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Plastics
The T<kv>ci>Io<iv of Synthetic h'esins
MX H. WILSON, M.D., and WILLIAM I. McCORMICK, M.S.. Akron, Ohio
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This presentation is the third revision of a paper originally written1 in 1954. It represents a compilation of the literature concerning the toxicological properties of synthetic resins. While not all-inclusive, the bibliography can be used as a reference for the investigator of the toxicology of plastics. The second revision - was presented in November, 1955.
1 Mastics is a familiar word to everyone. Who among us does not possess or use some thing made from a plastic? The manufacture of plastic articles and materials is both big and little industry. A small shop with few employees can make profitably a plastic water pistol. A large company makes nylon stock ings or plastic garden hose. Automobile bodies and telephones are molded from plastics. These plastic articles are important to our social progress, and the jobs resulting from their manufacture are important to our national economy.
Plastic compounds are ever changing. The public demand for articles made from plastics is so great that the growth possibili ties are seemingly endless. Vast sums of money are spent each year on plastic re search, resulting in new materials. The industrial physician and hygienist must know the toxic properties of these items. The working environment is only as safe as the industrial hygienist makes it. Any material can be handled safely if one knows what it is and then handles it properly. Overex posure to a toxic material represents care lessness or ignorance.
Received for publication Nov. 18, 1959. The II. K. (iomlricli Co. Presented at the Industrial Health Conference, Chicago, April .10, 1050
Numerous papers have been written by authors front many different parts of the world concerning the general hazards of the plastic industry.3'* Obviously, occupational hazards may exist in the production and processing of some plastic material. Toxic hazards can arise from the use of plastics which contain toxic substances, particularly in food-packaging applications where extrac tion into the food may occur. Polymerized synthetic resins, which form the base for many plastics, in themselves are usually not a hazard because of their insolubility and unreactivity. The risk arises from plas ticizers, lubricants, stabilizers, colors, and fillers used with them to form the finished plastic.10 There may also be significant hazards existing in the use or manufacture of the monomers of these resins, prior to polymerization.
In this discussion we have separated the resins into general classifications. In so doing we appreciate that there is considerable overlapping in many instances.
I. Acrylic Resins
The acrylic resins are used in many differ ent ways including the making of aircraft turrets, automobile tail lights, brttshbacks, signs, and various types of textiles. Non irritating contact lenses for the eye can be made from methyl methacrylate.11 These resins are extensively used in maxillofacial surgery. Prosthetic appliances for various parts of the human body can be fashioned from acrylic plastic material. An acrylic plastic materia! is used as a replacement11 for blood vessels and heart valves because it does not promote the clotting of blood.
Aubrey,13 F.mller,14 Schuller,lr' and other medical reporter'' have Mated that the
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crylie resins have the best properties of all if the synthetic resins for use in facial urgery and produce minimum tissue reacn>ns. They feel that the acrylics are better linn any other previous material for tissue oinpatihility 17 and that they can be used in osmetic surgery without causing skin irritaion. Human implants have been made.16 intraocular acrylic lenses have been used as substitute for the lenses of the eye for three -nd one-half years and over 150 successful ve operations have been reported without vidence of excessive foreign-body reacion.TM
The use of an acrylic plastic replacement i >r the femoral bone head has shown a high ercentage of failure due to sepsis.18 Howver, the septic process is not from direct . ntation by the acrylic material. The proluction of malignant tumors in rats by the mplanting of plastics of various types has een reported,18'2U but there are no reported kises of malignant growths developing in ^uman beings from their use.
Laskin21 referred to an experiment in which subcutaneous implantation of acrylic ini in mice results in a 25% incidence of obrosarcomas. These tumors developed beween 257 and 469 days after implantation, itccause of these findings he cautioned further use of acrylic in humans for pur poses of femoral heads, intraocular pros! Weses, and jaw reconstruction.
