Lubricants and the environment

Tribology International Vol.31,Nos 1–3,pp.35–47,1998©1998Elsevier Science Ltd.All rights reservedPrinted in Great Britain 0301–679X/98/$19.00+0.00PII:S0301–679X(98)00006–1Lubricants and the environmentWilfried J.BartzAbout 1%of the total mineral oil consumption is used to formulate lubricants.Everywhere the production,application,and disposal of lubricants has to cover the requirements of the best possible protection of our nature and the environment in general and of the living beings in special.Often health hazards do not follow the direct way to human beings,more often they follow indirect routes through our environment.For all cases of direct contact between lubricants on one side and human beings and the nature on the other side the compatability has to be checked.The gaining necessity for environmental compatability tests has to be understood by all those who are working in the fields of production,application,and disposal of lubricants.Simplified it can be stated that health hazards and water hazards have to be ing the three examples Coolants and Metal Working Lubricants,Engine Oils,and Fast Biodegradable Lubricants and Operational Fluids some of the most important aspects of the impairment of the environment will be discussed.©1998Elsevier Science Ltd.All rights reserved.Keywords :impairment of environment,laws and regulations,definition of health and water hazards,environmentally acceptable lubricants,environmental labellingIntroductionAbout 1%of the total mineral oil consumption is used to formulate lubricants.Everywhere the production,application,and disposal of lubricants has to cover the requirements of the best possible protection of our nature and the environment in general and of the living beings in special.Often health hazards do not follow the direct way to human beings,more often they follow indirect routes through our environment.For all cases of direct contact between lubricants on one side and human beings and the nature on the other side the compatability has to be checked.The gaining necessity for environmental compatability tests has to be understood by all those who are working in the fields of production,application,and disposal of lubri-cants.Technische Akademie Esslingen,Ostfildern,GermanyLubricants market—impairment of environmentFigures 1and 2reveal the volume of the worldwide lubricant and additive market showing that about one third of all lubricants are consumed in Europe,America and Asia,respectively.Between 13%(EC countries)and 32%(USA)of all used lubricants return into the environment more or less changed in properties and appearance 1.First of all,these are lubricants used in loss lubrication frictional contacts—about 40000tons annually in Germany—as well as for those lubricants used in circulation systems which are not collected and disposed.In addition,lubricants from leaks and the amounts remaining in filters and containers or empties have to be taken into account.Altogether,the environment,eg.in Germany,is exposed to about 150000tons annually,based on the 13%share mentioned above,of the total lubricants volume thich return to the environment A calculation based on the actual lubricants consumption in Germany and the disposal rates for the different lubricant typesLubricants and the environment:Wilfried J.BartzFig.1Worldwide consumption of lubricantsresults in about 250000tons annually.Including the undefined rest volume as well as the volume for lost lubrication,the total amount of lubricants in Germnay returning to the environment might be in the order of magnitude of at least 300000t/a.Taking into account Germany’s share of the worldwide lubricants consumption as well as the fact that in parts of the world the collecting and recycling rate of used lubricants is lower than in Europe or in Germany,the total amount of lubricants returning into the environ-ment will be in the order of magnitude of 12million t annually.Therefore all measures have to be taken in order to keep the impairment of the environment to the lowest possible level.For evaluating the allowable detrimental effect upon the environment,the benefit of lubricants,eg.their performance or their economic properties must be considered,on one hand,and the risks caused by these lubricants,eg.their ecological properties,have to be taken into account on the other 2,3.Table 1reveals the applications of lubricants to which the aspects mentioned above apply.In this paper,the problems related to the ecological