Document MMgaBxJ0o4pLkVErogRrVOJ67

FILE NAME: Flooring (FLR) DATE: 1982 DOC#: FLR010 DOCUMENT DESCRIPTION: Journal Article - Indoor Airborne Asbestos Pollution: From the Ceiling to the Floor 'jrniinioum value during that cycle (Fig. dined to about 20 to 22C before there 1C7. The cycles of Vo, were closely was any regulation. Thereafter, their followed by oscillations in 7lb. with the metabolic response to a decrease in 7'., peaks in V0, slightly preceding the peaks was qualitatively similar to that of birds in Tth (Fig. 1C). We assume that the and mammals. How-ever, instead of cycles in V0, and T,h coincide with cy maintaining 7b constant, there was an cles of activity in the thoracic (light oscillation over a range of 3 to 4C with muscles. The 7ab values sometimes the frequency but not the amplitude of showed similar, but smaller oscillations the oscillations increasing with AT. The which lagged behind those of the thorax. beetles appear to have a definite set Our experiments usually lasted 2 to 3 hours, and during this interval the bee tles were almost completely motionless and r th was continuously elevated. We did not determine the maximum duration of the homeothermic response of Mega soma. As long as 7b remains constant, heat Fig. 2. A comparison of the relation of massspecific VG, to AT in scarab beetles and heteromyid rodents of similar size. The curves for rodents are the regressions of their euthermic energy metabolism below the thermal neutral zone (S). The points for the beetles are the means of 16 or more measurements taken while rth was constant at a given Ta. point below which they " defend" Tb. The greater the AT, the more rapid the heat loss and the more rapid the oscilla tions in V0, and 7b. K. R. M organ G. A. Bartholomew Department o f Biology, University o f California, production is necessarily equal to heat Los Angeles 90024 loss. Heat loss is proportional to the difference between Tb and Ta (IT): in the the pattern we observed in the labora tory at Ta below 20 to 22C; that is, that References and Notes case of endothermic insects Tb refers to r th. A mammal with a Tb of 37C at a Ta of 23C should have the same heat loss as a Megasoma of the same mass with a Tb of 27C at a Ta of 13C. (This parity requires that the mammal and beetle have similar thermal conductances.) It is instructive to compare the Vo. (which is proportional to heat production) of a homeothermic Megasoma with that of placental mammals of similar mass expe riencing the same AT (Fig. 2). For com parative purposes we have selected two small rodents whose metabolic rates were measured with an open-flow respirometry system smiiiar to that used for Megasoma (8). The rodents, a kangaroo mouse (Microdipodops pallidas) and a pocket mouse (Perognathus californi- variation in heat production rather than variation in heat loss to the abdomen is the primary mechanism of control of Tb. Megasoma is certainly capable of sup porting normal activity levels by regulat ing a high 7b at Ta below 20 to 22C (Ta values as low as 15C have been record ed on Barro Colorado Island), but we do not know whether the beetles could fuel the metabolic increase required, should Ta remain low for more than a few hours. To our knowledge, among insects, a homeothermic metabolic response to de creases in Ta in the absence of locomotor activity has only been reported in worker honey bees (9) and in incubating queen bumble bees (10). The homeothermic responses of the beetles reported here were not as fine-tuned as those of birds 1. B. Heinrich, Science 185, 747 (1974); M. L. May. Anna. Rev. Entomoi, 24, 313 (1979); B. Heinrich. Insect Thermoregulation (Wiley. New York, 1981). 2. A. Krogh and E. Zeuthen. J. Exp. Biol. 18, I (19411. 3. G. A. Bartholomew and T. M. Casey. Science 195. 882 (1977); G. A. Bartholomew and B. Heinrich. J. Exp. Biol. 73. 65 (1978). 4. K. R. Morgan, unpublished data. 5. G. A. Bartholomew, D. Vleck. C. M. Vleck. J. Exp. Bioi. 90. 17 (1981). 6. Studies were carried out at the Barro Colorado Station of the Smithsonian Tropical Research Institute in the Republic of Panama. 7. G. A. Bartholomew and T, M. Casey. J. Therm. Biol. 2. 173 (1977). 8. V. A. Tucker. J. Cell. Comp. Physiol. 