Document RJYkJ709NaxYvLGGx3pjY3dqE

% 46 for io of jrred i the ratic atio with t the conI exi the Jatic m ition ition ified a is :cur,,*ntly v of that Jiag- tcate fort, gists, erra) ition osed .sent fted. hese incer e of f all ding 47 Sci non of Occupational Medicine 305 past occupations, toxic exposures, and places of residence is underway. Table J Lung cancer among workers at PVC polymerization plants in the United States by histologic type and extent of VC exposure Medical Screening oj VC Workers Together with the Occupational Health Studies Group of the University of North Carolina, NIOSH-CDC recently concluded a cross-sectional medical screening examination of 530 workers at a plant in Pennsylvania which contains both a large tyre-building facility as well as one of the oldest PVC polymerization plants in the United States, Included in the study were approximately 130 current PVC polymerization workers and a similar number of control workers from the tyre plant who had never worked in the polymeriza tion facility The 2 groups were comparable in age, alcoholic intake, and socioeconomic back ground: ihe controls were chosen from those areas of the tyre plant where exposure to solvents and dusts was least. Preliminary review of the results shows no significant differences between the 2 groups for any of the 6 liver function tests performed (SGOT, bilirubin, alkaline phosphatase, LDH, GGTP, and ornithine carbamyl transferase). Additional analyses based on levels of VC exposure, duration and type of job, and other subgroupings are being done; these preliminary results however do not suggest the occurrence of liver function abnormalities on a broad scale secondary to VC exposure. One should of course be cautious about generalizing from the results at a single plant, and it will be important to compare these findings to studies at other PVC plants. It is also important to realize that since liver function tests are rela tively insensitive to the early finding of VCinduced hepatic disease (i.e. fibrosis), the results of this type of testing are not a reliable estimate for the prevalence of VC-induced disease. Liver scans were also performed on all workers with more than 10 years duration of work in the PVC polymerization plant, and no cases of HAS were detected. Some increase in frequency of palpable livers on physical examination was found, how ever, among VC workers. A full report of findings from this comprehensive medical screening study is in preparation and will be available shortly. Cohort Mortality Study at Four P VC Polymerization Plants One of the results of this NIOSH-CDC study was the demonstration of an increased SMR for respiratory system cancer among members of the cohort (Waxweiler et al. 1976). On preliminary pathologic review, it was also noted that of the 12 lung cancer cases all 8 for which pathologic specimens were available were either large cell undifferentiated or adenocarcinoma of the lung; Extent of VC exposure Histologic type Sone Epidermoid 1 Small cell undifferentiated 0 Adenocarcinoma 1 Large ceil undifferentiated 4 Unclassified 1 Less than one year t 3 1 0 0 More than one year 0 0 4 6 0 Tot 2 3 6 10 I 75 10 22 if confirmed, this unusual cell type distribution may support the association between VC exposure and occurrence of lung cancer. There are, however, two additional features which should be considered in evaluating this potential relationship. When all of the workers at these 4 plants are considered, including those who were not part of the defined VC-exposed cohort, a total of 22 cases of lung cancer (out of 48) were available for pathologic review. The increased incidence of large cell undifferentiated and adenocarcinoma of the lung was seen in VC workers with more than 1 year of exposure, while a distribution more closely resembling the ex pected small cel! predominance was seen for VC workers with less than 1 year of exposure. Interestingly, however, cases of lung cancer in non-VC workers at these plants, although small in number, appeared to have a cell type distribu tion which was also ''predominantly large, cell undifferentiated (Table 3). In addition, unlike the situation for HAS in these plants where all but one of the cases were long-term reactor cleaners and operators, the workers with large cell un differentiated and adenocarcinoma of the lung were distributed in a number of different job categories. As a result, cases of lung cancer seem not to correlate as tightly with VC exposure as cases of HAS and it is conceivable therefore that some additional chemical exposure at these plants may be working together with VC (or even separately) to produce this effect. Further studies are currently underway in an effort to confirm these preliminary pathologic findings. REFERENCES Landrigan P J & Heath C W jr (!976)On preparation) Lilia R, Anderaon H, Nicholson W J, Daum S, Fischbeia ASA Selikoff IJ (1975) Annals of the Sew York Academy of Sciences 246, 22 Lloyd J W (1975) Journal of