and the economic aspects of lubricant use will be discussed,taking the situation in Gemany as an example 4.Driving forces for reducing the impairment of the environmentWays and measures to reduce the impairment of the environment which means to overcome or at least toreduce the problems caused by contacts of lubricants with the environment in general are initiated or enhanced by the following driving forces:¼Environmental Facts ¼Public Awareness¼Government Directives and Regulations ¼Globalisation of Markets ¼Economic IncentivesThe environmental facts and the public awareness resulting from these facts were described above.The information on government laws and regulations will be given below.Simplified it can be stated that the behaviour regarding ecotoxicity and biodegradability governs the impair-ment of the environment by lubricants which are unac-counted for when returning to the environment.The preferred course of action is to reduce toxicity and to increase biodegradability.In general terms biodegradability means the tendency of a lubricant to be ingested and metabolized by pletely biodegradability indicates the lubricant has essentially returned to nature.Partial bio-degradability usually indicates one or more component of the lubricant is not degradable.Regarding ecotoxicity a general rule of thumb exists according to which materials with an LD 50value >1000ppm/kg are low or non-toxic.In fact ecotoxic-ity represents the toxic effect of a lubricant on plants and animals (not on human health).Lubricants and the environment:Wilfried J.BartzFig.2Additive consumption (estimated)(Oronite)worldwide additive marketTable 1Fields of application for environmental acceptable lubricants ¼Outboard two stroke engine oils ¼Chain saw and saw frame oils ¼Railway wheel tread lubricants ¼Mold parting compounds ¼Wire rope lubricants¼Truck centralized system lubricants¼Hydraulic oils for machinery in building and bridge construction,deep workings and underground workings¼Hydraulic oils for forest and agricultural equipment¼Lubricants for sewage-treatment plants,water weir plants and lock gate mechanisms ¼Lubricants for food machinery¼Lubricants for snow mobiles and ski run maintenance equipment¼Metal working and metal forming processes ¼(Internal combustion engines and hydraulic systems in general)Laws and regulationsInternational activitiesThe development of environmental regulation or even legislation to regulate the use of lubricants is existent inAustria,Canada,Hungary,Japan,Poland,Scandinavia,Switzerland,the USA and EU to mention a few coun-tries and areas of the world.In the USA currently there do not exist laws requiring the use of environmentally compatible lubricants.But two regulations may have a significant impact on the use and disposal of conventional lubricants 1.¼Executive Order 12873(EO 12873)¼Great Lakes Water Quality Initiative (GLWQI).The executive order 12873encourages the use of recovered materials and environmentally preferable products.Possible implications of EO 12873may cover the¼use of recycled oils for government contracts (military lubricants)¼use of environmentally compatible oils where poss-ible to meet requirements.The Great Lakes Water Quality Initiative is intended to maintain,protect and restore the unique Great Lakes resource (e.g.water quality).Within the GLWQI are proposals of zinc limitations to such low values that these essentially means a ban on the use of zinc compounds in the Great Lakes Basin.Austria is the only country with a law that bans the use of mineral oil based lubricants in particular applications,e.g.chain saw oils.Lubricants and the environment:Wilfried J.BartzFig.3EC dangerous substance directiveThe other countries mentioned above at least have established regulations to evaluate the lubricant caused impairment of the environment,belling schemes.Recently the European Community (EU)has released the Dangerous Substances Directive.It establishes cri-teria for a products potential hazards to the aquatic environment.This hazard potential is determined through assessment of aquatic toxicity,biodegrad-ability,and bioaccumulation pounds which fall into the highest risk categories are required to carry a special symbol (Fig 3).The criteria are shown in Table 2.German activitiesGermany has some of the best known guidelines for environmentally acceptable lubricants with an oriented interest in the lubricants market.But,at the momentTable 2EC dangerous substance directive Aquatic acute data Ready