2013_Semanova_Health Effects From Occupational Exposure to Metalworking Fluid Mist

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Health effects from occupational exposure to metalworking fluid mist

Petra SEMANOVÁ1, Marián KUČERA2 1Technical University in v!len, "ac#lty !$ Envir!n%ental an& Man#$act#rin' Techn!l!'y

(t#&ents)á 2*, +* -. v!len, Sl!va)ia

2Technical University in v!len, "ac#lty !$ Envir!n%ental an& Man#$act#rin' Techn!l!'y(t#&ents)á 2*, +* -. v!len, Sl!va)ia

1/etra0se%an!va1+'%ail0c!%, 2)#cerat#v!0s)

Keywords3 %etal4!r)in' $l#i&s, health ris)s, aer!s!ls $!r%ati!n

Abstract

Metalworking fluids (MWFs) are an essential part of a technological process. They are used inmachining operations for enhancing cutting process performance. The performance of MWFsdepends on properties such as specific heat, viscosity, density and thermal conductivity. MWFs areused to cool and lubricate the cutting one, flush away chips and inhibit corrosion during machiningoperations. !n the other hand, MWFs are associated with formation of li"uid aerosols (mists) thatrepresents two types of occupational risk factors for machine operators # chemical and biological.$pidemiological assessments with machine operators in the metalworking industry have identifieddermatologic and respiratory effects. The aim of this article is to review what is known about healtheffects from inhalation e%posure to mist from various types of MWFs.

Introduction

!ver the course of the past decade, the metalworking industry stakeholders have becomeincreasingly aware of non#infectious disease health risks posed by microbes present as

metalworking fluid system contaminants.Metalworking fluids (MWFs), also called cutting fluids, cutting oils, or lubrication fluids, are

widely used during machining operations of metal parts such as turning, grinding, boring, milling, broaching, drilling, hobbing ect.. Their purpose is to provide lubricity in order to remove frictionand control thermal distortion by carrying away the heat, thereby improving machinability. &t thesame time, they e%tend tool life, reduce power consumption and remove metal chips '. *owever,MWFs often produce airborne mists, smoke, gases or particulates that are intrusive to the factoryenvironment. Mists are aerosols comprised of li"uid particles of less than + microns which becomesuspended in the air for several hours, possibility in the workers breathing ones. The potentialhealth haard of to these MWFs mist have been the sub-ect of numerous epidemiological studies,which shown statistically significant increase in several types of cancer as well as an increased riskof respiratory irritation or illness due to prolonged e%posure to MWFs '+.

Metalworking fluids – applications and characteristics

MWFs play a significant role in machining operations and impact shop productivity, tool life and"uality of work. With time and use, fluids degrade in the "uality and the eventually re"uire disposalonce their efficiency is lost. Waste management and disposal have become increasingly morecomple% and e%pensive.

MWFs are generally classified into four types1. Straight oils (neat oil) MWFs are not mi%ed with water and will not form an emulsion with

water. They are generally mi%tures of mineral oil and animal, vegetable, marine or syntheticoils to improve the wetting and lubricating properties, which are used singly, or incombination and with or without additives. The advantages of straight cutting oils are goodlubrication, effective anti#seiure "ualities, good rust and corrosion protection, and stability./isadvantages are poor cooling, mist and smoke formation at high cutting speeds, high initial

Key Engineering Materials Vol. 581 (2014) pp 112-118 Online: 2013-10-07 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/KEM.581.112

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and disposal cost. 0traight oils do not work well in high speed cutting operations because theydo not dissipate heat effectively. 1ecause they are not diluted with water and the carry out rateon parts is high, these oils are costly to use and, therefore, only used when other types ofMWFs are not applicable.

+. Soluble oils (emulsifiable oil) are supplied as concentrates that are mi%ed with water to form

usually +#2 emulsion. 0oluble oils contain 3# 452 mineral oils. These emulsify form amilky white emulsion. &dvantages of water emulsifiable oils are good cooling, low viscosityand thus ade"uate wetting abilities, non#flammable and nonto%ic, easy to clean from smallchips and wear particles using standard filters, relatively low initial and disposal cost./isadvantages are low lubricity, rancidity and misting, low stability (components havedifferent degradation levels), in mass production re"uire everyday e%pensive maintenance inorder to keep the re"uired composition. Water emulsifiable oils are the most popular MWFsin use today. 1ecause they combine the lubricating "ualities of oil with the cooling propertiesof water they can be used in a wide range of both machining and grinding operations.