MacKay 21 referred to the use of methyl methacrylate implants for the repair of ranial defects. In over 100 cases he cited no significant reaction to the substance even when it was placed in infected wounds. He considered the plastic "biologically entirely inert and innocuous."
Morgenstern and associate22 described a case of sensitization to methacrylic acid and its polymerization products resulting front iltcir use in dental prosthesis.
Patty23 stated that polymerized methyl methacrylate is inert; only its stabilizers and antioxidants have adverse physiological vlfects, particularly dermatitis. Hecause of
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its inert properties, it was chosen to make an artificial kidney.
Karpov21'20 reported on the effects of monomeric methyl methacrylate vapors. Symptoms of irritability, tiredness, somno lence, headache, loss of apjietite, and a drop in blood pressure--attributed to a disturb ance of the dynamic equilibrum in the cortex of the brain caused by inhalation of these vapors--were observed. In human beings it lowers the blood pressure.
Deichman 27 and Spealman 28 have studied the effects of monomeric methyl methacry late vapors on laboratory animals. Deichman found that a concentration of 19 mg. per liter of air killed all exposed animals in 2.5 to 5 hours. Gross pathological changes were confined to the respiratory system. Spealman observed that the vapors were more acutely toxic than acetone for mice and less than those of ethyl acetate. An LCso for mice for three hours' exposure was found to be 55 mg. per liter.
Karpov 25 gave a suggested tolerance for monomeric methyl methacrylate vapors in industrial establishments of 0.05 mg. per liter. He also observed that the respiratoiy mucosa may be irritated when vapor con centration reaches 0.25 mg. per liter.
Raines20 called attention to the high toxicity of methyl methacrylate, widely used as a monomer in the polymerization of plastics and dentures. Upper limits of its vapor concentration in air which are per missible are stated as 0.05 mg. per liter.
Summary.--Methyl methacrylate vapors have some systemic effects on the brain cortex and on the blood pressure, resulting in lowering. The acrylic resins themselves appear to be substances which can be used successfully as bone replacements, artificial eyes, and other prosthetic appliances. When placed in certain regions of the human body, however, they should be kept under observa tion because tumor formation, tissue reac tion, and sepsis have been reported.
II. Alkyd Resins
The alkyd resins are being used in the manufacture of linoleum surf,'icings, paints
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for refrigerators and autos, ignition parts, magnetorotors, and food wrappings.
Morris,34 on reviewing the reactions in volved in the production of aminoplasts, phenoplasts, and alkyd resins, stated that the finished products are dermatologically inert.
Schwartz, Tulipan, and Birmingham31 found that the alkyd resins may produce dermatitis. Schwartz38 reported that alkyd resins when used as finishes for textiles have caused some cases of dermatitis.
Summary,--The alkyd resins are capable of causing occasional mild cases of dematitis.
III. Amino (Urea and Melamine) Resins
This group of plastics is used for many articles including buttons, dishes, laminated table tops, and housings for kitchen appli ances. They are used as soap fillers and finishes for textiles. They can be used to treat paper for food-wrapping purposes.
Elkins 33 stated, "nitrogen bearing plastics, such as melamine, have been said to give off hydrogen cyanide when heated, but the quantities are apparently not sufficient to produce real danger."
Hodgins 34 stated that heat-converted films of urea-formaldehyde-ethylene glycol resins used as food-wrapping material showed no toxic effect when fed to guinea pigs in single doses of 100 mg. Repeat doses to rats of 10 mg. per day for 30 days produced mild effects on the liver, kidney, and gastroin testinal tract. Moss 35 in studying the pyro lysis of melamine formaldehyde compounds, found that mixtures of 200 ppm carbon monoxide and 10 ppm hydrogen cyanide were produced which killed rats within 30 minutes. He noted that hydrogen cyanide increases the rate of respiration and, hence, intake of carbon monoxide. Schneider3* studied the effects on human skin of soaps containing urea-formaldehyde resin filler. No significant difference was observed !>ctween soaps filled with ttrea-formaldchvde and other soaps. Cases of dermatitis were found due to the fatty acids used.
