1998:12 The Nordic Expert Group for Criteria Documentation of Health Risks from Chemicals 124. Thermal Degradation Products of Polyethylene, Polypropylene, Polystyrene, Polyvinylchloride and Polytetrafluoroethylene in the Processing of Plastics Antti Zitting Nordic Council of Ministers arbete och hälsa vetenskaplig skriftserie ISBN 91–7045–472–8 ISSN 0346–7821 http://www.niwl.se/ah/ah.htm National Institute for Working Life National Institute for Working Life The National Institute for Working Life is Sweden's center for research and development on labour market, working life and work environment. Diffusion of infor- mation, training and teaching, local development and international collaboration are other important issues for the Institute. The R&D competence will be found in the following areas: Labour market and labour legislation, work organization and production technology, psychosocial working conditions, occupational medicine, allergy, effects on the nervous system, ergonomics, work environment technology and musculoskeletal disorders, chemical hazards and toxicology. A total of about 470 people work at the Institute, around 370 with research and development. The Institute’s staff includes 32 professors and in total 122 persons with a postdoctoral degree. The National Institute for Working Life has a large international collaboration in R&D, including a number of projects within the EC Framework Programme for Research and Technology Development. ARBETE OCH HÄLSA Redaktör: Anders Kjellberg Redaktionskommitté: Anders Colmsjö och Ewa Wigaeus Hjelm © Arbetslivsinstitutet & författarna 1998 Arbetslivsinstitutet, 171 84 Solna, Sverige ISBN 91–7045–472–8 ISSN 0346-7821 Tryckt hos CM Gruppen Preface The Nordic Council is an intergovernmental collaborative body for the five countries, Denmark, Finland, Iceland, Norway and Sweden. One of the committees, the Nordic Senior Executive Committee for Occupational Environmental Matters, initiated a project in order to produce criteria documents to be used by the regulatory authorities in the Nordic countries as a scientific basis for the setting of national occupational exposure limits. The management of the project is given to an expert group. At present the Nordic Expert Group consists of the following member: Vidir Kristjansson Administration of Occupational, Safety and Health, Iceland Petter Kristensen National Institute of Occupational Health, Norway Per Lundberg (chairman) National Institute for Working Life, Sweden Vesa Riihimäki Institute of Occupational Health, Finland Leif Simonsen National Institute of Occupational Health, Denmark For each document an author is appointed by the Expert Group and the national member acts as a referent. The author searches for literature in different data bases such as Toxline, Medline, Cancerlit and Nioshtic. Information from other sources such as WHO, NIOSH and the Dutch Expert Committee is also used as are handbooks such as Patty's Industrial Hygiene and Toxicology. Evaluation is made of all relevant scientific original literature found. In exceptional cases information from documents difficult to access are used. The draft document is discussed within the Expert Group and is finally accepted as the Group's document. Editorial work is performed by the Group's Scientific Secretary, Johan Montelius, and technical editing by Ms Karin Sundström both at the National Institute for Working Life in Sweden. Only literature judged as reliable and relevant for the discussion is referred to in this document. Concentrations in air are given in mg/m3 and in biological media in mol/l. In case they are otherwise given in the original papers they are if possible recalculated and the original values are given within brackets. The documents aim at establishing a dose-response/dose-effect relationship and defining a critical effect based only on the scientific literature. The task is not to give a proposal for a numerical occupational exposure limit value. The evaluation of the literature and the drafting of this document on Thermal Degradation Products of Polyethylene, Polypropylene, Polystyrene, Polyvinylchloride and Polytetrafluoroethylene in the Processing of Plastics was made by Dr Antti Zitting at the Finnish Institute of Occupational Health. The final version was accepted by the Nordic Expert Group November 20, 1997, as its document. We acknowledge the Nordic Council for its financial support of this project. Johan Montelius Per Lundberg Scientific Secretary Chairman Abbreviations ABS Poly(acrylonitrile-butadiene-styrene) CP Polypropylene-polyethylene copolymer FEF50 Forced expiratory flow at 50% of vital capacity FEV1 Forced expiratory volyme in one second FVC Forced vital capacity GC Gas chromatography GC/MS Gas chromatography-mass