biodeg.Bioaccum.potentialDead tree-fishRisk phrases (LC 50)(log P ow )symbolrequired If compound stability Ͼ1mg/l Ͼ1mg/l No Ͼ3.0Yes R50,R531–10No Ͼ3.0Yes R51,R5310–100No*n/a No R52,R53Ͼ100n/a n/a No None If compound stability Ͻ1mg/l n/a No*n/aNoR53*Unless other convincing scientific evidence to demonstrate no long-term effects from substance or its degradation products.R50–very toxic to aquatic organisms.R51–toxic to aquatic organisms.R52–harmful to aquatic organisms.R53–May cause long-term adverse effects in aquatic environment.exist no laws only quasi legal provisions and regu-lations which encourage the use of environmentally acceptable lubricants.The production,application,and disposal of lubricants have to be performed without any or at least without a remarkable impairment of human beings or of the environment.In order to ensure that this requirement be met the German legislative code has enacted a framework of laws 5which comprise ¼Chemical Substances Act ¼Waste Material Act ¼Water Protection Actonly to mention some of the most important laws.Chemical Substances ActAccording to this Act substances are discriminated with regard to their endangering potential.Based on this law,the marketing and application of lubricants are regulated in detail by the so-called Regulation for Dangerous Materials.Waste Material ActFor the disposal of used lubricants the regulations of the law apply.According to their endangering potential,waste materials are to be classified as follows:¼Waste material¼Special waste material.Special waste material is defined as material requiring special control.Within the Waste Material Act the following regulations have to be covered:¼Waste Allocation Regulation¼Waste and Remainder Material Monitoring Regu-lation¼Used Oil Regulation.In addition,there is the so-called Technical Regulation Waste which constitutes an administrative instruction and not a law.Lubricants and the environment:Wilfried J.BartzTable3Water hazard classificationWGK0=Generally not water endangeringWGK1=Slightly water endangeringWGK2=Water endangeringWGK3=Severely water endangeringTable4Criteria for evaluating the water endangering potential¼Acute toxicity,especially against mammals,fishes and bacteria¼Decomposition properties¼Long term effects and physical-chemical characteristicsRegarding the allocation of rape seed oils within this framework of laws and regulations in Germany as an example there is the following discrepancy:¼Used Oil Regulation:Rape seed oils are used oils not to be regarded as special material.¼Technical Regulation Waste:Rape seed oils are special waste materials requiring special control.Water Protection ActWithin this Act,substances are discriminated according to their water endangering potential.For this purpose, they are classified according to a water hazard classi-fication(Table3).The water endangering potential is evaluated using the criteria shown in Table4.It can be recognised form the framework of laws that the evaluation of environmental impairment of lubricants in Germany is very complex and not unequivocal at all.Environmental aspects of lubricantsDefinitions,terms and agreementsIn attempting to classify lubricants with regard to their impairment of the environment,many different terms have been established regarding the fact that the whole matter is not at all clear at the moment(Table5)2,6.Table5Terms regarding lubricants and environ-ment¼Environmentally positive¼Environmentally friendly¼Environmentally sociable¼Environmentally justified¼Environmentally careful¼Environmentally neutral¼Environmentally protective¼Environmentally conformable¼Biologically eliminatable Table6Graduating environment related termsFriendly(improving the environment)Neutral(unimportant,harmless)¼Threshold of PerceptionSociable(low,unsuitable)¼Start of Legal RegulationsAnnoying(disagreeable,unpleasant,impairing)Irksome(troublesome,inconvenient)¼Limit of BurdeningEndangering(excessive,unimputable)Harmful(dangerous,irreversible effectsIt seems useful to graduate the environment related terms as in Table6.According to this graduation,no lubricant can be environmentally friendly.,that is improve the environmental conditions.At best,the lubricant ban remain neutral against the environment. Nomally one has to be content with the fact that the lubricant is environmentally acceptable,that is that it affects the envirnment only to a less pronounced degree.Under this point of view,all aspects of impair-ment between the production of the lubricant,its