemtrails' for years. There are multiple theories about them, some even wildly suggesting they contain hazardous chemicals aimed at modifying the weather or controlling the population.

Believers says chronic asthma, flu, fatigue, and respiratory problems can be directly related to these chemtrails, but a leading climatologist disagrees.

"The idea of it falling to the ground in a concentration great enough to have an effect on our health is preposterous," said Dr. David Travis, a climatologist with the University of Wisconsin-Whitewater.

Travis began researching contrails after the September 11 terrorist attacks, when he noticed an increase in the Earth's temperature range in the three days air traffic was grounded. He said contrails have an effect on climate, but have no direct effect on human health.

"Their (chemtrail theorists) belief is that this is some kind of conspiracy, that they're being sprayed," he said. "It's not spraying; they see too many crop duster movies -- we don't spray contrails. They're not being done as some kind of conspiracy. It's just airplanes flying through atmospheres that happen to have the kind of conditions that support contrail formation."

Contrails that last longer than others are simply the result of a colder, more moist atmosphere that the plane is flying in, Travis said, and at the point when a contrail is persisting, it is mostly water vapour. He said air traffic is so high in the atmosphere that there's no way chemicals from jet exhaust could have an effect on people.

Coverage of contrails has increased dramatically over the past decade. Travis said this is the result of an increase in air traffic, not a sudden 'spraying' initiative.

"What's really happened is we've had a huge increase in the number of airplanes in the sky and the climate has become more favourable for the persistence of contrails," Travis said. "The climate's gotten warmer on the surface (and) it actually makes it colder at the altitude where airplanes fly and that actually makes it more favourable for contrails to persist."

The Greater Moncton International Airport announced earlier this year that domestic travel is up 11 per cent and international travel up nine per cent since 2007.

"The thing to worry about with contrails is not the direct human health effect, but their intervention in the climate system," said Dr. Michael Oppenheimer, a professor of geosciences and international affairs at Princeton University and 2007 Nobel Peace Prize winner.

According to Oppenheimer, the ice crystals formed by jet exhaust have two effects on the Earth's climate. The crystals reflect sunlight and act to cool the Earth, or they form the nuclei that clouds grow on, and by creating clouds, they trap heat and warm the Earth.

"They do have a direct effect; we don't know if it's large or small, we don't know if it's warming or cooling," Oppenheimer said. "We haven't yet really worked out what the balance is between those two effects."

The effect on the Earth's climate, whether it be warming or cooling, can lead to more illness and disease.

"Disease is now more prevalent in areas where they never were because they're able to flourish with the changes in climate," said Inka Milewski, an environmentalist with the Conservation Council of New Brunswick. "There's pressures on the environment that cause new diseases to emerge."

And while jet fuel is a major contributor to climate change, Milewski said there are more immediate dangers we should be aware of.

"There are pollutants in the community that are of far more concern (than) something that occurs five miles up," she said. "Immediately what comes to mind is your neighbours using pesticides on their lawn. That to me would pose a much more immediate concern."

The main concern with air traffic is the particulars, said Milewski, which are micro-fine particles that rain out in the atmosphere and can causes cancer and cardiovascular disease. Carbon dioxide and polycyclic aromatic hydrocarbons (PAHs) are also hazardous, but they are found in car exhaust too.

"It's like any fuel that gets burned; there are contaminants associated with it."

Milewski said the only way to reduce contrails is to reduce air traffic, which would require taking government action.

"Demand legislation that regulates the amount of emissions from air travel, just like from cars," she says. "These do work. Force the aviation industry to reduce these emissions through regulation."

And that's something Rod McKinnon can agree with.

"I'd like to see enough people have a voice," he said. "I'd like to see enough people make it an issue and draw enough attention to it so we can get some answers," he said.

(Original headline: Aircraft contrails raise questions )

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