COSHH regulations and chemical hazards associated with metal-working fluids

COSHH regulations and chemical hazards associated with metal-working fluids

Alan Hodges*

Keywords: metal-working fluids, chemical hazards, risk evaluation

Introduction The subject of hazards, both chemical and microbiological, arising from the use of water-based metal-working fluids (mwf) has for many years tested the temper, patience and reasoning of user and supplier alike as pungent complaint is followed by protestation of innocence that is followed in turn by counter attack and improvised defence until the problem goes away or the product (and occasionally, the supplier) is thrown out. In the United Kingdom, the introduction of the Control of Substances Hazardous to Health Regulations 1988 (COSHH) , which came into force in October 1989, is likely to have far-reaching effects on the way in which suppliers of mwf and their customers deal with potential and actual hazards, and with each other.

Hazards arizing from microbiological sources together with the role of biocides will be dealt with in the following paper.

Before going on to discuss the nature of the hazards that can arise, directly or indirectly, from the chemical constituents or contaminants in mwf, it is first necessary to consider the C O S H H regulations themselves, for they will in future provide the framework within which virtually all hazardous substances in the workplace will be judged.

The COSHH regulations In essence, C O S H H sets out measures that employers (and sometimes employees) have to take to effect satisfactory control of hazardous substances and to protect people exposed to them. At the heart of the regulations lies the requirement to assess the risks to health posed by substances and the way they are used. This has led to a certain amount of confusion as to the definitions of 'hazard' and 'risk', which in the context of C O S H H are not interchangeable.

The hazard arising from a substance is 'its potential to cause harm' whether by inhalation, ingestion,

*Greenhayes Cottage, Roberts End, Hanley Swan, Worcestershire, WR8 0DL, UK.

contact with the skin etc. In most cases, the hazard presented by a substance can be defined from data supplied by the manufacturer or from the literature but CO S H H also covers substances generated by a process whether deliberately or not, for example, the release of hydrogen sulphide gas by anaerobic micro- organisms in mwf.

The risk involved in using a substance is the likelihood that it will cause harm in the actual conditions of use in the workplace. It is a judgement that can be made only after all of the circumstances surrounding the use of the substance in question are considered and it is this duty to carry out an assessment of risk that sets the C O S H H regulations apart from any previous safety legislation.

It follows that where the risk to health from a substance is judged to be high, steps must be taken to reduce or eliminate exposure of the workforce to that hazard. The regulations specify that where necessary measures must be introduced to control risks; checks must be made to ensure that such measures are properly carried out; exposure to hazards should be monitored; if appropriate, the health of workers should be kept under surveillance; and full training should be given to relevant personnel to ensure that all designated precautions are observed. All assessments, control measures and procedures should be recorded in writing and reviewed whenever circumstances change. It is a requirement of CO S H H that from 1st January 1990 no work that is liable to expose someone to hazardous substances shall be carried out unless an assessment has been made I.

COSHH and metal-working fluids When a chemical that is known to be a serious hazard, eg, concentrated sodium hydroxide, is used in an industrial process, the assessment to evaluate the risks posed to health is reasonably straightforward. In this case, all contact with the skin and eyes must be eliminated as NaOH is extremely corrosive to tissue and therefore any consideration of a process that allowed the possibility of contact between the chemical and workers would conclude that the risk to health

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A. Hodges--COSHH regulations and chemical hazards associated with metal-working fluids

was unacceptable. If such a process existed, then it would have to be modified to eliminate the possibility of such contact occurring.

When one begins to assess mwf and their systems of use in the light of COSHH, it soon becomes apparent that they fall into a category that can assume several shades of grey, at least when compared with the black and white example given above. The assumption has to be made that a certain amount of contact, depending on the type of machine tool and the operation, will take place between the mwf and the operator, and that if decades of experience are anything to go by, such contact can be measured in hours per day for each operator rather than minutes. This is borne out by the wording commonly found on mwf product data sheets to the effect that 'unnecessary contact should be avoided', thereby implying that some necessary contact is inevitable.