65. 393 (1965): J. H. Brown and G. A. Bartholomew. Ecology 50. 705 11969), 9. A. Heusner and M. Roth, C. R. Acad. Sci. 256, 284 11963); A. Heusner and T. Stussi. Insectes Soc. 11, 239 (1964); E. E. Southwick and J. N. Mugaas. Comp. Biochem. Physiol. 40. 935 [197]); K. Cavbill and S. Lustic, ibid. 55A. 355 (1976). 10. B. Heinrich. J. Comp. Physiol. 88, 129 (1974). 11. Supported bv NSF grants DEB 80-23917 (K.R;M.) and DF.B 81-03513 (G.A.B.). cus) have lower V0, than Megasoma of and/mammals. In the beetles, Tb de- 5 February 1982; revised 13 April 1982 the same mass when AT is greater than 5 r/ to 7C (that is, at Ta below the thermal / neutral zone of the mammais). Below 1 / thermoneutraiity. the mass-specific ther Indoor Airborne Asbestos Pollution: mal conductances of the mammals did not change with 7a, whereas the mass- From the Ceiling and the Floor specific thermal conductances of the beetles decreased linearly with TV For Abstract. Electron microscopic measurements o f the concentrations o f airborne example, the conductance of an 11-g asbestos were carried out inside and outside an office building having ceilings beetle was 0.42 ml of 0 2 per gram per sprayed with a crocidoiite-containing material and floors covered with vinyl- hour per degree Celsius at a Ta of 26C chrysotile tiles. Under normal conditions in this building, constructed 0 years ago, but was only 0.30 ml of 0 - per gram per the two asbestos-containing materials released fibers into the air. This is the first hour per degree Celsius at a Ta of 8C. measurement o f elevated (up to 170 nanograms per cubic meter) concentrations o f The decrease was apparently caused by indoor airborne asbestos associated with the weathering o f asbestos floor tiles a decline in Tab from 27.1 to 15.5C during their service life. Asbestos flooring is used in a hu ge number o f buildings and while Tlh remained constant. Conse represents the third largest use o f asbestos fibers in the United States and in Europe, quently, heat loss from the abdomen ranking after roofing and asbestos-cement pipe. decreased with decreasing Ta. The dearth o f inform ation on the natu T h e p o te n tia l hazard arising from ex tos-containing materials in school build ral history of Megasoma elephas makes posure to airborne asbestos inside build ings (1). The Conseil Suprieur d'Hy- ecological interpretation of the homeo ings sprayed with asbestos-containing gine Publique de France has recom thermic metabolic response problematic. materials is currently the subject of mended controlling the concentrations of We assume that when 7b is regulated much concern. The Environmental Pro airborne asbestos inside buildings above Ta during terrestrial activity, the tection Agency has undertaken a large- sprayed with asbestos (2). Since 1975, pattern of Tb regulation is the same as scale program to control friable asbes analytical facilities for the measurement ecre- u> 3 . ' of asbestos, with an analytical transmis sion electron microscope (ATEM), have been available in our laboratory (5). Thus far, 493 air samples from 122 build ings have been analyzed. In December 1980, we were asked to monitor the airborne asbestos within a building, the ceilings of which had been sprayed in 1970. In this building, an additional and unexpected emission source of airborne asbestos was discovered: the asbestos floor tiles. The building, located 20 km south of Paris, was occupied by an engineering company that was marketing optimized electronic computer systems. The 300 workers were all white-collar employ ees, working under clean conditions in side offices, graphic studios, and work shops where electronic machines were being tested. The six floors (900 n r each) showed similar architectural configura tions with peripheral workrooms and a central core occupied by elevators, stairs, corridors, and blind storerooms. Measurements of the indoor airborne asbestos pollution were requested be cause of the presence on the corridors' Ceilings of a suspicious, friable, blue material that had been sprayed on. This material was located in an open plenum where it could be eroded by the circulat ing return air. Another possible cause of deterioration was the fact