Cutting fluids

What are cutting fluids and how are they used?

Cutting fluids are used to lubricate, cool and protect metal parts from oxidation during ‘cutting’, i.e., metal machining using a cutting or abrasive tool, as well as by electrical discharge machining or deformation. These products fall into two broad categories:

• neat oils;
• and water-based fluids.

The former primarily have a lubricating function (these are usually petroleum oils containing varying amounts of additives) while the latter are mainly used for cooling.

Dissolved substances and particles related to their use

Cutting fluids accumulate metal shavings and particles during use as well as newly-formed chemical compounds such as polycyclic aromatic hydrocarbons. These added elements are generally known to be toxic; for example, some metal compounds are carcinogenic (certain nickel, chromium, and cadmium derivatives, etc.).

Certain activities such as metalworking involve occupational exposure to cutting fluids. However, quantifying exposure to cutting fluids is complex and often imprecise, mainly due to the sampling techniques used.

The use of cutting fluids has been changing since the 2000s. Neat oils were the only fluids in use about 15-30 years ago. Currently, selection of oils depends on the type of application, but the use of neat oils has declined sharply since 2001, unlike that of water-based fluids (emulsions), which is increasing. There are two broad sectors that use these fluids: the metalworking and automotive industries. In all, more than a million workers may be exposed to cutting fluids, according to the French Medical Risk Surveillance survey (SUrveillance MEdicale des Risques professionnels [SUMER]).

Issues - Effects - Implications

Cutting fluids are associated with various malignant and non-malignant diseases. New fluids are mainly linked to mild skin and respiratory diseases, which may nevertheless be chronic and often debilitating, whereas used fluids are also associated with these diseases and some cancers as well. However, the carcinogenic potential associated with the use of new fluids has not been completely ruled out, particularly due to the concentration of toxic compounds during their use.

Conditions caused by cutting fluids are thus being recognised as occupational diseases carrying entitlement to compensation in France (Table 36, 36a and 66a of the general scheme).

Furthermore, allergic dermatitis and asthma may be compensated under other schedules of occupational diseases under the general French Social Security scheme (43, 49, 49a, 65 and 66).

The number of diseases reported and acknowledged in Tables 36, 36a and 66a, however, remains low.

In an occupational context where it is technically difficult to reduce exposure, it would seem essential to ensure and verify the application of regulatory risk assessment measures and use of personal and collective protective methods, by workers exposed to cutting fluids, whether they are users of these fluids or are exposed to oil mist in their workplace environment.

Implementation - Actions taken

In 2008, the Agency produced a preliminary report on these products at the request of the French Ministry of Defence. Its purpose was to provide a summary of the effects of some of these substances(1), and a review of diseases associated with their use. The findings of this work specifically stressed the need to ensure use of personal and collective protective methods by workers exposed to cutting fluids, whether they are users of these fluids or are exposed to oil mist in their workplace environment. The Agency also recommended that further studies be conducted to better assess exposure and risks associated with cutting fluids.

Further to this work, the Agency was asked to conduct a study in order to improve the assessment of levels of exposure to these products, to more effectively define how they are used as well as the collective and personal preventive and protective measures to be implemented, to gain a thorough understanding of the diseases that can result from their use, and finally to improve exposure monitoring and medical surveillance.

An updated inventory of cutting fluids

To address these different issues, ANSES published an inventory of knowledge to date on these products. The Agency thereby updated information about the type and amounts of cutting fluids used in France as well as the industrial sectors employing them. A literature review was conducted to identify existing measurement methods and sampling strategies. At the same time, an exposure assessment report was prepared to provide an account of the actual concentrations currently encountered in various workshops. Finally, the Agency conducted a review of existing equipment for the protection of workers and the prevention of risks associated with the use of cutting fluids, providing a complete inventory of the tools available to manufacturers and healthcare professionals.  

Conclusions

It is clear from this work that the types of cutting fluids used in the country have changed considerably in recent years. Around 15-30 years ago, neat oils were used exclusively. Today, the oils used vary according to the type of application, and while the use of neat oils has declined sharply since 2001, the use of water-based fluids (emulsions) has increased. By 2012, two major industries employed these fluids: metalworking and automotive. In total, more than a million workers may be exposed to these substances.

The Agency’s work also reveals that there are many factors involved in the prevention of risks related to the use of cutting fluids. However, most personal and collective preventive methods, while already known, are not always adopted, especially in small businesses. Furthermore, surveillance methods, despite being described in detail in many guides, are rarely deployed. 

Hazardous substances may be either found in the formulation of the cutting fluids (such as certain additives, biocides, etc.), or formed during storage (as is the case for NDELA(2)). Alternative practices already exist, such as micro-lubrication or dry machining. But finding and implementing substitutes is often challenging when adapting industrial processes.

Finally, there are grey areas with respect to the risks associated with the microbial growth that occurs when fluids age. The increasing use of water-based fluids is associated with problems such as microbial contamination of fluids as well as respiratory diseases that seem to be linked to it. However the lack of a benchmark standard precludes the interpretation of results for these microbial agents that are found in both fluids and aerosols.

Recommendations for more effective prevention

The Agency considers that, while it may be premature to make a quantitative assessment of the health risks associated with these products, given the lack of a reliable measurement for assessing exposure to them, it is necessary to take additional steps toward prevention. The Agency therefore considers that:

• a threshold value could be required with regard to the quantities of secondary amines as nitrosamine precursors in cutting fluids, such as is provided for under current German law;
• the search for alternatives, such as micro-lubrication, should be encouraged;
• support should be provided for the development of a microbiological benchmark standard that can take into account the quality of the fluids and the protection of workers.

(1) The substances referred to in this formal request are those used in connection with the activities listed in Annex I-A
(2) N-nitrosodiethanolamine