Document j9kOD305Drm4a9agpnaJrgaO

R&S 004618 Human Toxicol. (1988). 7. 517-527 Human Male Exposure to Vinyl Chloride and Possible Teratogenic and Mutagenic Risks: A Review L. Uzych 103 Canterbury Drive, Wallingford, PA 19086, USA Introduction Vinyl chloride, also known as vinyl chloride monomer (VCM), chlorocthylene, and chlorocthcnc, was first synthesized in 1833.1 Some years later in the mid 1930s, the polymerization process was discovered in Germany. The vinyl chloride related industries have developed rapidly in Europe, which accounts for about 50% of world production, and in the United States, which accounts for an estimated 25% of world production. Annual world production of vinyl chloride exceeds 10 billion kg.1 Total world-wide employment in the VCM and polyvinyl chloride (PVC) producing industries is estimated to be well over 70 000 workers. The number of workers employed in industries using PVC as a basic element is estimated to total in the millions. Data pertaining to the possib'j toxicity of vinyl chloride were published in the literature as early as 1930. At that time, Patty et reported gross patho logical changes in guinea pig; that died during exposure to vinyl chloride, including intense congestion and oedema of the lungs and a hyperemia of the kidneys and liver. Vinyl chloride may further be associated with reproductive related risks. Workplace policies, in fact, have been instituted prohibiting females from working in vinyl chloride polymerization areas, b.r-cd on the belief that vinyl chloride may pose a health risk to females and to their unborn children. Lawsuits have subsequently been filed charging that such policies arc discriminatory because vinyl chloride exposure may also adversely affect male reproductive functioning/'5 A growing body of data indeed suggest that the exposure of human males to vinyl chloride in the workplace, and elsewhere, may be associated with various chromosomal aberrations in lymphocytes and sister chromatid exchanges. Paternal exposure to vinyl chloride may further be associated with various adverse effects on pregnancy and possibly spermatic alterations. This review is intended to examine critically selected, available data concerning paternal exposure to vinyl chloride and possible reproductive related risks. The references included in the review date to 1983. It should be understood that these references were selected from among the best available published data known to the author. Chromosomal aberrations Data in the published literature arc conflicting regarding possible chromosomal aberrations associ ated with the exposure of human males to vinyl chloride. Some investigators have reported negative findings for chromosomal aberrations in vinyl chloride exposed males. Fleig & Thiess' in 1978 reported data from chromosome analysis undertaken on lymphocyte, cultures from male workers showing no symptoms of vinyl chloride illness. Compared with controls, there was no significant difference in the rate of chromo some aberrations; the frequency of aberrant metaphases totalled 3.1%, excluding gaps, and 7.5%, including gaps for exposed workers, corresponding values in the control group were 2.1 and 5.5%, respectively. Several factors confound the analysis of the Fleig data. The sample population of workers was relatively small (n = 10). A relatively small sample size raises questions about statistical `power', or an investigator reporting no association, when in fact one exists. In general, the smaller the sample size, the greater the chance that an association between an exposure and an effect will not be detected.7 Precise data on level of vinyl chloride exposure were not presented for all the cases. Data concerning possible alcohol con sumption were not presented. Although data were reportedly collected concerning age, occupational exposures, medical X-rays, recent viral diseases, drug consumption, and smoking habits, specific values were not given in the paper. Duration of exposure of cases ranged from 4 to 26 years. The age range of cases was 34 to 57. The controls were described as `healthy' persons who were not exposed to vinyl chloride or to any other `known' (not specified) chromosome damaging agent but worked in the same factory. This may raise the possibility that the controls were exposed to various clastogcnic agents in the factory. Fleig & Thiess further investigated 20 workers The Macmillan Press Ltd 1988 VOL ISS NO 1988 UMI * ',, , . .... - - --\-o - --:i-...*'* ' /' ; 518 L. UZYCH <o showing symptoms of vinyl chloride illness. Compared with ihc same control group, there was a significant difference in the rate of chromosome aberrations. The rate of aberrant nictaphascs in cases was 5.2%, excluding gaps, and 11.2%. including gaps; in the control group, the corresponding values were 2.1 and 5.5%. The further data are confounded by the fact that the 20 cases had an unknown rate of exposure. In addition, duration of exposure in the cases ranged from 4 to 30 years. Cases ranged in age from 32 to 64. In 1980, Rossncr et al* reported data following the investigation of 31 males occupationally exposed to vinyl chloride monomer. A group of males from the s >mc plant, but reportedly not exposed to vinyl chloride monomer, were chosen as matching controls. Several categories of chromosomal aberrations were analysed: chromatid and chromosome breaks, and chromatid and chromosome exchanges. Gaps were not included among aberrations. Two blood samplings were conducted, about a year ai-mi. In all subjects, only breaks were detected. No significant differences were found between the cases and controls, or between the first and second sample taking. Exact levels of vinyl chloride monomer exposure are not certain. Rosner ct al. reported `on average* the levels of vinyl chloride monomer concentration in the atmosphere of the workplace ranged below the Czechoslovak MAC level of 10 mg/m\ and that the peak concentration did not exceed 30 r,ig/m\ At the time of blood sampling, the workers being followed had been exposed to vinyl chloride monomer for 2 and 3 years. Cases ranged in age from 25 to 55. An analysis for drug and alcohol consumption habits was reportedly conducted for all subjects Data for these parameters were not presented. There is no indication that subjects were questioned concerning smoking habits, or X*ray or other radiation exposure. Some published studies reporting negative findings for chromosomal aberrations in vinyl chloride exposed workers do not state the sex of ca^es and controls. Kilian & Picciano9 reported preliminary data on 121 workers occupationally exposed to vinyl chloride and vinylidenc chloride. Pre-employment examination records from 75 persons were used as control data. Compared with cytogenic data from the pre-employ ment examinations, the vinyl chloride workers showed less chromatid breakage, a greater frequency of dicentric chromosimes and a lower percentage of abnormal cell'.. Data on the sex distribution of cases and controls are not presented by the investigators. The investi gators stated that only