appli-cation and its disposal have to be taken into account (Table7).The consideration of environment aspects of lubricants os focussed on¼Health Hazards¼Water Hazards.Often there is an agreement to define lubricants as environmentally acceptable if they cover the follow-ing requirements:¼Fast biodegradable¼Non toxic against human beings¼Non toxic againstfishes¼Non toxic against bacteria etc.Table7Aspects of environment impairment by lubricantsAt production environmentally neutral—low energy consumption,no waste materials, no emissionsIf possible using regeneratable resources—no depletion of resources,no greenhouse effectPhysiologically harmless—non toxic,not cancerous etc.Without toxic decomposition substances—non bio-accumulative potentialEco-toxicological acceptable—non water endangering,non water miscible, lower density than waterAfter usage fast biologically degradable—no toxic or unpleasant decomposition productsNo disposal problems—possibility of simple recycling processesLubricants and the environment:Wilfried J.BartzFig.4Advantages and disadvantages of additivesHealth hazardsHealth hazard aspects are characterized by endangering of living beings by fresh and used lubricants.Improve-ment of the refining processes for mineral oils and the optimized selection of additives have reduced the endangering of human health to only few remaining points.Nevertheless,the advantages and disadvantages of formulating lubricating oils and greases,using addi-tives shall be explained using coolants for metal work-ing processes as an example (Fig 4).Health hazards to human beings are mainly given where close contacts between the lubricant and the human being exists,eg.in the case of using coolants.Table 8reveals some aspects related to the health discussion in connection with lubricants.The most important aspects of health hazards by lubricants is their endangering potential and their toxicity.The endangering potential can be classiified based on physico-chemical properties as follows:¼Explosive ¼Oxidizing¼Extremely flammable ¼Highly flammable ¼Flammable.The toxicity of lubricants can be classified as follows:¼Very toxic ¼Toxic ¼Harmful ¼Corrosive ¼Irritant¼Carcinogenic ¼MutagenicTable 8Health discussion related to lubricants ¼Development of nitrosamines in coolants ¼Effect of oilfags and -fumes¼Skin diseases caused by contacts with coolants¼Bactericide effects in connection with coolants ¼Cancer generating substances in used engine oils¼Solvent containing products¼Heavy metal compounds in additives ¼Toxic to reproduction¼Dangerous for the environment.The description of the health hazards potential of lubri-cants has to be done in accordance with the EU Safety Date Sheet defined in the EU-Regulation 91/155/EWG and in the TRGS 220(for Germany).Regarding toxicity,the aspects listed in Table 9have to be taken into account.The allocation to different toxicological potential is shown in Table 10.Water hazardsSimplified the definition environmetally acceptable lubricants means¼Water hazard classification =0¼Fast biodegradable.The Water Hazard Classification is calculated using three evaluation numbers for the acute oval mammals toxicity,the acute bacteria toxicity and the acute fish toxicity (Tables 11and 12).Based on this classification number,fast biodegradable lubricants can be allocated to the next lower and persistent substances to the next higher classification number.Table 13reveals this relationship.This calculation is based on the allocation of different lubricants within the Water Hazard Classi-fication (Table 14).Lubricants and their health and water endangering potentialThe following two aspects shall be discussed:¼Fast biodegradability ¼ToxicityFast biodegradabilityGeneral relationshipThe period needed to degrade a certain percentage of the lubricant is defined to degrade a certain percentage of the lubricant regarding the biological degradation.Several testing methods have been developed to evalu-ate the biodegradability of the base fluid as well as of the additives of the lubricant.Widely used to evaluate the behaviour of lubricants—base oils and additives—are the tests mentioned in Table 15.Table 9Safety data sheet according to TRGS 220(toxicological effects)¼Acute toxicity (LD 50,LC 50-value)¼Irritation/caustic effect ¼Sensitivity effects¼Effect after repeated and long duration exposition (subacute or chronic toxicity)¼Carcinogenic,mutagenic and reproduction endangering effects¼Specific symptoms/practical experiencesLubricants and the