‘Van den Heuvel started flying with KLM in 2008 and by 2011 started to “develop headaches, tiredness and cramps in the legs and arms” around two to three hours into a flight. 
It began with the headaches and tiredness, which she initially put down to jet lag until she began to experience tremors and “couldn’t feel my hands and legs… at night I couldn’t walk up the stairs…this is not jet lag”.
Despite her symptoms, van den Heuvel said the airline kept pushing her to work and eventually dismissed her in 2016 when she refused to keep full-time hours. After a protracted legal battle, she was awarded the right to claim disability benefit at the Dutch Central Appeals Court in June. Her legal problems may have ended but her physical ones have not – today she still suffers from “very heavy headaches” and has to sleep for around two hours every afternoon.  

Damage to the central nervous system
Neurologist Gerard Hageman included the flight attendant alongside two pilots in his 2019 study, Three patients with probable aerotoxic syndrome, in which he concluded that there was “objective evidence of damage to the central nervous system”, but not of causation. “Whether the autoantibody profile is specific to engine oil emissions needs to be addressed in future studies,” states the paper.
Similar symptoms have been described in other studies of air crew, “although objective evidence of exposure is lacking in most of these studies”, according to Hageman. “Reduced levels of butyrylcholinesterases in one of our cases is suggestive of causation and elevated neuronal and glial autoantibodies provide objective evidence of damage to the central nervous system. We consider further research is warranted.” ‘
©️Source:
https://www.endsreport.com/article/1725702/i-couldnt-feel-hands-legs-toxic-air-poisoning-pilots-passengers-crew?fbclid=IwAR3woNt_6Xz7BWs3cNyk1Ry01loaGQbJDk9_vuJQKRIbFyOzqUAIiau1a5s

(Note: There is an error in the Ends Report article (above) regarding the death of Matt Bass who worked as Cabin Crew for British Airways. Matt did not take any sleeping pills, he fell asleep and never woke up.)

This is an excerpt from a letter written by the Coroner for Berkshire (2018) - after the inquest into Matt’s death, to The Chief Coroner - Judge Lucraft Q.C.
‘In light of the information that I now have surrounding Aerotoxic Syndrome as a direct consequence of my conduct of the Inquest into the death of Mr Bass, I am alert to the need for specialist pathological investigation of the peripheral nervous system in appropriate cases. In my opinion, I would be concerned if a death is reported of a relatively young person who dies in less than straight forward circumstances and who, for example works as cabin crew or a pilot for an airline. In such cases, I would request additional post mortem studies and retention of samples to address the issue of whether Aerotoxic Syndrome may have been relevant to that person’s death.’

These are the Court of Appeal pages regarding the recent success of the case of Evelyn Van den Heuvel - former KLM Cabin Crew:
‘Summary: in 2012 a dutch cabin attendant visited my medical practise with severe complaints during and after her work as a flight attendant. She was top fit at the start of her career, only to find herself in a severely compromised health condition after 3 years of service. Her symptoms fit those described in several scientific documents as Aerotoxic Syndrome.
Three court cases were held about her limited medical condition. Finally, in the highest court in The Netherlands, where no appeal is possible anymore, the verdict was spoken that she was eligible for a partial government payment through incapacity to work, based on the exposure to a “chemical substance” during her work.’
©️Source:
http://www.unfiltered.vip/uploads/6/0/3/8/6038702/case_evelyne_van_den_heuvel_court_of_appeal.pages-2-1.pdf

As we now know, both the central and peripheral nervous systems, circulatory system, respiratory system, reproductive system, lymphatic system, cholinergic system, endocrine system, immune system and digestive system can be damaged (usually permanently due to lack of proper diagnosis/misdiagnosis and the correct treatment) from breathing these fumes, even at low level and continually over a number of years.
During fume events the level of exposure is much higher and in a very short space of time.
It’s just the luck of the draw as to whether you will become injured and what injuries you might sustain (similar to Russian Roulette). The situation could be exacerbated due to a genetic defect - a lack of an enzyme called Cytochrome P450 (CYP450) in the liver which helps in the elimination of the toxins. It’s estimated that up to 20% of people have this genetic defect which makes them more susceptible to injury. However, even for those not affected by this genetic defect, repeated exposures to the harmful toxins in aircraft cockpits and cabins can alter the expression and activity of Cytochrome P450’s ability as catalysing proteins involved in the biotransformation of endogenous and xenobiotic compounds.

Much of this was known by scientists way back, but no one in the U.K. Government or the agencies employed by the Government (such as the Committee On Toxicity), felt that there was a threat to health or that there was a need for further research and instead released a paper titled ‘Position On Cabin Air’ in 2014 leaving many questions unanswered.
©️Source:
https://cot.food.gov.uk/sites/default/files/cot/cotpospapcabin.pdf

One scientist who knew about the issue is Professor Jeremy Ramsden. He used to be Head of Nanotechnology at Cranfield University who were responsible for the flawed UK Government funded ‘Air Sampling Study’.
Professor Ramsden was was removed from Cranfield University for expressing his views and opinion:
http://bleedfree.eu/documentation/o-r/prof-dr-jeremy-ramsden/
Professor Ramsden said that Airline tickets should come with a health warning similar to those on cigarette packets:
https://www.flightglobal.com/cranfield-professor-proposes-action-over-toxic-cabin-air/102851.article

The scientific adequacy of the present state of knowledge concerning neurotoxins in aircraft cabin air
Jeremy J. Ramsden - 2011

