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How to deal with harmful organophosphates in oil and Skydroll during aircraft maintenance!

Since the 1950’s, after the introduction of jet engines, the engines bearings are lubricated with high performance

synthetic oils. Some ingredients of these engine oils contains organophosphates mainly because of the lubrication qualities

at high temperatures. Most known of these organophosphates is TriCresylPhosphate TCP.

In hydraulic oil an organophosphate called TriButylPhosphate TBP has been added. Since the same 1950’s a discussion is

going on the health effects of these organophosphate additives.

The oil manufactures are mentioning these health risks on their safety data sheets and on the oil cans themselves. TCP en

TBP both contain possible neurotoxic substances (permanent damage to the nerve system) and TBP is suspected of causing

cancer. There is also no more discussion going on if the fumes are entering the cabin, there is only an ongoing discussion on

how often this happens and how high the dose could be. It seems that there is under-reporting going on due to little or no

awareness, but also another possible cause could be that oil smells have become a norm, we find the ‘smell’ normal. The

current facts show that a fume event occurs once per 2000 flights.


EASA research showed that with the pyrolyse (heating) of oil, 127 possible dangerous substances appear including carbon

monoxide. Maintenance personnel deal on a daily basis with the routine of maintenance, such as oil servicing and preflight

inspections. They are therefore often in contact with oil and skydroll, either via skin contact but also via inhalation of

vapours during leakages, engine run, de-airation of reservoirs and servicing of the oil system itself.

Even with current knowledge it still states in the Boeing manuals that they require you to do a “sniff -check” as to

check for fuel in the oil system.

Exposure to organophosphates can be divided into short term high level exposure, fume events, leakages etc, and long term

low level exposure. During normal operation of the engine there is always a little oil leaking via the bearing seals, the so

called “wet seals”. But also the oil drip tray under the engine and a presence close to the area around the exhaust after

engine shutdown gives exposure. Measurements on airports also always show low levels of TBP. Scientific research shows

that this low level exposure can cause complaints after years of working in aviation. There seems to be a defect in DNA

causing this, however this DNA defect does not seem to be rare, as some studies reveals. Complaints differ from difficulty

breathing, headaches and extreme fatigue to muscle weakness, tingling, dizziness and memory, concentration and other

cognitive complaints.

Recent scientific research showed that the ultra-fine particles exiting the engine have organophosphate molecules on the

surface. These ultra-fine particles are so small that they can pass through the blood/brain barrier get to the brain itself. At

this moment scientific brain research is ongoing involving 30 participants (+100 at later date) with complaints, amongst

them: pilots, cabin crew, frequent flyers but also engineers, all show the same brain damage..

Seeing the tasks technicians has to perform it is hard to prevent exposure, however it is wise to minimalize any kind

of exposure. On the platform it is advised to wait with the Preflight inspection or maintenance until five minutes after

engine shutdown, avoid being close tot the engine exhaust area. Also, try to avoid skin contact with oil and skydroll at all

times. There is a high presence of ultra-fine particles and oil vapours after engine shutdown, it is wise to clean work clothes

on a regular basis.

Wear protective clothes and if needed face masks with an A2P3 filter. Follow the guidelines as instructed by the

employer. When dealing with reports of fume-events the maintenance manuals has to be followed. A cause for the

fume-event has to be found and ARCO and or pressurisation ducting and Environmental control system parts involved

have to be cleaned. After that a test-run should be required to make sure there is no smell any more before an aircraft can be

released to service for the next flight. This means a fumeevent is a “No-Go” situation, the aircraft can not be released to

service or dispatched until it is made sure there is no exposure any more. This is also required as per EU/EASA rules.

Currently, there are multiple lawsuits ongoing, just in the UK about 51. As it all deals with human health and its sensitivity

in the industry it is wise, as a technician, to exactly follow the manuals as to prevent any future liability. Also be aware of

maintenance itself as a cause of the fume-events. Prevent overfilling of oil and hydraulic reservoirs. Pay attention to

leakages that can enter the airco packs or APU inlet like hydraulic leakages from the landing gear or the rudder. After a

leak has been occurred, clean the aircraft before next flight to prevent a fume event. When troubleshooting concerning a

fume event , e.g. an engine run, it is wise to use an oxygen mask, to prevent personal exposure.

In the discussion on this subject NVLT tries to play an important role by taking part in both national and international

discussions but also by cooperation with other unions and the industry in search of a solution. It is incorrect and not allowed

by Dutch law that the human nose is used as a biological sensor, to our point of view it is ethically and medically

irresponsible. The NVLT strives for cleaner oils, sensors, filters and better reporting systems. The NVLT also strives for

better awareness and medical support as that is still to our opinion inadequate.

Always Make an occurrence if an oil or skydroll incident occurs so that companies and authorities will have an insight

on how often this happens. If you have possible oil related health complaints report this to your general practitioner and

to your company doctor. As a union member it is also wise to report it to your union for assistance.

NVLT health and safety


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