about 50% of the vinyl chloride workers at the pertinent facility were included in the study. Cases and controls were not age-matched insofar as the pre-employment group contained only 2 persons over 50 years of age whereas the vinyl chloride group contained 30 persons more than 50-ycars-old. Picciano ct al.w reported cytogcnic findings from 209 workers employed at a vinyl chloride plant. Control data were obtained from a group of 295 `preemployment examinees* who had chromosome evaluation done as part of the routine preemployment examination. Data from the two groups were scored and compared on the basis of chromatid breaks, chromosome breaks, rings, dicentrics, exchange figures and the proportion of abnormal cells. The investigators stated that results, expressed in terms of the mean percentage for these categories of aberrations, showed no major differences between cases and controls for any of the classifications. Although Picciano ct al. indicate that cases and controls were matched as much as possible for various factors, including sex. t.:e investigators do not provide exact data on the sex distribution of cases and controls. Cases and controls were not age-matched. The average age of cases was 39.5 years (range of 18 to 67); the average age of contr, is was 25.1 vears (range of !8 to 50 years). Duration of occupational exposure of case;., at the time of investigation, ranged from 1 to 332 months (average of 48.3 months). Several studies have reported positive findings for chromosomal aberrations in human males exposed to vinyl chloride. In 1975 Ducntman ct al." presented data findings for 11 males exposed to vinyl chloride in a polyvinyl chloride polymerization piant. In com parison with 10 `healthy* male contr.'*". without known vinyl chloride exposure, cases showed a non significant increase in cells with simple aberrations, such as breaks and gaps, when using a /-test for the comparison of means, and marginally significant increases of such aberrations using a F ratio for the comparison of variance. The differences in cells with `stable* chromosome aberrations, such as monosomies trisomics, deletions and exchanges, were also non significant. However, cells with `unstable* chromo some changes, such as fragments, dicentrics and rings, were observed significantly more frequently in the cultures from cases. The total of simple breaks, including those from multiaberrant cells, was increased but not significantly in the exposed workers. Complex breaking events were significantly more frequent in cases, and total breaking events were also significantly increased in cases. The relatively small size of the sample population (;i = 11) affects the statistical significance of the Ducatman etal. data. Exact data on levels of exposure of the workers arc not provided. The investigators state that there is no record of ambient gas levels at the pertinent facility, but it was assumed that the levels must have exceeded 500 ppm at times, based on reports of dizziness, odour detection and headaches. Duration of vinyl chloride exposure of cases ranged . more than indings from loride plant, oof 295 `prechromosome outine pree two groups of chromatid . dicentrics, of abnormal ts, expressed categories of ces between cations, at cases and le for various o not provide and controls. . The average 8 to 67); the ango of 18 to expo of ,ed fr to ; findings for is exposed to ." presented yl chloride in ant. In comoM. without lowed a nonaberrations, /-test for the y significant ratio for the ; in cells with > monosomies :re also nonble' chromocentrics and frequently in mple breaks, was increased eis. Complex e frequent in o significantly le population cance of the Is of exposure investigators t gas at [hat tlfl)els es, basro on d headaches, cases ranged HUMAN MALE EXPOSURE TO VINYL CHLORIDE 519 from 4 to 28 years (average of 15 years). Cases ranged In 1976, Szcntesi et al14 reported data on chromo in age from 25 to 61. Cases and controls were not age somal aberrations in 45 PVC workers (41 males). matched. The average age of cases was 40; the cor Forty-four `industrial controls' (19 males) engaged in I responding figure for controls was 27. Because other chemical plants and reportedly not exposed to chromosomal aberrations may be associated with PVC but `indirectly' exposed to `other' (not specified) various factors, it is vitally important to question chemicals as well as 49 `normal' controls (34 males) subjects about prior and current exposure to known with no reported occupational exposure to chemicals and suspected mutagens, X-ray and other radiation were further examined. The investigators concluded exposure, drug use. smoking history, alcohol con that the rate of chromosomal aberrations did not sumption, and infectious diseases, particularly those differ significantly between PVC workers and controls. of viral origin. Ducatman et al. did not provide data However, the frequency of chromatid-type aberrations for cases and controls regarding these variables. was higher in PVC workers compared to the two Funes-Cravioto et ct.12 in 1975 reported an increased controls (P < 0.001). In addition, unstable chromo- frequency of chromosomal aberrations in seven males somc-typc aberrations were significantly higher in occupationally exposed to vinyl chloride. Three `non- PVC workers (P < 0.001). exposed' control subjects, from the same factory as Several factors confound the analysis of the Szcntesi the cases, were also studied. The frequency of ef al. data. Duration of exposure of cases ranged from abnormal cells in cases (9.52%) was significantly 0.5 to 12 years. The investigators do not provide data greater than in the controls (P < 0.001). on the level of exposure of cases. A problem of The small size of cases (n = 7) affects the epidemio relevant controls exists since the 44 `industrial controls' logic significance of this study. Funes-Cravioto ct al. were `indirectly' exposed to `other' (unspecified) do not provide precise data on levels of exposure to chemicals. Additionally, cases were not age matched vinyl chloride. It is stated that the level of exposure to with the industrial controls. The mean age of the vinyl chloride had `continuously decreased' during industrial controls was 43.9 whereas the value for past years, and that in the weeks preceding blood cases was 27.3. Data arc not presented for such sample collection for chromos 'mal analysis, the air potential confoundcrs as smoking history, alcohol concentration in the polymerization department was use, exposure to X-rays and other radiation, possible estimated to be 20-30 ppm. Duration of vinyl chloride drug use, and viral or other infectious diseases. exposure ranged from 9 to 29 years. A problem of Purchase etal.,s in 1976, reported data on chromo relevant controls is raised. Since *re three `non- somal abnormalities in 80 workers, including exposed exposed' controls were employed in i.ic same factory workers, non-exposed workers from the same indus as the cases, there is the possibility that they may trial site, and non-exposed workers from a