3. Semi-synthetic MWFs contain a lower amount of mineral oil (5#32), a higher proportion ofemulsifiers, and 3#52 water. They form a very fine emulsion that looks very much like a

solution, but in fact, is an emulsion. The cooling and 6owing properties are better while thelubricating ability is poorer than in the soluble oils.

7. Synthetic MWFs are water#mi%ed concentrates that no mineral oils and content 8#952 water.They form clear or translucent solution when added to water. 0ynthetic MWFs do not containany oil. &dvantages of synthetic MWFs are resistance to rancidity, low viscosity and thusgood cooling and wetting, good rust protection, little misting problems, non#to%ic, completelynon#flammable and non#smoking, good filtration with standard filters, biodegradable./isadvantages are insufficient lubricity for heavy duty applications, reaction with non#metal

parts, residue is often a problem. The ma-or problem is that lubrication has always been the big problem for synthetic coolants. &nother problem caused by synthetics is the sticky andgummy residue that is sometimes left when water evaporates from the solution mi%. Metalsafety on non#ferrous metals is a problem with some synthetics because of their relativelyhigh p* and the lack of oil to act as an inhibitor '3, 7, 5.

:riteria for the application and evaluation of MWFs are• the machining results (geometrical surface "uality),• energy consumption (cutting forces),• effectiveness of manufacture (min. tool wear),• productivity (min. essential operating time),• process safety (edge#holding property, chip breaking) ';.

Aerosol (mist) formation and health risks

MWFs may contain other substances such as emulsifiers, stabiliers, corrosion inhibitors, biocides, fragrances, e%treme pressure additives and contaminants. The using of MWFs is veryuseful, but on the other hand, is potentially dangerous < they are cause of formation li"uid aerosols(mists) that can cause a variety of health problems such as dermatitis, asthma and hypersensitivity

pneumonitis.Mist production during the machining process gives rise to several signi=cant negative effects.

Mist is a term loosely applied to a dispersion of li"uid particles, many of which are large enough to be individually visible without the assistance of a visual aid but are commonly less than + >m insie. ?ue et al. identified two primary mechanisms for MWFs mist formation evaporation< condensation and atomiation. /ue to the e%treme temperatures that are generated during

machining, the MWFs may vaporise and subse"uently condense around spontaneously generatedli"uid nuclei or other foreign particles to form droplets. &tomiation is a purely mechanical process.The impact of the fluid -et as well as the rotation of the workpiece or cutting tool transmitmechanical energy to the fluid, which becomes unstable and disintegrates into droplets '8, 4.

Key Engineering Materials Vol. 581 113



The MWFs formation mechanisms (atomiation and vaporiation@condensation) are shown inFigure .

Fig. MWFs mist formation mechanisms '8

The mist of small droplets are suspended in the air and can be inhaled and ingested. When thesefluids into a mist during the machining process, they can be very irritating to the eyes, nose throat.

The larger droplets can pass into the nose and windpipe and can be swallowed. The smaller dropletscan deposit into the lungs.

The inhalation of MWFs mist vapors and smoke over a period of time may cause asthma orhypersensitivity pneumonitis, and evidence has suggested that they may lead to lung cancer. Therepeated e%posures to these insoluble fluids may also cause sensitiation at different degrees.

The aerosoliation of the other contaminants that are present in the MWF sumps may posegreater threat than the mineral oil itself. These adverse health effects are currently being researched.MWFs are to%ic and e%tremely haardous and are e%posed to innumerable amount of people duringcourse of a single day '.

The MWFs aerosols that are generated during machining processes represent a significant wastestream as well as a health haard to humans. Aespiratory illnesses associated with MWFs inhalation

include respiratory irritation, bronchitis, occupational asthma, and loss of lung function. 0everalepidemiological studies have also shown statistically significant increases in cancer of theesophagus, stomach, pancreas, laryn%, colon, and rectum due to prolonged e%posure to MWFaerosols The parts of respiratory system, which can be affected by the e%posure aerosols, are shownin the Fig. +.

Fig. + Barts of the respiratory system '9

The !ccupational 0afety and *ealth &dministration (!0*&) have defined a permissiblee%posure limit of 5 mg@m3 for oil mist (4#hour time weighted average) that industry is legally

re"uired to meet. CD!0* recommends an even stricter e%posure limit to MWFs of .5 mg@m3 totalsuspended particulate (T0B) and .7 mg@m3 for thoracic particulate mass (#hour time weightedaverage) '4.

