Vinyl chloride concentrations in maxillofacial prosthetics laboratories Oscar N. Guerra, M.S.P.H., D.D.S.,* and Kenneth J. Kronoveter, M.S.** Ellis Fischel State Cancer Hospital, Columbia, Mo., and U.S. Department of Health, Education and Welfare, Cincinnati, Ohio

P o l y v i n y l c h l o r i d e (PVC) is a material widely used in the fabrication of maxillofacial prostheses. Vinyl chloride monomer, a derivative of ethylene, shown as the formula, H H

I

I

C=C

I

I

H

C1

can be polymerized in the presence of a free radical catalyst to form PVC, which has the following formula1: H

H

H

H

H

H

I

I

I

I

[

I

...-C-C-C-C-C-C-....

I

I

I

I

]

I

H

Cl

H

C1

H

Cl

PVC plastisols are received at prosthetics laboratories as fluid dispersions of high molecular weight polymers in plasticizing oils. Since PVC is soluble in the plasticizers at elevated temperatures, painting these dispersions on preheated (190 ~ C) metal molds with subsequent oven curing and cooling results in a solution (at about 150 ~ C) which solidifies upon Supported in part by U.S. Public Health Service Research Grant No. CA-08023 from the National Cancer Institute. Presented before the Academy of Maxillofacial Prosthetics, Lake Geneva, Wis. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the National Institute for Occupational Safety and Health (NIOSH). *Director, Department of Maxillofacial Rehabilitation, Ellis Fischel State Cancer Hospital. **Senior Sanitary Engineer, Division of Surveillance, Hazard Evaluation, and Field Studies, National Institute for Occupational Safety and Health Center for Disease Control, Department of Health, Education and Welfare.

200

FEBRUARY 1978

VOLUME 39

NUMBER 2

polymerization into a flexible material. ~ Preheating the metal molds facilitates the painting procedure by inducing a thicker consistency in the plastisol. During this procedure, vinyl chloride monomer, a potential residual component and a gas at standard temperature and pressure, m a y be released and possibly inhaled by the technician. Viola and associates 3 reported on the induction of tumors in rats exposed by inhalation to high concentrations of vinyl chloride. In J a n u a r y 1974; a manufacturer of PVC announced that three of its workers had died during the previous 3 year period of angiosarcoma, a rare tumor. 4 In February 1974 Maltoni, 5 from the Institute of Oncology in Bologna, Italy, "demonstrated angiosarqoma of the liver and other tumors in experimental animals at air concentrations of vinyl chloride which are known to be present at times as air contaminants in workroom atmospheres." Subsequent studies have demonstrated that vinyl chloride causes angiosarcoma of the liver and other malignancies a m o n g workers involved in the production and use of this material.6. 7 Also, a recent study suggests that vinyl chloride may be mutagenic in humans, s Vinyl chloride gas is an obvious health hazard, and because of the possibility that it might exist in maxillofacial prosthetic laboratories which utilize PVC resins, The National Institute for Occupational Safety and Health ( N I O S H ) undertook studies in three facilities at the request of the respective institutions. AIR SAMPLING STRATEGY A N D RESULTS The air sampling strategy was designed to determine whether vinyl chloride monomer was present as a residual in the liquid resin as purchased, evolved as a result of the process of pouring a n d / o r painting the

0022-3913/78/0239-0200500.30/0 9 1978 The C. V. Mosby Co.

VINYLCHLORIDEIN MAXILLOFACIALPROSTHETICSLABORATORIES

Table I. Vinyl c h l o r i d e e m i s s i o n s in t h r e e maxillofacial p r o s t h e t i c s l a b o r a t o r i e s Mean Samples collected sampling ~ 4 inches above No. of time heated molds samples (minutes}

Vinyl chloride concentrations (ppm)*

i

Samplers ran continuously over complete cycles of PVC application, curing, and stripping. Samplers ran only during the PVC application phase of consecutive work cy-

!

16

57

ND+ (3 samples)