Aerotoxic syndrome - the pilots grounded by cabin air injury

He said: "I had a really strong headache, I felt nauseous, hot and clammy, and when we landed I put the oxygen mask on myself because I thought 'this is serious'.

"When we parked the aircraft and I took the mask off, the left side of my face was numb, my left eye was frozen, and I had a metallic taste in my mouth.

"We asked for medical assistance, and when they came and assessed me my blood pressure was 220/160 - it was extremely high."

READ MORE: 

• Former pilot says contaminated air on planes is 'like breathing care exhaust fumes'
• Filmmaker behind Aerotoxic Syndrome docu says only 'tombstone event' will stop it
• Irish carrier increases frequency of flights from Edinburgh 

Anything higher than 180/160 is considered a hypertensive emergency.

Suspecting a stroke, medics rushed O'Riordan by ambulance to A&E but further examinations confirmed that no stroke had occurred.

He spent five days in hospital but, nearly a year later, remains on sick leave with a range of debilitating physical and psychological symptoms which had never troubled him prior to that flight.

He is also due to travel to Belgium later this month for brain scans in a bid to make sense of the strange neurological maladies which now plague him.

"Continuous headache, tremors, vertigo, tinnitus, issues walking, difficulty sleeping, anxiety, depression, concentration, memory problems," said O'Riordan, who lives in Clogherhead, Ireland.

"I haven't been able to fly again. It's unlikely I'm ever going to return to flying."

With his sick pay due to expire in around six months, O'Riordan wants his employer - Aer Lingus - to accept liability and compensate him for workplace injury.

He has publicised his experience via social media and alerted bodies including the Irish Aviation Authority and Air Accident Investigation Unit, as well as raising a petition in the Irish parliament, because he believes many more pilots - and passengers - are risking their health from similar exposures.

He is now facing disciplinary action, something he claims is retribution for whistleblowing.

"They want to shut me up basically," said O'Riordan, who is speaking exclusively to the Herald after seeking help from the Aerotoxic Association - a charity set up by Scottish pilot, John Hoyte.

Tom O'Riordan had been flying with Aer Lingus for 15 years before he fell ill in June 2023 (Image: Supplied/PA)

Of particular concern for O'Riordan is that on June 4, he and his co-pilot had reported an "unusual, burning, fumey smell" while flying the same plane between Dublin and Shannon, and later Shannon to Heathrow.

The incident was alerted to engineers and on June 5 the two pilots were told the would have to return to Ireland as passengers on a scheduled Aer Lingus flight as their plane was grounded.

Moments before boarding, however, they were told by the operations teams that their original aircraft was now fit for service and they should fly it back to Dublin without passengers.

O'Riordan said: "We went to the aircraft, they said it was fixed, all the paperwork was signed, so off we flew to Dublin.

"But as we were descending down into Dublin the fumes came back even worse."

A subsequent investigation report, seen by the Herald, blames the cabin smell on oil leaks affecting the engine.

An Aer Lingus Safety Progress Report also noted that the airline had made 32 mandatory occurrence reports (MORs) during 2023 in relation to "Smoke/Fume/Fire/Odour" events on its planes.

MORs highlight a potential risk to flight safety if uncorrected.

Aer Lingus did not respond to requests for comment.

Although he says it was never "on his radar" prior to falling ill, there are plenty of people who believe they know what has happened to O'Riordan: they call it Aerotoxic Syndrome.

John Hoyte is one of them.

The Edinburgh-born pilot, 68, gave up flying in 2005 after years of steadily declining health which first began when he joined freight carrier, TNT, in 1989.

It was the first time he was operating a pressurised aircraft.

Within months his previously excellent health was faltering with the onset of strange, unexplained symptoms, which he initially put down to the exhaustion of constant night flights.

"From the Spring of 1990 onwards, I was always chronically fatigued," said Hoyte.

"It was like a horrible developing illness. My speech went, and I couldn't think. I could only speak in five world blocks.

"I felt like I was permanently intoxicated by alcohol."

John Hoyte flew with TNT and then FlyBe over a 15-year period (Image: Mark Gibson/Herald&Times)

At one point he began to wonder if he had variant CJD - the human form of mad cow disease - but he hid his concerns from everyone, including his wife, GP, and employer.