different have been exposed to vinyl chloride. Also, data for environment. The population of exposed workers the control subjects showed that 11/566 cells contained was further divided into groups, base on the type of chromosomal aberrations. Funes-Cravioto et al. work carried out. Autoclave operators and main hypothesized that this finding might be associated tenance workers had higher percentages of B and C with previous diagnostic X-ray exposure. cells (classified according to Buckton & P;kc, 1964), Also in 1975, Purchase et al.13 reported findings for compared to those who worked in PVC production chromosomal aberrations in vinyl chloride-exposed but not with autoclaves and the non-exposed control workers. The investigators studied 80 workers. Fifty- subjects from another environment. Tlie difference six had been exposed to vinyl chloride monomer; the between the combined results from the exposed groups remaining workers worked in plants and laboratories and the control group was reported to be statistically where exposure to vinyl chloride reportedly did not significant, occur. A comparison of chromosomal aberrations in Purchase ct al. do not specify the sex of the cases the vinyl chloride exposed workers compared to and controls. The only information given concerning controls not exposed to vinyl chloride showed a signifi level of exposure to vinyl chloride was that the auto cantly increased (P < 0.05) percentage of B, Cu, and clave workers had the `highest' exposure and workers Cs cells (using the classification of Buckton & Pike, employed in PVC production but not with autoclaves Journal of Radiation Biology 1964; 8: 439-52) in the and maintenance workers in the same area had the exposed workers. `lowest' exposure. The duration of exposure of cases Purchase et al. did not state the sex of cases and is not given. Information about the age range of cases controls. Data concerning levels of exposure and and controls is not presented. In addition, data were duration of exposure were also not provided. The not given regarding smoking history, alcohol use and mean age, and age range, of cases and controls were viral infections of cases and controls. not given. Information about the smoking habits and Some studies have presented cytogenetic data alcohol consumption of cases and controls was also findings confounded by the fact that cases may have not included in the published study. been exposed to vinyl chloride as well as other R&S 004620 VOL *0 7 * ISS ; , ! NO * 1918 ' v-. *| * ; \/ UMI ro 520 L.UZYCH potential mutagens. Heath etal.lf> in 1977, reported from cultured peripheral lymphocytes from 81 men. chromosomal damage in men occupationally exposed Fifty-seven of the workers (cases) were employed at to vinyl chloride monomer and other chemicals, plants manufacturing vinyl chloride or PVC, 19 of the Cytogenetic analysis, primarily designed to measure workers were on-site controls, and the remaining 5 frequencies of chromosomal breakages, were per- were off-site controls. The 57 cases were further formed on peripheral blood lymphocytes of 35 mates, divided into six groups. The on- and off-site controls in three different job categories: 14 in PVC poly- were combined into a single control group, because mcrization, 4 in PVC processing, and 17 in rubber no significant differences were observed between iyre manufacture (industry contrc's). When initial them. In a study published in 1978, Purchase et at. analysis showed no significant differ mccs among the reported that the subgroup of cases consisting of three industry groups, a further control group was autoclave workers had the greatest number of signifi- selected, consisting of 4 males employed at the Center cantly increased values tor chromosomal abnor- for Disease Control and reportedly `not exposed malities. The values for total B cells, total Cu cells directly'to any laboratory chemicals (CDC controls). and total C cells (classified according to Buckton & Levels of breakage in all three industry gro'--s Pike) were significantly higher than control values (P were increased significantly over levels in the CDC < 0.01). Purchase etal. further reported a significant controls. However, no significant differences were correlation between smoking habits and total C cells, observed between the three industry groups them- Data pertaining to exposure levels in the Purchase et selves. Chromatid gaps comprised the majority (86%) al. study were imprecise. Any experience in a specified of observed aberrations. one-year time period, 7/73-7,74. of txposurc to vinyl It is difficult to interpret the data of Heath et al. chloride for short-term excursion winch could be Levels of exposure of cases and controls to vinyl detected by smell was recorded. The g.-vo of cases chloride, and other potential mutagens, arc not clear, who operated and cleaned the autoclaves w.nc con- Thc 14 PVC polymerization workers had `presumed sidcrcd, by virtue cf their jobs, as likely to be cxpos"d high'exposure to VCM, the 4 PVC processing workers to the highest average levels of vinyl chloride. The had `presumed low' VCM exposure, while the 17 investigators gave figures for estimated average workers in rubber tyre manufacture had `presumed operator exposure to vinyl chloride on PVC plants, negligible' exposure to VCM. In the opinion of the ranging from approximately 1000 ppm (1945-1955) investigators, the fact that overall breakage levels to approximately 5 ppm (in 1975). Average duration were similar in workers exposed heavily, lightly or of exposure to vinyl chloride ranged from 6.1 to 15.5 negligibly to VCM may imply the presence of other years, in the six groups of cases. There was an interval dastogcnic agents. Heath et al. concluded that, of about 18 months between the time of blood because of the wide range of chemicals to which sampling, and the obtaining of smoking histories. No rubber workers were exposed, primarily solvents, it data were provided on alcoholic habits in cases and was`impossible'to relate any particular agents to the controls. However, subjects with recent X-ray observed abnormalities. The average number of exposure,'prolonged'drug treatment, or recent viral months worked for the 14 PVC polymerization infections were excluded from the study, workers ranged from 215 to 346, for the 17 industry Some studies have presented data suggesting a controls the range was 114 to 357. The industry controls possible relationship between a reduction in exposure ranged in age from 31 to 58; the CDC controls had an to vinyl chloride and `normalized' chromosomal age range of 37 to 51. Data were not given pertaining breakage frequency. The blood sampling in the 1978 to smoking history, alcohol consumption, drug use, study by Purchase et al. was carried out in July 1974. radiation exposure, or viral infections affecting cases Since that time, threshold limit values for vinyl chloride and controls. and ,-iant exposure levels were reportedly reduced. In the Heath etal, study, cells were cultured for72 In a study published in 1980, Anderson etal.111 reported h in