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AtmosphericPollutionResearch2(2011)445Ͳ451 CriticalLiteratureReview
Atmospheric Pollution Research www.atmospolres.com Airborneasbestosfibresandmesotheliomainthelast20yearsin Egypt:areview
AbdelHameedA.Awad
AirPollutionDept.,NationalResearchCentre,Dokki,Giza,Egypt
ABSTRACT AsbestoshasbeenusedinEgypteversince2000–3000BCforembalmingthebodiesofEgyptianpharaohs.Little Keywords: dataisavailableonairborneasbestosfibrecountsintheoccupationalandenvironmentalsettings.Countsranged Air between 0.0–2.7f/cc and 0.007–3.0f/cc inside and outside various industrial workplace sites, respectively at Asbestos Sigwart (El–Maasara and Shoubra El–Kheima) companies in Cairo. Asbestos counts ranged between 0.0244– Mesothelioma th 0.1389f/ccinthesurroundingareasoftheORA–Egyptcompanyinthe10 ofRamadanCity,whichhasbeenshut Workplace down since 2004. Malignant pleural mesothelioma (MPM) is becoming an increasing problem in Egypt. MPM is Neighborhood related to the inhalation of asbestos fibres in low counts and is incurable when diagnosed. According to official registrydata,mostMPMcaseswerelivingclosetoasbestosproductioncompanies.Mesotheliomaincidencewas ArticleHistory: analyzedandstudiedintheavailabledataduringtheperiod1984–2005.Mesotheliomaincidencesincreasedfrom Received:08October2010 159cases during 1984–1999 to 733cases during 2000–2005. The age of the patients ranged between Revised:06February2011 17to90yearswithameanageof54years.Thesurvivalagevariedbetween6to15monthswithmediansurvival Accepted:13February2011 wasapproximately1yearfromdiagnosis.Femalesrepresenteda39%ofthecasesandmalesrepresenteda60%with maletofemaleratioofa1.7. CorrespondingAuthor: AbdelHameedA.Awad Tel:+202Ͳ23585162 Fax:+202Ͳ33370931 EͲmail:[email protected]
©Author(s)2011.ThisworkisdistributedundertheCreativeCommonsAttribution3.0License. doi:10.5094/APR.2011.051 1.Introduction Malignant mesothelioma is a rare neoplasm that could be favoredbyahereditarypredisposingfactorsuchasEhlers–Danlos Asbestosisanaturallyoccurringfamilyofmineralsformedby syndromeandMarfan’ssyndrome(Biscontietal.,2000).Genetic the combination of magnesium and silicon that have a strong predisposition to mineral fibre carcinogenesis has led to an fibrousandcrystallinestructure.Serpentineandamphibolearethe epidemic of mesothelioma in Turkey and some US families maingroupsofasbestos.Serpentineincludesonlychrysotile,while (Roushdy–Hammadyetal.,2001;Doganetal.,2006). amphibole contains amosite, actinolite, anthophyllite, crocidolite and tremolite (ATSDR, 2001). Chrysotile is the common asbestos IntheUnitedStatesthereare2500casesanddeathsperyear typeusedandaccountsfor95%oftheworld’sproduction(Smith of malignant mesothelioma which is often related to asbestos andWright,1996). exposure(Carboneetal.,2007).Mesotheliomaincidenceratesare predictedtoincreasedramaticallyindevelopingcountriesdueto Asbestos has been recognized in Egypt for a long time as it poor regulation of asbestos mining andproliferation of industrial was used by Egyptians for mummification (Abratt et al., 2004). and household utilization of asbestos (Giaccone, 2002). Industrialization utilizing asbestos started in Egypt in 1948 by Mesothelioma continues to be a global problem due to ongoing Sigwart El–Maasara Company in south Cairo, after which 14 exposuretofibresandasalegacyfrompastexposuretoasbestos, asbestosfactorieswerepresentedbytheyear2004(Allen,2006). evenincountrieswhereasbestosiscurrentlybannedorhasbeen regulated–out of use for decades (McElvenny et al., 2005). Asbestoshasbeenrecognizedasahealthhazardinindustrial Mesothelioma