Occupational Medicine 17, 333 L 306 Proc. roy. Soc. Med. Volume 69 April 1976 48 Lloyd J W, 0*coud* P A Moor* R M (1971) Journal ofOccupational Medicine 17* 263 Mokk L* Creech J L jr, Whelan J G jr St Johnson M N (1974) Journal ofthe American Medical Association 230,64 Maltom C A Lefemine C (1974) Environmental Research 7, 387 Monson R R, Peters J M A Johnson M N (1974) Lancet n, 397 Tabershaw I R & Gaffey W R (1974) Journal of Occupational Medicine 16* 509 Waxweiler R J, Stringer W, Jones J, Wagoner J K, Falk H A Carter C (1976) Annals ofthe Vew Lork Academy of Sciences lin press) DISCUSSION Dr Mitchell R Zavon (Baton Rouge, Louisiana) asked whether the clinical examiners at Pottstown knew whether or not the person being examined worked in vinyl chloride. Dr H Falk replied that none of the clinical examiners were aware of the occupational status of the workers at the time of the examination. Dr R I McCallum (University of Newcastle upon Tyne) asked Dr Falk to give in more detail the way in which histological diagnosis was made in the case of lung cancer shown in his slide. Was this done by one individual or by a panel of pathologists? How were the specimens of tissue obtained: by biopsy, surgical resection or at autopsy? It was remarkable that in none of the cases was an oat cell carcinoma diagnosed, as this was the type often considered a characteristic result of exposure to a chemical carcinogen. Dr H Falk replied that the WHO lung cancer classifica tion scheme of Kreyberg (1967) was used. Four patho logists reviewed the slides and agreed on the inter pretation (Dr Louis B Thomas and Dr T Powell, National Institutes of Health; Dr M Kuschner, State University of New York; and Dr Laszlo Makk, St Anthony Hospital, Louisville, Kentucky). All avail able pathological material for each case was reviewed. The expanded pathological review currently under way would include the selection of multiple control cases of lung cancer from the same hospitals (with simi lar age and date of diagnosis to the study cases) and a blind review by a panel of pathologists in a more detailed evaluation of available pathology material. To Dr Falk's knowledge large cell undifferentiated carcinoma of the lung had not been related to exposure to chemical carcinogens, which made the findings in the VC cohort even more intriguing. Dr A J Fox (Employment Medical Advisory Service, London) asked how many factories had been studied individually in the USA. What proportion of these had indicated vinyl-chloride-associateddisease? NIOSH-CDC study, the Tabershaw > study, and the Monson-Peters study) had all looked at the Louisville, Kentucky plant where the initial angiosarcoma cases occurred as well as at a varying number of additional plants. Compounding the problem was the fact that the definitions for entrance into the cohorts studied differed from study to study, so that the results even at the same plant were not identical. Dr J k Bonnell (Central Electricity Generating Board) asked whether, since vinyl chloride monomer was a carcinogenic agent, there was any evidence in experi mental animals or m human clinical experience that the skeletal or skin changes described might be premalig..ant conditions. Dr H Falk said that cases of angiosarcoma in the USA did not have a history of acro-osteolysis or skin problems, although they did not have the multiple tests for early changes of acro-osteolysis. It would seem, therefore, that the skin changes were not premahgnant conditions. Professor I J Selikoff (Afount Sinai School of Medicine, City University of Sew York) said that a review of known details of identified cases of vinyl-chlorideassociated angiosarcoma of the liver by Dr Lloyd (1975) of the National Institute for Occupational Safety and Health had demonstrated that the median duration from onset of exposure was approximately seventeen years. These cases were derived from the rather small number of polymerization workers em ployed during the establishment and initial growth of the vinyl chloride industry. Attempts were underway to identify and trace the initial groups of workers, employed during the years 1938-55, since analysis of their experience would allow evaluation of the risks which might be suffered by the very much larger group of vinyl chloride workers exposed more recently, in a period during which PVC production was in creasing at the rate of approximately 10o per annum. Limited data bearing on the problem had been obtained. In one polymerization process studied, 257 men had been employed for five years or more in the period between 1946, when the plant opened, and 1964. Each man had been traced to 1 July 1974, with 25 deaths from all causes; 3 of the deaths were due to angiosarcoma of the liver (Nicholson et at, 1975), each confirmed on review of autopsy material (Thomas & Popper 1975); in addition there was one death due to ruptured oesophageal varices. Another worker, examined during the clinical survey at this facility (Lilis et al. 1975) had had