the presence ofphytohaemagglutinin. The length two further samples from the same population of of culture time may have affected the frequency of workers analysed for chromosomal aberrations 18 observed chromosomal aberrations. In general, cells and 42 months after the initial sampling, will enter mitosis for the first time in about 48 h; in The second sampling consisted of 21 workers, approximately 72 h, there will be a second division.17 employed or formerly employed in plants nanu- In the judgment of some investigators, the 48-h facturing cither vinyl chloride or PVC. re-examined culture time may allow for a relatively more accurate in January 1976, together with 6 off-site controls. A indication of induced aberrations, because some third sampling, examined in January 1978, consisted changes may be lost or modified with each cell division, of 23 workers employed as before together with 8 on- However, the 72 h culture may allow recovery of a site controls. In both the second and third sampling, greater number of cells for analysis. the populations were classified into four groups. The Purchase et fl/.18 studied chromosomal morphology investigators reported that, in comparing the results HUMAN MALE EXPOSURE TO VINYL CHLORIDE 521 R&S 004622 between 1974 and 1976, the autoclave workers who factors, such as radiation and drugs, which may had remained as such showed a statistically signifi influence t'reakage frequency, 4 workers were omitted. cantly (P < 0.05) larger increase than controls in B The mean breakage frequency for the remaining 35 cells, total abnormalities and abnormalities excluding workers was then 3.41%, compared with a control gaps (classified using an adaptation of the method of value of 1.79%. The mean breakage frequency for Buckton & Pike). the heavily exposed workers (3.79%), was higher In the third sampling, the investigators reported a than the value for the rest of the workers (3.15%). tendency to a decrease in the percentage of cells with All tests for cases compared to controls showed that chromosomal aberrations of various types in com workers scored significantly higher on a 2.5% signifi parison with both prior samplings. When the results cance level in the initial study. However, in the of the 1978 sampling were considered alone, Anderson repeat cytogenetic study, no significant differences etal. reported that the exposed workers had a similar were found between chro' osome breakage frequen percentage of all types of abnormalities compared to cies in cases versus matched controls. The chromosome the control group, in contrast tc ;he 1974 and 1976 breakage frequencies for the three groups of workers samplings. The investigators further stated that the were back to normal. No significant difference was incidence of chromosomal aberrations had returned found between the control group in 1974 and the to control values during the time that levels of exposure matched controls. Hansteen etal. concluded that the had been reduced below 5 ppm. In the judgment of repeat study demonsTatcd that the chromosome the investigators, it appeared that by reducing exposure breakage frequency was back to normal after a to vinyl chloride, chromosomal abnormalities had `significant' reduction in exposure for 2 years. returned to values similar to those of controls. Imprecise data concerning vinyl chloride exposure Lack of precise data concerning levels of exposure levels affects the epidemiologic significance of the to vinyl chloride make it difficult to evaluate the Hansteen etal, study. Exact measurements of exposure possible 'normalization' occurrence reported by ir. the PVC plant were provided for 1974 (25 ppm). Anderson et ah The investigators state that although However, for other years, the air concentration of `no accurate' data on exposure levels were available vinyl chloride monomer in the PVC plant was esti at the time of the 197^ sampling, `marked' reductions mated, based on the level of production and the in vinyl chloride levels had supposedly occurred since number and types of autoclaves used in a particular that time due to modifications and control measures. time period. The estimated values were quite wide- Subjects completed a questionnaire, including details ranging (from 2000 ppm, for 1950-1954 to 1 ppm, for of `recent high' exposures, or exposures which could 1975). Employment in years ranged from 1 to 18.5 in be detected by smelling. In the second sampling, it was the workers chosen at random, 4 to 21 in the workers reportedly not possible to exclude persons suffering examined on clinical grounds, and from 10.5 to 24 in from viral infections, as 11 sample members were the heavily exposed workers. The age range in the suffering from colds. However, Anderson et ah stated cases and controls was considerable: 23 to 66 in the that there was no evidence of increased aberrations in randomly chosen workers; 26 to 67 in the workers individuals with colds; this infection was not considered examined on clinical grounds; 39 to 63 in the workers in the third sampling. heavily exposed; and 27 to 66 in controls, Hansteen et More data on the subject of normalized chromosome ah reported that matching for age between cases and breakage frequency were published in a 1978 article controls was attempted, but was `not entirely' success by Hansteen et ah Cytogenetic studies were carried ful. Although a medical history, including viral out on 39 workers from a PVC plant in 1974. Fourteen infections, radiation exposure and drug intake, was of the workers were chosen at random, 13 were reportedly obtained for all participants in both studies, chosen because they had been `heavily' exposed to no specific data are presented regarding drug use, vinyl chloride monomer for years; and 12 were workers smoking history, alcohol use, radiation exposure, or whose first health screening revealed abnormalities viral infections. but on clinical re-examination all laboratory tests Chromosomal changes may be reversible. Based proved normal. Sixteen healthy males, with no on data from the Anderson ci at and Hansteen et ah connection with the PVC plant, were chosen as studies, a reduction in chromosomal aberrations may controls. The cytogenetic study was repeated for 37 occur after lowering of exposure to vinyl chloride. of the 39 workers 2 to 2.5 years later. The repeat A failure to take repeated samples from persons study was done with 32 matched controls. In addition, 6 exposed to varying levels of vinyl chloride may be a of the previous control group were re-examined. The limitation of studies examining possible chromosomal exact sex distribution of cases and controls is not aberrations in vinyl chloride exposed workers. The clear. process of replacement of aberrant cells by normal The mean breakage frequency for the 39 workers cells may occur at the rate of 1 to 2% per year.21 was 3.7% in the initial study. Because of different Thus, if very high levels of aberrant cells are observed r VOL . 