What sets mwf apart from almost any other category of hazardous substance is the degree and variety of contamination to which they are subjected even in normal use, and the extent and variability to which each chemical constituent is consumed or degraded according to its individual function. Contamination of mwf has always been and always will be a problem even when the tendency to use the machine-tool sump as a rubbish bin is eradicated - the influence on the safety of operators of micro-organisms, excess lubricating oil (including hydraulic oil), dissolved metal complexes, particularly iron, nickel, chromium, cobalt and work-hardened metallic swarf can be neither underestimated nor easily quantified.

In considering the toxicological effects of any substance, the concentration of the substance (whether in solution, or in vapour or droplet form in the air) and the length of time of exposure of the worker to the substance are of fundamental importance. This is especially so in the case of water-based mwf where the concentration and exposure time can vary widely between different users and machining operations. In assessing the general risk to health, one must be aware of the potential for both acute and chronic effects. Short exposure to high concentrations of a hazardous material may produce acute reactions, which pass once the affected person is moved away from the hazard. Long exposure to sub-acute concentrations can generate chronic complaints, which can eventually be more disabling than the acute effects. The evaluation of long-term risks to health is particularly important in the case of mwf because of the nature of long- established working practices, the design of machine tools and the layout of machine shops.

When worker exposure is unavoidable and where the hazard is significant but below a threshold when the toxic effects become apparent, then the concept of 'susceptibility' of the worker must be taken into account. Genetic and constitutional factors make some individuals more likely to suffer ill effects, for example, skin irritations and disorders 2-~ even when normally inoffensive mwf are being used in the correct manner. To comply with COSHH in these instances, it may be necessary, as a last resort, to move susceptible individuals to work areas in which contact with mwf can be eliminated completely.

Formulation requirements

The chemist given the task of formulating a successful product can construct a list of essential characteristics for the new mwf that will vary in detail depending on the proposed area of use but that will include the following general features:

(1) some performance criteria, eg, extended tool life. good surface finish etc.,

(2) stability in hard/soft water, (3) corrosion inhibition of ferrous and non-ferrous

metals, (4) resistance to the growth of micro-organisms, (5) unreactive to paint finishes, (6) non-foaming, (7) cost-effective, (8) environmentally acceptable, (9) safe to use.

This is a formidably complex list of requirements somewhat analogous to giving a motor car engineer the brief of designing a vehicle with the looks and performance of a Ferrari with a maximum fuel consumption of 40 mpg (unleaded) and the load- carrying capacity of a 10 ton truck. Added to this it should cost no more than an average small car.

From the point of view of safety, the chemist faces the familiar dilemma that while it is relatively easy to show that certain substances are dangerous, it is almost impossible to prove that alternatives are safe.

Most raw materials in common use in the oil industry can be deployed effectively at concentrations below the threshold at which risks to health begin to appear. Difficulties arise in the prediction of increased risks when raw materials are used in intricate combinations or at concentrations close to the 'safety threshold'. The problem is that the 'safety threshold' can be determined only by trial and (sometimes bitter) experience.

The author can remember a situation that occurred some years ago in which, employed by a major oil company and acting as stand-in quality control supervisor, he had to discover why a particular batch of a cresylic acid-based (phenolic) soluble oil did not meet its designated specification. It was not possible then (and is scarcely more so now) to analyse the product in a chemical sense - apart from a few simple tests such as the pH and specific gravity; examination of the batch consisted of testing for certain effects, eg, corrosion inhibition and stability in water of standard hardness. When a product batch failed one or more tests, quality control staff used their knowledge and experience to 'adjust' samples of the batch by adding various raw materials in different concentrations until, after long and laborious trials, an adjustment of the whole batch could be made to bring it within the approved specification limits. This batch of phenolic soluble oil could be adjusted only by the addition of a further 2% w/w of the cresylic acid (to the 18% or so already in the formulation). No-one will ever know what the actual composition of that batch was but it had to be recalled from the car engine manufacturing plant to which it had been consigned because it caused an outbreak of (fortunately not serious) skin irritation for almost everyone that used it. Whether the addition

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of the extra cresylic acid caused the problem or whether the batch accidentally contained an unspecified raw material, there was no reason at the time to suspect that the product could suddenly become hazardous - it did, after all, meet the test specification agreed between manufacturer and customer. If you ask what happended to the idiot stand-in quality control supervisor, well he had obtained approval for his recommended adjustment of the batch from the head of quality control, so perhaps he was not such an idiot after all.

