The chemicals nobody talked about: Aviation maintenance and the legacy we're still living with

The Chemicals Nobody Talked About

Every aircraft engineer over fifty can name someone.

A colleague who developed cancer.

A painter who spent decades spraying chromate primer.

A fuel tank technician who now struggles with chronic respiratory issues.

Nobody can prove the job caused it. That's part of the problem.

What we were exposed to

If you entered aviation maintenance more than twenty years ago, your working environment included a chemical inventory that would make a modern WHS officer reach for the incident report form before their morning coffee.

The list was long and largely unremarkable at the time because it was simply the job:

Jet A-1 fuel: Handled daily, skin contact routine, vapour inhalation at aircraft, ramp, and fuel farm a constant background condition. Long-term dermal and inhalation exposure now associated with central nervous system effects and suspected carcinogenicity.

Skydrol hydraulic fluid: The purple fluid that gets on everything and stays there. Phosphate ester-based, highly corrosive to skin and eyes, requiring specific chemical-resistant gloves that were not always available and not always worn. Ask anyone who's had a hydraulic line fail in their face whether they were wearing eye protection at the time.

Trichloroethylene (TCE): A chlorinated solvent widely used as a degreaser in maintenance shops for decades. The EPA and IARC now classify TCE as a known human carcinogen. A long-term cohort study of over 14,000 aircraft maintenance workers tracked from 1952 found elevated relative risks for several cancers among solvent-exposed workers, non-Hodgkin's lymphoma, oesophageal cancer, and kidney cancer among them. The science stops short of definitive causal links in most cases. That is not the same as saying there are none.

Zinc chromate primer: The distinctive yellow-green primer applied to aircraft structures for corrosion protection. Chromate compounds are classified as known human carcinogens. Inhalation of zinc chromate dust and spray during surface preparation and painting is associated with lung cancer risk. The same long-term aircraft worker mortality studies found statistically significant excess mortality from non-malignant respiratory disease among workers exposed to zinc chromate.

Composite cleaners and MEK: Methyl ethyl ketone and related solvents used in composite structure work, cleaning, and adhesive application. Neurotoxic at sufficient exposure levels. Historically used with minimal respiratory protection in poorly ventilated environments.

Engine oils and combustion products: Jet engine oil contains tricresyl phosphate compounds. Fume events, where hot oil enters bleed air systems are a known risk. The longer-term occupational exposure picture for ground maintenance staff working in proximity to running engines in enclosed environments is less studied than it should be.

This was the working environment. Not occasionally. Routinely. Daily.

For careers spanning decades.

The RAAF and the F-111: when the bill finally came due

The clearest Australian case study in aviation chemical exposure and its consequences is not a commercial airline story. It is a military one, and it is extensive, documented, and deeply uncomfortable.

The Australian Defence Force established the F-111 Deseal-Reseal Health Care Scheme to compensate workers exposed to chemicals while cleaning F-111 fighter aircraft between 1977 and the late 1990s. More than 800 RAAF personnel were involved in fuel tank maintenance work, physically entering the aircraft's fuel tanks to remove deteriorating sealant using dental picks and other tools, then resealing.

In January 2000, the RAAF ceased F-111 fuel tank maintenance after concerns were raised at Amberley airbase about adverse health effects reported by workers, including skin rashes, gastrointestinal problems, headaches, fatigue, and loss of memory.

A formal Board of Inquiry followed. Then a parliamentary inquiry. Then compensation schemes administered through Defence and the Department of Veterans' Affairs. What the Board of Inquiry found was that the OH&S structure often existed only on paper, with meetings not always being held as required and coordination not functioning as intended, and the personnel who were part of the structure were often unaware of their own role in it.

In other words: the paperwork said people were protected. The people were not protected.

The F-111 case was followed by a separate and equally significant issue. The Commonwealth paid more than $130 million in a settlement over the use of PFAS, polyfluoroalkyl substances, used in firefighting foam on RAAF bases, with around 30,000 landowners near seven RAAF sites sharing in the settlement over soil and groundwater contamination. The Commonwealth did not admit liability.

The pattern across both cases is identical: exposure occurred over decades, the health consequences emerged slowly, the institutional response lagged the evidence by years, and the burden of proof fell on the people who had been exposed.