that electri cians sometimes operated on the plenum electric lines. We took five bulk samples by pene trating the total depth of the sprayed material with large-mouth containers in five randomly predetermined locations. Analysis of their fiber content with the polarized light microscope (PLM) re vealed that they were almost pure crocidolite (4, 5). Neither man-made miner al fibers nor chrysotile were detected. Further analysis with the ATEM (Fig. 1, a and A) did not reveal the presence of fine chrysotile fibers unresolved by the PLM. Air was sampled simultaneously at four indoor sites and on the roof where fresh air entered the air-conditioning sys tem. Air-sampling units had been operat ing for five consecutive working days but only during building activity periods. Air sampling during activity periods is of primary importance, since it has been observed that the concentrations of in door airborne asbestos measured during periods of active use are much higher than those measured during nonuse peri ods (.?). It is believed that human activity not only contributes to the degradation of materials but is also a factor in the fragmentation and secondary dispersal of settled dust t6). ii t k t r Airborne asbestos measured outside the building showed the usual features encountered in the urban area of Paris and its suburbs. Only chrysotile was encountered, with a mass concentration of 0.1 ng/m3. Earlier measurements of 249 air samples from 35 locations in this area revealed a homogeneous back ground of ambient airborne chrysotile. Concentrations were in the range of 0.1 to 9 ng/m3 (median. 0.4 ng/nrr1), with 95 percent below 3 ng'm3. Commercial amphibole-type asbestos fibers have not as yet been detected in significant quanti ties in urban air samples. Inside the building, both crocidolite and chrysotile were present in the air samples (Fig. IB). Concentrations were 0.2, 0.5, 0.9, and 33 ng/m3 for crocidolite and 8, 21, 25, and 170 ng/m3 for chryso tile at sites 1, 2, 3, and 4, respectively. Sites 1, 2, and 3 were corridors; site 4 was a workshop including part of a corri dor. The concentrations rose from site I to site 4 in the same order for crocidolite as for chrysotile. Obviously, the airborne crocidolite fi bers within the building were released from the crocidolite-containing material sprayed on the ceilings. The concentra tions can be compared with those mea sured earlier inside a series of 36 build ings sprayed with a material containing amphibole-type asbestos, generally amosite or crocidolite (Fig. 2). Fifty percent of such buildings showed detectable con centrations of amphiboie-type asbestos fibers in the air: only 22 percent of the buildings showed concentrations in ex cess of 33 ng nv. which was the maxi mum concentration of amphibole-type asbestos fibers in the air of the building reported here. Bearing in mind these reference data and because the architec- Fig. 1. C haracterization with the analytical transm ission electron m icroscope |n conventional transm ission electron m icroscope lined with an x-ray energy -dispersit e spectrom eter I l-il)Si| of asbestos libers isolated from the material sprayed on the ceilings .aid A), an ait sample (II). and a vinyl floor tile Ic and C). The FIDS spectra of individual libers are typical of crocidolite (a) and chrysotile t o . Fibers of both asbestos types were encountered in the air sam ples III). turaf. configuration of the building was not favorable, we recommended that some corrective action be taken (7) to prevent further crocidolite fibers from becoming airborne. The elevated concentrations of indoor airborne chrysotile were very surprising in view of the absence of detectable chrysotile in the sprayed material. A further warning sign was the shortness of the airborne chrysotile fibers; no fiber longer than 3 p,m was encountered on the membrane filters. Further investigations were undertaken to discover the origin of such fibers. Inquiries revealed no use of asbestos products by the workers. The air-conditioning system was carefully in vestigated; no asbestos-containing mate rial was discovered. Water used to dampen the conditioned air was ana lyzed with the ATEM; no chrysotile fi ber was