Document 3ebX6x2y2Go8Ln0gO4Y3ZmQJO

OCCUPATIONAL HAZARDS IN PRODUCTION AND PROCESSING OF STYRENE POLYMERS - EPIDEMIOLOGIC FINDINGS William J. Nicholson and Diane Tarr Environmental Sciences Laboratory, Mount Sinai School of Medicine of CUNY, New York 10029 INTRODUCTION Of the major plastic monomers, styrene is exceeded only by ethylene, propylene and vinyl chlorid^ in terms of produc tion. In 1977, approximately 3 X lo| metric tons were produced in the United States and 7 x 10 metric tons world wide (IARC, 1979). Approximately 60% of the monomer pro duced was used in homopolymers, largely for the packaging industry. Other important uses of styrene are in the pro duction of copolymers with acrylonitrile (SAN) and acryloni trile and butadiene (ABS). Styrene also finds widespread use as a copolymer with butadiene in the production of the synthetic elastomer, styrene-butadiene rubber (SBR), which forms the basis of approximately 80% of U.S. rubber products. Finally, it is extensively used as a solvent and cross-link ing agent for polyester resins in the fiber reinforced plastic (FRF) industry. Estimates of the number of workers employed in the various industries using styrene-based polymers are given in Table 1 along with typical exposure levels (Tossavainen, 1978). In addition to occupational exposure, low-level environmental contamination can occur from combustion of styrene-based products, as the thermal decomposition of polystyrene leads to evolution of the monomer, in contrast to other polymer materials. MORTALITY STUDIES OF STYRENE-EXPOSED WORKERS Studies on the mortality of populations exposed to styrene are fraught with difficulty because of confound- CMA 007786 Tibia 2 Population and follev-up characeariatlea of thro* atudlaa of (tyrant axpoaad worfcara Scud? Analyiia cohort Countrr alia Humbar of Parctnt Fartanc daatha of eracad analvzad total Oct at al. 1980 Slebolaoo at al. 1978 Francxal-Bayaa at al. 1978 0SA USA GZX 2904 360 1960 97.4 100.0 93.0Gar 29.0For 303 83 73 10.4 14.8 3.7 Mlnlaaa Minima axpoaura latancy Taata (vaart) (Tiar*) follov-uo Oct at al. 1980 Nleholxon at al. 1978 Fraatxal-Iayaa at al. 1970 1 5 1 so. 1 1940-1975 10 1960-1973 1 ao. 1956-1976 txpcauraa <10 ppa C3)" < 20 ppa (5) 1 ppsb * ( ) * Eltlsatad avaraga axpoaura * Currant oaaaurtsaoc aftar inatallatlon of controla The study of Nicholson et al (1978) successfully traced all of 563 men employed la styreae production, polymerization and polymer processing who had 5 years of employment on Hay 1, 1960 and were 10 years from onset of work in a large U.S. production facility. The basic mortality data are shown in Table 3 and demonstrate no excess mortality from any cause of death. Analyses according to years from onset of exposure and calendar years of observation did not reveal any pattern of excess mortality. However, because of the limited number of deaths, the data can be used only to establish upper limits of risk. For example, the data are only suffici ent to indicate that the SMR for lymphoma or leukemia is less than 280 at the 0.05 level of significance and that of lung cancer, less than 220. Vhile no excess mortality was identified in the cohort observed, the above publica tion mentioned the existence of 7 deaths from leukemia and 5 of malignancy of the lymphatic system among 444 deaths known to have occurred in the plant workforce. While the ages of death were not available for exact proportionate mortality calculations, the number of lymphomas is in line with expectations, while leukemia appears to be in excess by as much as a factor of two. However, the possibility of high exposures to benzene in the facility during earlier years weakens the likelihood 007797 Tsble 4 Observed aad expected deaths by cause or total productles sod non-professional rtitarch employees (2310 man), 1940-1974 Qbssrved Causes deaths 411 causes 282 Malignant neoplasms 33 Hespirstory system 14 Digestive system 16 Lymphatic and hematopoietic 6 ayacam except leukemia Leukemia 6 Other sites 13 Cardiovascular disease 143 Konmalignant respiratory dil. 12 all other causes 72 Expsetad dsschs US vhlts males 337.8 64.2 20.8 18.0 4.3 2.9 18.0 172.4 14.3 106.9 SKR 79 87 67 89 133 207 72 83 84 67 Fran Oct t 1. 1980 Expeeesd deaths i Compasy eomesrisom 267.6 63.0 23.9 21.2 2.6 98 83 39 67 230 1.6 13.7 141.3 10.0 71.1 373 83 101 120 101 concentrations of styrene (5-9 ppm). Because of a lack of a definitive exposure-response-relationship and the presence of possible confounding exposures, the authors refrained from drawing any conclusions on an etiological relationship. In 1976, nine cases of various types of leukemia were identified in two SBR plants and reported to the U.S. National Institute for Occupational Safety and Health (Meinhardt et al, 1978). All occurred after 1971 in a population of 5,600 workers. No data were presented on the expected numbers of deaths from leukemia in the group. Concern generated by the findings in the two plants led to reports on the leukemias present in two large ongoing studies of rubber workers. McMichael et al (1976) reported a relative risk of 6.2 for lymphatic and hematopoietic malignancies among employees producing elastomers, including SBR. However, this was based upon only 6 