environment:Wilfried J.BartzTable 10Safety data sheet according to TRGS 220(toxicological potential)LD 50(Oral,rat)Ͻ25mg/kgVery toxic LD 50(Oral,rat)Ͼ25and Ͻ200mg/kg Toxic LD 50(Oral,rat)Ͼ200and Ͻ2000mg/kgHarmfulTable 11Influences on the water hazard classi-ficationAcute mammals toxicity (LD 50oral,rat,mg/kg)Fish toxicity (LC 50or LC 0,fish,mg/l)Bacteria toxicity (EC 50or EC 0,Pseudomonas putida ,mg/l)Fast biodegradabilityTable 12Calculation of the water hazard classification LD 50(mg/kg)Ͼ2000Ͼ200–2000Ͼ25–200Ͻ25BWZa1357LC resp.EC (mg/l)Ͼ10000Ͼ100–10000Ͼ1–100Ͻ=1BWZb and BWZcϽ1.92–3.94–5.9Ͼ=6BWZa +BWZb +BWZc3=WGZ (water hazard number)WGZ Ͻ1.92–3.94–5.9Ͼ=6WGK123Table 13Water hazard classification Biodegradability OECD 301E Ն70%Յ70%WGZWGKBiodegradable WGKResistant WGKWGZ =ST +BT +FT3ST:Toxicity against mammals 0bis 1,9001BT:Toxicity against bacteria 2bis 3,9102FT:Toxicity against fishes 4bis 5,9213Ͼ6323White oil 1(changed 1992)Base oil 1Lubricating oil with addition 2Lubricating oil water miscible 3Used oil 3WGZ =water hazard number.WGK =water hazard classification.Table 14Allocation of lubricants within the water hazard classification ¼WGK 0Not water endangering Vegetable oils¼WGK 1Low water endangering Plain lubricating oils,base oils,white oils¼WGK 2Water endangeringAdditivated lubricating oils,engine and industrial oils ¼WGK3High water endangeringAdditivated water miscible lubricating oils,water miscible coolantsBase fluids for fast biodegradable lubricantsAccording to Table 16three different groups of sub-stances are available which can be used as base fluids to formulate fast biodegradable lubricants and oper-ational fluids.They can be allocated to the following classes 6:¼Water miscible fluids ¼Vegetable oils¼Synthetic ester oilsLubricants and the environment:Wilfried J.BartzTable 15Testing methods for evaluating the biodegradabilityDuration,daysMeasured Fast degradable parameteraccording to OECDRAL For components with Ͼ5wt –%CEC decomposition test CEC-L-33-A-9421IR Ͼ70%For components with Ͻ5wt –%Zahn-Wellens-Test OECD 302B28DOCϾ20%Ͼ20%DOC –Reduction of DOC (dissolved organic carbon).IR –Measuring the reduction of organic part of test substance by IR.Table 16Groups of substances for fast biode-gradable lubricantsWater miscible fluids –Monoethyleneglycol –Monopropyleneglycol–Polyethyleneglycol (M-wt 200–1500)–Ethylene/propylene mixed polymers Non water miscible fluids Vegetable oils –Rape seed oil –Castor oil –Soya oil –Peanut oilSynthetic ester oils (with steric hindrance)–Trimethylpropane –Pentaerythrite–NeopenthritepolyolOf the group of polyakyleneglycols (PAG),polyethyl-eneglycols (PEG)are used most exclusively,because they are eco-toxicologically acceptable and fast biodeg-radable.The properties last mentioned apply only for the low molecular weight types as shown in Fig 5.The advantages of these fluids are good oxidation stability,the viscosity temperature behaviour,excellent low temperature behaviour,and good mixed film lubri-cation properties.The disadvantages arecharacterizedFig.5Biodegradability of polyethyleneglycolsby their nonmiscibility with mixed oils and their behav-iour against seal materials.Of the group of synthetic ester oils,especially diester and polyol ester are used to formulate fast biodegrad-able oils.Their advantages are characterized by their good miscibility with mineral oils,their good low temperature behaviour,and their high oxidation stab-ility.The poor hydrolytic stability resulting in a prob-lematic corrosion protection is one of the disadvantages of this group of fluids.Vegetable or natural oils are triglycerides of natural fatty acids,eg.palmitic acid,stearic acid,oleic acid,vegetable oils,linolenic acid etc.One of the most important natural oils ist rape seed oil.Due to the rather high content of unsaturated fatty acids,natural oils tend to have a low oxidation stability.A high content of unsaturated acids is characterized by lower odine Numbers which in turn tend to result in higher solidification temperatures.Thies means a worse cold flow behaviour.Rape seed oils exhibit a rather good compromise between low temperature behaviour and oxidation stability (Fig 6)6.Low temperature flow properties and oxidative stability and especially the relationship between both are related to an oil’s fatty acid profile.Oils containing highlevelsFig.6Solidification temperatures of natural oils with different jodine numbers.Decreasing jodine number improves oxidation stabilityLubricants and the environment:Wilfried J.Bartzof