Segal37,3* found little indication of toxici ty in rats fed Amberlite resin, a polyamine
formaldehyde resin, when diets containing 0.5% to 2% of the crude resin were used. There was no histological evidence of dam age resulting from ingestion of the resins noted. He stated that the over-all toxicity of Amberlite, even at 20%, is negligible.
Markuson3 reported on the prevention and control of dermatitis due to formalde hyde resins.
Vil'kovich 40 noted that the introduction of powdered aminoplastic resin, used in kitch enware, into the regular diet of white mice led to 70% to 80% fatalities. He also found both hot and cold aqueous extracts, obtained by placing water into aminoplastic dishes, led to considerable intoxication.
Schwartz31,31 felt that urea-formaldehyde resins, when used as finishes for textiles, caused occasional cases of dermatitis.
Lehman 41 stated that a polymer of ureaformaldehyde is acceptable as a treatment of paper for food-wrapping purposes. He also stated that melamine formaldehyde polymer is satisfactory for the same purpose.
Lieber,3 in discussing industrial derma titis, stated that the amino resins can affect many people who have hereditary hypersen sitivities.
Summary.--The amino resins (urea and melamine) can in certain combinations, particularly melamine formaldehyde com pounds, pyrolyze into hydrogen cyanide and carbon monoxide. Urca-formaldehydc-cthylenc glycol resins can safely be used as foodwrapping material. The aminoplasts may be very toxic. Dermatitis has resulted in work ers handling these resins.
IV. Cellulose Plastic Materials
Cellulose plastic materials are used ex tensively in display packaging, irrigation pipe, frames for eyeglasses, cigarette filters, tire cord, and in rayon acetate textiles. Some of the cellulose plastics arc suitable for food packaging.13
Marainorosch 13 staled that sheets of cel lulose acetate were found to lie toxic to plants and fish. This toxicity is due to diethyl phthalate.
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w Oppenheimer1950 noted that malignant tumors including sarcomas were produced in groups of rats and mice by subcutaneuusly imbedding cellophane films. He stated that additives, plasticizers, etc., apparently do not account for the production of these malignant tumors.
Schwartz, Tttlipan. and r.irminghaiu41 found only rare cases of dermatitis due to cellulose resins.
I'armeggiani and associates," in discussing the occupational risks and pathology in the production and manipulation of some plastic materials, stated that in the manufacture of cellulose acetate, the acetic acid content in the air caused mucosal irritation, blackening of the skin, and erosion of the teeth.
Summary.--Cellulose plastics can be used safely externally. They only rarely produce dermatitis. Internal use may be hazardous. There is some occupational risks in the manufacture of cellulose acetate.
V. Coumarone-indene Resins
Coumarone-indene resins are used in the manufacture of asphalt floor tiles, aluminum paints, waterproof coatings, printing inks, pnd chewing gum.
Geiger'*4 stated that coumarone-indene resins present little if any industrial hazard from the point of view of toxicity, as wit nessed by their long-continued use in chew ing gum. The main hazards are involved in ;he use of the monomers, to which some individuals exhibit allergic tendencies.
Cases of dermatitis among workers han dling coumarone-indene resins31 have been reported.
Summary.--A relatively nontoxic variety `if resins. The hypersensitive person can acquire a dermatitis from handling these materials.
VI. Epoxies
During the past few years there have been marked advances made in the chemical technology of the epoxy resins. Currentlv these resins are widely manufactured and ire available under a variety of trade names.
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They are used in corrosion-resistant sur face coatings, molding compounds, castings, laminating or reinforcing plastics, encap sulating electronic circuits, printed circuit backing, and adhesives. Metal-to-metal bonding can be accomplished with an epoxy adhesive.