cases, 3 leukemias and 3 lymphomas. In a subsequent case control study of the same plant, a relative risk of 2.4 was found for the same exposure group (Spirtas et al, 1976). The difference in the two values reflect the uncertainties associated with small numbers of cases. A similar investigation by Monson et al (1978) showed an excess of leukemia to be present in calendering, extrusion, tire building and rubberized fabrics. However, the excess was associated with exposure to solvents and not to styrene. various respiratory symptoms, and gastrointestinal dis turbances, such as nausea, vomiting and loss of appetite, are commonly reported by styrene-exposed workers. Other abnormalities reported include headaches, tiredness and sleep disturbance. After a period of exposure, adaptation stay occur and there can be a decrease in the various symp toms. Nevertheless, significant alterations still exist among currently employed workers. Several systematic studies of the various clinical ef fects from styrene exposure have been conducted in recent years. Many of these focused on possible neurological alterations and clearly demonstrated adverse findings at moderate styrene exposures (less than most national stand ards). The most extensive of these is that by investigators from the Institute of Occupational Health of Finland (Seppalainen and Harkonen, 1976; Lindstrom et al, 1976; Harkonen, 1977; Harkonen et al, 1978). They examined 98 workers employed at 24 plants manufacturing FRP products. Air concentrations were sampled and ranged from 5 to 300 ppm. The means of five post-workday urine mandalic acid (MA) concentrations ranged from 7 to 4,700 mg/1 with a lin ear relationship existing between the log of the MA concen tration and the log of the styrene concentration. The mean value of MA in the population was 808 mg/1 and corresponded to an exposure of about 40 ppm of styrene. Abnormal EEG's were found in 30% of those with MA in excess of 700 mg/1, compared to about 10% for those with lower MA values and normal controls (Seppalainen and Harkonen, 1976). Lindstrom et al (1976) noted increased visuomotor inaccuracy (symmetry drawing and Bourdon -Wiersma tests) and lowered psychomotor performance (Mira test) for various MA concentrations rang ing from 800-2,000 mg/1 (See also: Harkonen et al, 1978). Fatigue, irritation, difficulty in concentration, nausea, dizziness, and lightheadedness were more frequently reported by the styrene-exposed workers than by unexposed controls (Harkonen, 1977). A deteriorating EEG among styrene workers has also been described by Klimkova-Deutachova et al (1973). Alterations of nerve conduction have been documented by Rosen et al (1978) who observed an increased duration and decreased amplitude of sensory action potentials. Lilia et al (1978) suggested the possibility of a decrease in peroneal nerve conduction velocity. The decrease, however, was only asso ciated with length of employment and not intensity of expo- CMA 007789 to other chemicals, such as benzene. The studies are se verely limited because of the relatively low styrene expo sure of the groups studied. They provide no guidance on carcinogenic risk in populations much more heavily exposed as in the FRP industry. The significant clinical findings among styrene-exposed workers are largely limited to abnor malities of the central nervous system, where a variety of objective and subjective symptoms have been reported in the FRF industry. Concern for long-term degnerative neurologi cal disease exists for continued long-term exposure in this industry. The possibility of pulmonary effects from styrene exposure has also been noted. REFERENCES Axelson 0, Gustavson J (1978). Some hygienic and clini cal observations on styrene exposure. Scand J Work Environ Health 4:215-219 (suppl 2). Checkoway H, Williams TM (1982). A hematology survey of workers at a styrene-butadiene synthetic rubber manu facturing plant. Am Ind Hyg Assoc 43:164-169. Cherry N, Waldron HA, Wells GG, Wilkinson RT, Wilson HE, Jones S (1980). An investigation of the acute behavioral effects of styrene on factory workers. Brit J Ind Med 37:234-240. Delzell E, Monson RR (1982). Mortality among rubber workers: VI. Men with potential exposure to acrylonitrile. J Occ Med 24:767-769. Frentzel-Beyme R, Thiess AM, Wieland R (1978). Survey of mortality among employees engaged in the manufacture of styrene and polystyrene at the BASF Ludwigshafen works. Scand J Work Environ Health 4:231-239 (suppl 2). Hane M, Axelson 0, Blume J, Hogstedt C, Sundell L, Tdreborg B (1977). Psychological function changes among house painters. Scand J Work Environ Health 3:91-99. Harkonen H (1977). Relationship of symptoms to occupa tional styrene exposure and to the findings of electroencephalographic and psychological examinations. Int Arch _Occ Environ Health 40:231-239. Harkonen H, Lindstrom K, Seppalainen AM, Asp S, Hernberg S (1978). Exposure-response relationship between styrene exposure and central nervous functions. Scand J Work Environ Health 4:53-59. Hotz P, Guillemin MP, Lob M (1980). Study of some hepa tic effects (induction and toxicity) caused by occupa tional exposure to styrene in the polyester industry. Scand J Work Environ Health 6:206-215. 00779 m