a successful portacaval shunt operation for the same condition. These experi ences suggested'that vinyl-chloride-associated disease would be aw important hazard for vinyl chloride workers in the future, unless control of exposure resulted in at least some reversal of the risk. Dr H Falk replied that cases of hepatic angiosarcoma had been seen at 5 of the 8 PVC polymerization plants opened prior to 1950. There was some confusion in this area in that a number of the VC worker mortality studies had been overlapping. Three separate studies, for example, (the Lillis R, Anderson H, Nicholson W J, Dsum 5, Fischbeia A 5 St Selikoff I J (1975} Annals of the Sew York Actulemy of Sciences 246, 22-41 Lloyd J W (1975) Journal of On upottonal Wet/inne 17, 33J-J34 Nicholson W J, Hammond E C, Setdman H & Sehkoff I J (1975) Annals of the Sew York Acudemv of Sciences 246, 225-230 Thomas L B & Popper H (1975) Annals o/'ihe Sew York Academy ofSciences 246, 268-277 49 Dr B VV Duck t Occupational Heah BP Research Centre Stinbttry on Thames Medical Surveiltanc Following the anni the first cases of workers exposed tc Chemical Industri Kingdom set up with a number < including one on h> The first task ct which comprised four British comp; of vinyl chloride (PVC), was to rev toxicological infc what action shoul of exposed employ one aspect of the f At that time, sarcoma of the li' rarity, there was its natural histoi early diagnosis, malignant forms fibrotic changes, vinyl chloride w suspected, but tl ances of liver to the dew: be estabiisnt.. respect of the pr acro-osteolysis C tions, since it wa some common ur To complicate term carcinogem had not only pro also a considers i tumours. The situation , leagues in Gover I and specialists i advice was recei overseas source United States. It that there was early detection serve as a basi; gramme in ir possibilities wt diagnostic valu certain, vinyl asked to volur the grounds tha disease of the 49 Section of Occupational Medicine 307 Dr B W Duck (Occupational Health Unit, BP Research Centre, Sunburvon Piames, TW16 7LH) Medical Surveillance of Vinyl Chloride Workers Following the announcement in January 1974 of the first cases of angiosarcoma of liver among workers exposed to vinyl chloride in the USA, the Chemical Industries Association in the United Kingdom set up a Vinyl Chloride Committee, with a number of specialist working groups, including one on health aspects. The first task confronting this working group, which comprised medical representatives of the four British companies engaged in the production of vinyl chloride (VC) and polyvinyl chloride (PVC), was to review all the relevant medical and toxicological information available and decide what action should be taken to protect the health of exposed employees. This ts an interim report on one aspect of the group's work. At that time, little was known about angiosarcoma of the liver and its treatment. Due to its rarity, there was considerable doubt about both its natural history and appropriate methods of early diagnosis. Reports indicated that nonmalignant forms of liver pathology, such as fibrotic changes, might be more prevalent among vinyl chloride workers than had hitherto been suspected, but the significance of such disturbances of liver function and structure in relation to the development of angiosarcoma had yet to be established. Similar considerations arose in respect of the previously recognized condition of acro-osteoly sis (AOL) and its various manifestations. since it was speculated that there might be some common underlying vascular pathology. To complicate the situation still further, longterm carcinogenicity tests on laboratory animals had not only produced many angiosarcomas, but also a considerable number of renal and other tumours. The situation was discussed with medical colleagues in Government and Trade Union agencies, and specialists in iiver disease, and much helpful advice was received from them and from various overseas sources, especially from doctors in the United States. It soon became apparent, however, that there was no established procedure for the early detection of liver angiosarcoma that could serve as a basis for a large-scale screening programme in industry. As practical screening possibilities were very limited and the early diagnostic value of suitable techniques was uncertain, vinyl chloride workers- could not be asked to volunteer for medical examination on the grounds that this would detect early malignant disease of the liver; nor could they assume that such examinations would be beneficial to individuals in terms of preventive medical action. In the latter context, effort had to be concentrated on urgent measures to reduce exposure to vinyl chloride, a task which was being energetically tackled by our technical colleagues. Nevertheless, there were many arguments in favour ofinviting vinyl chloride workers to attend site medical centres to participate in a standard medical examination programme: (1) Opportunity