Chapter 13 SOLVENTS, FLUOROCARBONS, AND PAINTS · 2020. 7. 1. · mixed solvents: house and car painters and jet-fuel handlers have reported impairment of visual percep-tion, hand–eye

Solvents, Fluorocarbons, and Paints

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Chapter 13

GLENN J. LEACH, Ph.D.* AND LEROY W. METKER†

SOLVENTS, FLUOROCARBONS,AND PAINTS

*Toxicologist, Toxicology Division, U.S. Army Environmental Hygiene Agency†Chief, Toxicity Evaluation Branch, Toxicology Division, U.S. Army Environmental Hygiene Agency, Aberdeen Proving Ground, Maryland 21010-5422

INTRODUCTION

SOLVENTSGeneral ToxicityRespiratory Uptake of SolventsSpecific ToxicityExposure Controls

FLUOROCARBONSCurrent Status of Ozone-Depleting SubstancesCivilian and Industrial ExposuresMilitarily Unique ExposuresPharmacological EffectsPhysical Effects

PAINTSToxic ConstituentsChemical Agent Resistant CoatingsExposure Controls

MEDICAL SURVEILLANCE

MEDICAL TREATMENTSolvents and PaintsFluorocarbons

SUMMARY

Occupational Health: The Soldier and the Industrial Base

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INTRODUCTION

A large segment of the Department of Defense(DoD) industrial workforce, including both civilianand military personnel, is employed in occupationsthat involve potential exposures to toxic environments.Organic solvents are a major source of exposure. Asolvent is a material, usually a liquid, that is capable ofdissolving another substance. Solvents include highlypolar substances like water, as well as nonpolar or-ganic compounds. Because the vapor pressure ofwater-based solvents is low, and therefore the poten-tial for inhaling their vapors is also low, water-basedsolvents are not discussed in this chapter. Many of thenonpolar organic solvents, however, are relatively

volatile and pose significant inhalation hazards.The organic solvents include aliphatic and aro-

matic hydrocarbons, chlorinated hydrocarbons,alcohols, ether esters, and ketones. This textbooktreats fluorocarbons separately from the other haloge-nated hydrocarbons; they are used as solvents, buttheir nonsolvent uses as refrigerants, propellants, andin fire-suppression systems have greater military andmedical significance. Oil-based paints not only con-tain solvents that are used as diluents, they also con-tain resins, vehicles, and additives that are associatedwith a variety of illnesses to which occupational healthprofessionals must respond.

SOLVENTS

The DoD is a major user of solvents. More than 25installations—including shipyards, air logistics cen-ters, army depots, and aviation repair and mainte-nance facilities—each use over 27,500 gallons of sol-vent per year, and at least 120 installations use lesseramounts.1

In general, occupational exposures to solvents inthe uniformed and civilian defense workforce dupli-cate those found in civilian industry. Solvents areused as dry-cleaning agents, chemical intermediatesin manufacturing, drying compounds, general-pur-pose cleaners, paint thinners and removers, and in themanufacture of materiel. This chapter considers sol-vents as they are used in four military applications:vapor degreasers, cold-dipping cleaners, precisioncleaners, and solvents that are associated with paints.

In vapor degreasing, solvent contained indegreasing tanks is heated to the boiling point—which is low, relative to water—and the vapors forma cloud over the surface. The items to be cleaned arelowered into the vapors, which then condense on thecold item and dissolve its surface oils and greases. Thedegreasing tanks are usually fitted with a cooling coilnear the top that condenses the vapor, minimizing thesolvent loss. The solvents that are commonly used inthese operations include perchlorethylene, methylchloroform, trichloroethylene, methylene chloride, andtrichloro-fluoroethane.2 Vapor degreasing is used bythe army for a number of industrial operations includ-ing cleaning engines and other vehicle parts in ve-hicle-maintenance facilities and degreasing large-boregun tubes after milling (Figures 13-1 and 13-2).

In cold-dipping degreasing, the item to be cleanedis simply dipped into a tank of solvent. These sol-vents—from petroleum distillates to mixtures thatinclude aliphatic and aromatic hydrocarbons, ketones,cellosolves, and creosote—tend to have lower volatil-ity than those used in vapor degreasers and thereforethe risks of inhalation are less for workers. Theseprocedures are also typical at vehicle maintenancefacilities, particularly for smaller parts.

Precision cleaners—generally fluorocarbons—arealso used in their liquid state, usually in cold dippingor as sprayed aerosols. They are generally used toclean sensitive electronic components. Large quanti-ties of solvents are also used in paints and relatedproducts such as varnishes and lacquers, and paintthinners, primers, and strippers. Exposures occurduring mixing, applying, or drying.

General Toxicity

The potential health effects from exposure to sol-vents depend on a number of factors including thephysical and chemical properties of the solvents, howthe solvents are used, the way in which workers areexposed, and the duration (acute or chronic) of theexposure. In the industrial setting, there are twoprimary routes of exposure: inhalation of vapors oraerosolized mists and dermal absorption. The con-centration of solvent vapors in air is expressed involume per volume units (eg, parts per million). Con-centrations can also be expressed as milligrams percubic meter, which is a weight per volume measure.


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Fig. 13-2. Degreasing tanks located in a pit must besurrounded by a railing. Only authorized personnel canoperate a vapor degreaser, and they must be wearingappropriate personal protective equipment. During rou-tine operations, employees should wear chemical safetygoggles and solvent-resistant aprons and gloves. Duringtank cleaning operations, a rescue harness, lifeline, andself-contained breathing apparatus should be worn. Asecond person, fully equipped to enter the tank, shouldbe stationed outside the tank ready to assist if required.

Fig. 13-1. A typical degreasing tank. Vapor degreasing is accomplished by lowering the object to be cleaned into thevapor zone above the liquid solvent. Solvent vapors condense on the cold item and loosen grease and oil, which thencollect in the bottom of the tank. Condensing coils located near the top of the tank condense the solvent vapors, whichcollect in the condensate trough and are returned to the reservoir. The item is held in the vapor zone until the partsreach the temperature of the solvent vapor. At that time, condensation stops and the item is dry.


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Particulates suspended in air, such as dusts, are onlyexpressed as weight per volume units.

Acute exposures are isolated and of short duration(minutes to several hours). In the occupational setting,acute exposures usually occur when pipes or supplylines are accidentally broken, spills occur, or workersenter chemical storage tanks to clean or paint. Acuteexposures to most organic solvents cause central ner-vous system (CNS) depression and narcosis. Signs oftoxicity include disorientation, euphoria, giddiness,and confusion, which are reversible in most caseswhen the victim is removed from the toxic environ-ment. With sufficiently high exposures, the signs mayprogress to paralysis, convulsions, unconsciousness,and death due to respiratory or cardiovascular arrest.3

Airborne concentrations of solvents sufficient to causeacute toxic effects are typically in the range of 1,000 to10,000 ppm, although these are compound specific.

Chronic exposures to solvents are repeated, dailyexposures to low concentrations. Again, concentra-tions sufficient to cause chronic toxicity are com-pound specific, but generally range from hundreds ofparts per million to less than 1. Dermatitis is a com-mon result of prolonged or repeated dermal contact.This is a result of the defatting of skin by the solvents,which causes dryness and fissuring of the skin.

The organic solvents are toxic to a number of organsystems. Well-defined CNS lesions have been de-scribed for n-hexane and n-butyl ketone. There arealso reports of nonspecific behavioral, intellectual,and psychological effects among workers exposed tomixed solvents: house and car painters and jet-fuelhandlers have reported impairment of visual percep-tion, hand–eye coordination, and memory, as well asabnormal results on psychological tests.4

Many solvents are also toxic to the blood, liver, andkidneys. In many instances, the specific toxicity re-sults from biotransformation products of the parent sol-vent with the formation of reactive metabolites.3 Thehepatotoxic effects of carbon tetrachloride and alco-hol are thought to result from biotransformation prod-ucts; however, they have yet to be thoroughly de-scribed. Similarly, some blood dyscrasias producedby benzene are believed to occur as a result of reactivemetabolites.