Commercial aviation: the conversation we're not having loudly enough

The RAAF cases are documented, litigated, and publicly recorded. The commercial aviation maintenance equivalent is a quieter story, told not in courtrooms but in the cancer diagnoses, the respiratory conditions, and the neurological symptoms that accumulate across the careers of people who spent thirty years in hangars.

Ask anyone who has worked in commercial aircraft maintenance for more than two decades.

Do a straw poll of colleagues. Count the number of people in your professional network who have been diagnosed with conditions, respiratory, neurological, oncological, and that correlate with the known effects of long-term chemical exposure.

The science is careful about causal links and rightly so. Among TCE-exposed aircraft maintenance workers in the largest long-term cohort study, there was no statistically significant increased risk of all-cause mortality or death from all cancers overall, but positive associations with several specific cancers were observed, consistent with the published literature, with interpretation limited by small event numbers for specific exposures.

Statistically inconclusive is not the same as safe.

Statistically significant excess mortality from non-malignant respiratory disease was found among workers exposed to a range of chemicals including zinc chromate, with relative excess risks ranging from approximately 30% to 80%.

These are not abstract numbers. They are the lungs of the people who built and maintained the aircraft that Australia flew on for half a century.

What changed, and it did change

The industry response to chemical exposure risk over the past two decades has been genuine and meaningful. This is worth acknowledging.

Material Safety Data Sheets, now Safety Data Sheets under the GHS system, moved from being documents filed in a drawer to being active, accessible references at the point of use. Hazardous chemical registers became mandatory. Personal protective equipment standards were tightened significantly: chemical-resistant gloves for Skydrol work, supplied air respirators for confined space and fuel tank entry, half-face respirators as standard for primer and paint operations rather than exceptions.

Ventilation requirements in maintenance facilities improved substantially. Biological monitoring programs for workers with significant solvent exposure were introduced by some operators. Confined space entry procedures, directly relevant to fuel tank work, became heavily regulated with permit systems, atmospheric testing, and standby rescue as baseline requirements rather than aspirational standards.

Safe Work Australia and state WHS regulators brought aviation maintenance chemical exposure into a framework that had teeth. CASA's safety management system requirements pushed operators to identify and manage chemical hazards systematically rather than informally.

The engineer entering a fuel tank today has more protection, better information, and more clearly defined rights than the person who did the same job in 1985.

That is the good news. The asterisk is that the person who did the job in 1985 is now in their sixties, and the consequences of what they were exposed to are still unfolding.

The link nobody can quite prove

This is the uncomfortable centre of this conversation.

Occupational cancer and chronic illness operating over decades of low-to-moderate chemical exposure is extraordinarily difficult to prove causally. The latency periods are long. The exposure records from decades ago are incomplete or non-existent. The confounding variables, such as smoking, other occupational exposures, genetic predisposition, are difficult to isolate. Legal causation requires a standard of proof that epidemiology often cannot meet for individual cases.

So, the engineer who spent fifteen years working with TCE degreasers, zinc chromate primers, and Skydrol in a poorly ventilated shop in the 1980s, and who is now managing a non-Hodgkin's lymphoma diagnosis, faces a system that acknowledges the association in the literature but cannot confirm the causation in his specific case.

That is not a legal failing. It is a scientific reality. It is also deeply unsatisfying for the people living it.

The obligation to the next generation

Aviation maintenance is not a chemically clean environment today. It is however, a significantly safer one.

But the chemicals have not gone away. They have changed, been better characterised, been more carefully controlled, and in some cases replaced with alternatives that carry their own as-yet-unquantified long-term profiles. The composite materials revolution has introduced new dust exposure profiles from carbon fibre and glass fibre cutting and sanding that are still being studied. The shift to waterborne coatings has reduced solvent vapour but introduced different respiratory sensitisers.

The obligation on the generation that absorbed the exposures of the 1970s, 80s, and 90s is straightforward: be honest about what it was like, what the consequences appear to be, and what the people coming into the industry deserve to know.

Wear the PPE. Not because the form requires it. Because the person who didn't, thirty years ago, is still finding out why it mattered.

The label on the tin told you. It just took the industry a while to start listening.

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Jotore Aviation Consulting provides maintenance strategy, regulatory compliance, and CAMO/AMO advisory services to Australian aviation operators.