Document 9JwrbeJpevpxKzJGEEv9qGR6p

TO F>OM k. I. Ardla AT Kiehard Hndaraen AT Vairaraitj at HUhlfai Stady F ^ . ^ ) M Sapta*r IS, 1969 RATS FUa ( TO teolMod aro efla of ttiw wm t*an tfca ttdimUf af Siatolga i^wt. Zb addition to to* nvn fMittvi and (pn faaitlaaatla aatLeoad in tftia wpart, than nra alia rapotrte if paaltlaaa ftoo Frioa and al|l, toto ttoa raaawaitatl an tkat aafaaaia ta rlagrl Alarida ananr dkaald to kapt bale* SO parts par allUon lnataad of $00 parfca par nllllon, Hileh la tho earrout lhraahold tlnlt Talo* of tha Anarlean Coafaranoa of Osvamnaatal Industrial tyglanlats. BHtaph bal.-pagaa 1QL-103. if/, 0 lizard taidaraon i OLI 2392 VHY riLC THIS COSYf |F YOU MUST OBTAIN IT, SStCtrV A OttNNlTl OfTKNTIOM PKIIIODi ONI VIA*. OTNIR^ or elsewhere, followed by healing after removal from the Job but with per sistent Raynaud's phenomenon. 1. Reactor Scraping This Job appears to be the greatest single factor in the precipitation of AOL. In the overwhelming majority of cases, a history of work in this Job can be found. In same few cases outside this study, AOL has been seen to oc cur in maintenance mechanics. The cleaning of lines from the reactor tanks may afford these workers occasional exposures qualitatively similar to that of reactor cleaners. 2. Compounding Operations No definitive cases of AOL were found in operations involving compounding or fabrication of the finished polymer. Neither was there undue Raynaud's phenomenon occurrence in such plants. The relatively small population Involved (l.e., 557 individuals) does not prove, of course, that the disease never occurs In this operation. The one questionable x-ray (Dx Cat. 4) seen in this population is not unexpected in view of the common occurrence of such border line x-rays in the control population. 7. MATERIAL EXPOSURE AND AOL x1 1. Despite computer assisted caparison, no one compound or class of compounds clearly or exclusively was associated with the plants having AOL in Icomparison to plants without AOL. 2. As regards Raynaud's phenomenon, there is a possibility that exposure to vinyl chloride per se may precipitate a response. While it is understood that the exposure to vinyl chloride in such unique operations is minimal, nevertheless, the rather unexpected higher incidence of Raynaud's phenomenon in Plant G is noteworthy. If this tuns out to be the case, the iimplications for the etiology of AOL are obvious. Accordingly a close surveillance of VC monomer production population may prove valuable. G. WORK PRACTICES AND AOL 1. Recovery Phase The use of a short period for recovering unreacted monomer from the poly mer might lead to more residual monomer in the reactor (e.g., in voids of PVC 101 OLI 2393 residue on reactor walls). A study of the temperature and time characteristics of the recovery phase In several plants failed to show differences in practices between plants with AQL and those without. 2. Air Flush of Reactor Before Entry of Cleaner While operating procedures have been established by plant supervision, it appears that these are being shortcut by hourly employees resulting in in creased potential for exposure. J. Reactor Cleaning Procedures Hand scraping of reactors has been practiced in all plants except one that started operation in 1966 and which has always used solvent cleaning. Among the seven plants with AOL, all hand scraped the reactors, generally after every batch, though one of these started using water jets in 19^5 and another cleaned a portion of the reactors with water jets from 1962. Among the 17 plants without AQL, only 10 hand scraped the reactors after very batch and one of these changed to solvent cleaning in 1965- Others manually cleaned reactors every 2 to 10 batches. The plant that started opera tion in 1966 with solvent cleaning has had no cases. 1 In the two plants with questionable cases, one hand scraped the reactors after every batch and one after "several" cycles. The latter utilized solvent cleaning intermittently for a portion of the reactors in 1966. Size differences in plant populations between the "positive" and "negative" plants reduce the validity of meaningful comparisons between the two groups ss related to cleaning methods. Use of high pressure water jets and solvents for reactor cleaning greatly reduced the time that workers were inside the reactors following discharge of the batch and also their contact with materials remaining in the reactor. H. CONTROL MEASURES IN PREVENTION OF ACROOSTEOLYSIS In suggesting control methods, it would seem in order to reduce exposure to suspect materials even though the Identification of them as the causative agents is not conclusive. Decrease in the time spent scraping reactors could be accomplished by more extensive utilization of high pressure weter or sol vents in cleaning procedures. The severity of exposure of reactor cleaners to vinyl chloride and also of personnel on the charging floor should be kept at a minimum, desirably below 50 parts per million as suggested by Torkelson et al. 102 OLI 2394 rather then merely below the current threshold limit value of 500 parts per million. To assure that atmospheric concentrations are below this level, air analysis instruments of adequate sensitivity should be used. Ttxe flamnable vapor detector at most of the plants gives a positive reading only down to hOO to 800 parts per million of vinyl chloride. A more sensitive Instrument of this type is commercially available that reads to a tenth of these levels. Also a portable gas chromatograph has recently become coonercially available that has even greater sensitivity. Both of these Instruments give immediate readings of the concentration present. The current practice of venting the reactors by means of a portable blower placed an the charging floor with the vinyl chloride laden air from the reac tor being discharged into the general charging room atmosphere may result in excessive vinyl chloride concentrations in this area occupied by the reactor operators and others. Since the odor threshold is 4000 parts per million, freedom from odor does not assure safe concentration. Certainly the concen tration varies greatly depending on the enclosure, general ventilation, and the number of reactors being vented during the day. Air analysis using ade quately sensitive methods should be conducted in these areas. If vapor con centrations at locations where personnel is exposed are above 50 parts per million for any appreciable duration, consideration should be given to provi sion of an exhaust system to remove residual vinyl chloride from the reactor to the outside of the building or to a vapor recovery system. OLI 2395 105