monounsaturated fatty acids,like high oleic acid rapeseed,combine relatively high oxidative stability with good low-temperature performance.Fig 7compares the biodegradabilty of different oils including those allocated to the group of fast biodeg-radable oils evaluated according to the CEC-L-33-A-94Test.A relative evaluation and rating of different important properties is given in Fig 8.Toxicology of lubricantsRegarding the toxicological potential of lubricants,base oils and additives have to be regarded.Base oilsThe most useful general information on the toxicologi-cal behaviour of base oils can be found in the CON-CAWE report ‘Health Aspects of Lubricants’7.The findings published in this report have been confirmed by a SHELL study recently presented 8.The results of the CONCAWE report can be summar-ized as follows:¼The acute dermic LD 50for ratswas higher than 2000mg/kg.This is the maximum dose which can be applied and is normally classified as harmless.For human beings no detrimental consequences are known for short-time dermal contacts.¼For solitary application to the skin of rabbits,base oils exhibited no to mild irritations.For human beings skin irritations as the result of short-time contacts have been proven,as without any im-portance in practice.¼For solitary application into rabbit eyes,base oils exhibited no to mild irritations.For human beings no problems were found.¼Using the so-called skin sensitiveness test with guinea pigs,base oils exhibited no sign of sensi-tivity,for human beings too,no sensitivity was observed.¼For all oils tested the accute oral LD 50for rats was higher than 10000mg/kg.This value represents a low toxity.However,swallowing by accident low viscosity products will cause serious effects,because aspiration after vomitting can produce chemicalpneumonitis.Fig.7Biodegradability of different base oils (CEC-L-33-A-94test)The results of the SHELL study can be summarized as follows:¼The acute toxicity of mineral oil base oils,extracts and destillates,is so low that any health danger by accute effects can practically be excluded.,with the exception,that low viscosity products were swall-owed.¼Testing many base oils of different sources and grades of refining,the below mentioned products may exhibit carcinogenic potentials for long-time and repeated applications:¼Vacuum distillates¼Acid-refined oils from distillates ¼Aromatic extracts from distillates ¼Mild hydrogenated/refined base oils.As a conclusion it can be stated that:Conventional mineral base stocks have low toxicity by inhalation and by skin absorption.Eye irritation is not usually a problem,but skin irritation leading to dermatitis may occasionally occur from prolonged exposure to automotive lubricants,although these oils do not represent nearly as great a hazard as soluble cutting oils.Inhalation of vapour or oil mist for short periods may cause mild irritation of the mucuous membranes of the upper respiratory tract.AdditivesThe most useful information about the toxicity of additives can be found in a report released by the Additive Technical Committee (ATC)9.The results can be summarized as follows 10:In general,lubricant additives exhibit few,if any,physical hazard.Due to their low mammalian toxico-logical potential,the majority of lubricant additives are not classified as dangerous.To facilitate a risk assess-ment and labelling,ATC has developed a classification system,naming 35classes of additives divided into six broad groups of classification.All similar additives from different manufacturers are classified in the same way.Of the most important additive types only zinc dialkyl dithiophosphate and some long chain calcium alkaryl sulphonates are classified as irritant.According to Eur-opean legislation they must be classified ‘dangerous’.Some,but not all sulphonates have been shown to be skin sensitizers in laboratory tests.Some more details regarding the acute toxicity of additives are shown in Table 17.Experience has shown that the toxicological properties of fully formulated lubricants are related to those of the base oil and additive components.There is also a close relationship between human health and environ-mental hazards.Measured toxicity of mixtures is gener-ally found to be close to the arithmetic sum of compo-nent toxicities.Due to the different fate of lubricants during their use—e.g.contamination by fuel and combustion pro-ducts of engine oils—the toxicity of used lubricants may be significantly different than that of fresh oils.。