I ,ea and associates49 have attempted to assess in a general manner the irritating and sensitizing capacity of the com]>onent ma terials in the epoxy resin formulations. The resins were found to be irritating to the skin by means of human patch-testing,
Hine and associates 49 discussed the tox icity of six epoxy resins.
Morris47 stated that exposure to epoxy resins in industry has resulted in dermato ses. He said that the epoxies, the curing agents, and some of the additives are severe skin irritants.
Bourne 48 stated that contact with triethylenetetramine used as a polymerizing agent will give rise to an erythema of the face and arms.
Dorman48 stated that uncured liquid epoxy resins and amine type curing agents are capable of causing allergic epidermal eczema. He outlined preventive measures that can be undertaken.
Grandjean90 stated that dermatoses oc curred in half the workers using an epoxy resin in 11 factories making electrical equipment.
Pitt and Paul 91 stated that a series of V-hydroxy alkyl-polyamines were evaluated as cross linking agents for polyepoxy resins. The availability of these cross linking agents with lower toxicity offers a means of overcoming one of the major deterrents in the widespread utilization of epoxy resins.
Summary.--The epoxy resins are rela tively inert chemically and are resistant to heat. Severe skin irritation can occur in their manufacture and use. They must be handled with care. The curing agents used with these resins appear to be the primary cause of the skin irritant effects.
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VII. Fluorocarbons
The fluorocarbons are used in the manu facture of such articles as pump diaphragms, chemical tubing, high temperature insula tion, coating of molds and bread pans, and gasket material in jet engines. Teflon is being used extensively in surgery for su tures and tubing.
Recent work by Zapp and associates:'2 indicates various fluorine compounds to be present in the decomposition products, the specific ones, as well as the amounts of each, depending on the temperature of de composition. In the range of 300 to 360 C, hcxalluorethane was observed: above 380 C, an extremely toxic compound, octafluoroisobutylene, was detected; from 500 to 550 C, the chief pyrolysis products were tetrafluoroethylene, hexafluoropropylenc, octafluorocydobutane, octafluoroisobutylene, a Cj olefin, and a complex mixture of perfluoroolefins.
Fairhall S3 stated that polytetrafluoroethylene (Teflon) is physiologically inert and has been rated as nontoxic. However, when heated above 400 C, unidentified volatile gases are evolved which may be toxic. In halation of Teflon dust appears to produce a condition resembling nietal-fume fever. Pulmonary edema may result.
Stokinger 54 stated that industrial hazards from Teflon are due to exposure to its dust and to its decomposition products derived from heating. In the first instance, a con dition resembling metal-fume fever, "the shakes," is observed. The effect usually dis appears within 24 hours with no after-effect. There is pain and aching in muscles and joints, accompanied by chills and profuse perspiration alternating with fever. When heated above 360 F, the Teflon sublimate is believed to contain absorbed hydrogen fluoride. This can produce irritation of nasal membranes and may ultimately result in pulmonary edema.
Wilson and McCormick1 stressed the need for adequate ventilation when using Teflon to avoid ill effects.
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I-aVeen,'"1 in reporting on the tissue rv action to plastics used in surgery, mad special reference to Teflon. He felt that could be safely used. However, Oppei heimer 10 noted that malignant tumors hn\ been induced by Teflon when it was im bedded in rodents.
Treon and associates114 reported anima fatalities resulting from exposure to t! decomposition products of Teflon and Kelwhen heated to 752 F.
Lehman42 found that polytetfafluon ethylene, when used as a coating for brea pans, created no significant increase in ti fluoride level of the bread.
Sendroy,TM in studying the effects of pyi lyzed products of PTFF (a fluorocarb polymer) when used on electric motor wim ings, under conditions simulating those submarine operations, concluded that i, carbon monoxide hazard would exist w operating conditions in excess of 250 C hi that excessive concentrations of fluorii compounds might arise.