is an increasing problem in Egypt (Eldin and workplaces (Selikoff and Lee, 1978) and inhalation of asbestos Mourad,2003)andtheincidenceofmesotheliomaisrising(Gaafar fibrescancauseasbestosis,lungcancer,bronchogeniccarcinoma and Eldin, 2005). Epidemiological and environmental studies and mesothelioma (Hughes, 2005). Mesothelioma is a cancer regardingexposure–responserelationshipsbetweenasbestosfibre arisingfromthemesothelialcellsthatlinethepleural,pericardial counts and mesothelioma rates are lacking in Egypt. This review and peritoneal surfaces (Carbone et al., 2002). Mesothelioma aims to present the current available data of airborne asbestos occurs in selected individuals among population groups, with fibrecountsandmesotheliomacasesinthelast20yearsinEgypt. known exposure to asbestos either in the workplace or in the community.DiMariaandComba(2004)havereportedthatmost 2.Methods persons exposed to asbestos inhalation do not develop mesothelioma, whereas others are affected by mesothelioma in 2.1.Airsamplingandanalysisofasbestosfibres the absence of association with previous occupational or environmentalexposuretoasbestos. Airborne asbestos samples were taken inside and outside of different industrial workplace sites at Sigwart El Maasara and 446 Awad–AtmosphericPollutionResearch2(2011)445Ͳ451
Sigwart Shoubra El Kheima that are located in south and north occupational asbestos exposure, but all had been living near the Cairo,respectively.Asbestossampleswerecollectedfromtheair Sigwart El–Maasara Company. In the period 1989–1999, surroundingtheresidentialareasinacircularareaa0.5–7kmin 148cases of mesothelioma were diagnosed and treated at NCI, radius. Sigwart are considered the biggest asbestos–cement CairoUniversity.Femalesrepresented36.5%,withmaletofemale manufacturing companies in Egypt. Airborne asbestos samples ratio of 1.7. Residential asbestos exposure was 81.1% whereas werealsocollectedaroundORA–Egyptfactorywhichislocatedin occupationalexposurewas13.5%(Eldinetal.,2005)(Table2). the 10th of Ramadan City a60km north–east of Cairo. The ORA Egyptfactoryhasbeenshutdownsince2004. Table 1. Age and sex of patients with pleural mesothelioma during the period1984Ͳ1987(Zakariaetal.,1989) Airsampleswerecollectedonmembranefilters(0.45μmpore Age/year Male Female Total size, 25mmdiameter) mounted on an open face filter holder No % accordingtoNIOSHmethodNo7400(NIOSH,1994),foraperiod varying between 60–120minata flow rate of 5L/min. The <20Ͳ2 2 15.38 collectedsampleswerestoredinupwardpositioninsealedboxes 20Ͳ30 1 Ͳ 1 7.69 and brought to the Air Pollution Laboratory at the National 31Ͳ40 1 1 2 15.38 Research Centre for analysis. The membrane filters were made 41Ͳ50 1 3 4 30.77 transparentbymountinginimmersionoil. >50 1 3 4 30.77 Mean/age 43.25 43.55 43.46 The mounted samples were analyzed for the presence of asbestos fibres at a magnification of 400X using phase contrast rd In the first 4years of the 3 millennium (2000–2003), microscopy (Olympus, Tokyo, Japan). Asbestos fibres with 635casesofmesotheliomawerediagnosedatNCIandACH,Cairo. dimensions >5ʅm in length, <3ʅm in diameter and aspect ratio Both hospitals drain and serve most of the high risk populations 3:1 were considered for counting. A minimum of 25–50fields livingintheneighborhoodsoftheSigwartCompanies(Eldinetal., werescreenedforcountingoffibresusingWaltonBeckettreticule 2005). The median age was 53years (19–90). Females in the eye piece. Zakaria and his coworkers (1989) counted represented39.2%andyoungadultsч40yearsrepresented19.1%. asbestossamplesbyusingaCarl–ZeissKonimeter10.Thismethod