for personal discussion. (2) Establish prevalence of disease. (3) Establish prevalence and significance of liver dysfunction. (4) Correlate positive findings. (5) Identify possibly susceptible individuals. (6) Compare findings in VC workers and controls. (7) Assess feasibility and value of medical surveillance. (8) Establish data base for further studies. For these reasons it was decided to carry out an initial clinical survey on all sites where VC and PVC were produced, based as far as possible on the application of standard procedures to both vinyl chloride workers and controls. A programme of action was discussed and agreed with medical representatives of Government and Trade Union agencies and it was accepted that one of the main objectives was to gather clinical and epidemiological data to provide a reasonable foundation for future decisions concerning regular medical surveillance, The survey population was divided as follows: Vinyl chloride workers Group 1 - all autoclave floor workers, vinyl chloride monomer (VCM> production workers with five or more years' service; Group 2-vinyl chloride monomer production workers with less than five years' service, all other VCM/PVC production workers. Controls - workers from same sites with no history of VC exposure. A standard medical examination procedure was adopted: Initial examination comprising medical history (questionnaire), physical examination, biochemical tests (SGOT, SGPT, GGTP, alkaline phosphatase, bilirubin), platelet count. urinalysis. Follow up of abnormal findings, with repeat biochemical tests and platelet count, and persisting abnormalities referred to consultant for specialist investigation, The programme was introduced simultaneously on the six production sites and the employees concerned were informed that it was not an individual screening test, but a joint investigation to provide data that would help to establish future medical policy. It was also explained that any individuals with suspicious findings, notably persistently abnormal test results, would be referred for appropriate specialist investigation by arrangement with their family doctors, Due to a variety of reasons, not least the problem of interpreting the significance of borderline 308 Proc. roy. Soc. Med. Volume 69 April 1976 51 abnormalities and workload difficulties ex interest in view of the apparent rarity of AOL in i perienced by both medical advisers on sites and the cases of liver angiosarcoma that have been j consultants and laboratory staff in National reported in the literature. The routine urinalyses Health Service hospitals, the programme has have revealed no relevant abnormalities. taken longer than expected and is still incomplete. Hence interim findings only can be presented at Tentative Conclusions this stage and no firm conclusions can be drawn Abnormal liver function test findings were until all the facts have been elicited and the mass relatively common in both vinyl chloride workers of data obtained has been appropriately analysed. (12.5%) and controls (16.5%) even though So far, 1357 vinyl chloride workers and 429 results had to fall well outside (2 or 3 standard controls have been examined. The examinations deviations) the normal range in order to be of vinyl chloride workers include 882 from classified as abnormal. Repeat testing revealed Group 1 (representing an average response rate of persistent abnormalities in one third of the vinyl 80%) and 475 from Group 2 (in which the pro chloride workers in whom the initial findings portion volunteering for examination is lower). were abnormal and these 56 men were referred Initial liver function test abnormalities have been for further investigation. Comparable data for found in 12.5% of the vinyl chloride workers and the controls are at present unavailable. 16.5% of the controls. Repeat tests on vinyl ' If less stringent criteria of abnormality had chloride workers with abnormal findings have been adopted, the number of individuals for revealed persistent abnormalities in about one- retesting would have been considerably greater third of the individuals concerned (56 men, 4.1 % and the effect this might have had on specialist of the original group). No comparable data for investigation and disease detection is a matter the controls can be presented at this stage. for conjecture. The definition of abnormality is The 56 vinyl chloride workers with persistently critical in this context and merits further con abnormal liver function test results have been sideration and study if the correct balance is to be referred to consultants at local NHS hospitals achieved. for further investigation. These investigations In view of the findings to date, it is not sur have not revealed any cases of angiosarcoma and prising that opinions of working group members the consultants concerned have already attributed about the value of periodic liver function tests in many of the persistent abnormalities to patho vinyl chloride workers are