‘One area that has definitely been neglected is establishing whether there are synergies not only between different toxins—and we do now have quite a variety of data for different substances [46]—but between the inhalation of TCP under the particular conditions typical of a pressurized airliner flying at high altitude, and between the neurotoxin TCP and other attriting factors including disruption of the circadian rhythm (“jetlag” [67]), cosmic radiation [68] and disturbance to the immune system [69]. All of these factors, omnipresent in long-distance travel by jet aircraft, seem likely to exacerbate damage to the central nervous system by TCP.
Finally, the concentrations of potential toxins still need to be measured, in a statistically appropriate fashion, during actual “fume events”. ‘

‘It should be emphasized that for a relatively involatile, lipophilic substance such as tricresyl phosphate, especially in view of its even more toxic metabolic breakdown products, there may effectively be no threshold exposure limit below which it can be deemed to be safe. Provided the appropriate cytochrome P450 enzymes are available in the liver, organophosphates such as TCP can be hydrolysed; the question is whether the detoxification happens faster than toxic injury. Such detailed knowledge of the reaction kinetics is not yet available; we can, however, say with fair certainty that for an appreciable proportion (10–20%) of the population, prolonged exposure to a TCP concentration of 0.038 mg m–3 is likely to lead to central and peripheral nervous system damage and, hence, chronic neural illness. Since no fume event was measured, the presumably much higher concentrations during such an event remain, regrettably, unknown, but already cases of near-incapacitation of pilots experiencing such events are known (ref. 3, pp. 547 ff.).’

‘At the very least, the present oppressive atmosphere of denial must be blown away to allow genuine sufferers to receive the diagnosis and treatment that will, hopefully, allow them to start moving along the road to recovery. The next priority is to minimize the actual contamination. Even without updating any technology, comprehensive reporting of problems when they do occur will assist appropriate engineering maintenance. The quantitative monitoring of contamination through sensorization of the airframe (i.e., installing chemical sensors) is the obvious practicable technology update. If the aerospace industry acts energetically in response to the latest knowledge, in accord with the principles of the “knowledge-based economy”, hopefully this will give it the confidence to be able to move forward constructively.
Is more research needed before taking concrete action? There seems already to be overwhelming evidence in favour of the proposition that tricresyl phosphate is leaking into aircraft cabins (e.g., ref. 46) and causing both chronic illness through relatively low-level but long-term exposure as well as acute illness (incapacitation) through a sudden fume event that might properly rank as an accident. A large-scale epidemiological study with a control group would of course be decisive in this regard (cf. ref. 65) but would also be very expensive and it may be that all the existing data, including much hitherto unpublished or unanalysed material, if centrally collated and properly analysed, will suffice if further evidence is still considered to be necessary. The case would already seem to be made if one uses Sir Austin Bradford Hill’s criteria [66].’

‘Nevertheless, in so far as there now appears to be an incontrovertible link between even low-level organophosphate exposure and physiological abnormality in the brain, liability seems to be ultimately unavoidable and it would, therefore, be prudent to take all practically possible steps to minimize exposure, starting with what can be achieved within existing procedural frameworks [62].
Airline employees (and their unions) are placed in a difficult position, for if individuals flag up their health problems their pilot’s licences may be withdrawn, and if the problem becomes more widely known to the public, plummeting passenger numbers and liability suits may force airlines into bankruptcy. This in itself raises a safety issue, for it implies that there are currently pilots flying with damaged central nervous systems, who might be well able to cope with routine flights but adversely challenged by any sudden emergency.
In the past it has certainly been difficult to provide firm evidence for a link between organophosphate exposure in the aircraft cabin and ill health. In the absence of chemical meters continuously monitoring organophosphate levels one cannot “prove” that organophosphates (notably, TCPs) were present in the atmosphere on a particular flight.28
Similarly, in the absence of reliable blood (or other biofluid) test convenient enough to be carried out shortly after landing one cannot “prove” that a given individual was exposed to TCPs and absorbed them. But it can be confidently anticipated that a suitable blood test will soon be available [60]. Furthermore, knowledge of the brain activity patterns characteristic of TCP intoxication is constantly increasing [63]. The ability to provide significant and substantial evidence for both the actual exposure and its adverse health consequences is imminent. Once this happens, it will obviously no longer be possible to credibly deny the problem [64].’

‘A complete understanding of the mechanisms of toxicity would certainly require identification of the oil pyrolysis products that may enter the cabin along with both unaltered and isomerized tricresyl phosphates, but this is a luxury not essential for taking effective action to combat the problem.’

‘Screen aircrew and passengers for susceptibility to organophosphate poisoning. It would appear that susceptibility is genetically determined; it depends on the available and potentially available variety and quantity of cytochrome P450 enzymes in the liver. There are possibly different degrees of susceptibility, according to which the occupational risk, or risk from frequent flying, may be too great or even a single flight might constitute an unacceptably high risk of health damage. Research work still needs to be done in this area but it seems likely that genetic screening would be useful.22 It would certainly be easier to accomplish than a liver biopsy.’
©️Source:
http://www.itcoba.net/27RA11A.pdf

You see, all of this was known a long time ago, but the ‘establishment’ and the aviation industry have constantly ignored and dismissed the science as they do not care about the health of passengers & employees and certainly do not want anymore research conducted into the mechanisms of toxicity and subsequent ill health as a result of exposure to aircraft oil, hydraulic fluid or the exhaust from other aircraft drawn into aircraft cabins, because causation could then be proved.
Furthermore, if anyone cared, the urgently awaited EASA Facts 1. project (Dec 2016-Dec 2019) results on Cabin Air Contamination would have been published but for some reason they haven’t.
Perhaps some ‘FACTS’ have come to light which they don’t want revealed.