Keywords

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FormalPara Core Messages

  • Allergic contact dermatitis from polyester resins is rare.

  • Allergic reactions are more likely to occur from other components of the resin system, but are still uncommon. Irritant contact dermatitis may occur from peroxides and styrene.

  • Contact urticaria may occur from anhydrides.

1 Introduction

Polyester resins are polycondensates prepared in two different forms: saturated and unsaturated. Saturated polyesters, alkyd resins, are produced from polybasic acids and polyalcohols. Polybasic acids, mainly phthalic acid or maleic acid, are used in their anhydride forms. The polyalcohols most often used are glycerol, pentaerythriol, or trimethylolpropane.

The saturated polyesters, synthesized in this way, are also named unmodified alkyd resins, macromolecules commonly used as plasticizers for other plastic materials. Alkyd resins can be modified by oil-containing fatty acids to be used in water-based paints and surface coatings (Kanerva et al. 1996a; Björkner 2006).

Unsaturated polyester (UP) resins are produced through esterification of dicarboxylic acids or their anhydrides, such as maleic anhydride, phthalic anhydride, or fumaric acid, and diols, such as diethylene glycol or 1,2-propylene glycol (Fig. 54.1 ). Styrene is the most commonly used monomer for the cross-linking of UP resins. Vinyl toluene and methyl methacrylate are examples of other cross-linking agents.

Fig. 54.1
figure 00541figure 00541

Unsaturated polyester resin is made by condensing 1,2-propanediol, maleic anhdyride, and phthalic anhydrides. Styrene is used as a cross-linking monomer

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An initiator or catalyst is required to start the cross-linking process, and is usually a peroxide such as benzoyl peroxide or methyl ethyl ketone peroxide. Accelerators, such as cobalt naphthenate or octoate, or tertiary amines such as dimethyl aniline, diethyl aniline, and dimethyl-p-toluidine, are also necessary for the curing of plastics at room temperature. The ultraviolet light (UV)-curable polyester system is used in the furniture industry as top coating and for orthopedic casts. The UV-curable polyester system contains vinyl toluene as the cross-linking agent and a benzoin-ether molecule as photoinitiator (Kanerva et al. 1996a; Björkner 2006). UP resins have been used extensively in the reinforced plastics industry in the manufacture of products for transportation, construction, and marine applications. They are also used for coatings, finishes, lacquers, cements, and glues (Kanerva et al. 1996a; Björkner 2006).

2 Skin Problems from Polyester Resins

Saturated polyester resins are generally not considered to be sensitizing. Allergic contact dermatitis (ACD) has, however, been caused by an epoxy compound, triglycidyl isocyanurate (TGIC) used as cross-linker in polyester paints (Mathias 1988). Phthalic anhydrides have been reported to cause ICD (Malten and Zielhuis 1964), immediate IgE-mediated hypersensitivity with asthma, allergic rhinitis, urticaria (Jolanki et al. 1987, 1997; Tarvainen et al. 1995a) and, rarely, ACD (Kanerva et al. 1997). The contact urticaria reaction from methyl hexahydrophthalic anhydride was reported to be enhanced by wiping off the substance with an alcohol disinfectant, which was presumed to enhance penetration of the allergen (Kanerva et al. 1999a).

Most reports of skin problems involve workers in plastics manufacture. In one workplace study (Minamoto et al. 2002a), ACD was most common but irritant contact dermatitis (ICD) was also reported, from both chemicals and mechanical irritants such as glass fiber and dust. As manufacturing processes become increasingly automated, exposure to alkyd resins is generally a result of accidents or maintenance work.

3 Irritant Contact Dermatitis

ICD from UP resins occurs from cross-linking styrene (Rietschel and Fowler 2008) or, in earlier times, diallylphthalate (Fregert 1971). Styrene is classified as a mild irritant, although it has been reported to cause blisters (Bourne and Milner 1963) and even chemical burns (Bruze et al. 2000).

Prolonged exposure to styrene has caused a case of skin atrophy, neurogenic muscular atrophy, and anxiety reaction (Araki et al. 1971). Levels of styrene vapor exceeding 300 ppm (1,260 mg/m³) have been reported to induce erythema of the skin (Stewart et al. 1968). Even at levels of 50 ppm (215 mg/m³), styrene vapor may irritate conjunctival and nasal mucous membranes (Gotell et al. 1972). The mucous membrane irritation may be caused by the vinyl group in styrene (Alarie 1973). However, workers may develop a tolerance to the irritation after prolonged exposure (Gotell et al. 1972).

Organic peroxides, used as 3–10% solutions to catalyze the hardening reactions of UP, are weak sensitizers but strong irritants (Haustein et al. 1985). In the plastic composite industry, organic peroxides have caused severe ICD (Bourne and Milner 1963). Reactive organic peroxide molecules in unhardened resin dust may cause stinging on uncovered areas of the skin during spray lamination (Schumes 1990).