Respiratory Uptake of Solvents

Among other physiological factors, the rate anddepth of pulmonary ventilation and the cardiac out-put affect the respiratory uptake of solvents, and theseultimately influence the toxic effects. Solvent uptakein the lungs is through simple diffusion: the difference

in concentration between inspired air and the bloodis the driving force that causes a solvent to enterthe blood and be distributed throughout the body. Gasin the alveoli equilibrates rapidly with blood in thepulmonary capillaries. Blood solvent levels dependon the solubility of the solvent vapors in blood. Forvery soluble solvents such as chloroform, very littleremains in the alveolar gas for expiration. Solublecompounds, however, require longer to equilibratewith the blood than low-soluble compounds becausea greater amount of compound is required to reachequilibrium. An increasing ventilation rate willincrease the delivery of solvent vapors to the lungsand decrease the time required for equilibration. Up-take of these solvent vapors is said to be ventilationlimited (ie, equilibration is dependent on the rate anddepth of respiration). In contrast, the vapors of sol-vents with low solubility take less time to equilibratewith the blood, and the rate is dependent on bloodflow through the lungs. Uptake of these substances issaid to be perfusion limited.3,5 The solubility of a sol-vent, the time necessary for it to reach equilibrium inthe blood, and the concentration of the solvent in theblood at equilibrium are (a) related through the solu-bility coefficient (S) and (b) limited by ventilation,perfusion, and cardiac output (Table 13-1). The solu-bility coefficient represents the ratio of the concentra-tion of a vapor or gas in an aqueous medium to theconcentration in the gas phase.

Specific Toxicity

Specific toxicological effects can be described forindividual solvents (Table 13-2). However, in mostindustrial settings exposures will be to complexmixtures; the chemical composition of these solventmixtures will vary with the particular lot of solventfurnished by various suppliers, in many cases. Theonly way to be certain of the specific solvent compo-sition is to consult the Material Safety Data Sheetsupplied by the manufacturer for the specific lot ofsolvent in use.

Aliphatic Hydrocarbons

The aliphatic hydrocarbons include the saturated,straight-chain paraffins (alkanes) and the unsatur-ated olefins (alkenes). Compounds with chain lengthsof 5 to 16 carbon atoms are usually liquids, and thoseexceeding 16 carbons are usually solids. Most com-pounds containing carbon chains exceeding eight unitshave low volatility and pose little inhalation threat.Typical aliphatic hydrocarbons include hexane, which


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Ethanol 1,100.0 Slow High VentilationAcetone 245.0Methyl 202.0

ethyl ketoneBenzene 7.8Carbon 2.4

tetrachlorideEthylene 0.15 Fast Low Perfusion

TABLE 13-1

RESPIRATORY UPTAKE

*Solubility coefficientSource: Alarie Y. Inhalation and Toxic Responses of Lung. Kansas City, Kan: Mid America Toxicology Course; 1981: 285–400.

Equilibration [Blood] at Physiological ParameterChemical S* Time Equilibrium Limiting Uptake

is used frequently as a solvent in adhesives and isfound in many paints and varnishes6; kerosene, whichis used as a fuel, a carrier for pesticides, and a cleaningsolvent; and stoddard solvent, which can be a mixtureof more than 100 different aliphatics and is usedextensively as a degreasing agent.

Hexane. Commercial hexane, sometimes calledhexane isomers, can consist of up to 100% n-hexane.Until the mid-1960s, n-hexane was considered to berelatively nontoxic because workers could be exposedto high concentrations of vapor with no discomfort.However, in l964, workers using products containingn-hexane began to exhibit sensory and motor deficits.Exposures were estimated to be 500 to 2,500 ppm.Methyl-n-butyl ketone (MNBK) was shown to pro-duce a similar neuropathy.3

Hexane is readily absorbed and has an affinity forfatty tissues. An extensive research program in bothanimals and humans identified 2,5-hexanedione as acommon metabolite of both n-hexane and MNBK, andthis metabolite is believed to be responsible for theneurotoxicity.5 2,5-Hexanedione was also shown toproduce a neuropathy in animals that was identical tothat produced in humans by n-hexane and MNBK.3

The American Conference of Government Indus-trial Hygienists (ACGIH) has recommended a Thresh-old Limit Value (TLV) of 50 ppm (176 mg/m3) forn-hexane, although recommended levels for otherhexane isomers are 10-fold higher.7 The current Occu-pational Safety and Health Administration (OSHA)permissible exposure limit (PEL) follows the ACGIHguidance: 50 ppm for n-hexane and 500 ppm formixed hexane isomers.8

Stoddard Solvent. Several commercial solvent mix-

tures are derived from the distillation of petroleum.The nomenclatures for stoddardlike solvents includevarsol, mineral spirits, and white spirits. Althoughthese mixtures differ in their distillation ranges andperformance characteristics, their toxicological prop-erties are similar. Stoddard solvents cause the typicalhydrocarbon-solvent effects of CNS depression fromhigh inhalation exposures and skin irritation fromdermal exposures. In addition, scattered reports inthe literature demonstrate that chronic exposures tostoddard solvents cause myelotoxic effects and livertoxicity.6 Both the ACGIH TLV and OSHA PEL forstoddard solvent is 100 ppm (525 mg/m3).7,8

Kerosene. Kerosene is a mixture of petroleumhydrocarbons with carbon chain lengths of 9 to 16units, although its composition varies with the sourceof crude oil and the refining methods. Other commonnames for kerosene include astral oil, coal oil, and No.1 fuel oil. Typical constituents of kerosene includemixtures of aliphatic, naphthenic, and aromatic hy-drocarbons. Regardless of its name and exact compo-sition, kerosene has a relatively low acute systemictoxicity, although it is a significant health hazardwhen the liquid directly enters the trachea and lungsor is aspirated from the stomach. Milliliter quantitiesof kerosene can cause pneumonitis, pulmonary edema,hemorrhage, and necrosis. Other petroleum-derivedsolvents pose a similar threat.6 Dermal exposure tokerosene has also been shown to cause skin irritation,and inhalation exposures may cause bone marrowdepression, although the latter response may be dueto contamination of the kerosene with benzene (dis-cussed later in this chapter).9 TLV and PEL Valueshave not been established for kerosene.


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TABLE 13-2

TOXICITY OF REPRESENTATIVE SOLVENTS

Toxicity Target Organ or Effect of TLV PELSolvent Rating* Chronic Toxicity WOE† (ppm)

Aliphatic Hydrocarbonsn-Hexane 2–1 neurotoxic, testicular atrophy UE 50 50Kerosene 3 pneumonitis, edema NE — —VM&P naphtha 2 CNS depression, skin irritation NE 100 —Stoddard solvent 1 — — — —

Aromatic HydrocarbonsBenzene 3 CNS, aplastic anemia, leukemia A 10 —Toluene 3 CNS depressant, dermal irritant D 100 100Cresol 2 cancer, dermal irritant C 5 —Phenol 3 developmental toxicity D 5 —Xylene 2 liver D 100 100

Chlorohydrocarbons1,2-Dichloroethane 2 circulatory system B2 200 100Trichloroethylene 3 lung, liver B2 50 50Carbon tetrachloride 3 liver B2 5 2Perchlorethylene 3 liver, blood B2 50 25Methylene chloride — lung, liver B2 50 —

FluorocarbonsDichlorodifluoromethane 1 lung, liver NE — —Trichlorofluoroethane 2–1 — — — —Trichlorotrifluoroethane 1 — — — —Chloropentafluoroethane 2–1 — — — —Bromochloro- 1 — — — —

difluoromethaneDibromotetrafluoroethane 2 — — — —

Aldehydes and KetonesFormaldehyde 3 irritant, sensitizer B1 0.30 0.75Acetone 2–1 liver, kidney carcinogen D 200 200Methyl ethyl ketone 3 CNS neurotoxin, fetotoxin D — —Methyl n-butyl ketone 2 CNS — — —

GlycolsEthylene glycol 2–1 liver, kidney NE 50 50Propylene glycol 2–1 kidney, blood NE — —

Glycol EthersEthylene glycol 2 toxic encephalopathy, NE 5 5

monomethyl ether bone-marrow depressionEthylene glycol 2 testicular atrophy NE 5 5

monoethyl ether

*Toxicity Rating: a qualitative ranking of compound toxicity; categories range from 1 to 3. 1: low or slight; 2: moderate; 3: severe.Source of toxicity rating: Sax NJ. Dangerous Properties of Industrial Materials. 6th ed. New York: Van Nostrand Reinhold; 1984.