Summary.--The fluorocarbons are e tremely resistant to corrosive agents ,r solvents. The end-products arc inert ai nontoxic, but toxic decomposition prodis may be produced. Inhalation of Teflon du may cause an effect resembling "metal-fui fever." Irritation of the mucous membran, and pulmonary edema can occur from inh. ing the decomposition products.
VIII. Nylon
Nylon is used extensively in the man faeturc of gears, slide fasteners, cornl tumblers, lire cord, tennis racket strim. and textiles. It is used as surgical sum material, catheters, and toolltbrush brisl!
Kxpcrimcnts have proved that the t v of nylon polymer used in yarns is not to\ and does not cause any skin reaction. Nyl> has met the rigid suture requirements the medical profession.
Gipstein r' reported that a papulovesicm dermatitis was observed on a 20-yearwoman and found that patch tests reven' that the nylon fabric, dyed or undyed, v.
the agent.
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I nderfurth **' stated that undyed and un.hed nylon possessed no toxicological perty and caused no skin reaction. Its as suture material and toothbrush bris, confirms this report. Last0 noted no intra-arterial toxicity an nylon catheters, and Schweisheimer1 ted that nylon was well tolerated and ulicable for bone sutures. \Tylon button type closures11 are safely i d for openings between the two auricles the heart. Also surgical tubing has been ide of nylon and has l>een used perfectly iely. I Hunt17 noted that nylon, when studied tissue inertness in dogs for periods up six months, showed less reaction than k or cotton. There was a small foreignutein reaction about the implant after six >nths. Oppenheimer18 noted that some maligmt tumors have been induced from imdding nylon in rodents. Summary.--Nylon is a perfectly safe iterial. The fashionable women of the >rld have proved this by wearing nylon ><e. In spite of its widespread use, only vasional cases of proved contact derniatis have been reported. Nylon can be imianted in the human body with little or no '.sue reaction,
IX. Phenolic Resins
The phenolic resins are used in the manuicture of telephone handsets, electrical intlation, radio-TV cabinets, varnish, shell okling, dials, grinding wheels, plywood, urgical braces, and other external surgical rosthetic devices.
Demole03 studied the effect of phenolormaldehyde resins on gastric juice. The iction on gastric acidity was variable and of hort duration, and there was no influence in the proteolytic enzymes.
Elkins63 reported that phenol-formaldetyde varnishes have been particularly bad iroducers of dermatitis.
Vedorov64 made a clinical study of the sensitization and development of allergy' in
chemical workers exposed to various sub stances including phenol-aldehyde resins.
Luvoni05 reported that several foundry workers handling phenolic-cresolic resins developed an eczematous dermatitis. Re moval of the affected persons from exposure resulted in the disappearance of the skin affections. He felt that a form of allergy was responsible.
Sendroy 56 stated that electric motors in sulated with CNSV, a phenolic resin, when operated continuously for 96 hours under conditions simulating submarine operation, gave off carlnm monoxide in concentrations up to 1,620 ppm.
Phenolic laminates11 have been safely used for braces and other external prosthetic devices.
Fairhall8 stated that dermatitis may re sult from repeated or prolonged contact with low concentrations of phenol in any form. It causes about 20% of the derma titis cases of the phenol-formaldehyde in dustry.
Lieber s believed that phenolic resins may affect many people who have hereditary hypersensitivity.
Summary.--The pbenolics as finished lam inates are inert and nontoxic. They can be used safely as external prosthetic appliances. Many workers exposed to these resins dur ing manufacturing processes have developed severe dermatoses.
X. Polyethylene
Polyethylene plastic is used in the manu facture of squeezable bottles, semirigid kitchenware, packaging materials, coaxial cables, surgical tubing, cartilage and bone substitutes, and surgical repair materials.
Polyethylene13 is used safely in surgical repair, suture tubing, skull covering, plastic lung prosthesis, arterial reinforcement, and hernial repair. Polyethylene has been used extensively as surgical repair materials, both in and out of the body, with no apparent adverse effects. Occasional skin reactions have been reported. In general, it appears to be a perfectly safe, nontoxic, inert mate-
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rial. It does not change composition when it is autoclaved.