Residentialexposurewasevidencedin64.7%ofcases(ShoubraEl onlycountsparticlesusingrelativelylowpoweredmicroscopyand Kheima, 35.6%, El Maasara, 23.6%, El Zeytoon 5.2% and other overlooks many of the respirable fibres and is a very indirect exposed areas 0.5%). Twentyfivepercent of the mesothelioma measureofthefibrelevel. cases came from other Cairo areas while 9.8% came from other governorates(Eldinetal.,2005)(Table2).TheNCIhospital–based AirsamplingwasmainlydonebyaresearchteamfromtheAir registryshowedanincreaseintherelativefrequencyofMPMfrom Pollution Department, National Research Centre, Egypt. A 0.47%intheyear2002to1.3%intheyear2003. minimum of 3samples were collected at each sampling site. The sampling period was between 10am and 3pm and no clear Table 2. Epidemic features of mesothelioma in Egypt during the periods patternforsamplingdays hadbeenchosen.Thecountofasbestos 1989Ͳ2003(Eldinetal.,2005) fibreswasexpressedasthenumberoffibrespercubiccentimeter (f/cc). Years Epidemicfeaturesofmesothelioma 2.2.Epidemiologicaldata Ͳ148casesofMPMwerediagnosedandtreatedatNCI,Cairo Univ.,Egypt. Information on mesothelioma cases were obtained from the ͲMedianagewas48(17Ͳ85)years National Cancer Institute (NCI) and the Abbassia Chest Hospital ͲYoungadults<40yearsrepresented29.7%. (ACH) in Cairo during the period between 1989 and 2007. Other ͲMale/female1.7 1989Ͳ1999 information on mesothelioma was extracted from the available ͲResidentialasbestosexposurewas81.1% reports and research articles. The diagnosis of malignant ͲOccupational13.5%. mesothelioma is dependent on an assessment of clinical and ͲMediandurationofexposurewas32years radiologicalfindingsinconjunctionwithpleuralfluidcytopathology Ͳ Medianoverallsurvivalwas7months. andpleuralbiopsy(Suzuki,1992). Ͳ635casesofMPMwerediagnosedatNCIandAbbasiaHospital Cairo,Egypt. The main limitations of this review were the absence of ͲMedianagewas53(19Ͳ90)years. specific procedures for mesothelioma identification and counting ͲYoungadults<40yearsrepresented19.1%. aswellasnodataavailableonthepresenceofothermesothelioma ͲFemalesrepresented39.2% types(asperitonealmesotheliomas). 2000Ͳ2003 ͲResidentialexposurewasevidencedin64.7%ofcases (ShoubraElͲkheima 2.3.Statisticalmethods 35.6%,ElMaasara23.6%,andElZytoon5.2%). Ͳ25%camefromotherCairoareasand9.8%fromother Thedifferencesbetweenairborneasbestosfibrecountsinthe governorates. different workplace sites inside and outside of asbestos plants were analyzed by t–test and Mann Whitney U test. Correlation Hussin(2007)studiedtheepidemicmesotheliomaamong487, coefficient was used to find out the correlation between the 2913, and 979 people occupationally, environmentally and numberofMPMcasesandasbestosfibrecounts. control, exposed to asbestos in Shoubra El–Kheima, north Cairo, respectively.Herecordedatotalof88MPMcases,amongthem4 3.Results cases were occupational, 83 environmental and 1 non–exposed person(Table3).MPMwasmoreprevalentintheenvironmentally 3.1.Epidemiologicalfeaturesofmesothelioma exposedgroup(83/2913,2.8%)thanintheoccupationallyexposed group(4/487,0.8%)andcontrolgroup(1/979,0.1%)(Table3).The Epidemiological features of mesothelioma in Egypt. Zakaria and controlareawasanagriculturalvillagelocatedatBanhacitya40 coworkers (1989) diagnosed 13 (9females and 4males) kmnorthoftheasbestosplant.Peoplewhoagreedtobeincluded mesotheliomapatientsbetween1984–1987whichcamefroman in the study were 979 people chosen by cluster sampling, a areaofa4.7kmradiusintheneighborhoodofSigwartEl–Maasara responserateof94%.Noneof thoseindividualshadahistory of Company,southCairo(Table1).Noneofs thecase hadahistoryof occupationalorenvironmentalexposuretoasbestosfibers. Awad–AtmosphericPollutionResearch2(2011)445Ͳ451447