†Weight of Evidence: a qualitative classification of the potential for a compound to produce cancer in humans (developed by theEPA)

A: Human carcinogen (based on sufficient information from epidemiology studies to support a causal relationship)B1: Probable human carcinogen (based on sufficient information from animal studies and limited information from human

epidemiology studies)B2: Probable human carcinogen (based on sufficient information from animal studies, but evidence of carcinogenicity in humans

is inadequate)C: Possible human carcinogen (based on limited information from animal studies)D: Cannot be classifiedE: No evidence of carcinogenicity in humans

UE: Compound is undergoing evaluation for carcinogenicityNE: Compound has not been evaluated for its potential human carcinogenicity


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Aromatic Hydrocarbons

Aromatic hydrocarbons containing an unsaturatedsix-carbon ring structure are used extensively and aretoxic to multiple organ systems. These solvents areprimary skin irritants, due to their defatting proper-ties, and their vapors are irritating to the mucousmembranes and airways. Systemically, aromatic hy-drocarbons are CNS depressants, and several of thesecompounds have toxic actions on other target organs.Aromatic hydrocarbons are important in the produc-tion of plastics and rubber products, and are used insome paints.9

Benzene. Benzene is the most toxic member of thisgroup. It is a common ingredient in paint and varnishremovers and paint thinners as well as a contaminantof many of the petroleum-based solvents. In additionto its CNS-depressing actions, chronic exposure tobenzene suppresses the hematopoietic system. Acuteand chronic lymphocytic leukemias and aplasticanemia (which has a mortality rate of 70% over a5-y period) have been associated with worker expo-sures.3,9 Epidemiological studies have also implicatedbenzene as a cause of acute myelogenous leukemia.The mechanisms and etiology of chronic lymphocyticleukemia and aplastic anemia have not been described;however, they appear to be initiated by an unidentifiedmetabolite of benzene.3 Clinically, chronic benzeneexposures have been associated with decreased num-bers of circulating erythrocytes and leukocytes, con-ditions which may be an early indication of benzenetoxicity.3 The ACGIH TLV for benzene is currently 10ppm; however, the ACGIH has proposed loweringthis value to 0.1 ppm.7 The OSHA PEL for benzeneis 1 ppm.8

Alkyl Benzene. The alkyl benzenes include toluene(methylbenzene), the xylenes (ortho, meta, and paraisomers of dimethyl benzene), and the cresols (mono-methyl phenols). The evidence from studies done withanimals suggests that this group of solvents does nothave the hematopoietic toxicity that is characteristicof benzene. The acute and chronic effects of tolueneare CNS depression and dermal irritation.10 The xy-lenes are also CNS depressants; the most commonsymptoms reported from occupational exposuresare headache, fatigue, lassitude, irritability, and gas-trointestinal disturbances.8 Cresol is a strong dermalirritant with systemic effects on the kidneys andliver; its toxicity is similar to that of phenol. Forwork-place exposures to toluene and xylene, theACGIH TLVs and OSHA PELs are 100 ppm; for cresol,both values are 5 ppm.7,8

Halogenated Hydrocarbons

These solvents are composed of carbon, hydrogen,and a halogen (usually chlorine or fluorine), and canbe divided into the simple chlorohydrocarbons andthe chlorofluorocarbons. The simple chlorohydrocarb-ons contain chlorine as the only halogen moiety andare excellent solvents for oils, fats, and other organiccompounds. Simple chlorohydrocarbons are oftenused in both vapor and cold-dip degreasing. They arealso used extensively in paint removers, solvents, andthinners.

The most common acute toxic effect of the simplechlorohydrocarbons is CNS depression; high expo-sures may cause respiratory depression or circulatoryfailure resulting in death. The vapors of the simplechlorohydrocarbons are not especially irritating to theupper airways, but repeated skin exposures may causedermatitis due to their defatting actions.2

The solvent methylene chloride (dichloromethane)has a unique toxic action of which occupational healthprofessionals should be aware. This very volatilechlorohydrocarbon is widely used in paints, paintstrippers, degreasing operations, and as an aerosolpropellant. In addition to the typical CNS depression,methylene chloride has also been found to be rapidlymetabolized to carbon monoxide. Short exposures tohigh levels of this solvent have been shown to producecarboxyhemoglobin levels over 10%. This could havea significant adverse health effect in workers withexisting cardiovascular disease.9

With chronic exposures, many of the chlorinatedhydrocarbons are hepatotoxic, causing both fatty in-filtration and necrosis. Carbon tetrachloride, chloro-form, and 1,1,2-trichloroethane are also toxic to thekidneys; however, the other chlorohydrocarbons donot share this effect.3 A number of chlorinated solv-ents have been demonstrated to cause cancer in labo-ratory animals (see Table 13-2). Despite extensivedata from studies on animals that indicate poten-tial carcinogenicity, however, evidence from epidem-iological studies on humans has been inconclusive.Data on worker exposures to trichlorethylene, fluoro-carbons, and methylene chloride have all been nega-tive.9

One further concern is the potential toxicity of thethermal decomposition products of halogenated hy-drocarbons. At high temperatures, the chlorohydro-carbons decompose to hydrogen chloride and phos-gene. Toxic levels of these hazardous gases can beproduced during welding operations in atmospheresof chlorinated hydrocarbon solvents.10


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The chlorofluorocarbons contain both chlorine andfluorine as the halogen moiety and are used exten-sively in the military as precision cleaners for elec-tronic components and in vapor degreasing. Theirnonsolvent uses are discussed separately in this chapter.

Aldehydes and Ketones

Although aldehydes and ketones are grouped to-gether based on their chemical structures, they areused for distinctly different purposes. The most com-mon aldehyde, formaldehyde, is used in adhesives,industrial coatings, and in the production of certaindyes. The ketones are widely used as solvents.

Aldehydes and ketones also have somewhat differ-ent toxicological effects. Formaldehyde is a potentskin and eye irritant and a well-known sensitizer.Allergic responses are commonly seen in persons whocome in contact with formaldehyde. Studies withanimals also show that inhalation of 15 ppm of form-aldehyde produces carcinomas in the nasal cavities ofrats.8 The common ketones including acetone, methylethyl ketone (MEK), and methyl isopropyl ketone(MIPK) are also irritants to the eyes and mucousmembranes. At high concentrations, ketones are CNSdepressants. MNBK is uniquely neurotoxic, as wasdiscussed previously.

The potential health effects that distinguish thealdehydes from the ketones are also the rationale forthe differences in their exposure limits. The ACGIHTLV for formaldehyde is 1 ppm, but this value may bereduced to 0.3 ppm.7 OSHA has established a PEL of1 ppm, with a 2 ppm ceiling value, and is also consid-ering a reduction (a ceiling value is an exposure levelthat cannot be exceeded at any time during an 8-hourworkday). Both the ACGIH TLV and OSHA PEL are5 ppm for MNBK and 200 ppm for MEK and MIPK.7,8

Glycols and Glycol Ethers

Glycols and glycol ethers differ in both their degreeand their mechanisms of toxicity, although they areusually grouped together by virtue of their chemicalstructures. The two are also used differently. Glycolsare used commonly as industrial solvents for nitrocellu-lose and cellulose acetate, and in the production of pharma-ceuticals. The glycol ethers are used extensively assolvents for lacquers, varnishes, resins, dyes, and inks.

Glycols have low vapor pressure and do not presenta significant inhalation hazard unless they are heatedor aerosolized. However, ethylene glycol has greateroral toxicity in humans than has been demonstrated inother mammalian species. The primary toxic action

associated with ethylene glycol is metabolic acidosis,which is caused by its metabolite glycolic acid. Cal-cium oxalate, another metabolic byproduct of ethyl-ene glycol, tends to accumulate in the proximal renaltubules and causes necrosis and functional changes inthe kidneys.3

The glycol ethers include ethylene glycol mono-methyl ether (EM), ethylene glycol monoethyl ether(EE), and the propylene series of glycol ethers. Whilethey are not acutely toxic when ingested or inhaled,they have a unique reproductive toxicity: testicularatrophy and hematological effects were found whenanimals were administered EM and EE by variousroutes. The propylene series of glycol ethers does notappear to cause these reproductive effects.3

Due to these toxic effects, the ACGIH recentlylowered the TLV for EM and EE; current recommen-dations are 5 ppm.7 The OSHA PELs for thesesolvents are also 5 ppm.8

Exposure Controls

Two of the many controls used in vapor degreasingoperations are condensers and local exhaust ventila-tors, although other controls may be designed forother operations that require solvents. Properly de-signed vapor degreasing units are equipped with con-densers that surround the tank, which minimize theescape of solvent vapors into the ambient environmentof the workplace. All of these units should be equippedwith thermostatic controls mounted above the normalvapor level, which will shut off the heat source if thevapors rise above the condensing surface. Local exhaustventilation controls may be necessary depending onthe type of installation. Even with these controls,open flames, electric heating elements, and weldingoperations must not be located near a degreaser.2

Vapor degreasers also require periodic cleaning toremove the sludge and metal chips that have accumu-lated at the bottom of tanks. This requires that thesolvent be distilled off until the heating surface isnearly exposed. The unit is then allowed to cool, andthe sludge and remaining solvent are drained off.Personnel who enter a degreasing tank to perform thisoperation should wear respiratory protective equip-ment and a lifeline that is held by an attendant.2

The exposure controls for cold-dip degreasing andprecision cleaning operations are much less extensive.Lids should be provided for the dip tanks to minimizeevaporation of the solvent. Personal protective equip-ment (PPE) such as a faceshield and gloves must beworn to prevent the solvent from coming in contactwith the skin and eyes.