Patty 07 stated that polyethylene is inert and that only its antioxidants and stabilizers have adverse effects.
Lehman42 found polyethylene to be satis factory as a food-packaging material,
Bing* stated that physical rather than chemical characteristics influence the body reaction to polyethylene. Implantation of irregular pieces causes more reaction. Poly ethylene mesh and nylon suture materials produce similar reactions. Macrophages are found to absorb a plastic sponge of formal ized polyvinyl alcohol formerly thought use ful as a permanent prosthesis,
Tusing * found no skin reactions and no evidence of systemic toxicity in rabbits after prolonged dermal contact with polyglycols.
Because it has no adverse effect on body tissue70 and is not affected by normal tem perature ranges, polyethylene is a satisfac tory substitute for human cartilage and bone.
Tuell71 stated that prolonged intravenous use of polyethylene tubing sometimes causes thrombophlebitis in the vein containing the tube. Tissue reactions are stated to arise from dicetyl phosphate in the mix or from the breakdown products of polyethylene which have been extruded at 250 C.
Oppenheimerfound that malignant tumors including sarcomas were produced in groups of rats and mice by subcutaneous imbedding of polyethylene.
Summary.--Polyethylene is a perfectly safe, nontoxic, inert material. It can be used as a surgical repair material both in and out of the body. Occasional tissue re action can occur, probably only in the sensitive person.
XI. Polyester Resins
The polyester resins arc used in the man ufacture of reinforced plasties for automo bile lxxlics, 1mmts, and translucent panels, and in Dacron textiles. They are excellent for the formation of artificial limbs.
They are weather-resistant, can be formed with low pressure, are strong and colorful,
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and are compatible with many fillers. Very little has been reported concerning their relative toxicity. The end-products contain ing polyester resins are considered to be inert and nontoxic. Some of the organic peroxides used in their manufacture pre sent safety and dermatology problems.
Polyester resins and glass doth are used to form artificial limbs of light weight and great strength. Virtually no one seems to be allergic to this material.73
Lieber* said polyester resins may have a dermatitis effect in people who have hered itary hypersensitivity.
Summary.--The polyester resins are rela tively inert, nontoxic materials. Virtually no one appears to be allergic to them.
XII. Silicones
The silicones are used for insulation for generator coils, auto polishes, waterproof coatings, silicone rubber, and circuit break ers. They are used in the medical field7* in needles, syringes, tubing, and in ointment bases.
It is reported that silicones74 in protective creams, suntan lotions, and other pharma ceutical preparations are nonsensitizing and nonirritating. .
Schoog73 found no evidence of silicone causing skin irritation and felt that it was safe to use it as an ointment base.
Lesser73 stated that silicone fluids are practically inert physiologically and appear to be nontoxic. They have little or no effect when administered up to 2rc of body weight. Certain silicone fluids cause a transitory conjunctival irritation in the eye but no corneal damage. Silicone-containing foods fed to rats showed a low order of toxicity. In skin tests silicone showed no irritation. Silicones used in the medical field in needles, syringes, taping, etc., are chemically inert and have no effect on blood samples taken for hematologic, bacteriologic, or biochemi cal study.
Taylor70 reviewed the properties and their effects of the silicates and silicones.
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Walker77 studied the toxicity of silicone insulation in submarines.
Cutting 78 noted that DC 200 silicone pro duced renal tubular damage when fed as 1% of the diet of rabbits for three to four months. DC Anti foam A caused widespread cellular infiltration in the kidneys and the liver when fed as 0.25^f to 1 r/c of the diet for the same period.
MacDougall70 reported that silicone rub bers appeared to be nontoxic when used in tissue culture techniques. This was in contrast to results with vulcanized rubber.