By 1998, he felt his cognitive function was so impaired that he would struggle to learn and retain any complex, new information.

He left TNT for a job with FlyBe, hoping that a switch from night to daytime flying might help.

But he continued to be plagued by an "awful multitude of invisible symptoms" which included "poor memory, a constant echo in my head and difficulty in speech, which had by then become ‘normal’".

Eventually feeling too sick to continue - but without any medical diagnosis - Hoyte piloted his final flight in June 2005, between Edinburgh and Birmingham.

He was not yet 50.

In the months after his career ended, his health began to improve, and in January 2006 he received a phonecall out of the blue from a former British Airways captain, Tristan Loraine, asking whether he "wanted to be tested for toxic cabin air exposures".

"I had absolutely no idea what Tristan was talking about, but - as I was doing very little else - I agreed."

READ MORE: 

• Miami murders, Black Lives Matter, Sheku Bayoh: Why 'excited delirium' links them all
• 'Leave now': Council in legal action to evict sepsis survivor from care home
• NHS crisis: Power cuts, near misses, and 'black mould' in crumbling estate 

Loraine had gone from completing an Ironman triathlon to being medically retired one year later, aged 44, after being deemed unfit to fly.

He suspected that repeated exposures to oil fumes onboard his aircraft had led to the rapid deterioration in his health, and took his concerns to Dr Sarah Mackenzie Ross, a clinical neuropsychologist at University College London.

She embarked on a study analysing blood samples from Loraine and 26 other pilots - including Hoyte - who had all experienced similarly bizarre cognitive impairments.

They were found to have highly abnormal levels of jet engine oil by-products in their blood and fat, although MacKenzie Ross cautioned that it was not possible to draw a "causal link with contaminated air" and called for further research.

Nearly 20 years on, the Civil Aviation Authority insist that there is "no positive evidence of a link between exposure to contaminants in cabin air and any long-term health effects", and Aerotoxic Syndrome is not a medically recognised condition.

Yet some experts - including former pilot Dr Susan Michaelis - insist that it should be classified as an occupational disease.

In 2017, Michaelis - at the time a researcher in environmental and occupational health at Stirling University - warned that it would take a catastrophic air crash for the industry to act.

She was the lead author on a World Health Organisation study into cabin air contamination, and in May 2023 spearheaded a landmark report which detailed the medical protocol which should be used to diagnose and manage "persons suffering from the toxic effects of inhaling thermally degraded engine oil".

Dr Susan Michaelis said the problem is still being 'downplayed' by industry (Image: Supplied)

The issue - documented from the 1950s onwards - relates to the way that modern passenger jets are designed to pressurise the cabin using compressed air taken directly from the aircraft engines.

The theory goes that this "bleed air" can become contaminated with engine oils and hydraulic fluids, causing chronic exposure to low doses of poisonous chemicals and occasionally high-dose, disabling "fume events".

It is thought that some aircrew are genetically more susceptible than others.

Michaelis, who was medically retired from flying in 1997, aged 34, has previously described how she would get "headaches, fatigue, nausea, difficulty concentrating" as soon as she switched on the air supply, with symptoms easing once she left the aircraft.

She said she is "disappointed" that the aviation industry "is still trying to downplay the whole issue", but believes a turning point is on the horizon.

"A French oil company recently published a patent about how it is developing a new oil that is supposed to be less hazardous and they say in their patent that it's 'to prevent Aerotoxic Syndrome'," said Michaelis.

Most anticipated, however, is a new blood biomarker test - some 17 years in the making and due to be unveiled at the International Conference on Aircraft Cabin Air in London in September.

Michaelis said: "That will get a lot of attention within the industry because it will be able to show that there has been an exposure consistent with the compounds in the engine oils.

"It will give airlines an incentive to do things like filter the air, to have warning systems, to look at alternative ways of providing air instead of through the engines, and to use less hazardous oils."

As for John Hoyte, the stress of campaigning in vain for 20 years has taken its toll.

He is still contacted daily via the Aerotoxic Association by pilots around the world seeking help, but has become despondent at the situation and is turning his attention instead to setting up a flight simulator business in Oban. 

"What can I do to help?," he said. 

"It's wrecked my life, I've lost everything. People say to me 'it's the next Post Office scandal'.

"I think they're right."