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FLUOROCARBONS

The first fluorocarbon, carbon tetrafluoride, wasisolated in 1926.11 Although no such compound oc-curs in nature, numerous additional fluorocarbonshave been synthesized in substantial quantities sincethe 1940s. Commercial interest in fluorocarbons cen-tered around their chemical and thermal stability andled to their extensive use as aerosol propellants, re-frigerants, plastic foaming agents, heat-exchangeagents, and solvents; as propellants for therapeuticagents and antiasthmatic drugs; and as general anes-thetics. By the mid-1970s, production of these chemi-cals—originally considered to be inert refrigerants—had exceeded 2 billion pounds, most of which wasreleased eventually into the environment.12

Fluorocarbons can be divided into the fully haloge-nated (nonhydrogenated) and the hydrogenated spe-cies. A further subdivision of these two groups—intothe chlorinated and nonchlorinated species—is neces-sary to understand the significance that these chemi-cal structures have in the current depletion of theearth’s ozone layer (Table 13-3). This process involvesthe nonhydrogenated fluorocarbons, which are themore stable and therefore have the greater probabilityof reaching the ozone layer. Of the nonhydrogenatedspecies, the chlorinated fluorocarbons are postulatedto be the most detrimental.

The fluorocarbons are similar in composition to thechlorinated hydrocarbons, with the addition of a fluo-rine moiety. Numerous possible moiety combina-tions of carbon with hydrogen, fluorine, bromine, andchlorine have been prepared with the aliphatic hydro-carbon series. The fluorocarbons are usually clear,colorless, highly volatile liquids with a mild, some-what ethereal odor. They are nonflammable, havehigh density, low viscosity, low surface tension, lowtoxicity, and are very stable.

Fluorocarbons do not react with most metals attemperatures below 200°C, or with most acids oroxidizing agents. However, under unusual circum-stances, they can be made to react with highly reactivemetals: for example, trichlorofluoromethane (CFC-11) reacts with concentrated sulfuric acid and sulfurtrioxide at room temperature.

With few exceptions, the fluorocarbons are rela-tively inert to chemical reactions on earth and in thelower atmosphere. When compared to other haloge-nated compounds, the hydrolysis rates for the fluoro-carbons are quite low, although there is considerablevariation within the group. At atmospheric pressure,the rate of hydrolysis is too low to be measured by mostanalytical methods. This low rate of hydrolysis pre-vents the fluorocarbons from degrading in the tropo-sphere.13 However, it is their inherent stability—whichallows them to migrate, intact, as high as the strato-sphere—that is the source of concern surrounding thedepletion of the ozone layer. Through photodegrada-tion and free-radical reactions, chlorofluorocarbonsprovide a large reservoir of free chlorine atoms, whichthen catalyze the destruction of ozone:

Cl

ClO

O3

O2O

O2

It is postulated that this is a chain reaction; it allowsone chlorine atom to continue to react, thus destroy-ing thousands of molecules of ozone. Much of theresearch done on this problem is, of necessity, theo-retical; furthermore, the contribution that free chlo-rine from natural sources might make to this processis neither well documented nor well understood.However, sufficient data exist for the internationalscientific community to call for a ban on the release of

TABLE 13-3

REPRESENTATIVE FLUOROCARBONS

NonhydrogenatedChlorinated

Dichlorodifluoromethane CCl2F2Trichlorofluoromethane CCl3F

NonchlorinatedOctafluorocyclobutone C4F8Dibromotetrafluoroethane C2F4Br2

HydrogenatedChlorinated

Chlorodifluoromethane CHClF2Chlorodifluoroethane CH3–CClF2

NonchlorinatedDifluoromethane CH2F2Trifluoroethane CH2CF3

Type Formula


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chlorofluorocarbons into the environment. Thenonchlorinated fluorocarbons are more stable, are notsources of free chlorine, and are therefore not of suchenvironmental concern.

Current Status of Ozone-Depleting Substances

The Montreal Protocol, an international agreementto limit the release and production of ozone-depletingsubstances, was signed in September 1987.14 Thisagreement, ratified by the U.S. Senate, became effec-tive in January 1989; it stringently restricts the interna-tional production and use of chlorofluorocarbons andhalons (a trademarked name for several tetrafluoro-ethylene polymers) (Exhibit 13-1). A DoD Directive(DoDI) issued on 13 February 1989 clarified the army’sposition concerning specific chlorofluorocarbons andhalons (Table 13-4).15 This directive affects all DoDcomponents, establishes policy, and assigns the re-sponsibility for

• managing the production of chlorofluorocar-bons and halons,

• identifying chlorofluorocarbon and halon ap-plications and prioritizing their uses,

TABLE 13-4

CFCs AND HALONS AFFECTED BY THE DoDDIRECTIVE AS OF AUGUST 1988

CFC-11 CCl3F TrichlorofluoromethaneCFC-12 CCl2F2 DichlorodifluoromethaneCFC-113 C2Cl3F3 TrichlorotrifluoroethaneCFC-114 C2Cl2F4 DichlorotetrafluoroethaneCFC-115 C2ClF5 ChloropentafluoroethaneHalon 1211* CBrClF2 BromochlorodifluoromethaneHalon 1301* CBrF3 BromotrifluoromethaneHalon 2402* C2Br2F4 Dibromotetrafluoroethane

OzoneDepleter Formula Chemical Name

*Registered trademark of Allied Chemical Corporation.Source: US Department of Defense. Chlorofluorocarbons (CFCs)and Halons. Washington, DC: DoD; 1989. DoD Directive 6050.9.

EXHIBIT 13-1

Year ofRestriction Accomplish-mentFreezing of CFC consumption 1989

at 1986 levels*

Freezing of halon consumption 1992at 1986 levels

Further reduce CFC consumption 1993by 20%†

Further reduce CFC consumption 1998by 30%‡

*Represents an initial reduction of approximately 15%†Reduced from 1986 level‡Reduced from 1993 levelSource: Treaty Document 100-10. December 21, 1987.Montreal Protocol on Substances That Deplete the OzoneLayer. Done at Montreal on September 16, 1987, to theVienna Convention for the Protection of the Ozone Layer.Ratified by the US Senate March 14, 1988. A copy of thetreaty document may be obtained from the Library ofCongress, Washington, DC.

CFC AND HALON RESTRICTIONS OF THEMONTREAL PROTOCOL

• identifying a long-term process to decreasethe DoD’s dependence on chlorofluorocarbonsand halons,

• developing research and development pro-grams to produce or evaluate suitable substi-tutes for chlorofluorocarbons and halons, and

• designing a tracking system to document theDoD’s annual requirements for chlorofluoro-carbons and halons.

Both the Montreal Protocol and the DoDI will sub-stantially affect the use of chlorofluorocarbons andhalons in the near future. The phased-in restrictionsshould result in a reduction of CFCs by over 60%, asmeasured from 1989 consumption levels.

The effects of compliance will be at least these two:(1) the use of present compounds will be curtailed,and (2) replacement chemicals will enter the DoD’ssupply channels. Unfortunately, replacement chemi-cals have not yet been designated and therefore can-not be discussed in this chapter, but the search forreplacement chemicals will obviously center aroundthe hydrogenated nonchlorinated compounds.

The mandated phaseout of the chlorofluorocar-bons and halons has generated tremendous interest indeveloping replacement chemicals. However, cur-rent research appears to be driven more by the need tofind and produce chemicals that are environmentallysafe rather than physiologically nontoxic. Occupa-tional health professionals may soon find themselvesconfronting new replacement chemicals that are ac-companied by little or no medical or toxicologicalinformation.


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Civilian and Industrial Exposures

The fluorocarbons and halons are used as refriger-ants, polymer intermediates, propellants, anesthetics,fire extinguishers, foam-blowing agents, dry-clean-ing agents, and as degreasing solvents in the electron-ics industry. Workers who produce and packagefluorocarbons are at highest risk of exposure to highconcentrations of these chemicals, but significant ex-posures also occur when fluorocarbons are used assolvents or cleaners. Because fluorocarbons disperserapidly when released, only minimal exposure ap-pears to occur from their use as refrigerants andpropellants. However, recent uses of fire extinguish-ers to protect computer and electronic areas havecreated the potential for short-term, high-concentra-tion exposures when large volumes of the material arereleased in confined spaces. Chronic occupationalexposure to hospital operating-room personnel fromthe use of anesthetic gases is also significant.