7 i . iss' 4 . I , I * I NO i . i I t j 19 88 / *4 ( -4 UiVII * 522 L. UZYCH Tabic 1 Summary: chromosomal agnations in human males exposed to vinyl chloride Rrfrrrnet Ducatmanetaf.11 No. of case" 11 males Funes-Cravioto11 7 males Kiliin St Pictiano' 121 Purchase ere/.11 56 Purchase ti at.11 56 Szentesi etal.'1 41 males: 4 other Heath rial.1* 18 males Pieciano era/.10 209 Fleig A Thiels* 10 males 20 Hanstecr. era/. 39 (initial) 37 (repeat) Purchase era/.1* 57 males Anderson flat.1* 21 23 Rossner tt at.* 31 males 1 ^o 3o *8 Average duration of tipoiurt 1years) Dose of exposure Major findings Study limitations 15 Inexact 10 Significant increase in total breaking and complc't breaking events and 'unstable' chromosomal changes; non-significant increase in simple and 'stable1 aberrations Small sample size; inexact exposure data; no age matching 16.5 Inexact 3 Significant increase in abnormal celts Small sample size: inexact exposure data Not given Varying 75 Less chromatid breakage: lower % of abnormal cells; greater frequency of dicentric chromosomes Sex distribution ofcases/ controls not given Not given Not given 24 Significant increase in B. Cu and Cs cells Sex of cases/controls not given: no exposure data Not given Not given 24 Significant mutagenic effect Sex of cases/controls not given: no exposure data Not given; but range of 0*5-12 years Not given 44 `industrial* 49 `normal* Higher frequency of chromatid-type aberrations; significantly higher 'unstable' aberrations No dose data: inexact duration data: some controls 'indirectly' exposed to `other' chemicals Varying Inexact 17 industrv* 4 CDC' Significant increase in breakage levels compared to CDC controls Small sample size; inexact exposure data 48.3 months Inexact 295 No major differences reported for mutagenic effects Exact sex distribution of cases/controls not given: Inexact exposure data 15.4 Inexact 10 12.4 Not known 20 No significant difference in rate of chromosomal aberrations: Significant difference in rate of chromosomal aberrations Small sample size: inexact exposure data Unknown exposure rate Varying Inexact 16 (initial) 32 + 6 (repeat) Significant mutagenic effect; No significant difference in chromosomal breakage frequencies Exact sex distribution of cascs/cont'ols ur dear; inexact exposure data: no specific data on drug use, smoking, or alcohol use Varying Inexact 24 Significant increase in chromosomal abnormalities: significant correlation between smoking and total C cells Inexact exposure data: about 18 month gap between blood sample and taking of smoking history Varying Inexact, but 6 reduced' 8 over time Tendency to a decrease in chromosomal aberrations, compared to prior :^mplings Inexact exposure data; small sample size Varying Inexact 35 No significant mutagenic effect Inexact exposure data ly limitations imple size; exposure deta: Hatching unple size: exposure data ribution ofcases/ ; not given sex/controls not id exposiurreudaattaa 'V 1pases/conl <oexposuuirnata : data; inexact i data; some i `indirectly' J to `other' Is imple size: exposure data :x distribution of ntrols not given: exposure data imple size: exposure data vn exposure rate HUMAN MALE EXPOSURE TO VINYL CHLORIDE 523 initially, the return to normal levels may take quite comprised of 21 male workers and 6 controls. The some time. cases and controls represented a second sampling Tabic 1 summarizes major data findings and infor from a group of vinyl chloride exposed workers and mation from the foregoing studies on chromosomal controls first examined 18 months earlier ana described aberrations. in the 1978 study by Purchase et al.IS Sample members were examined for the presence of chromosomal Sister chromatid exchanges aberrations or SCEs. in their peripheral lymphocytes. In all exposed groups significant increases were reported for most types of chromosomal abnormalities. In addition to examination of gross chromosome The number of SCEs per cell was slightly increased in abcriations, the investigation of sister chromatid the exposed groups, with the highest value in the 10 exchanges (SCEs) may provide a promising meal's of cases who were autoclave workers. However, the biological monitoring in instances of exposure to increases were not statistically significant. vinyl chloride, or other known or suspected mutagens. The invcstigator> postulated possible mechanisms SCEs reflect intrachromosomal rearrangements of for the data results. It was hypothesized that the the DNA helices.-- Crossing over between the sister exposure levels of vinyl chloride which the work chromatids of a single chromosome is a phenomenon force were exposed to were not high enough to that was recognized after the development of a special nducc SCEs. Anderson et al. concluded that the technique.Cultured cells arc permitted to replicate analysis of SCEs may be of limited value after very twice in bromodeoxyuridinc (BUdR), allowing low chronic chemical exposure or if some time has incorporation of BUdR into newly synthesized DNA elapsed after acute exposure. However, analysis of in place of thymine. BUdR affects the staining proper SCEs may be of value during high chronic chemical ties o' chromatids. If a SCE has occurred, this may be exposure and during the first few days immediately recognized by the fluorescence patterns along the following acute exposure. chromatids. Some investigators have reported significantly The molecular mechanism of SCE induction is not increased levels of SCEs in workers occupationally clear. However, SCEs may be a sensitive indicator of exposed to vinyl chloride compared to control values. DNA damage, particularly directly following the Kuccrova el al.,-* in 1979, reported data from an exposure in question. Gross morphological changes analysis of three blood samples from each of 9 workers in chromosomes may persist for several years whereas occupationally exposed to vinyl chloride monomer. the SCE frequency in lymphocytes may remain at a In the third blood sample scries, the investigators high level for4 to 16 weeks following exposure." The also used the SCE technique and compared the time lag between exposure and analysis, as well as frequency of observed chromosomal abenations with the type and duration of mutagen exposure, may the number of SCEs in each sample. Blood samples thus affect the relative suitability of gross chromo from 8 healthy persons were used as controls. The sex * some aberrations and SCEs as means of biological distribution on cases and controls is not stated. The monitoring. investigators reported an increase in the frequency of Data arc available from several studies pertaining chromosomai abenations and the number of SCEs per to SCEs in industrial populations exposed to vinyl cell in 7 blood samples in cases compared to controls. chloride. Anderson et al.'4 in 1 yS1reported data The level of significance for the frequency of SCEs in from a study designed to assess whether the SCE cases compared to controls was P < 0.001, according technique may offer advantages over conventional to the r-test. It was the opinion of the investigators chromosomal analysis in monitoring human popula that evaluation of the frequency of chromosomal