Poleman 80 noted no acute or chronic toxic effects of methyl polysiloxane, anti foam sili cone emulsion, and the resin used for coat ing capsules.
Rowe8I'82 studied methyl silicones, methyl phenylsilieones, and methyl polysiloxane and found them to be relatively nontoxic. He reixjrted that DC Anti foam A is very low in chronic oral toxicity but did cause transitory conjunctival irritation but no cor neal damage,
Lehman4142 found methyl polysiloxane satisfactory for treating paper for foodpackaging applications.
Coppack8,1 reviewed the toxicological irobletns of silicones and plastics associated with organic chemicals in food processing.
Oppenheimerln noted malignant tumors were induced from imbedding silastic fsilinne) in rodents.
Summary.--The silicones are practically physiologically inert and nontoxic. They may cause a transitory conjunctival irrita'ion when introduced into the eye but no orneal damage. Silicones are nonsensitizmg and nonirritating.
XIII. Polystyrene
Polystyrene resins are used in the manu facture of kitchen housewares, refrigerator parts, food packaging, toys and novelties, vail tiles, and light fixtures.
Goggin84 stated that polystyrene is nonoxic and in molded form has no taste or 'dor.
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Lehman 45 approved of the use of poly styrene as a food-packaging material.
Patty 85 stated that jxtlystyrene is inert; however, the antioxidants and stabilizers may cause dermatitis.
Struthers 841 reported that polystyrene may be used in contact with the skin and food without danger. Polystyrene, free from low molecular weight polymer or addition agents, presents no health hazard from oral inges tion.
Oppenheimer 10 reported that malignant tumors have resulted from imbedding poly styrene in rats.
Lieber5 stated that polystyrene resins may have a dermatitis effect in many people who have hereditary hypersensitivity.
Parmeggiani and associates* stated that nervous excitation, leukopenia, and occa sional dermatitis followed exposure to ethyl benzene among polystyrene workers.
Summary.--Polystyrene presents no health hazard from oral ingestion or skin contact, being inert and nontoxic. In its manufacture some hazards are encountered, especially from ethylbenzene. Dermatitis can occur.
XIV. Vinyl Resins
The vinyl resins are used in the manufac ture of floor tiling, packaging film, rainwear, toys, upholstery material, pipe and pipe fit ting, valves, electrical insulation, sponge, machine and structural parts, and metal and fabric coatings. They are used for plastic blood-transfusion equipment and an atomical repair film.
Plastic blood-transfusion equipment87 made of vinyl with nylon and phenolic molded parts has no toxic properties.
According to Lehman,'*2 several of the vinyl resins have been found to be satisfac tory for food-packaging materials.
Morris 88 studied the dermatological and chemical aspects of the vinyl plastics. Patty8 stated that vinyl chloride and vinyl acetate plastics have proved to be inert; only their antioxidants and stabilizers have ad verse physiological effects.
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Pulaski u" nuk'd no signs t>( toxicity when large amounts, oven up to 20 liters, of ]>olyvinyt pyrrolidone Had been given to human subjects. There is some storage of [wlyvinyl pyrrolidone ill the tissues. I le also stated that a decision as to the presence of chronic toxicity lias not been determined as yet.
Armstrong * stated that dextran and polyvinyl pyrrolidone are much superior to saline in the maintenance of blood volume after venisection. Systemic allergic reac tions occurred in some subjects who re ceived dextran but in none who received polyvinyl pyrrolidone.
Bernhard82 stated that polyvinyl pyrrolidonc is not toxic, antigenic, pyrcjgenic, or infectious.
Lesser " stated that polyvinyl pyrrolidone is nontoxic by oral administration, skin ab sorption, inhalation, or injection. Studies made on its storage in the body do not show any toxic effects.
However, Hueper24 has reported poly vinyl pyrrolidone to be carcinogenic to rats, and Lusky and Nelson 05 produced fibrosar coma in rats with multiple subcutaneous injections.