divided. No obvious logical conditions unrelated to vinyl chloride liver disease due to vinyl chloride exposure has exposure. At present, the causes of liver dysfunc been identified so far, but evidence of non- tion remain uncertain in about one third of these cirrhotic fibrosis has been found in some cases 56 cases, where precise diagnosis rests largely on and until the results of blind interpretation of the the final conclusions reached by expert patho liver biopsy specimens become available no firm logists who are studying relevant liver biopsy opinions can be expressed about the presence or specimens. To put these interim results in per absence of any specific pathology related to vinyl spective, it should be noted that almost all the chloride in the survey population. The procedure men in the latter group remain in full employment, has enabled individuals with persistent liver although many of them have been transferred to dysfunction to be detected and removed from work involving no further exposure to vinyl exposure to vinyl chloride, and some doctors chloride in case their liver dysfunction renders propose to continue regular liver function tests them unduly susceptible to potentially hepato- for this and other reasons, such as the need to toxic agents. assess sequential changes. On other sites, the While this survey was in progress, previously yield of significant clinical findings has been so established procedures for the detection of AOL low in comparison with all the difficulties en and related conditions among vinyl chloride countered that it is considered liver function workers remained in force and 2 new cases of tests should only be applied on a discretionary AOL have been diagnosed. The survey provided basis in future. In this connexion, it is argued that, an opportunity to assess the prevalence of in order to be effective, the tests used should: (a) Raynaud's phenomenon among controls on yield positive findings at an early stage of disease; three sites and comparisons with findings .in vinyl (b) produce few false positive and negative chloride workers suggest that the condition may results, and (c) ideally, be able to differentiate be equally prevalent in the two groups. However, between pathological conditions due to vinyl no standard diagnostic criteria were applied and chloride and those due to other causes, such as the prevalence of the condition varied widely alcohol. between sites. No association has been observed It is also argued that continued application of a between Raynaud's phenomenon and liver battery of tests to vinyl chloride workers is likely function abnormalities in individuals, which is of to cause considerable alarm and disquiet if the results serve only to ra fusion. At the present non of structural rath in the liver is likely ' screening purposes, ar is now being focused ultrasonography as a technique for the per chloride workers. In conclusion, alt complete, it has alre value for planning intended. From now concentrate effort on studies that are desi specific hypotheses, fact that the stnnge now in force are e: eliminate, any risks exposure to vinyl chi discussion Dr A John Robertson ( for those whose tests, were abnormal. A ma refused life insurance tion tests, Taking a p. suspended because o could then be refused he did not have a set ployer would not pay Dr B W Duck repl abnormal liver rimer consultants for doctors were sept of the findings the cc cerned decided whet work was indicated advised accordingly, decide whether to acc only one man had r the rest had been tra no loss of pay. Dr Robert Murray ( real problem which 1 Employment Protec in Parliament. This preventive reasons, absorption, the rigt of lay-off. The mo diagnosis or the exposure, the great' system to cover the which was not corr In large organizati the individual, wit work not involving this might be diffici Dr L Magoa (MR< that in Dr Duck between data on ' ucc 107033 50 51 Section ofOccupational Medicine 309 in results serve only to raise further doubt and con ien fusion. At the present time, it appears that detec ses tion of structural rather than functional changes in the liver is likely to be more rewarding for screening purposes, and for this reason attention is now being focused on evaluation of grey-scale ere ultrasonography as an acceptable, noninvasive ers technique for the periodic examination of vinyl igh chloride workers. ird In conclusion, although the survey is in be complete, it has already yielded information of led i value for planning purposes, as originally nyl intended. From now on, it seems advisable to ngs concentrate effort on smaller and more detailed red studies that are designed especially to evaluate for specific hypotheses, particularly in view of the vinyl monomer pollution had decreased rapidly over the past few years fas in the plant desc ribed by Mr A W Barnes) and data on those employed in a factory where (as in Dr Anne Walker's cases) even in recent years acute narcotic episodes had