detected. The only material in the building that was found to contain chrysotile fibers was the vinyl floor tile. The fiber content of a floor tile was analyzed with the ATEM and showed very abundant chrysotile fibers (Fig. 1, c and C). The owner of the building con firmed that' the 5400 n r of floor were covered with asbestos vinyl tiles, These tiles were black and showed a decorative relief on their surface. Damage to some tiles was clearly apparent (Fig. 3). In the absence of any other explanation, we concluded that the short chrysotile fibers present in the air of the building had escaped from the vinyl matrix of the floor tiles. The fact that the highest con centrations were measured in the work shop on the third floor, where the activi ty was greatest, reinforced our conclu sions. It might be hypothesized that, in this workshop, breakdown forces such as walking, scraping, and machine scrub bing were higher than in other places. High activity might also be an explana tion for the higher concentration of air borne crocidolite at this site. The compa ny that occupies this building now in tends to cover the asbestos floor tiles with another flooring material. It is well known that the building in dustry is the primary consumer of asbes tos products, such as asbestos-cement pipes, asbestos-cement sheets for roof ing and cladding, asbestos vinyl and as phalt floor tiles, insulation products, spe cial-purpose decorative textiles, and as bestos-coating and paint compounds (0. The interest of environmentalists in posriMe indoor airborne asbestos pollution caused by (fig Weathering of asbestoscontaining materials began in the I970's. f onsnJerable attention has been devoted 1o buildings insulated with sprayed as- uo Concentration (ng/m3) Fig. 2. Distribution of maximum concentra tions of airborne amphibole-type asbestos fi bers measured inside 36 buildings sprayed with a material containing amphibole-type as bestos (dashed line). Corresponding curve for chrysotile asbestos inside 58 buildings (solid line). The vertical lines indicate the maximum concentrations of airborne asbestos (Cr for crocidolite and Ch for chrysotile) fibers inside the building examined in this study. bestos, where the concentrations of in door airborne asbestos can be several orders of magnitude higher than the am bient background (i, 9). Some countries such as the United States and France have now banned the use of spray-ap plied asbestos-containing materials for insulation in buildings. It has been reported that the sanding of old asbestos floor tiles that are to be replaced is an important source of asbes tos exposure U0). To our knowledge, this report presents the first measure ment of elevated concentrations of in door airborne asbestos associated with the weathering of asbestos floor tiles during their service life. Daly et al. ill) have predicted that the average asbestos concentration in the air above an asbes tos floor in service can theoretically be increased by 80 ng/m3. Some concentra tions measured in this particular building were close to the predicted level of 80 ng/ m3. Up to now, in spite of this predic- Fig. 3. View o f the asbestos vinyl flooring in the building. Note' the toning down of the black color and of the surface relief, as well as scraping marks. lion, the presence of asbestos flooring within a building has not been eonsidered a serious source of potential indoor airborne asbestos. In the Environmental Protection Agency's control program in schools (/), the nature of the floor is not taken into consideration. In their survey of the asbestos-containing materials in 336 schools in Vermont, Novick et al. {12) did not report the presence of asbes tos floor materials. In France, up to now, our measurement program in buildings was not designed to document the pres ence or absence of asbestos floor tile. The weathering of asbestos flooring under normal use patterns can yield con centrations of indoor airborne asbestos similar to those measured in sprayed buildings (Fig. 2), which are the subject of much concern. In 1976, flooring mate rials represented about 15 percent of the total U.S. market for asbestos, making it the third largest asbestos consumer, af