Militarily Unique Exposures

In addition to the civilian and industrial uses al-ready discussed, fluorocarbon use in the military in-cludes specialized applications such as the use of CFC-114 for submarine refrigeration to eliminate vibrationthat might lead to detection by the enemy. Halon 1211and Halon 1301 are used to suppress fires in the crewcompartments of tactical vehicles, aircraft, shipboardsystems, and in command, control, and communica-tion centers (see Chapter 6, Health Hazard Assess-ments). Significant amounts of these materials areused by DoD workers. Based on 1986 productionfigures, the DoD procured just under 35% of the UnitedStates’s total production of Halon 1211, approximately6% of Halon 1301, and just under 5% of the totalproduction of the regulated chlorofluorocarbons.16

Fluorocarbons, as they are used in submarines andother tactical vehicles, expose military personnel tohazardous situations not usually encountered by ci-vilians: specialized weapons systems are used inessentially closed environments. Military personnelare not always able to simply leave a contaminatedenvironment; their duties may oblige them to stay andman their equipment, thereby exposing them to higherconcentrations for longer times than may be typical inthe civilian community.

For example, the crew of an M60A3 tank can beexposed to Halon 1301 if the tank’s automatic fireextinguishing system is activated during a systemmalfunction or an actual fire. In either situation, thecrew could be exposed to oxygen deficiency, the toxic

effects of Halon 1301 itself, or the toxic effects of thedecomposition products of Halon 1301:

The discharge of four 7-pound (net weight) bottles ofHalon 1301 into the closed, unventilated M60A3 crewcompartment (estimated volume 12.7 m) would beexpected to initially depress the oxygen concentra-tion in the crew compartment to an average value of17.5 percent. This figure is based on the assumptionthat the discharged Halon displaces crew-compart-ment air with nearly 100 percent efficiency.…[M]inimum oxygen concentrations at variouslocations…range from about 13 percent to 19 percent,with the lowest concentrations occurring near floorlevel. Exposure to oxygen concentrations in the 13 to16 percent range can cause increased breathing andpulse rate, and slight impairment of concentrationand muscular coordination.

. . . .

[The toxic] effects of exposure to Halon 1301 concen-trations in the 7 to 20 percent range are varyingdegrees of central nervous system depression. Expo-sures in the 7 to 10 percent range cause mild anes-thetic effects including dizziness and tingling of theextremities. Exposures to concentrations above 10percent are usually accompanied by pronounced diz-ziness, and reduced physical dexterity and mentalacuity.

. . . .

Halon 1301 decomposes upon exposure to flame. Thedecomposition products (hydrogen fluoride, hydro-gen bromide, free bromine, and phosgene analogues)are severely irritating (even at low concentrations) tothe eyes and the respiratory tract….Therefore, theoccurrence of any crew-compartment fire duringtraining necessitates immediate evacuation of theM60A3.17(pp2–4)

It is the risk of exposure to the decompositionproducts of halon fire-extinguishing agents withinenclosed spaces that is the immediate hazard to thecrew (Table 13-5). These decomposition products areall significantly more toxic than their parent com-pounds; even at low concentrations, they are severelyirritating to the eyes and respiratory tract. As theintensity of the fire increases, the concentration of thetoxic byprod-ucts also increases; in enclosed spaces,halon decomposition products can reach extremelytoxic concen-trations.

Pharmacological Effects

Although they are relatively nontoxic, numerousfluorocarbon injuries have occurred. The ban onfluorocarbon propellant use has already substantiallyreduced human exposure, but the Consumer Product


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TABLE 13-5

HBr 3.0 Ceiling†

HCl 5.0 CeilingHF 3.0 CeilingBr2 0.3 STEL‡

Cl2 1.0 STELF2 2.0 STELCOBr2 (Carbonyl bromide) 0.1§ —COCl2 (Phosgene) 0.1 8-HourCOF2 (Carbonyl fluoride) 5.0 STEL

*All exposure limits, except carbonyl bromide, established byACGIH

†Ceiling: the value above which concentrations must never rise‡STEL: short term exposure limit§No value established (phosgene value assumed)Source: US Department of the Army. Health Hazard Evaluationand Test Support of the Special Study of Halon Fire ExtinguishingAgents. Washington, DC: DA; 1985. TECOM Project 1-VC-080-060-153.

ExposureProduct Limit* (ppm) Type of Limit

EXPOSURE LIMITS FOR COMBUSTION ANDDECOMPOSITION PRODUCTS OFCOMMON HALONS

other sensitization reactions, the myocardial sensiti-zation is a transient occurrence that quickly and com-pletely disappears if the affected individual is re-moved from contact with the chemical.12

Similar and equally serious consequences resultedfrom the use of pressurized bronchodilator aerosols.The original bronchodilators were mixtures of thesympathomimetic drugs epinephrine and isopro-terenol, which were aerosolized by both trichloro-fluoromethane (CFC-11) and dichlorodifluorometh-ane (CFC-12). During the few years that thesebroncho-dilators were used, physicians began to docu-ment a high incidence of bronchospasm and death. By1968, sufficient evidence had accumulated to ban theover-the-counter sale of these devices.20

As a group, the fluorocarbons have a low lipidsolubility and are poorly absorbed in the lung. Oncein the bloodstream they are apparently not metabo-lized and are slowly excreted through the lung, un-changed, via expired air.

Chronic Exposure

Because fluorocarbons are rapidly disseminated inthe environment, chronic exposures are limited torelatively few occupations. Workers who manufac-ture and package these chemicals, electronics workerswho use them as cleaning solvents on printed circuitboards, refrigeration mechanics, and hospital operat-ing-room personnel appear to have the highest expo-sure potential. Federal workplace exposure stan-dards have been promulgated for most of thecommercially important fluorocarbons and range from100 to 1,000 ppm for the entire series.21

Current epidemiological data indicate that no signifi-cant hazards are involved with chronic exposure to mostfluorocarbons at low concentrations. Their rapid dis-semination limits the possibility of high exposureconcentrations in most applications. Some fluoro- andchlorofluorocarbons are used as anesthetic gases; thisappears to be the most prevalent route of chronicexposure to chlorofluorocarbons (see also Chapter 5,Health Hazards to Healthcare Workers). The handlingand processing of waste anesthetic gases (as well astheir intended use) cause the potential for daily expo-sure to operating room personnel. Epidemiologicalstudies of nurse anesthetists and other female hospitalpersonnel have indicated a correlation between expo-sure to anesthetic gases and the occurrence of cancersand spontaneous abortions in the study population,and congenital anomalies in their infants. Based onthese findings, the National Institute for Safety andHealth (NIOSH) recommended severely lowering theoccupational standard for anesthetic gases to 5 ppm.22

Safety Commission records for 1975 (prior to anypropellant restrictions) show that 5,700 aerosol-re-lated injuries were treated in hospital emergency rooms.These injuries resulted from spraying (66%), inhala-tion and ingestion (12%), fragmenting of the container(10%), and cold (3%); the causes of 8% were unspeci-fied (the published data were not rounded to 100%).18

Acute Exposures

Fluorocarbons as a class have very low toxicity andthe predominant hazard they pose is from simpleasphyxiation. Early in the history of fluorocarbon use,deaths associated with exposure were usually attrib-uted to asphyxia, but sufficient data were accumu-lated during the late 1960s and early 1970s to associatemortality with abuse of these products. In particular,deaths due to propellant “sniffing” warranted closerscrutiny. The possibility of fluorocarbon toxicity andabuse was raised in 1970 when the deaths of more than100 youths who had died while sniffing various aero-sol products were investigated.19 Other research led tosimilar findings; these clearly documented that fluo-rocarbons sensitize the myocardium to sympathomi-metic drugs, which can lead to severe cardiac arrhyth-mia and death on subsequent exposure. Furtherexperimental and epidemiological data tend to cor-roborate the unusual finding that, unlike most


475

A researcher who performed an extensive mutage-nicity study on a series of 21 different chlorofluorocar-bons concluded that they are not biologically inert:the series contains bacterial mutagens, cell-transform-ing agents, and rodent carcinogens. For this series ofcompounds at least, prokaryotic mutation does notaccurately predict carcinogenic potential. 23

Long-term carcinogenicity bioassays have beencompleted in rats and mice for the three major chlo-rofluorocarbons: trichlorofluoromethane (CFC-11), di-chlorodifluoromethane (CFC-12), and chlorodifluo-romethane (CFC-22). These inhalation studies ran for104 weeks in rats and 78 weeks in mice. All three of thesechemicals failed to demonstrate any carcinogenicity.24

Physical Effects

Exposure to fluorocarbons such as Halon 1301 cancause both traumatic auditory damage and cold in-jury. Military vehicles are frequently equipped withautomatic fire-suppression systems that contain fluo-rocarbons stored under very high pressures (750 psi).These systems rapidly trigger when they sense a fireand quickly flood the vehicle. The extremely highstorage pressures and short response times requiredof the system cause noise levels to be exceptionallyhigh: impulse noise levels greater than 160 dBP havebeen measured with these systems, a level sufficientto cause permanent auditory damage. Furthermore,

transitory subzero temperatures can be producednear the discharge nozzles and cause medically sig-nificant cold injury to crew members who are closeto the discharge. The Health Hazard Assessment ofthe M60A3 tank found that

During gunnery training and M60A3 motion, crewmembers are likely to be at their normal stations andare required by U.S. Army hearing conservationpolicy…to wear [hearing protective devices]. Atthese positions, the impulse noise levels caused by[the automatic fire extinguishing system] activationrange up to 161 dBP at over 200 millisecond B-dura-tion. Such levels exceed the 140 dBP hazard criterionbut are within the allowable exposure range for per-sonnel wearing [hearing protective devices]. Activa-tion of the [automatic fire extinguishing system] atsuch time would not expose protected personnel tohazardous impulse noise. If personnel are not wear-ing [hearing protective devices] and the [automaticfire extinguishing system] is activated, permanenthearing loss may occur with repeated exposure, but isless likely for a once in a lifetime exposure.