. Table3.TheprevalenceofMPMcasesamongenvironmentally,occupationallyandnonͲexposedgroups indifferentareassurroundingSigwartShoubraElKheimaovertheperiod2003Ͳ2005(Hussin,2007)
No. Mesotheliomacases No.ofpopulation Area examined exposed No % Environmentallyexposed 322 109 2 913 83 14.8 ElWehdaElArabia(100m) 56 228 873 39 4.5a ManshiyatElGadida(800m) 20 000 644 17 2.6 ManshiyatElHorriya(1km) 67 832 335 8 2.4 EzbetOsman(1km) 25000 412 9 2.2 ManshiyatAbdelMoniemRaid(2km) 128215 318 6 1.9 EzbetRostom(2.5km) 24834 331 4 1.1 Occupationallyexposed487 4 0.8 NonͲexposed(control)979 1 0.1 aPч0.001 Therewasasignificantly(P<0.001)higherprevalenceofMPM 3.2. Environmental and occupational assessment of airborne casesinEl–WehdaArabiaarea(4.5%)whichlies100mawayfrom asbestosfibers theasbestoscompanycomparedtoEzbetOsmanareawhichhad the lowest prevalence (1.1%). Moreover, there was a significant Neighborhood areas in Egypt. Zakaria and coworkers (1989) positive correlation (P<0.001) between airborne asbestos fibre evaluated asbestos fibre counts in the air environment near to counts andnumberofmesotheliomacasesamongenvironmentally Sigwart–El Maasara Company in an area of a5 km radius. They exposed patients (Hussin, 2007). The mean age of patients with foundfibrecountsintherangeof0.00–5.4f/ccwiththehighest MPM was 51.3 years; 54.1±8.5years (range 39–70 years) for mean count at the Autostrade road site (4.6f/cc), located males and 49.5±7.4years (range 35–60years) for females immediatelyclosetodisposalsiteoftheasbestosplant(Table4). (Hussin,2007). Femalesandmalesrepresented61.4%and38.6% Eldinandcoworkers(2005)investigatedasbestosfibrecountsina of MPM cases respectively, diagnosed between Shoubra El– anareaofa0.5–7kmradiussurroundingtheSigwartEl–Maasara kheima,sresidents(Hussin,2007). Company.Theyfoundasbestosfibercountsintherangeof0.002– 3.02f/ccwiththehighestcount(3.02f/cc)attheAutostraderoad Evidencefromothercountries.Sheardetal.(1991)foundthatthe sampling site (Table 5). These results agree with thosereported meanageofMPMcaseswas54.1years.Themedianlatencyfrom previouslybyZakariaandcoworkers(1989).Thisobservationsare timeofasbestosexposuretodiseasedevelopmentisa32yearsand attributed to the improperly disposed asbestos wastes near the rangedfrom20toa50years(Passetal.,2005).Theshortestlag road.However,TagEldinetal.(2002)foundasbestosfibrecounts time between first exposure and death with mesothelioma was in the range of 7–13f/cc in an area of 0.5–1.5km radius from 20years for residents compared with 13years in the former SigwartEl–MaasaraCompany. workers(Berryetal.,2004).Forexposuresstartingatage30,the excessmortalityestimateisappliedtothetotalexpectedmortality Table 4. Airborne asbestos fibre counts at various locations surrounding fromage40toage79andabout70%ofsurvivorstoage30willdie SigwartElMaasara(Zakariaetal.,1989) between the ages of 40and80years in Cappadocia, Turkey f/cc (Umran,2003). Location Range mean Incidence of mesothelioma was found to be higher in North 0.21Ͳ2.5 0.21 populations living near naturally occurring asbestos than those Northwest 00 00 non–exposed.Mesotheliomaisrarebetweencohortsthatarenot Southeast(Autostraderoad) 0.42Ͳ8.3 4.6 exposedtoasbestos,butitisfrequentinworkerswhoareexposed Southwest 0.17Ͳ0.25 00 to it (Sluis–Kremer, 1991). In central Cappadocia, Turkey East 3.8Ͳ5.4 3.45 mesotheliomacaused50%ofalldeathsinthreevillages,Tuzköy, Karain, and Sarihidir. Initially, this was attributed to erionite, a Eldin (2008) evaluated airborne asbestos fibre counts in the zeolite