ter roofing and asbestos-cement pipes (8). If this first measurement is con firmed in other places and by other labo ratories. the use of asbestos flooring, a very common practice, could become an important environmental issue, P. S e b a s t ie n Laboratoire d'Etude des Particules Inhales, Direction des Affaires Sanitaires et Sociales de Paris, 44, rue Charles Mottreu, 75013 Paris, France J. B ig n o n Clinique de Pathologie Respiratoire et d 'Environnement, Unit 139 de l'Institut National de la Sant et de la Recherche Medicale, et Equipe 845 du Centre National de la Recherche Scientifique, 40, avenue de Verdun, 94010 Crteil Cedex, France M . M a rtin Ecole Centrale des Arts et Manufactures de Paris, 5 avenue Gustave Eiffel, 91420 Morangis, France References and Notes 1. Fed. Regist. 45, 61966 ( ]9K0). 2. Annual Report (Conseil Suprieur d'Hygine Publique de France, Paris, 1978). 3. P. Sebastien. M. A. Billon, G. Dufour, A. Gaudichet. G. Bonnaud, J. Bignon, Ann. N.Y. Acad. Sri. 330. 401 H979). 4. D. Lucas. T. Harwell, A, V. Rao, Document EPA 560 I3~SO-OI7A (Environmental Protection Agency. Washington, D.C., December 1980). 5. Split bulk samples were sent to (he Midwest Research Institute, Kansas City. Mo., where a PLM method was used to identify asbesros fibers on the basis of (heir optical properties and to determine the asbestos percentages within the samples by a point count method. Midwest reported that the samples contained between 75 and 80 percent crocidolite. carbonates, and oth er unidentified nonfibrous materials. 6. N. Sauver and C. M. Spooner, Document EPA 450 (Environmental Protection Agon es, W.iNnmgion. D.C.. March 1978). ", Corrective actions include ii) removal of the sprayed material: (ii) encapsulation of the mate rial bv coating it with a bridging sealant or a penetrant sealant; and liill enclosure of the material by constructing a harrier between the asbestos material and the huiklint! emironmcnt. 8. N. M. Meylan. F. H. Howard. S. S, Lunde. A. Hanchett, Ihniwirnf l.t'A .Sb(h'6-7X-OO.S lEmi- ronmental Protection Agency. Washington. D.C., August 19781. 9. W, J. Nicholson, report to the National Institute of Environmental Health Sciences under con tract l-ES-7-211.1, Research Triangle Park. N.C'., June 1978. 10. R. L. Murphy. B. W. Levine. F. J. Al Bazzaz. J. J. L.vnch. W. A. Burgess. Am. Rei . Rc^pir. l)i.\, 104. TM 11971). 11. A. R. Daly. A. J. Zupko. J. I.. Hebb. report prepared for the Asbestos Information Associa tion of North America. Washineton. 29 March 1970. 12. L. F. Novick. O. Rice. M. A. Freedman. D. Oillson. Am. .1. I'ublU H ealth 71. ' 44(1981). n . We thank Ci. Petit who pert'ormcJ all :he analy ti cal work with the electron microscope. 27 October 1981: revised 5 February 1982 York River Destratification: An Estuary-Subestuary Interaction Abstract. Destratification in the York River during hit'll sprint; tides is the result o f the interruption 'of normal two-layer estuarine flow by the advection o f relatively fresh water into the. river mouth from the Chesapeake Bay. This advection is due to the presence o f a longitudinal salinity gradient in the bay and a difference in the tidal current phase between the river und the bay. Similar behavior is seen in other subestuaries o f the Chesapeake Bay and may be common in suhesruary-estuary interactions. \\ Vertical homogeneity in subestuaries // River, (ii) This produces a reduction or of th Chesapeake Bay. which normally possibly a reversal of the pressure gradi exhibit moderate stratification, has been ent driving estuarine circulation. The shown by Haas (/) to be correlated with concomitant diminution of two-layer cir high spring tides. Identified by a surface- culation reduces the tendency toward to-bottom salinity difference of less than stratification by limiting the importation 1 per mil in contrast to normal values as of more saline bottom water, (iii) This high as 10 per mil. these episodes have permits the establishment of homogene been termed destratification events (2). ity by the unopposed action of normal For example, the lower York River be comes vertically homogeneous 3 to 4 / > days after the predicted tide height ex August 1378 ceeds 0.8 m (7). and