spectrometry OEL Occupational exposure limit OR Odds ratio PE Polyethylene PP Polypropylene PTFE Polytetrafluoroethylene PVC Polyvinyl chloride RD50 Decrease of respiration rate by 50% SB Styrene-butadiene Contents Introduction 1 1. Polyethylene; PE 3 1.1 Composition of polyethylene 3 1.2 Processing of polyethylenes 3 1.3 Products of thermooxidation at processing 4 1.4 Occupational exposure data 5 1.5 Effects in animal and in vitro studies 6 1.6 Observations in man 8 1.7 Conclusions for polyethylene 9 1.7.1 Critical exposing agents 9 1.7.2 Critical effects 10 1.7.3 Approaches to workplace monitoring 10 1.7.4 Recommended basis for an occupational exposure limit 10 1.8 References 11 2. Polypropylene; PP 12 2.1 Composition of polypropylene 12 2.2 Processing of polypropylene 12 2.3 Products of thermooxidation at processing 12 2.4 Occupational exposure data 12 2.5 Effects in animal and in vitro studies 13 2.6 Observations in man 15 2.7 Conclusions for polypropylene 16 2.7.1 Critical exposing agents 16 2.7.2 Critical effects 16 2.7.3 Approaches to workplace monitoring 16 2.7.4 Recommended basis for an occupational exposure limits 16 2.8 References 17 3. Polystyrene; PS 18 3.1 Composition of polystyrene 18 3.2 Processing of polystyrene 18 3.3 Products of thermooxidation 18 3.4 Occupational exposure data 19 3.5 Effects in animal and in vitro studies 19 3.6 Observations in man 20 3.7 Conclusions for polystyrene 20 3.7.1 Critical exposing agents 20 3.7.2 Critical effects 20 3.7.3 Approaches to workplace monitoring 21 3.7.4 Recommended basis for an occupational exposure limits 21 3.8 References 21 4. Polyvinylchloride; PVC 22 4.1 Composition of PVC 22 4.2 Processing of PVC 22 4.3 Products of thermooxidation 23 4.4 Occupational exposure data 24 4.5 Effects in animal and in vitro studies 25 4.6 Observations in man 25 4.7 Conclusions for polyvinylchloride 29 4.7.1 Critical exposing agents 29 4.7.2 Critical effects 29 4.7.3 Approaches to workplace monitoring 29 4.7.4 Recommended basis for an occupational exposure limits 30 4.8 References 30 5. Polytetrafluoroethylene; PTFE 32 5.1 Composition of PTFE 32 5.2 Processing of PTFE 32 5.3 Products of thermal decomposition 33 5.4 Occupational exposure data 33 5.5 Effects in animal and in vitro studies 33 5.6 Observations in man 34 5.7 Conclusions for polytetrafluoroethylene 35 5.7.1 Critical exposing agents 35 5.7.2 Critical effects 35 5.7.3 Approaches to workplace monitoring 35 5.7.4 Recommended basis for an occupational exposure limits 36 5.8 References 36 Summary 38 Summary in Swedish 39 Databases Used 40 Introduction The thermal degradation of plastics is a complex process, which usually produces complex mixtures of individual products. This fact is reflected in the structure of this document, which differs from the standard documents of the Nordic Expert Group. The toxic properties of numerous emerging individual degradation products have not been examined. There exist a lot of publications on the analysis of degradation products, but only some examples that seemed to be representative and relevant for the occupational setting are presented. The document also ignores the studies in combustion toxicology and is focused on degradation conditions, which typically occur in the processing of plastics. Polytetrafluoroethylene is somewhat of an exception – its typical occupational hazards originate from degradation at very high temperatures, for instance from smoking contaminated cigarettes. Plastics are typically divided into two major groups: thermosets and thermo- plastics. The former are polymerised or mechanically processed to the final form, while the latter are processed in molten state. This document deals with poly- ethylenes (PE), polypropylenes (PP), polystyrene (homopolymer) (PS) and polyvinylchloride (PVC), which all are thermoplastics. These polymers are the most used plastic materials. Polytetrafluoroethylene (PTFE) is included because its thermal degradation products are widely known to cause the so-called polymer fume fever. The toxic effects from synthetic polymers may arise from: • Toxicity associated with the use of the final plastic products • Toxicity that arises during the manufacture of the plastic materials • Toxicity due to the thermal decomposition products of plastics • Toxicity from compounds leaching from materials The toxic properties of the monomers (e.g. vinyl chloride, butadiene) used to produce synthetic polymers have been the subject of extensive research. The investigations on the toxicity of thermal decomposition products have focused mainly on "combustion toxicology"; actual fires have been simulated to reveal the acute toxic hazards of smoke. The polymeric organic materials are in general combustible and involve risk of fire when heated in air. In actual