Wilson and McCormick1 rei>orted no signs of toxicity in a chronic study of a vinyl-vinylidene chloride copolymer with which rats were fed for two years and dogs for one year at a 5% dietary level. Geon polyvinyl chloride* was found least toxic in a series of experiments on resins for use in the chest cavity. Vinyl copolymers and polyvinyl alcohols are reported under study for anatomical repair purposes.
Oppenheimer18 20 did note that some ma lignant tumors resulted from imbedding polyvinyl chloride film in rodents.
Hcdri and associates 7 stated that poly vinyl chloride V-10 is considered unsuitable for use in surgery due to toxic effects in the liver, kidney, and spleen of dogs and mice. These effects appear to be related to high monomer content and lead contamina tion of the V-10.
Roubal and Pokorny* stated that acne on the face and forearms of workers han-
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dlitig polyvinyl chloride sheets or products is caused by chlorinated naphthalene. Addi tion of paraffin to prevent adhesion facili tates the rise of this chemical to the surface and should be avoided.
Tticll11 stated that polyvinyl chloride does not change chemical composition upon auto claving.
Parmeggiani " stated that in the manufac ture of polyvinyl chloride only slight signs of irritation existed.
Summary.--The vinyl resins are used for a variety of purposes. Polyvinyl pyrroli done (PVP) is nontoxic and can be used in the human body. Polyvinyl chloride (PVC) has been stored with little reaction in the chest cavity. Some slight skin irrita tions have been observed in workers manu facturing PVC.
XV. Polyurethanes
This class of polymers is relatively new, having been commercialized in the United States primarily during the past decade. They are high molecular weight polymers and may be used in the manufacture of ad hesives, plastics, rigid or elastic foams, or synthetic rubber.
Finished polymers are rather inert chemi cally and no more hazardous than more common plastics or rubbers.
The polymers are manufactured from a class of materials called diisocyanates. These materials present serious inhalation hazards. Common raw materials are toluene diisocyanate (TD1), methylene bis (4-phenyl isocyanate) (MDI), and para phenylene diisocyanate (PPDI).
In general, all the diisoevnnates so far investigated show similar toxicological prop erties. Animal experimentation and limited human experience indicate that this type of chemical is extremely hazardous via inhala tion. In acute inhalation studies on TDI, Zapp* found that 600 ppm for six hours was lethal to rats, while 60 ppm was not. Animals which died showed acute pulmo nary congestion and edema. Six ex insures, averaging 9 ppm, killed three of six rats.
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Thirty six-hour exposures of 1 to 2 ppm caused microscopic evidence of tracheobron chitis. Zapp concluded that TDI is a rather powerful irritant to the eyes, skin, and respiratory tract. Chronic exposures to I 10 2 ppm of TDT resulted in bronchitis in experimental animals with the attendant hazard of bronchial pneumonia.
Zapp staled that, although jmlyisoeyanate ]>olymers are physiologically inert, the monomers may cause irritation to the skin, ves, and respirator}- tract and allergic reictions. Polyurethane foam plasties caused
irtually no skin irritation or sensitization. I 'yrolysis products show some toxicity but ire not more hazardous than those of other lastomers tested.
Industrial use of TDI has caused many ases of asthmatic type reactions, some very -erious.
The high inhalation toxicity is reflected in he fact that the threshold limit value for !DI is 0.1 ppm.101
It is interesting to note that the odor iireshold of TDT is about 0.4 ppm, and this neans that odor cannot serve as a warning f hazardous concentrations.
.Summary.--The polyurethanes are a relaively new class of polymers. The finished iiilymers are inert chemically and present :io toxic hazards.
During manufacture severe industrial icalth hazards occur because of the use of -ocyanates. These compounds can be lethal i il in small amounts are very irritating to uncoils membranes, producing an asthmatic ivpe of effect. Great care must be taken n their use. Close medical supervision of workmen is desirable.
The B. F. Goodrich Co
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