Mass poisoning. Mind control. And weather tampering. The TRUTH about 'chemtrails'

The white lines seen following airplanes as they fly could be full of harmful chemicals that are toxic in Americans' health, some people claim.

The streaks left across the sky from planes, called contrails, are formed by water vapor from the plane's exhaust freezing in the cold air at high altitudes.

However, conspiracy theorists, as well as some politicians, believe some trails that linger longer than usual actually contain toxins, referring to these as 'chemtrails.'

The theory has been widely debunked by scientists, but that hasn't stopped some, including Health and Human Services Secretary Robert F Kennedy Jr, from declaring chemtrails a threat to citizens' health.

The idea hit the public in the 1990s, with people claiming the government or an unknown force was using commercial aircraft to release chemicals into the atmosphere.

Followers of the theory believe it is done for a number of reasons, including weather modification and mass mind control. They argue chemtrails look and behave differently from contrails, which consist of condensation that dissipates over time.

This year some states across the US have tried to enact legislation to ban 'chemtrails', and leaders have introduced, or are considering, legislation to clampdown on activities related to it.

Beginning in October, publicly owned airports in Florida will have to submit monthly reports listing any aircraft 'equipped for geoengineering or weather modification activities'.

Violations could result in fines up to $100,000 and up to five years in jail.

President of the Florida Senate Ben Albritton said in April at news of the senate passing the bill: 'I am grateful to Senator Garcia for bringing forward a great piece of legislation that addresses real concerns from our constituents.

'I have heard the conspiracy theories out there, but the fact is we should not be shutting down legitimate concerns. Healthy skepticism is important.

'People have a right to know what is happening. There's a lot we don't know in this field of science and people are rightfully concerned.

'This bill goes a long way to bring peace of mind to our citizens so they can report what they are seeing, and we can make sure its lawful activity, not geoengineering or weather modification.'

And in July, Marla Maples, the ex-wife of Donald Trump, spoke in support of Florida's legislation.

She said she was motivated to 'start digging' after seeing a rise in Alzheimer's nationwide.

Currently, an estimated 7.2million people aged 65 and older have Alzheimer's, a number that is expected to reach 13.8 million by 2060.

Louisiana has become the latest state to create legislation tackling chemtrails.

The Louisiana bill, which became effective August 1, prohibits intentionally dispersing chemicals into the atmosphere to affect weather or climate.

It also mandates the Department of Environmental Quality collects reports from people who believe they have witnessed such activities.

In June, as Louisiana Representative Kimberly Landry Coates stood before her colleagues in the state's Legislature she warned that the bill she was presenting might 'seem strange' or even crazy.

Some lawmakers laughed with disbelief and others listened intently as Coates started discussing chemtrails.

As she urged lawmakers to ban the unsubstantiated practice, she told skeptics to 'start looking up' at the sky.

'I'm really worried about what is going on above us and what is happening, and we as Louisiana citizens did not give anyone the right to do this above us,' the Republican said.

Louisiana State Senator Mike Fesi expressed belief in the debunked 'chemtrails' conspiracy theory and associated it with the spraying of sulfur dioxide into the atmosphere.

The idea of spraying sulfur dioxide (SO2) into the atmosphere is a proposed method of solar geoengineering, specifically stratospheric aerosol injection (SAI).

The idea is to increase the amount of aerosols in the stratosphere, which would reflect sunlight back into space and potentially cool the planet.

But the EPA warns SO2 can harm human health and the environment. Health experts say short-term exposures to can harm the human respiratory system and make breathing difficult.

People with pulmonary diseases, particularly children, are sensitive to the effects of SO2.

Additionally, it can 'react in the atmosphere leading to acid rain or form particles that harm health and impair visibility'.

Tennessee Governor Bill Lee signed a similar measure into law last year targeting the spraying of undisclosed chemicals into the atmosphere and more than a dozen other states, from New York to Arizona, have also introduced their own legislation.

New York bill A05476, which is currently being reviewed by committee members 'prohibits the intentional injection, release or dispersion, by any means, of chemicals, chemical compounds, substances or apparatus within the borders of this state into the atmosphere with the express purpose of affecting temperature, weather or the intensity of sunlight'.

Some health experts worry bills like these are indicative of how misinformation is moving beyond the online world and into public policy.

Elevating unsubstantiated theories or outright falsehoods into the legislative arena not only erodes democratic processes, according to experts, it provides credibility where there is none and takes away resources from actual issues that need to be addressed.

'Every bill like this is kind of symbolic, or is introduced to appease a very vocal group, but it can still cause real harm by signaling that these conspiracies deserve this level of legal attention,' said Donnell Probst, interim executive director of the National Association for Media Literacy Education.

Chemtrail conspiracy theories are not new.

The publication of a 1996 Air Force report on the possible future benefits of weather modification is often cited as an early driver of the narrative.

Ken Leppert, an associate professor of atmospheric science at the University of Louisiana Monroe, said the streaks left behind by planes are actually primarily composed of water and that there is 'no malicious intent behind' the thin clouds.

He says the streaks are formed as exhaust is emitted from aircrafts, when the humidity is high and air temperature is low, and that ship engines produce the same phenomenon.

A fact sheet about contrails, published by multiple government agencies including NASA and the Environmental Protection Agency, explains that the streaks left behind by planes do not pose health risks to humans.

Scientists have overwhelmingly agreed that data or evidence cited as proof of chemtrails 'could be explained through other factors, including well-understood physics and chemistry associated with aircraft contrails and atmospheric aerosols,' according to a 2016 survey published in the journal Environmental Research Letters.

In the survey of 77 chemists and geochemists, 76 said they were not aware of evidence proving the existence of a secret large-scale atmospheric program.

Leppert added: 'It's pure myth and conspiracy.'