The point of this anecdote is that formulating and manufacturing 'safe' products is not as straightforward as it might be in an ideal world and care should be taken when attempting to assess products from a consideration of their chemical constituents.

The formulation of a modern oil-based soluble cutting fluid may contain more than a dozen ingredients, most of them process chemicals, which are themselves complex mixtures. A commonly used type of emulsi- fier/corrosion-inhibitor package is known as a 'borate ester'. This is formed by esterifying an alcohol with boric acid and then reacting the product with an alkanolamine, usually diethanolamine. The alcohol and the amine are normally technical grade and therefore contain impurities (isomers and other alco- hols, plus monoethanolamine and triethanolamine) and it is possible to calculate that this type of ingredient can consist of up to 16 or so discrete chemicals (reaction products and unreacted starting materials). Whilst not all raw materials are as complex as this, the chemical composition of a typical water-mix soluble oil is an analytical chemist's nightmare and requests from customers for precise details of the make-up of every product ingredient, together with Hazchem and UN numbers and exact concentrations, have raised a wry smile or two among members of more than one oil company's technical department. All suppliers must, of course, do their best to comply with such requests but it is the author's view that these are often paper exercises designed to satisfy the letter of the law rather than its spirit. Both raw materials and finished oil products are manufactured by batch processes, and interbatch variations in the composition of both are inevitable and permissible because as ha.s been mentioned before, the final product is tested for certain effects, not composition. Safety assessments based on nominal compositions cannot by themselves resolve the real issue of reducing the risk of exposure of operators to hazards.

There are questions that can and should be asked about all mwf and these will be considered in due course.

Types of metal-working fluid Cutting oils are traditionally divided into three types: neat oils, oil-based solubles and oil-free synthetics. In the context of COSHH, these divisions have to be extended to cover the storage and handling of unused concentrates including sterilizing and cleaning agents. Thus, different types of mwf are the following:

(1) neat oil, (2) oil-based soluble concentrate,

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(3) water-based (synthetic) concentrate, (4) in-use emulsion/solution, (5) sterilizer/cleaner.

Attempts have been made in the past to evaluate the risks associated with different categories of mwf ingredients 2~4=6 but for reasons already given, the author believes that the number and variety of raw materials now available makes this an unrewarding exercise for COSHH purposes. Instead of trying to describe typical constituents of mwf and their potential hazards, it may prove more meaningful to consider known hazards and then highlight possible sources.

Hazards associated with metal-working fluids

Skin irritation (dermatitis) In practice, the vast majority of complaints about mwf concern skin irritation in one form or another. The variety of symptoms are described in detail elsewhere 2"4-~ but irritant-contact dermatitis is the most commonly encountered problem, with defatting of the skin on the hands as the most frequent cause. The detergency of water-mix soluble oils is chiefly responsible for this but the risk is directly proportional to the exposure time and more importantly, to the concentration of the emulsion in use. In the author's opinion, variation in in-use concentration (given a recommended 3 or 5%, anywhere between 0.5 and 20% is likely to be found) has a far greater bearing on every aspect of performance and safety than the difference between two different products used at the same concentration.

Cancer of the skin caused by contact with oil is now very rarely encountered thanks to the widespread use of solvent-refined oils with an aromatic carbon content (CA value) of typically 8% or below, to the ever- increasing use of water-based products instead of neat oils and to improvements in standards of hygiene. All users of oil products obtain assurances from their suppliers that mineral oil constituents are solvent refined.