tions expose to mutagens. The sample population aberrations and the number of SCEs may be equally Table 2 Summary: sister chromatid exchanges in human males exposed to vinyl chloride Reference Kuccrova et al}' No. of cases y Average duration of exposure Dote of exposure (avg ppm) Not given Inexact but range of 10-27 yean Anderson tt a!.u 21 males Varying Inexact No. of controls 8 6 Majorfindings Study limitations Increased frequency of chromosomal aberrations and SCEs Sex distribution of cases/controls not qiven: small sample size; inexact exposure data Significant mutagenic Inexact exposure data effect; 'slightly increased* SCEs R&S 004624 VO L IS S 'V .8 NO 1988 UMI suitable methods for testing high'dose vinyl chloride mutagenicity in vivo. The relatively small size of the sample population in the Kucerova et al. study (9 cases, and 8 controls) affects the statistical significance of the study. The 9 cases had been exposed to `relatively high' mean annual doses ot vinyl chloride monomer, estimated to be about 20--150 ppm of air. The controls were reportedly not exposed to `known* (not specified) mutagens, during the 3 months before the time of blood collection. Duration of exposure for the 9 cases ranged from 10 to 27 years. Controls were matched for age and sex. Several of the cases and controls were smokers and/or rsed alcohol. Six of the cases used 1 or more drugs. Precise data for these variables are not presented. However, the investigators stated that the smoking and other habits of workers appeared to have no effect on the frequency of any chromo somal changes. A summary of information concerning human male exposure to vinyl chloride and SCEs is presented in Table 2. Effects on pregnancy The exposure of human males to vinyl chloride may be associated with various adverse pregnancy out comes. Published data on this subject are inconclusive. Some of the difficulties potentially involved in reaching definitive conclusions in this area arc mentioned in a review piece by Clcmmescn.26 In 1978, Edmonds et al.11 reported data from an epidemiologic investigation undertaken in Kanawha County (Charleston), West Virginia. The investiga tion was undertaken because of concern that high rates of congenital central nervous system (CNS) defects observed in Kanawha County might be associated with environmental exposure to vinyl chloride monomer. During the pertinent time period, 1/1/70-31/12/74, 47 residents of Kanawha County at time of birth had confirmed CNS defects. All cases were white. For each confirmed case, 2 controls were selected from birth certificate records. The controls were live born infants whose parents lived in Kanawha County and whose birth certificates immediately preceded and followed that of an infant with a CNS defect and gave no indication of congenital malformation. The families of affected infants and matched controls were inter viewed by telephone. The investigators reported that `dose' case control matching was achieved for the following variables: paternal education, maternal age, and Hollingshead Index. Edmonds et al. further stated that cases and controls were `comparable* with respect to maternal education, proportion of previous fetal deaths and other children with congenital anomalies. The investigators reported initially high, albeit declining, rates of CNS defects. Defect rates for 1970-1972, particularly rates for anenccphaly, were 1.5-2 times higher than those recorded for white bit ths in surveillance systems using similar data sources in Florida, Nebraska and Georgia. However, the rate of total CNS defects declined from 1970 to 1974. In 1970, 14 cases of CNS defects were confirmed (including 9 cases of anencephaly, 4 cases of spina bifida, and 1 `other' CNS defect). However, in 1974, only 1 case (of spina bifida) was confirmed. The investigators stated that the decrease was not unique to Kanawha County insofar as a similar, though less marked, trend was evident in available data for other parts of the country. The Edmonds et al. data do not provide a clear basis for evaluating the possible relationship between parental exposure to vinyl chloride and other possible atmospheric pollutants and the rate of various con genital CNS defects. Edmonds et al. reported no differences between cases and controls concerning parents' possible exposure to vinyl chloride at the time of, or for 5 years before, their child's conception, either by direct occupational exposure or by location of work place with respect to the PVC polymerization plant in Kanawha County. The investigators therefore concluded that, on that basis, there was no evidence that the observed higher CNS defect rates could be related to parental exposure to vinyl chloride at the place of occupation. If there is an association between community exposure to atmospheric vinyl chloride and observed rates of CNS birth defects, a decrease in atmospheric vinyl chloride levels might reasonably be followed, after an approximate 9 month time lag, by a corres ponding decline in rates for CNS malformations. However, Edmonds et al. reported that the greatest decrease in rates occurred in 1973, and preceded the decline in levels of vinyl chloride emissions. Data on vinyl chloride emissions from the Kanawha County PVC plant showed that the annual mean vinyl chloride emissions (Ib/h) decreased from 265 in 1973 to 180 in 1974 and 76 in 1975. Edmonds et al. further indicated that there are seven major chemical plants and several smaller ones in the Kanawha River Valley. Thus, to conclude that vinyl chloride alone may be associated with high rates of CNS malformations disregards over 100 other compounds emitted from Kanawha Valley area plants. Studies pursued in communities containing chemical industrial facilities, producing or using multiple known or suspected toxins, in general may be confounded by difficulties in determining whether one or more of the substances, either independently or in an additive or synergistic manner, may be associated with observed levels of abnormalities. Some investigators have reported a significant ft d initially high, albeit fects. Defect rates for for anencephaly, were >sc recorded for white sing similar data sources rgia. However, the rate i from 1970 to 1974, In fects were confirmed rhaly, 4 cases of spina ct). However, in 1974, i was confirmed. The :crease was not unique a similar, though less .vailablc data for other 0 not provide a clear ? relationship between ride and other possible e rate of various con* Is er al. reported no 1 controls concerning vinyl^Hride at the eir dWconccption, posure or by location ; PVC polymerization nvestigators therefore ,iere was no evidence defect rates could be vinyl chloride at the between community htoride and observed Tease in atmospheric onably be followed, ime lag, by a corresTNS malformations, ted that the greatest *3. and preceded the : emissions. Data on <c Kanawha County I mean vinyl chloride 265 in 1973 to 180 in al. further indicated al plants and several /er Valley. Thus, to j may be associated mat ions disregards ted from Kanawha containing