114 Precision Machining VII



The health effects from variety types of MWFs are describe in Tab +.

Tab *ealth effects from variety types of MWFs 'Type of MWFs ealth effects

MWFs

0traight

&cute inflammation of the lungs (lipid pneumonitis) and asthma .!il acne andfolliculitis are the most common skin conditions reported for straight oils. Eight oils candefat the skin and denature membrane proteins. 0ymptoms characteried by redness,swelling and occasionally pustules. Drritant action decreases as the boiling point of theoil increases. :hemical additives and contaminants may increase carcinogenicity ofMWFs, cause irritation of the respiratory tract, cause respiratory or dermal sensitiation.1iological contaminants may cause respiratory symptoms and changes in lung function.

0oluble

The concentrate and the diluted emulsion may be irritating to the skin, eyes andrespiratory tract. Microbiological e%posure concerns have also been raised.

Con#allergenic contact ecema normally appears on the hands in connection with wetwork using emulsified cutting oils. &llergic contact ecema is not common andcommonly results from e%posure to additives. *ealth effects associated with water <mi%ed MWFs include irritation of the upper respiratory tract, occupational asthma,chronic inflammatory reaction of the lungs and a form of pulmonary fibrosis.

0ynthetic

Most synthetic based oils have a low order of acute to%icity and are only slightly ormoderately irritating to the eyes and skin. Brolonged and repeated contact may result indermatitis. :onsideration of all of the different compounds used in synthetic MWFs andtheir health effects is beyond the scope of this report, however, it is reported that thesecompounds do not pose a significant additional health haard compared with straightmineral oils. 0ynthetic coolants, which do not contain mineral oil, present similar healthhaards to mineral oil based soluble oils.

0emi #synthetic

0emi#synthetic coolants, which contain a small amount of mineral oil, present similarhealth haards to mineral oil based soluble oils.

Mineral

oil eneral

Eight petroleum distillate vapours, such as kerosene, gas oil or solvents, may cause mildrespiratory irritation. Dnhalation of oil mist for short periods may cause irritation of the

upper respiratory tract. Brolonged and repeated e%posure to high concentrations maylead to the formation of lung fibrosis. Dnhalation of large amounts of oil mist can resultin lipid pneumonia and increased lung markings.Mineral oils have a low order of acute oral to%icity. &bsorption in the digestive tract isminimal. &ccident ingestion results in nausea, vomiting and diarrhoea. Gomiting of lowviscosity mineral oils can result in aspiration of the product into the lungs resulting inchemical pneumonitis. Mineral oils have a low percutaneous to%icity. &pplication ofmineral oils to the skin causes mild to moderate skin irritation in animals. Aepeate%posure may cause defatting of the skin leading to irritation. 0kin rashes, ecema or oilacne may occur following repeated and prolonged e%posure.

ealth risk of using MWFs

!espiratory "iseases# Dnhalation of MWFs mist or aerosol may cause irritation of the lungs,throat, and nose. Aespiratory effects fall into three main categories upper respiratory irritation,asthma, and hypersensitivity pneumonitis (*B).

Dn general, respiratory irritation involves some type of chemical interaction between the MWFsand the human respiratory system. Drritation may affect one or more the following areas nose,throat (pharyn%, laryn%), the various conducting airways or tubes of the lungs (trachea, bronchi,

bronchioles), and the lung air sacks (alveoli) where the air passes from the lungs into the body.$%posure of MWFs or aerosol may also aggravate the effects of e%isting lung disease.

$%posure of MWFs has been also associated with asthma. & variety of components, additives,and contaminants of MWFs can induce new#onset asthma, aggravate pre#e%isting asthma, and

irritate the airways of non#asthmatic workers.:hronic bronchitis is a condition involving inflammation of the main airways of the lungs thatoccurs over a long period of time. :hronic bronchitis is characteried by a chronic cough and bycoughing up phlegm. The phlegm can interfere with air passage into and out of the lungs. This




condition may also cause accelerated decline in lung function, which can ultimately result in heartand lung function damage.