homogeneity per sists for three or more days. These events are not correlated with changes in the flow of fresh water into the river (I ). Some of the significant consequences of destratification events in the York River include a periodic resupply of oxygen in the bottom water wdth an accompanying renewal of nutrients near the surface (3) and changes in primary productivity in cluding blooms of dinoflagellutes and other phytoplankton (4). Two theoretical discussions' of spring- F EF EF E,FE,F,EFEFE F E F E F E F E F E F E F F, neap tidally related stratification varia tions have been presented (5). Both of these models describe reductions in stratification that coincide with the oc currence of strong tidal currents and do not persist in the absence of such cur rents. This coincidence is in contrast to destratification in the lower York River, where vertical homogeneity first appears a few days after the onset of strong tidal currents and persists for several days thereafter (7, 2). A conceptual model for the onset and disappearance of vertical homogeneity in Fig. 1. Salinity data (p er mil) from the York River m outh for the periods lb throught 23 the Yoj'k River is as follows, (i) Destratificaliori'commences when spring tides exceed a critical height and relatively fresh u'ater from the Chesapeake Bay is August 1978 (A) and 25 August through Sep tem ber 1980 (B). The arrow s jn d icates the dates o f maximum spring tide; A is the dailymean of differences in salinity from I in to the bottom . Periods of ebb i/-,i and Hood l/T are advected into the mouth of the York indicated. Points indicate m easurem ents ( I I I. mixing processes enhanced by strong spring tidal currents, (iv) Destratification ceases when the decrease in tide height after spring tides halts the advection of the fresher water into the York River. (v) This allows the reestablishment of a nor mal horizontal salinity gradient, which produces the eventual reinitiation of two-layer estuarine circulation and verti cal salinity stratification. This hypothesis developed from an examination of salinity data (Fig. 1, A and B) collected during intensive studies of two destratification events that were predicted on the basis of earlier work (/, 2). The intrusion of relatively fresh wa ter. which initiated the destratification process, is indicated by the sharp down ward displacement of isohalines on 16 August 1978 and 26 August 1980. In each case, this was followed by a progressive reduction of stratification in the water column. As expected, the introduction of fresher water into the river mouth caused a reversal of the longitudinal sa linity gradient, producing a midriver sa linity maximum. This condition is illus trated in Table 1. where York River salinity values at l-m depth are shown tor the period from 0 to 3 days after the intrusion of fresher water observed on 25 August 1980 (Fig. IB). The data indi cate a reversal of the norma! longitudinal salinity gradient as far as 18 km upriver. A similar reversal was observed on sev eral occasions between 15 and 20 August 1978 (2). /T h e reversal of the longitudinal salini/ \ y gradient is also evident from the be havior of the isohaline at 23 per mil in the 1980 data (Fig. IB). The assumption is made that the salinity changes at the station are caused in large part by the advection of water of differing salinity up and down the river by tidal currents. Depressions in the isohaline, indicating the presence of fresher water, coincide with slack before ebb through 28 August, the date of highest tidal heights. After that date, the isohaline at 23 per mil shows a phase reversal. The depressions are coincident with slack before flood, indicating the reestablishment of the normal longitudinal salinity gradient. While tidal heights were increasing, there was a continuing source of fresher water. As tidal heights recede, more saline water is once again present in the river mouth. The only reasonable source for the relatively fresh water is the Chesapeake Bay. An upriver source is discounted first because the writer is introduced into the river mouth on flood tide (Fig. IB) and second because the nearest riverine source of water of comparable salinity is