occurred. This lack of distinction might completely distort Dr Duck's statistical evaluation of clinical data obtained during the survey. Dr B W Duck replied that Dr Magos' point was well taken. However, as explained in the text, the paper presented interim findings from which no firm con clusions could be drawn. When all the data were complete it was envisaged that the industrial doctors and their consultant colleagues would publish the results obtained from individual factories. tad for iter list :ter t is on> be ous has onises the irm or nyl ure iver om ors jsts . to the so enion ary tat, (a) se; :ive ate nyl i as )f a ely fact that the stringent environmental standards now in force are expected to minimize, if not i eliminate, any risks to health associated with exposure to vinyl chloride. Mr H F Henning (Health and Safety Executive, 403-405 Edgware Road, London NW26LN) discussion Dr A John Robertson (Liverpool) asked what was done for those whose tests, under the surveillance scheme, i were abnormal. A man had been mentioned who was refused life insurance because of abnormal liver func, non tests. Taking a parallel with lead, a man could be suspended because of a raised blood lead level, and could then be refused industrial compensation because he did not have a scheduled disease, and yet the em ployer would not pay his wages. Dr B W Duck replied that men with persistently abnormal liver function test results were referred to consultants for further investigation and their family doctors were kept informed throughout. In the light of the findings the consultants and other doctors con cerned decided whether removal from vinyl chloride work was indicated and the men in question were advised accordingly. It was then left to the men to decide whether to accept or reject this advice. To date, only one man had rejected such medical advice and the rest had been transferred to alternative work with no loss of pay. Dr Robert Murray (Sudbury) said that this was a very real problem which it was proposed to deal with in the Employment Protection Bill currently under discussion in Parliament. This would give to a man laid off for preventive reasons, because he showed early signs of absorption, the right to full wages during the period of lay-off. The more sensitive the methods of early diagnosis or the more stringent the standards of exposure, the greater would be the need to have some system to cover the no man's land between absorption which was not compensatable and disease which was. In large organizations it was usually easy to transfer the individual, without loss of money, to alternative work not involving exposure, but in smaller industries this might be difficult or impossible. Dr L Magos ( V1RC Toxicology Unit, Carshalton) said that in Dr Duck's paper no distinction was made Environmental Monitoring It is a common misconception that environmental monitoring is easy, just a matter of collecting a sample, analysing it and getting a figure. Environ mental monitoring is never easy and when an industry is faced with a sudden and substantial tightening of the standard to be applied there are equally suddenly many questions to be asked and answered. In addition, when industry and Govern ment have to write a Code of Practice before the event, and therefore without the benefit of experi ence or hindsight, there are many more questions. Some of these are discussed in this paper. Instrumental Techniques When the threshold limit value (TLV) for vinyl chloride monomer (VCM) was 200 parts/10*. that is before 1974, the instrumentation used for monitoring was relatively fairly crude and in sensitive. One common instrument had a lower response at about 200 parts/10* so that a nil reading was taken to indicate a concentration below 200 parts/10*, a very convenient situation. Even the chemical indicator tubes were not designed to show concentrations below 100 parts/ 10*. With the introduction in early 1974 of the new standard of 25 parts/10* (time weighted average) and 50 parts/10* (ceiling value) other existing instrumental techniques had to be adopted for use in the VCM atmospheres. Unfortunately some of the equipment which had been designed for laboratory use was not flame proof and so could not be installed directly in factory workplaces. However, many of the difficulties were overcome and all the VCM and PVC manufacturing plants between data on workers from a factory where poly have now installed what we originally called r*r <** Hi? 157; * I i : ijrf'.i 'i k* i 310 Proc. roy. Soc. Med. Volume 69 April 1976 52 continuous monitoring but which is more correctly termed automatic sequential fixed point sampling. This is supplemented where necessary by short-term sampling for investigations or for checks on equipment and by long-term personal sampling to show the work people's actual exposure over long periods, e.g. four or eight hours. Presentation ofResults The Code of Practice requires the results to be available to the workforce and for