. . . .

The rapid discharge of the 7-pound Halon 1301 bottleshas the potential for freezing tissues in the dischargestream.…[S]ubzero temperatures would be expectedon skin surfaces for very short durations.…Coldinjuries…have been documented with [the automaticfire extinguishing system] in…vehicles [other than theM60A3] during accidental Halon discharge….17(pp4–6)

PAINTS

Paints are widely used in industry and the militaryfor aesthetic purposes and also to produce a surfacecoating for protection against weathering.2 Workerscan be exposed during application of the paint, duringdrying and curing as a result of solvent evaporation,and during paint-grinding or -stripping operations.For this discussion, the term paint refers to a range ofsolvent-based products including conventional andepoxy paints, varnishes, enamels, and lacquers. Con-ventional paints consist of a pigment dispersed in avehicle. Varnishes are usually a nonpigmented resinthat is dissolved in a solvent. They dry by solventevaporation and the oxidation and polymerization ofthe binder. Most enamel paints are like varnishes, butwith a pigment added. Lacquers are clear or pig-mented finishes, usually based on a cellulose ester ina solvent, and cure through solvent evaporation.25 Anumber of water-based paints and enamels are alsoavailable, but because these coatings do not pose asignificant inhalation hazard, they will not be dis-cussed further in this chapter. Epoxy paints consist of

epoxy resins in reactive diluents. These are mixedwith curing agents to create tough, inert surface coat-ings. Generally the components are not volatile andare not an inhalation hazard.26

Solvent-based paints generally consist of three com-ponents: a vehicle, fillers, and additives (Table 13-6).The vehicle, which includes a binder dissolved in thesolvent, makes up the liquid portion of the paint andallows it to be thinned to a consistency suitable for thechosen method of application. The binder, either anaturally occurring oil or resin or a synthetic material,cements the paint film to the substrate.25 Fillers in-clude pigments to color the coating and extenders tocontrol gloss, texture, and viscosity. Pigments areusually finely powdered, insoluble solids that aredispersed in the liquid medium. In addition to pro-viding color and opacity to the finish, some pigmentsalso act to inhibit corrosion. Additives include agentsthat promote drying, inhibit mildew growth, andprevent the pigment from settling and the paint filmfrom sagging. Although a variety of additives are


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TABLE 13-6

Solvents Adjust viscos-ity(thinners)

XyleneTolueneBenzeneNaphthasPerchlorethyleneMineral spiritsMethyl ethyl ketoneMethyl isobutyl ketoneEthyl acetateTrichlorethyleneButyl alcoholEthyl alcoholCyclohexanol

Resins Form filmAlkydPhenolicAcrylicVinylAminoCellulosePolystyrenePolyurethane

Calcium carbonateSilicaBentonite

Driers Speed drying

Biocides Prevent growthof molds andfungus

Flattening Agents Reduce luster

Epoxy

Pigments Providecolor,opacity

Titanium dioxideZinc oxideIron oxidesLeadChromiumCadmiumAluminumBronzeCarbon blackLamp black

Extenders Build bodyTalc

COMPOSITION OF PAINT

Vehicles Function Fillers Function Additives Function

Source: Burgess WA. Recognition of Health Hazards in Industry: A Review of Materials and Processes. New York: John Wiley & Sons; 1981.

used in formulating paints, they generally composeonly a small percentage of the paint.

Toxic Constituents

The toxic constituents of paints are contained in thesolvents, pigments, extenders, and resins. Dermaland ocular exposures and inhalation can occur whilepaints are being mixed or applied; the route anddegree of exposure depend to some extent on themethod of application. During roller or brush paint-ing, solvent vapors can be inhaled as these constitu-ents volatilize from the freshly painted surface. Spraypainting, however, poses a much greater respiratoryhazard because both the liquid and solid constituentsare aerosolized.

Chronic exposure to the mixed solvents that arefound in paints can also cause a neurasthenia that issometimes referred to as painter’s syndrome. Toxic

symptoms include headache, fatigue, difficulty inconcentrating, deficits in short-term memory, irrita-bility, depression, and alcohol intolerance. (Thesesymptoms have also been reported by workers in theplastic boat industry and among jet-fuel handlers).4 Ingeneral, as the severity of the solvent-related effectsincrease, reversibility becomes less likely.27 The sol-vent-related neurasthenia was first described in theScandinavian literature during the late 1970s, but isstill not universally recognized. A recent study evalu-ated workers in two paint-manufacturing plants inthe United States, but failed to document these spe-cific symptoms of toxicity.28 This study evaluated187 workers using three standardized psychological/neurological assessment batteries. Exposure dura-tions ranged from 6 to 36 years and concentrationswere below the TLVs or PELs. No significant associa-tions were found between solvent exposure and testscores.29


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Solvents

Paints can contain solvents from virtually everychemical class and toxicity level (described previouslyin this chapter). Because many are highly toxic, suchas benzene, and potentially carcinogenic, such as thehalogenated hydrocarbons, attempts have been madein recent years to reduce the use of these toxic solventsin paints by substituting less-toxic solvents.30 How-ever, the workplace hazard remains significant be-cause workers continue to encounter these agents inolder formulations, or as constituents of current paints.

Inorganic Pigments

Pigments provide paint with opacity, color, dura-bility, and film hardness. They typically constitute20% to 60% of a paint by weight, and are composed offinely divided inorganic solids.31

Titanium Dioxide. Titanium dioxide is a whitepigment that has virtually replaced the older lead-based white pigments. (It is also used in food productsand cosmetics as a whitening agent.) Titanium diox-ide is generally thought to be physiologically inert.3

Other white pigments include calcium carbonate,barium sulfate, and aluminum silicate.31 Historically,these pigments have been considered physiologicallyinert, and they have a low order of toxicity. Recently,however, concerns have been raised over pulmonaryalveolar proteinosis, a physical condition thought toresult from exposure to particulates. The conditionhas been reported among workers exposed to severalparticulates including the inert dusts. Other studiessuggest that these may, in fact, be biologically active,and NIOSH has reported data suggesting that tita-nium dioxide is a potential occupational carcinogen.8

The ACGIH TLV for these white pigments is 10mg/m3. OSHA PELs are 10 mg/m3 for barium sulfateand titanium dioxide, and 15 mg/m3 for calciumcarbonate. OSHA also set a PEL of 5 mg/m3 as arespirable dust for all three pigments.7,8

Carbon Black and Lamp Black. Carbon black,produced during the incomplete combustion of petro-leum gas, and lamp black, produced during the in-complete combustion of oil, are the most commonblack pigments used in paints. Incomplete combus-tion may produce a variety of polynuclear aromatichydrocarbons (PAHs), which are likely to contami-nate these black pigments. A number of the PAHshave been found to be both mutagenic, when tested inin vitro test systems, and carcinogenic in animal bio-assays. No excess tumor incidence has been found inepidemiological studies of carbon black workers, how-ever.31 The ACGIH TLV for carbon black is 3.5 mg/m3;

OSHA has not set a PEL for this substance. Noexposure limits have been set for lamp black.7

Iron Oxides. Iron oxides, found in red and browninorganic pigments, have low dermal and oral toxic-ity. Workers in the metal or pigment industries whoinhale iron oxide dust or fumes may develop a mildform of pneumoconiosis. Because the causal agent isiron, this condition is more specifically termed a sid-erosis, and apparently does not become fibrotic.7,8 TheACGIH TLV for iron oxide is 5 mg/m3; the OSHA PELis 10 mg/m3.7,8

Chromium. Chromates, used extensively in yellowand orange pigments, can act as sensitizers. Chro-mate dermatitis has been reported in workers in anumber of industries. Exposures to chromium in thechrome-production and -pigment industries have beenassociated with an increased incidence of respiratorycancers.32

Chromium exists in oxidation states ranging fromdivalent to hexavalent; the trivalent state is the mostcommon form found in nature. The carcinogenicactivity associated with exposure to chromium hasbeen attributed to the hexavalent form. Epidemio-logical studies suggest that the acid-soluble, water-insoluble hexavalent chromium is produced in refin-ing operations. This form is also corrosive andreportedly can cause chronic ulceration and perfora-tion of the nasal septum. In contrast, trivalent chro-mium is neither irritating nor corrosive.8

The ACGIH recommends a TLV of 0.5 mg/m3 forchromium metal, di- and trivalent chromium andwater-soluble hexavalent chromium compounds.Water-insoluble hexavalent chromium is a knownhuman carcinogen and has a TLV of 0.05 mg/m3.OSHA has a PEL of 0.1 mg/m3 as a ceiling value forCrO3.

