Aircraft engine lubricants: risk assessment

Lubricants in aircraft engines

Leakage of fumes containing organophosphates (OPs) in air-circulation in commercial aircraft has been responsible for alarming incidents of pilots blacking-out or becoming seriously disorientated.

The OPs involved, used in high performance lubricants in aircraft engines, are tricresylphosphate (TCP) and triorthocresylphosphate (TOCP). Dr T C Marrs, who has been the government's senior scientific adviser on OPs at the DOH, has said: "Certain OPs, for example TOCP, have weak or absent anticholinesterase effects, but are powerfully neuropathic". (Dr T.C. Marrs, Organophosphate Poisoning, Pharmac. Ther. Vol.58, pp51-66, 1993)

Polyester compounds of neopentyl polyols, including trimethylol propane esters, are in common usage as base oil stocks for hydraulic fluids, lubricants, and use in particular aircraft engine lubricants, especially in US Government specification MIL-L-23699 turbo oils. Tricresylphosphate and other phosphate esters are commonly added in the same synthetic oil blends as antiwear additives and to prevent interaction of the lubricant with engine surfaces… TMPP or its analogues might therefore be formed when these lubricants are overheated which may be dangerous in aircraft engines where a proportion of the air from the engines is used in cockpit or cabin ventilation. (Clinical and Experimental Toxicology of OPs and Carbamates p 394, Edited by Marrs and Ballantyne, Butterworth/Heinemann 1994)

Dr Marrs has said that these OPs are "known to cause delayed polyneuropathy".

Bruce D’Ancey is technical secretary of the British Air Line Pilots Association (BALPA). He has raised his concerns with the BALPA Medical Study Group, who are very concerned about this issue.

Legal cases are being pursued by pilots and cabin crews in Australia, the USA and Britain, for compensation for long-term neurological damage (Independent on Sunday 27 December 1998). Legal consideration should be being given to the risks run by passengers who may be exposed to OPs, and indeed by members of the public who may be at risk from the danger of air accidents which could be caused by OP exposure. Several UK airline pilots are already looking for legal compensation for chronic neurological damage, though they are prevented from talking to the press or media by a clause in their contract of employment.

Licensing and Risk-Assessment in the UK

OPIN has made enquiries of several government departments about licensing and risks. The Health and Safety Executive (HSE) have no jurisdiction over air-crew, as the HSE's responsibilities end when the aircraft is airborne. The HSE has said that OPs used in this context do not require licensing, as they are "industrial chemicals".

The Department of Environment, Transport and the Regions said that, as TCP has been in use since before 1982 it would not come under the review of toxic chemicals currently being carried out to comply with the EC legislation, as it was used in quantities under 1000 tons pa. TCP falls under the "Existing Substances Regulation", but is not subject to licensing or approval procedures, therefore risk assessments would not be necessary. Each of the departments approached agreed that aircraft safety regulations, in regard to toxic chemicals, are "a difficult area".

A spokesman in the Department of Health (DOH) confirmed that, as far as he knew, neither DETR, HSE, the Environment Agency, COSHH regulations nor DOH deal with human health considerations, once an aircraft has left the ground.

It would appear that this is an area of occupational and public health which has not been given any consideration, although tricresyl phosphate has caused delayed polyneuropathy in aircrew and pilots in other countries, and may well be being brought to the attention of the EC and British courts; it seems the UK government should take some action to remedy this.

The Transport minister said in the House of Commons that the air intake could be isolated from the aircraft engines, and that engines could be shut down if there was a problem. Firstly, there is no mechanism for detecting the presence of OPs in the air circulating in the aircraft, the measurements would have to be so precise and sensitive that they would be extremely expensive to install. Secondly, the reason that air has to go via the aircraft engines is that that is the only way to warm and pressurise the air before it is suitable for the crew and passengers to breathe.

One of the product data sheets for a gas turbine lubricant warns of the effects of the additive TCP but makes no mention of skin absorption, or, more importantly, inhalation.

Questions:

how was the use of these highly neurotoxic OPs sanctioned for use in aircraft engines, when the dangers had been pointed out in a variety of scientific papers?
how can a manufacturer be allowed to include the words "Safe if used according to instructions" when there is a detailed note on neurological damage included in one specific report, which is never seen by pilots or aircrew, and certainly never pointed out to passengers?
what action will now be taken to rectify this hazardous situation, and what guarantees can be given to commercial passengers and air crews that these chemicals will not be used in the way described in the newspaper article?
as these OPs are used in military aircraft, including helicopters, what measures are taken by the MOD to warn pilots of the risks, or to protect them from sealant leaks?
are OPs used as lubricants in other forms of fuel?

Civil Aviation Authority

OPIN spoke to the Press Officer of the CAA on 20 May 1999. In the course of the discussion it was stated that the CAA has carried out a study on "smoke and fumes in aircraft cabins", but that this did not include any information on the presence of OPs. The reason for this was that the CAA does not have detection systems capable of detecting the presence of OPs. When asked what plans were being discussed to deal with this serious matter of health and safety for UK pilots, aircrew and passengers, we were told that "the CAA is awaiting the results of research being carried out in other countries". When asked why such research was not planned for the UK we were told that there was no sense in duplicating such work. We were also told that until they receive complaints of ill-health from British pilots or aircrew the CAA cannot take action; so far, they say, they have had none.