There are many types of oil product in use in plants where metalworking takes place, including quenching and hydraulic oils, and these should also be taken into account. Indeed, the leakage of hydraulic oil into the mwf in a machine-tool sump is probably greatly underestimated as a source of skin irritation. Low- viscosity hydraulic oils are excellent 'solvents' for natural skin oils and while warnings are always given about the dangers of washing hands in paraffin etc., little attention seems to be paid to the same potential danger from a 'hidden' source.

Other contributory factors to the irritancy of an mwf are microbiological degradation (see the following paper) , dissolved metal compounds, usually soaps, which can promote allergic reactions in some individuals 2,3 and the presence of fine metallic swarf that can abrade the skin, an effect that can be unpleasant enough in its own right but that is also a contributory factor in other sources of irritation.

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Eye irritation

Irritation of the eye can occur through direct contact with the mwf and through high concentrations in the air of volatile constituents from, for example, cleaning agents in circulation in a machine-tool system. These conditions are temporary (though extremely painful in the case of direct splashing into the eye) and the author is not aware of any incidents resulting in permanent damage to the eye from cutting fluids (as opposed to damage from flying metal swarf).

Inhalation of metal-working fluids

Inhalation of aerosolized droplets of mwf is a subject causing some concern at the present time largely because there is uncertainty about what the precise medical effects may be. Inhalation of droplets containing micro-organisms will be dealt with in the following paper but there are also fears that the inhalation of mineral oil over a long period of time can lead to pulmonary disorders 3. The threshold limit value (tlv) for oil mist is 5 mg m 3 with a recommended maximum for comfort of 2.5 mg m- 3 but the distinction between oil that finds its way into the atmosphere by mechanical means, for example, from a high-speed machining operation, and smoke and fumes from localized overheating of the cutting fluid is one that is not made very often, if at all. Yet experience shows that in the majority of cases in which high concentrations of atmospheric 'fog' have affected operators with symptoms of coughing or eye irritation, the cause has been misapplication of the cutting fluid, whether neat oil- or water-based emulsion, to the tool/workpiece.

The most common fault is to direct the fluid as a high- pressure jet, which impacts on the hot metal surface and rebounds in all directions, leaving only a small fraction of the original volume to effect the cooling and lubrication function. Any water present in this thin film is very rapidly vaporized and the remaining oily constituents are 'burned' , evolving among other things, volatile compounds of sulphur, nitrogen and phosphorus together .,/ith organic and chlorinated compounds depending on the composition of the original product. The atmosphere surrounding the machine tool can therefore contain a mixture of the cutting fluid in aerosol form and its products of decomposition.

For some years, the possibility that carcinogenic nitrosamines can be formed in mwf containing sodium nitrate and amines, particularly alkanolamines, has been debated. It is now beyond doubt that nitrosamines can exist in water-based mwf 7-1° even in the absence of either 'added' nitrate or amine. However, the highest levels have consistently occurred when both nitrate and amine were present in the original concentrate. What is also beyond question is that many nitrosamines are highly carcinogenic to a wide variety of animals and it seems unlikely that man alone can be resistant to their effects It. The aspect of the debate that is unresolved is the amount and rate of intake of nitrosamine that would be required to cause cancer in man and in particular what is the risk faced by machine- tool operators in this respect. The evidence so far suggests that the risk is extremely small but as one of

the routes by which nitrosamines can enter the body is inhalation, it is prudent to consider the possibility in this section. For a realistic perspective of the nitrosamine question, there can be few better expo- sitions than that of Bennett and Bennett 7.

The microbiological influence on nitrosamine formation is also dealt with in the following paper as is the generation of hydrogen sulphide gas by the action of anaerobic micro-organisms on sulphur-containing compounds in the mwf.

One report 3 mentions the incidence of very high levels of cobalt in the coQlant mist associated with toolroom grinders (cobalt being extracted from tungsten carbide tools). A rare condition, fibrosis of the lungs, is attributed to the inhalation of cobalt over long periods.