Organic Pigments

In addition to the inorganic pigments, there arehundreds of organic pigments used in the paint in-dustry. However, data on the toxicity of most organicpigments are limited: in most cases, the only dataconsist of acute oral LD50 values for rodents. Thehuman toxicology of chronic exposures to most or-ganic pigments remains largely unknown.25

Extenders

A number of minerals such as silicas, silicate clays,mica, and talc are used as extenders, which act to buildbody in paint formulations. While the toxicologicaleffects of pigments depend on the specific type ofpigment, all extenders have the potential to produce


478

fibrosis of the lung. Limited epidemiological datasuggest that a mixed-dust pneumoconiosis is preva-lent among painters, which might be due, in part, toexposure to extender materials.25

Resins

Resins are polymers. As a group they include thealkyd, acrylate and methacrylate, vinyl, cellulose, ep-oxy, and polyurethane resins. They have low volatil-ity and are generally soluble in organic solvents andinsoluble in water. In paints and varnishes, resinsprovide film hardness, gloss, surface adhesion, andresistance to weathering.31

Alkyd Resins. Alkyd resins form as a condensationproduct of a polybasic acid and a polyhydric alcohol.Their toxicity is relatively low and they have a longhistory of use without indication of a chronic hazard.31

Acrylate and Methacrylate Resins. Acrylate andmethacrylate resins are polymers formed from acrylicand methacrylic acids. These substances are usedextensively in latex paints. Unreacted monomers areprimary irritants and skin sensitizers. Once they arepolymerized, however, they are no longer health haz-ards. Reacted polymers have a low order of toxicity,and the Food and Drug Administration has approvedpolymethacrylate as an indirect food additive.31

Vinyl Resins. The vinyl resins are polymers of anumber of monomers including vinyl chloride, vinyli-dene chloride, vinyl acetate, and derivatives of sty-rene. The principal health hazard associated with thevinyl resins is the potential for exposure to unreactedvinyl chloride, which the EPA considers to be a knownhuman carcinogen. Epidemiological studies haveassociated workers’ exposures to the vinyl resins withincreased incidence of liver angiosarcoma and, possi-bly, brain tumors.33 The ACGIH recommends a TLV of5 ppm for exposure to the vinyl resins.7

Cellulose Resins. The cellulose resins are naturalproducts and include nitrocellulose, cellulose acetate,and cellulose acetate butyrate. These compounds donot present any known toxic hazard.25,31

Epoxy Resins. The epoxy resins used most fre-quently in paints and coatings are usually made byreacting epichlorhydrin and bis-phenol-A. Exposuresto epoxy resins that have not cured completely havebeen associated with skin and eye irritation and aller-gic skin reactions. Liquid epoxy resins are used pri-marily in two-component epoxy paints. These liquidresins are modified when reactive diluents—whichare also skin, eye, and respiratory irritants—are added.Aliphatic and aromatic polyamines and polyamidesare also typically used as curing agents in two-compo-

nent epoxy coatings. These substances are also poten-tial sensitizers and irritants.25,31

Because they are not volatile compounds, there areno TLVs or PELs. Operations such as grinding andsanding can produce nuisance dusts, however, and theTLVs for the individual components are then relevant.

Polyurethane Resins. Polyurethane resins areformed by polymerization of an isocyanate such astoluene diisocyanate (TDI). Uncured polyurethaneresins contain small quantities of unreacted mono-mers and these monomers can cause health problemsin exposed workers. Isocyanates can cause severeirritation to the conjunctiva, may cause respiratorydistress, and are associated with sensitization-typereactions. Inhalation of isocyanate vapors or aerosolscan produce asthmalike symptoms including con-stricted airways, difficulty in breathing, and a dryirritant cough. In sensitized individuals, even a verylow exposure to an isocyanate can produce anaphy-lactic shock or other such dramatic response.25 TheACGIH TLV and OSHA PEL are both .005 for theunreacted monomer.7,8

Additives

Until recently, mercury biocides were added tolatex paints as a preservative to prevent bacterial andfungal growth and to control mildew on exteriorsurfaces. These biocides were derived from mercurialcompounds including phenylmercuric acetate (PMA),3-(chloromethoxy)propylmercuric acetate (CMPA),and phenylmercuric oleate (PMO). At least one reporthas linked these mercury compounds to acrodynia, arare form of mercury poisoning found in children.This disease is characterized by pink-colored fingersand toes, peeling of the soles and palms, pain in theextremities, impaired motor control, photophobia,and mental apathy. The EPA, working with paintmanufacturers, decided to remove mercury from inte-rior paints. Only PMA will remain registered for usein exterior paints and for miscellaneous interior uses(spackling and patching compounds).34

Chemical Agent Resistant Coatings

Until the early- to mid-1980s, military vehicles werepainted with standard alkyl and acrylic paints, butthese absorbed chemical warfare (CW) agents. Up to25% of liquid CW agent applied to surfaces paintedwith standard paints is absorbed within 30 minutes.The CW agent can then desorb slowly over severalweeks, creating a residual toxic hazard. Standardalkyl paints are also soluble in decontamination solu-


479

tions. To avoid these hazards, the military convertedto polyurethane paints (PUPs), which are chemicalagent resistant coatings (CARCs), on all combat, com-bat-support, and tactical-wheeled vehicles, and air-craft and essential ground-support equipment.

There are two primary paints in the CARC system.The first, for exterior use, consists of aliphatic PUPapplied over epoxy paint, which is used as a primercoat. The second, for interior use, consists of an epoxy-polyamide paint used over the epoxy primer.35 Ep-oxies were initially considered for all CARC applica-tions. However, because they break down withprolonged exposure to ultraviolet light, they can onlybe used indoors.

PUPs provide a measure of chemical resistance.However, the camouflage pigments and flatteningagents required for military vehicles are more porousthan are high-gloss paints. CW agents can enter thepores of PUPs, but are not adsorbed to CARC paints—unlike alkyd and acrylic paints—and they can beremoved with standard decontamination procedures.

CARC paints are also resistant to the components ofthe decontamination systems.

Two polyurethane topcoats—a two-componentpaint and a single-component paint—are available.The two-component system incorporates componentA (containing the polyester resin, solvent, and pig-ment), which reacts with component B (an aliphaticpolyisocyanate combined with volatile solvents) toform a tough, resilient coating. In the single-compo-nent system, the paint cures by reacting with moisturefrom the air.35

Both of the PUP CARC systems contain unreactedisocyanate groups in the uncured resin, which irritatethe skin and sensitize the respiratory system. Thenewer PUP used currently in CARC paints includeshexamethylene diisocyanate. The monomerichexamethylene diisocyanate is usually reacted to forma higher-molecular-weight prepolymer that is lessvolatile than the hexamethylene diisocyanate mono-mer, which tends to reduce the potential hazard frominhalation.35

Fig. 13-3. The operator in this walk-in spray booth is wearing coveralls, gloves, a head cover, and an air-purifying respirator.He has also positioned the items to be painted between himself and the booth’s exhaust ventilation. This serves two purposes:it minimizes the potential for the painter’s exposure and it prevents vapors and aerosols from leaving the spray booth.