chemical sing multiple known y be c^hunded by rone^Poreofthe or in an additive or ated with observed jned a significant HUMAN MALE EXPOSURE TO VINYL CHLORIDE excess of fetal loss among wives of workers following indirect vinyl chloride exposure from the father m exposure to vinyl chloride. In 1976, Infante et al. be considered. However, in their view, these mcci reported data from a study of pregnancy outcome isms seemed unlikely because of the highly voir among the wives of workers exposed to vinyl chloride nature of vinyl chloride. Based on the study findir monomer. Data for the wives of vinyl chloride poly taken in conjunction with the prior demonstratioi merization workers were contrasted with data for the a mutagenic response in microbial systems and wives of PVC fabrication workers and rut tier workers. observations of significant excesses of chromosoi A total of 95 vinyl chloride polymerization workers aberrations in workers exposed to vinyl chloride and 158 rubber and PVC fabrication workers were was the authors' opinion that the leading possibilit interviewed. germ cell damage in the father through direct vi Because fetal loss is known to increase with chloride exposure. increasing parental age, the fetal death rates for the Several variables affect the analysis of the data vinyl chloride polymerization workers v/crc age Infante ctal. The investigators do not provide prec adjusted to the control group, infante et al. found data on the level of exposure to vinyl chloride. 7 that mong pregnancies occurring prior to exposure, rubber workers were selected from work an fetal death rotes were 6.9% for controls versus 6.1% described as being `relatively free' from kno (age adjusted) for the vinyl chloride polymerization (unspecified) toxic materials. Data on duration workers. These rates were not significantly different exposure were not provided. Significant risk facu by Mantel-Hacnszcl chi square testing. However, for spontaneous abortion may include a maten among pregnancies occurring subsequent to the age of 30 years of more, excessive cigarette smoki husband's exposure, the difference in the frequency and alcohol use during pregnancy. Infante et al. t of fetal deaths between cases and controls was signifi not obtain data concerning maternal age. exec cant, at P < 0.05. The investigators stated that the indirectly through paternal age. Data concerning I significant difference subsequent to exposure reflected smoking habits, alcohol use, drug use. radiatii the relatively greater fetal mortality rate associated exposure, or infections in cases and controls arc n with younger aged husbands in the group of poly presented. Although some investigators suspect th merization workers. For pregnancies occurring after women may he more accurate reporters of repr exposure, the fetal mortality -ntes associated with ductivc history than their mates. Infante et al. did n husbands 30 and older were 13.0% for the polymeriz conduct any interviews with workers' wives.7 ation workers and 12% fr. the control group. The study by Infante et al. has been critical However, for husbands less than 30. fetal mortality examined in the literature. In a letter published in tl rates were 20.0% for the polymerization workers but Lancet, Paddle'1'stated that the assertion by Infan only 5.3% for the control group. et al. of a significant excess of fetal loss among wives ( Since one spontaneous abortion may be associated workers following exposure should be supported by with a 66% increase in the risk of a subsequent specification of the methods of data collection and abortion, it is possible that part of an observed tabulation of the raw data before analysis. It w; increased loss occurring in the wives of men exposed Paddle's view that the use of a questionnaire, and th to vinyl chloride may be associated with a high ensuing low response rates, where the subject percentage of spouses with a history of previous spontaneous abortion, mest detract from the study abortions.7 To determine whether women who had accuracy. It is further observed that the Infante et a. chronically experienced abortions might have weighted data arc presented after an age adjustment proccdur the results in the current study, in favour of a higher which behaves `very misleadingly'. For instance, fetal death rate in the group of polymerization workers crude percentage of It). 1 for a sample whose averag subsequent to the husband's exposure, the investi age is 26.4 was adjusted down to 6.1, while a figure o gators stated that pregnancies of women who had more 16.5 tor a sample of average age 30.2 was reduce! than two abortions were eliminated from analysis. only marginally, to 15.8. Infante ct M. reported that with this adjustment the In a responding letter, subsequently published ir trend was maintained. Prior to exposure, the fetal the Lancet Infante et al. stated that the question: death rates for controls and polymerization workers about pregnancy outcome were contained in : were 6.9 and 3.1% (age adjusted), respectively. After questionnaire which was part of a cross-sectional health exposure, the rates were 6.8 and 10.8% respectively. survey.-1 The rcsui.s of the survey reportedly shower Infante et at. concluded that fetal loss was signifi no consistent bias towards a higher prevalence for tlu cantly more among wives of workers following indices measured in the study or control group. With exposure to vinyl chloride. Several possible mechan regard to age adjustment, they explained that the isms for the observed fetal loss were suggested. It was study group rate became 6.1 % after direct age adjust hypothesized that cither fetal or maternal toxicity or ment, as a result of a younger paternal age foi germ cell mutagenesis in the mother associated with pregnancies in the control group. Additionally, with VOL *r NO 19 88 i UMI direct age adjustment, the 16,5% figure was reduced to 15.8%. They stated that age adjustment for the subsequent to exposure comparisons resulted in little change in the rates because the age distributions for pregnancies in both the study and control groups after exposure were similar. It is difficult to determine precisely the causes of observed adverse reproductive outcomes. Spon taneous abortions may result from the cmbryotoxic effects of various environmental agents and from various other factors, including maternal endocrine disturbances, abnormalities of the placenta, faulty embryo development, intrauterine infections, and severe maternal trauma.51 Congenital malformations may be associated with various toxic chemical agents. A number of toxins may be associated with impaired fertility in men. Future studies intended to document a possib'c relationship between impaired pregnancy outcome and paternal exposure to vinyl chloride must carefully validate information on pregnancies and take into account various confounding variables. Spermatic alterations A 1980 study by Sanotsky eta!.32 raises the possibility that human male exposure to vinyl chloride may be associated with spermatic alterations. The paper was not