Hydrogen peroxide is an irritant but very rarely an allergen (Aguirre et al. 1994; Kanerva et al. 1998). Phthalic anhydride used in the manufacture of alkyd resins can cause ICD, and even caustic blisters especially on moist skin, where the anhydride is transformed into the corresponding acid (Malten and Zielhuis 1964).

In addition to chemicals included in the resin system, mold-releasing chemicals have also caused ICD (Bourne and Milner 1963). Acetone is used to clean equipment in UP resin industries. With repeated contact, acetone may defat the skin and disrupt the epidermal barrier (Fartasch 1997). It has been reported to be a contributing factor for ICD in this industry (Bourne and Milner 1963; Tarvainen et al. 1993b, 1994). Chlorinated hydrocarbon solvents such as methylene chloride and trichloroethane are often used for cleaning purposes and are also skin irritants (Midtgard and Knudsen 1994).

4 Allergic Contact Dermatitis

ACD was first reported from UP resins in 1955 (Lieber 1955). Five patients with ACD and positive patch tests to UP resins were reported from a group of 30 workers in an airplane factory (Malten 1956). Most cases of ACD have been caused by exposure to UP resin in lamination work (Malten 1956; Bourne and Milner 1963; Lidén et al. 1984), in painting (Kadlec et al. 1974), or in the use of UV light-cured inks (Björkner 1982).

UP dust from reinforced plastic products (Bourne and Milner 1963; Tarvainen et al. 1993b, 1995b) or UP automobile-repair putty (Tarvainen et al. 1993a; Kanerva et al. 1999b; Dooms-Goossens and De Jonge 1985) have also caused ACD.Guin (2001) reported a machine repairman who had developed ACD from adipic acid while working in the synthesis of polyester resins.

Adipic polyester, produced from adipic acid and propylene glycol, is a thermoplastic polyester used as a plasticizer in vinyl gloves, and has also caused ACD (Sowa et al. 2005). Nonoccupational ACD from UP resin is infrequent, but has been reported from “hypoallergenic” nail varnish (Shaw 1989), UP glue (Sjoborg et al. 1982), and limb prostheses (MacFarlane et al. 1986; Freeman 1986; Vincenzi et al. 1991; Haddad et al. 1996).

The allergens are often the auxiliary chemicals used, such as cobalt naphthenate (Key et al. 1961; Bourne and Milner 1963; Malten and Zielhuis 1964; Kadlec et al. 1974), cobalt octoate (cobalt-2-ethylhexanoate) (Kanerva et al. 1996b) and more recently in a spa bath laminator (Anavekar and Nixon 2006); dibutyl phthalate, dimethyl phthalate, dioctyl phthalate (Malten and Zielhuis 1964), tricresyl phosphate (Key et al. 1961), or a cross-linking monomer, such as styrene (Key et al. 1961; Bourne and Milner 1963; Sjoborg et al. 1982; Conde-Salazar et al. 1989), or a catalyst such as benzoyl peroxide (Bourne and Milner 1963; Malten and Zielhuis 1964; Vincenzi et al. 1991), cyclohexanone hydroperoxide (Malten 1964), or methyl ethyl ketone hydroperoxide (Bourne and Milner 1963; Malten and Zielhuis 1964). Lymphomatoid-like contact dermatitis in a marble worker was reported from cobalt naphthenate (Schena et al. 1995).

The allergens have been summarized in Table 54.1 . Eight patients were reported to be allergic to UP resins from car-repair painting and mold manufacturing (Tarvainen et al. 1993a; Kanerva et al. 1999b).

Table 54.1 Allergens in unsaturated polyester (UP) resins
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A patch testing strategy was developed by Kanerva’s group in order to clarify the allergic components of UP resins and has been summarized in Table 54.2 . All patients reacted on patch testing to the UP resin component of a cement they had used in their work.

Table 54.2 Allergic and nonallergic (negative) patch-test reactions to the components of polyester resin (Kanerva et al. 1999b, Pfaffli et al. 2002)
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Five patients also reacted to hardened UP resin cements, indicating that the hardened UP resin contains reactive monomers. Grinding the resin can give airborne allergic reactions many years after it has been hardened (Kanerva et al. 1999b). The causative allergen was found to be diethylene glycol maleate (DEGM) (Tarvainen et al. 1993a; Kanerva et al. 1999b; Pfaffli et al. 2002).

In another workplace study, ACD was caused not only by UP resin, but by cobalt, benzoyl peroxide, methyl ethyl ketone peroxide, para-tertiary butyl catechol, styrene, and formaldehyde (Minamoto et al. 2002b).

UP resins have been patch tested at concentrations of 0.5–10% (Tarvainen et al. 1993a; Kanerva et al. 1999b) but also at 20% in acetone (Foussereau et al. 1982). In one patient, a concentration of 1% caused a weak allergic reaction (Tarvainen et al. 1993a), and it was suggested that the test concentration may need to be as high as 5% (Kanerva et al. 1999b). However, it is not clear at what concentration active sensitization may occur.