480

Exposure Controls

Industrial painting operations use several methodsto control worker exposures and reduce potentialhealth effects. Most flow- and spray-painting opera-tions with solvent-based paints require exhaust venti-lation to reduce the airborne paint mists and solventvapors to acceptable levels. Ventilation controls in-clude spray booths and rooms or tunnels, which aredesigned to contain the aerosol mists (Figure 13-3).These enclosures are equipped with a filtration sys-tem (or mist arrestor) to remove paint mists from theexhaust air. Spray-paint operators must wear effec-tive PPE: goggles and a face mask with a charcoalfilter. Effective spray-booth controls also require thatthe operator not position him- or herself between theobject being painted and the point of exhaust. Person-nel should also ensure that booths equipped with dryfilters receive regular maintenance and cleaning toprevent the filter from clogging.25

The method of paint application influences workerexposures. Conventional air spraying is the most

common method used in spray-finishing operations.Exposures to paint mists as a result of overspray and re-bound are principal hazards of these operations. Air-less spray techniques reduce overspray by approxi-mately 50% when spraying flat surfaces. Another applica-tion method, electrostatic spraying, involves chargingthe paint mist so it is attracted to the item to be painted.This technique eliminates almost 90% of the oversprayassociated with conventional air atomization.2,25

Spray-finishing applications in which engineeringcontrols are impractical, or operations in which highlytoxic materials are present require that PPE, includingrespiratory protection, be used. Airline respiratorsmay be required during painting operations in con-fined spaces such as storage tanks, boilers, ventilationducts, or other areas where airflow is restricted. Inother situations, conventional half-facepiece respira-tors with mist-removing prefilters and organic-vaporfilters may provide adequate protection. AdditionalPPE should include cloth coveralls, eye protection,gloves, and head coverings. Workers should be pro-hibited from wearing contact lenses while painting.35

MEDICAL SURVEILLANCE

Workers who could be exposed to the constituentsof paints should be enrolled in a comprehensive medi-cal surveillance program designed to prevent or con-trol occupational diseases. Exposure to solvents canoccur in a variety of occupations and often involvescomplex mixtures; therefore, the installation’s medi-cal authority should determine the specific detailsconcerning the scope and frequency of medical sur-veillance examinations. The physician can find de-tailed recommendations on medical surveillance fromthe Medical Information Module of the OccupationalHealth Management Information System (OHMIS),which is discussed in Chapter 4, Industrial Hygiene,or from other medical guidance.

Medical evaluations should include a preemploy-ment examination and a regular periodic examina-tion, both of which should include detailed medicaland occupational histories. In addition to the stan-dard evaluation for smoking and alcohol use, thephysician should pay particular attention to any his-tory of previous exposures to toxic substances, espe-cially organic solvents or other agents associated withneurotoxic effects (see Table 13-6). Due to the neuro-toxic effects of solvents, the physician should alsoconsider obtaining a neuropsychiatric evaluation.

Because painters can be exposed not only to sol-vents but also to the other constituents of paint, they

require medical surveillance. The most serious occupa-tional health concerns for painters are their potentialfor exposures to mixed solvents and isocyanates. Dur-ing the preplacement or baseline evaluation, the physi-cian should screen for previous exposures to isocyan-ates. The physician should note the patient’s allergies,respiratory diseases, and smoking habits. Because sensi-tized individuals who are subsequently exposed toisocyanates may have serious allergic reactions, hyper-sensitive individuals and workers with a history of chronicrespiratory illness should not work with these substances.The physical examination and clinical tests should alsothoroughly evaluate the respiratory system and in-clude, in addition to the routine chest X ray, pulmo-nary function tests with forced expiratory volume in 1second (FEV1), forced vital capacity (FVC), and FEV1/FVC. A periodic examination should be performed atleast annually after the preplacement examination.35

For a medical surveillance program to be effective,health education must accompany the evaluations.Health education includes training for both employ-ees and employers, and should provide informationon the potential hazards of the chemicals in use, themeasures to control exposures, and the proper use ofpersonal protective equipment. Training should alsobe updated and repeated when new chemicals areadded to the workplace.36,37


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MEDICAL TREATMENT

There are no militarily unique medical treatmentsfor exposure to solvents and paints or to chlorofluoro-carbons. In most cases, simply removing the victimfrom the hazardous environment is the only treatmentrequired. Contaminated clothing should be removedto prevent additional exposure. The physician shouldensure that an adequate airway and respiration aremaintained. Urinary output should be monitored andfluids administered either intravenously or orally.Diazepam can be used to treat convulsions.

Solvents and Paints

Usually, the only treatment necessary for acuteexposures to solvents is removal from the toxic atmo-sphere. However, acute exposures in high-enoughconcentrations can cause paralysis, convulsions, andunconsciousness that can progress to death. In instancesof ingested solvents (including halogenated hydro-carbons, kerosene, and stoddard solvent), medicalpersonnel must take care to prevent the victim fromaspirating the toxic agent into the lungs. Even smallquantities of a solvent like kerosene in the respiratorytract can cause pneumonitis, pulmonary edema, hem-orrhage, and necrosis. If aspiration occurs, the emer-gency treatment is the same as for any oily liquid.

Fluorocarbons

As a group, fluorocarbons and chlorofluorocarbonshave very low acute toxicity; the greatest hazard ofexposure to these compounds is simple asphyxiation.Exposure to very high concentrations (> 50,000 ppm)has been shown to produce CNS depression andeventual respiratory failure. Simply removing thevictim from the hazardous environment is usuallythe only treatment required; all toxic signs rapidlydisappear when the patient is removed to fresh air.The most severe threat from fluorocarbon exposure isthe ability of these chemicals to sensitize the lungs and

myocardium. In some individuals this can causebronchospasm and cardiac arrhythmias. Should over-exposures to halogenated hydrocarbons—including the chlo-rofluorocarbons—occur, epinephrine or other sympatho-mimetic amines and adrenergic activators arecontraindicated. These solvents are cardiac sensitizersand will further sensitize the heart to the developmentof arrhythmias. They must not be administered.

Toxic Combustion and Decomposition Products

Exposure to the combustion and decompositionproducts of halons when they are used as fire extin-guishers is probably the most significant medical prob-lem posed by chlorofluorocarbons. These productsare extreme irritants; consequently, exposed individu-als will attempt to escape from the contaminatedenvironment. Personnel inside vehicles or confinedspaces, where escape is difficult, may be exposed tolong-term, high concentrations of these severe irri-tants and can suffer chemical burns of the eyes, skin,mucous membranes, and lungs. Medical treatmentshould be the same as that for any other severe irritant.Pulmonary edema will undoubtedly be a complica-tion if exposure to high concentrations has occurred.

Physical Trauma

Halons used in fire-extinguishing or other pressur-ized, closed systems can cause hearing damage fromexcessive noise. Hearing protection should be recom-mended for areas where the probability of suddenrelease of these chemicals is high. The subzero tem-peratures that occur when pressurized fluorocarbonssuch as the halons are suddenly released can alsofreeze unprotected skin, eyes, and mucous membranes.Treatment for freezing injury requires no special pro-cedures; the fluorocarbons will rapidly volatilize andthe resultant injuries can be treated like any routinecold injury.

Although large quantities of solvents, fluorocar-bons, and paints are used annually in DoD industrialoperations, exposure potentials in the military aresimilar to those in comparable civilian occupations.Despite the increased use of engineering controls andPPE, severe injury or debilitation can result from

overexposure to these compounds.Solvents are used extensively in the military to

degrease metal parts, in paints and paint removers,and as intermediates in the manufacture of otheritems. Most of the organic solvents discussed in thischapter have similar acute, toxic, anesthetic-like ef-

SUMMARY


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fects to the CNS. Chronic exposures also may affect theCNS; other target organs include the liver, kidneys,and blood. Some solvents, including benzene andthe chlorinated hydrocarbons, are animal carcin-ogens, and some are human carcinogens. Targetorgans for carcinogenicity are blood, liver, and skin.

Fluorocarbons as a class are relatively nontoxicafter acute exposure. Chronic exposure also does notappear to pose a high level of risk. They are poten-tially toxic to both the cardiovascular and bronchop-ulmonary systems; this fact is of major significancewhen medical personnel are required to treat exposedindividuals. The greatest medical hazard posed byfluorocarbons is the extreme toxicity of their highlyirritant combustion and decomposition products.Current use in the military is significant and will

probably rise. As replacement chemicals for bannedfluorocarbons are selected, the toxicological and medi-cal databases for them will be fragmentary at best.

Painters can be exposed to a variety of toxic compo-nents. The most prevalent exposures are to the sol-vents. Other constituents of paint can also have toxiceffects. However, most constituents of paint are rela-tively safe in the concentrations used in paint formu-lations. Allergic sensitization reactions can still occurin sensitized individuals who are exposed to the iso-cyanates used PUP and CARC paints.

Military occupational health professionals shouldcontinue to work with industry to minimize the po-tential risks through engineering controls and,where possible, through substitution with less-toxicmaterials.

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Chapter 13 SOLVENTS, FLUOROCARBONS, AND PAINTS · 2020. 7. 1. · mixed solvents: house and car painters and jet-fuel handlers have reported impairment of visual percep-tion, hand–eye