published in English. However, an English language abstract states that reproductive functioning was studied in men occupationally exposed to either chloroprcnc, vinyl chloride or antimonite ore dust with reproductive functioning assessment being based on `indirect' evidence and from analyses of ejaculates. The abstract states further that `pathologic changes' were detected in the ejaculates. This study is the only published literature known to the author pertaining to human male exposure to vinyl chloride and possible rcsultat.f adverse effects on sperm. A salient research need may thus exist for extended investigation of this aspect of paternal vinyl chloride exposure, including study of possible effects on sperm count, motility and morphology. Conclusion On the basis of selected, available data, the exposure of human males to vinyl chloride may be associated with various chromosomal aberrations in lymphocytes as well as increased levels of sister chromatid ex changes. Paternal exposure to vinyl chloride may further be associated with adverse reproductive out comes. The possibility of adverse effects on sperm associated with human male exposure to vinyl chloride must also be considered. Data pertaining to the possible biological effects associated with paternal vinyl chloride exposure are relatively sparse, conflict ing and inconclusive. The mechanisms for the possible reproductive related risks posed by paternal exposure to vinyl chloride arc not certain. Extensive, carefully designed studies should be undertaken to further elucidate the biological effects, and associated mechanisms, possibly associated with paternal exposure to vinyl chloride. References 1 Binns CHB. Vinyl chloride: a review. Journal of the Society of Occupational Medicine 1979; 29; 134-141. 2 Messite J & Bond MB. Reproductive toxicology and occupational exposure. In: Developments in Occupational Medicine, ed. C. Zenz. pp. 59--129. Chicago; Year Book Medical Publishers, 1980. 3 Patty FA, Yam WP & Waite CP. Acute response of guinea pigs to vapors of some ne*.v commercial organic compounds. Public Health Reports 1930; 45: 1963-71. 4 Doerr v. B.F. Goodrich, 484 F, Supp. 320 (N.D. Ohio 1979). 5 Complaint filed in Doerr v. B.F. Goodrich, C81-1745 (N.D. Ohio. Aug. 24,1981). 6 Fleig I & Thiess AM. Mutagenicity of vinyl chloride. Journal of Occupational Medicine 1978; 20: 557-61. 7 Hatch M, Kline J & Stein Z. Power considerations in studies of reproductive effects of vinyi chloride and some structural analogs. Environmental Health Perspectives 1981:41: 195-201. * Rossner P, Sram RJ, Wovakova J, et at. Cytogenetic analysis in workers occupationally exposed to vinyl chloride. Mutation Research 1980; 73: 425-7. v Kilian DJ & Picciano DJ. Industrial monitoring: a cyto genetic approach. Annals of the New York Academy of Sciences 1975: 269: 4-11. 10 Picciano DJ, Flake RE, Gay PC, et al. Vinyl chloride cytogenetics. Journal of Occupational Medicine 1977; 19: 527-30. 11 Ducatman A, Hirschhorn K & Sclikoff 1J. Vinyl chloride exposure and human chromosome aberrations. Mutation Research 1975; 31: 163-8. 12 Funes-Cravioto F, Lambert B, Lindsten J, et at. Chromosome aberrations in workers exposed to vinyl chloride. Lancet 1975; I: 459. 1J Purchase 1FH, Richardson CR & Anderson D. Chromo somal and dominant lethal effects of vinyl chloride. Lancet 1975: ii: 410-1. 14 Szentesi I, Hornyak E, Ungvary G, et al. High rate of chromosomal aberrations in PVC workers. Mutation Research 1976; 37: 313-6, Purchase 1FH. Richardson C & A-derson D. Chromo somal effects in peripheral lymphocytes. Proceedings of the Royal Society of Medicine 1976: 69: 290-1. " Heath CW, Dumont C. Gamble J, et al. Chromosomal ;nt being based s of ejaculates. )Iogic changes' iture known to 'e exposure to idverse effects y thus exist for ; paternal vinyl possible effects logy. .the exposure be associated n lymphocytes chromatid ex chloride may rodn^^^outccts cHperm > vinyl chloride aining to the with paternal tarse, conflictor the possible :mal exposure sive, carefully en to further id associated riih paternal litoring: a Cym ric Academy of Vinyl chloride dicine 1977; 19: . Vinyl chloride tions. Mutation iten J. tt al. posed to vinyl on D. Chromo chloride. Lancet l. Hig( <ers. m D. ChromoProceedings of XM. Chromosomal HUMAN MALE EXPOSURE TO VINYL CHLORIDE 527 damage in men occupationally exposed to vinyl chloride monomer and other chemicals. Environmental Research 1977; 14: 68-72. 17 Kilian DJ & Picciano D. Cytogenetic survcillancc of industrial populations. In: Chemical Mutagens: Principles and Methods for Their Detection, volume 4. cd. A Hollaendcr pp. 321-39, New York: Plenum Press, 1976. 18 Purchase 1FH, Richardson CR. Anderson D, ct al. Chromosomal analyses in vinyl chloride-exposed workers. Mutation Research 1978; 57: 325-34. Anderson D, Richardson CR, Weight TM. ct al. Chromo somal analyses in vinyl chloride exposed workers results from analysis 18 and 42 months after an initial sampling. Mutation Research 1980; 79: 151-62. 10 Hansteen IL, Hillcstad L.Thiis-Evcnscn E.etal. Effects of vinyl chloride in man a cytogenetic follow-up study. Mutation Research 1978: 51: 271-8. 21 Kucerova M. Chromosomal aberrations induced in occu pationally exposed persons. In: Mutagenicity: New Horizons in Genetic Toxicology, cd. JA Hcddlc pp 241-- 66. New York: Academic Press. 1982. 22 Vainio H, Sorsa M, Rantancn J, ct al. Biological moni toring in the identification of the cancer rick of individuals exposed to chemical carcinogens. Scandinavian Journal of Work and Environmental Health 1981; 7: 241-51. 22 Thompson JS & Thompson MW. Genetics in Medicine. p. 18. Philadelphia: WB Saunders. 1980. 24 Anderson D. Richardson CR. Purchase IFH, ct al. Chromosomal at alysis in vinyl chloride exposed workers: comparison of the standard technique with the sisterchromatid technique. Mutation Research 1981; 83: 13744. 25 Kucerova M. Polivkova Z & Batora J. Comparative evaluation of the frequency of chromosomal aberrations and the see numbers in peripheral lymphocytes of workers occupationaMy exposed to vinyl chloride monomer. Mutation Research 1979; 67: 97-100. 26 Clcir.mcnscn J. Mutagenicity and teratogenicity of vinyl chloride monomer (vt.u) epidemiological evidence. Mutation Research 1982: 98: 97-100. 27 Edmonds LD. Anderson CE. Flynt JW, etal. Congenital ccntial nervous system malformations and vinyl cnloride monomer exposure: a community study. Teratology 1978: 17: 137-42. 28 Infante PF. McMichael AJ, Wagoner J. et al. Genetic risks of vinyl chloride. Lancet I97u; i: 734-5. *' Paddle GM. Genetic risks of vinyl chloride. Lancet 1976: i: 1079. 2,1 Infante PF, Wagoner JK. McMichael A. et .it. Genetic risks of vinyl chloride. Lancet 1976; i: 1289-90. 21 Bang KM, Lockcy JE & Kcyc W. Repioductivc hazards in the work place. Family and Community Health 1983; 6: 44--56. 22 Sanotsky IV, Davtinn RM & Glushchcnko VI. Study of the reproductive function in men exposed to chemicals. Gigicna Trudai Profcssionalnye Zabo'.cvanha (Moskva) 1980; 5: 28-32. (Received 28 March 1988; accepted IS June 1988) R&S 004628