summaries to be posted in work rooms. Each fixed point monitoring system takes a sample once per minute and therefore provides nearly 500 readings per shift so that trying to decide beforehand how the results should be summarized and presented was a major problem because there was little previous experience of monitoring, and recording the results of monitoring, on such a scale. One way of presenting the results would be to take an overall average. This has recently been done and figures provided by the industry show that the average concentration in the UK. factories had been reduced in a matter of months from 24 to 6 parts/10*. Recent figures from some of the plants even show long-term averages of about 2 parts/10*. This suggests enormous progress, as indeed it is, and compares favourably with aver ages published by other countries. However, an overall average such as this is influenced very considerably by selection of the sampling sites and by the frequency of sampling, two aspects which are completely lost in this method of presentation and of course it offers little of use in the protection of the worker, which is the main objective of monitoring. Influence ofPeaks An average over any period of time is influenced very considerably by peaks. For example, in a 20 point system sampling every minute a single peak of 600 parts/10* due to a transient leak from nearby plant would add 25 parts/10* to the shift average. In the UK we feel that it is essential to record these peaks, because they indicate escapes of VCM due perhaps to defective plant or perhaps to incorrect work practice, both matters which ought to be remedied. If the monitoring points are selected to provide a balance between operator work stations and areas where leaks may occur then we must expect to obtain some high readings. These occasions will generally be investigated and will therefore play an important role in the long-term reduction of atmospheric concentration of VCM, but in the short term they make the picture look bad, both by their presence as peaks and by their contribution to the overall shift average. There is-of course no suggestion that any operator is necessarily exposed to such peaks or to such a raised average, since many of the peaks may have occurred in specially selected areas where no person works regularly or the operator may have known about the situation and worn a respirator during that period. Influence ofSampling Frequency The frequency of sampling can also have an in fluence on the picture. Let us assume that some of the sampling points have been chosen to pick up leaks from the plant so that, say, 10% of the readings are above the ceiling value of 50 parts/ 10*. In a multi-point monitoring system sampling every minute this means that 48 readings per shift for that system alone will be above the ceiling value. Sampling at the minimum frequency required by the Code of Practice, i.e, once per shift, would give on average one high reading in each work area every tenth shift. Sampling at the minimum frequency required by the US standard, i.e. once per month, would give on average one high reading in each work area every tenth month. We see therefore that frequent static sampling at carefully chosen points can provide much useful information but it does not necessarily tell us exactly what concentrations the work people are actually exposed to. This can be shown best by personal monitoring which is normally done at less frequent intervals because it is time-consum ing for the testing staff and somewhat restrictive for the operator wearing the equipment. Never theless this is an extremely useful supplement to the general workroom monitoring. Other Problems I have said nothing in this short paper about preservation of records, which provides many problems not previously encountered in industry, nor about atmospheric monitoring in the PVC user industry where general atmospheric con centrations are less than 5 parts/10* and usually less than 2 parts/10*. with a few known and controllable problem areas. In short, we in the UK believe that atmospheric monitoring should be used to provide the maxi mum amount of information. This means that the monitoring schemes incorporating extensive multi-point systems can provide (a) useful information on deficiencies in plant or in operat ing procedures, (b) information with which to demonstrate progressive improvements in our aim to reduce exposure to near zero, (e) information on personal operator exposure which can be kept for future reference. Unfortunately in the short term it also provides much ammunition for our critics. This, however, is a small price to pay for the long-term benefits which we know will accrue from our efforts. 11 Acanthosis Nigric and Eruptive Xan R W Emmerson t (Royal Berkshire BAH, man aged History: 1972: F in axillae and gre and neck had b and pigmented, had appeared o had recently bee was controlled < tions into the c were negative ai of a large fatty 1 Mr -* & UCC 107035