Assessment of risks

Having defined the hazards, it is now necessary to assess the risks. For the purpose of complying with COSHH, it is necessary to assess cutting fluids with respect to their composition and to the way in which they are used in each individual workplace. Some concern has already been expressed at the lengths to which suppliers are sometimes expected to go in defining the chemical nature of their products' ingredients but there are questions concerning raw materials used in mwf that it is essential to ask.

Are all mineral oils properly refined to cut the concentration of polycyclic aromatics (pcah) to 8'/o or below? What type of biocide is used and is it normally present at a concentration high enough to control the growth of micro-organisms but not so high that health risks increase? Does the product contain certain materials associated directly or indirectly with health hazards and if so, at what concentration? These materials include sodium nitrite, diethanolamine (or other amines), sulphur (in an additive) and some phenols.

In looking at operating systems, a further series of questions become apparent.

To what extent does skin contact between operator and mwf occur? Is eye contact possible? Are aerosol mists generated and if so, for how long are individual workers exposed to them? Does microbial spoilage of the mwf occur, characterized by falling pH and unpleasant smells? Do hydraulic and other lubricating oils find their way into the machine-tool sump? Does the coolant filtration system work efficiently? Is the concentration of the mwf checked regularly?

Controls If an inspection of products and operating systems reveals that workers are exposed to hazards sufficient to put them at risk, for example, continuous exposure to dense clouds of 'oily' fumes, then it becomes necessary to implement some controls to reduce or eliminate the risk. The following list of control measures should cover most situations and most types of product and should, hopefully, already be familiar to mwf users.

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(1) Monitor fluid concentration and adjust as often as necessary.

(2) Monitor microbial populations. (3) Reduce skin contact to an absolute minimum. (4) Eliminate eye contact. (5) Ventilate, or introduce extraction equipment , to

reduce aerosol mists. (6) Minimize leakage of hydraulic oils into sumps. (7) If appropriate , monitor concentrations of dis-

solved metals. (8) Clean machine tools thoroughly and regularly

using a proprietary cleaning/sterilizing agent. (9) Use all products strictly in accordance with the

manufacturer ' s instructions.

Conclusions Although the introduction of the C O S H H regulations will have been greeted by some sections of industry with dismay as yet another example of bureaucratic interference adding to the workload of already over- loaded individuals and depar tments (and there is no denying that at least initially complying with C O S H H is a t ime-consuming business), it should be evident that making assessments and implementing controls on metal-working fluids will in the long term not only improve the prospects for safer working practices but will also bring other benefits by increasing coolant life, reducing down-time, aiding cutting performance and

minimizing wastage. These are all desirable conse- quences.

References 1. COSHH Assessments. HMSO, London, 1988

2. Taylor J.S. Dermatoses associated with metal-working fluids. Proc. 2nd Int. Conf. on Lubrication. ITT Research Institute, Chicago, 1979

3. Kipling M.D. Health hazards from cutting fluids. Tribology International, February 1977

4. Hodgson G. Cutaneous hazards of lubricants. Industrial Medicine, 1970, 39, 2

5. Hodgson G. Health problems arising from contact and exposure of workers to metal working fluids. J. Inst. Pet., 1973, 59, 565

6. Alomar A. et al Occupational dermatoses from cutting oils. Contact Dermatitis, 12, 129-138

7. Bennett F.O. and Bennett D.L. Metalworking fluids and nitrosamines. Tribology International, 1984, 17(6), 341-346

8. Nitrosamines in synthetic metal cutting and grinding fluids. Guidance Note EH49. Health and Safety Executive, London, 1987

9. Anon. Nitrosamines formation in metal working fluids. Pet. Rev., August~September 1980

10. Loeppky, R.N. et al Reducing nitrosamine contamination in cutting fluids. Fd, Chem. Toxic., 1983, 21(5), 607-613

11. Fribush H.M. The effects of TSCA on the metalworking fluid industry: increased awareness of the presence of nitrosamines in metalworking fluids. Am. Chem. Soc. Natl Mtg. Las Vegas, April 1982

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COSHH regulations and chemical hazards associated with metal-working fluids