*ypersensitivity pneumonitis (*B) is an inflammatory disease that affects primarily the deeplung or peripheral airways. *B is not the same as asthma, which involves constriction of theconducting airways leading to the lower lung. Moreover, although both diseases involve the activity

of the immune system, the mechanism of action differs between the two. *B is associated with thecell#mediated response arm of the immune system, whereas asthma is more typically amanifestation of the humoral # or antibody#mediated immune response ', +.

$kin "isorders# 0kin contact occurs when the worker dips his@her hands into the fluid or handles parts, tools, and e"uipment covered with fluid without the use of personal protective e"uipment,such as gloves and aprons. 0kin contact may also result from fluid splashing onto the employeefrom the machine if guarding is absent or inade"uate. Two types of skin disease associated withMWFs e%posure are contact dermatitis and acne. The two kinds of contact dermatitis are irritantcontact dermatitis and allergic contact dermatitis. Dn irritant contact dermatitis the rash is confinedto the area in contact with the irritating substance. Dn allergic contact dermatitis the rash can spread

beyond the area directly in contact with the irritant. 0traight oils are often associated with acne#like

disorders characteried by pimples in areas of contact with the MWFs. Aed bumps with yellow pustules may develop on the face, forearms, thighs, legs, and other body parts contacting oil#soakedclothing '3, .

%ancer# !ver the years a number of studies have found an association between working withMWFs and a variety of cancers, including stomach, rectal, pancreatic, laryngeal and skin. Thesestudies, depending on interpretation, found e%posure#response associations for cancer of the laryn%,esophagus, pancreas and rectum of e%posed workers. $pidemiology based on smaller and earlierstudies found an increase in stomach, rectal, pancreatic and laryngeal cancers associated withe%posure to metalworking fluids. There are, however, multiple confounding factors that work tomodify the conclusion that there were increases in stomach cancer '+.

%onclusion MWFs are among the most commonly used process materials in the metal working industry.They help to achieve a prescribed result in terms of tool life, surface finish and accuracy#to#sie,and make chip#breaking and chip#transport easier. Cevertheless, they do give rise to certain

problems in the immediate working environment and in waste disposal. /ue to the increasingnumber of laws and directives governing industrial safety and environmental protection, the use ofcutting fluids is putting intense economic pressure on manufacturing companies '8.

The four types of MWF, straight, soluble, synthetic and semi#synthetic, have different chemicalingredients. :hanges in the composition of fluids over time may have been driven by the need toimprove performance. Dt is likely that the occupational health risks caused by the use of MWF varydepending on not only the type of process and fluid, but also the operation environment in which

they are used. The !$E has only been applicable to straight MWF, without consideration ofdifferent particle#sie fractions.

The assessments of occupational health risks caused by airborne MWFs emissions is either basedon the sum of aerosols and vapour or based on aerosols solely. The inhalation haards of MWFsmist are caused by e%posure to three agents neat fluid, microbial contaminants, and other chemicalcontaminants of the fluids.

Fluids must be monitored to prevent problems. &n important aspect of fluid monitoring is asystem of controls and periodical measurements of the fluids properties, such as concentration, p*and biological growth. The health effects associated with e%posure to the more recently#developedwater#soluble fluids such as synthetic and semi#synthetic fluids are not yet fully understood. Therisk that each fluid type poses to workers may vary due to various degrees of refining, recycling,

improperly reclaimed chemicals, different degrees of chemical impurity, and chemical reactions between components. Therefore, an !$E that is applicable to all types of fluids withoutconsideration of sie characteristics, and which is based on the assumption that there are nosignificant differences in risk among fluid types, could be contentious '3, 7.




The article mentioned the health risks of different types of MWFs (Tab. ) in the workplace,which generate a risk that in term of safety and health of workers is a potential source of danger.For this reason, it is important to know assess the potential haard operator and globally "uantifythe risks of using MWFs.

Acknowledgements

The authors gratefully acknowledge to 0& 0A for funding assistance of research pro-ect G$&@7@.

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Precision Machining VII

10.4028/www.scientific.net/KEM.581

Health Effects from Occupational Exposure to Metalworking Fluid Mist

10.4028/www.scientific.net/KEM.581.112

http://dx.doi.org/www.scientific.net/KEM.581

http://dx.doi.org/www.scientific.net/KEM.581.112

http://dx.doi.org/www.scientific.net/KEM.581.112

http://dx.doi.org/www.scientific.net/KEM.581

2013_Semanova_Health Effects From Occupational Exposure to Metalworking Fluid Mist

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