mineral with similar properties to asbestos, however, surrounding area of Sigwart El–Maasara after asbestos was detailedepidemiologicalinvestigationshowedthaterionitecauses banned.Shefoundasbestosfibrecountsintherangeof0.0044– mesothelioma mostly in families with a genetic predisposition 0.358f/ccwiththehighestcount(0.358f/cc)detectedatthemain (Umran, 2003). There was statistically significant interaction gatesamplingsite.Moreover,shefoundairborneasbestosinlower between asbestos exposure, mesothelioma and sex (Reid et al., count(0.1407f/cc),attheAutostraderoadsamplingsite,thanthe 2007). The rate of mesothelioma is higher in males and those count found (3.02f/cc) in the year 2005 (Table 5). This was ш15yearsofageatfirstexposure,butwomenhadasteeperdose– attributed to asbestos wastes which have been covered by responsecurvethanmen;howevertheirriskwaslowerthanthat constructionmaterialsandnomorewastewasbeingdisposedon for men (Reid et al., 2007). Reid et al. (2008) concluded that the roadside. Surprisingly, asbestos fibres were recorded at El women who were former residents of Wittenoom, Western Maadiarea(a7kmnorthofElMaasaraCompany)atmeanvalues Australia, exposed to asbestos in their environment or in their of 0.05f/cc and 0.0044/f.cc in the years 2004 and 2008, houses, had excess cancer mortality including mesothelioma respectively. This was attributed to the fact that asbestos fibres compared with the Western Australian female population. can travel toconsiderable distances owing totheir aerodynamic Madkouretal.(2009)attributedthepredominanceofMPMcases properties without mechanical breakdown. Moreover, chrysotile betweenfemalesinthevicinityofSigwartCompany(ShoubraEl– fibresmaysplitintofibrilsthatareeasilyreleasedandtransported Kheima)totheirlongdurationofresidency. intheatmospherebywindandhumanactivities. 448 Awad–AtmosphericPollutionResearch2(2011)445Ͳ451
Table5.Airborneasbestosfibrecountsintheresidentialareassurrounding disposedofinlandfillswithspecialprecautions,butwerethrown theSigwartElMaasara improperlynearthefactory. f/cc Table7.Themeancountsofairborneasbestosfibresatthebordersofthe Location Eldinetal.(2005) Eldin(2008) ORAͲEgyptCompanyin10thofRamadancity mean mean Location f/cc ElͲMaadi(~5kmnorth) 0.002 0.0044 East 0.0244 HadaykHelwan(100msouth) 0.02 0.069 North 0.069 ElMaasara(100mnorth) 0.062 0.0887 West 0.1318 ElͲMaasara(themaingate) 0.057 0.358 South 0.1389 Autostrade 3.02 0.1407 East,25mofthefactorywall 0.058 Occupational assessment of airborne asbestos fibres in Egypt. Fewstudieshavebeencarriedouttodetermineairborneasbestos Hussin (2007) evaluated airborne asbestos fibres at the fibre counts in the occupational environments. The highest surrounding residential areas in a0.5–2.5km radius, at Sigwart asbestos fibre count was found at the disposal site (2.79f/cc), ShoubraEl–Kheima,northCairo.Thefibrecountsrangedbetween outsidetheworkingenvironmentofSigwartElMaasaraCompany 0.021to2.6f/cc, and the counts decreased downwind as the (Table 8). Significant differences (P<0.001) were found between distanceincreasedfromthecompany.TheresidentsatAlWehda asbestosfibrecountsatthedisposalsitesandothersites(Table8). Al Arabia (100m away) were exposed to higher fiber count Thedisposalsitesatbothcompanieswereuncoveredandasbestos (2.6f/cc) compared with the other residential areas surrounding was exposed to mechanical and environmental factors. Asbestos theCompany(Table6). fibrecountsdecreasedfrom0.16f/ccjustoutsidetheproduction hall (El Maasara Company) to 0.05f/cc at the nearby residential Table 6. The mean counts of airborne asbestos fibres in the surrounding homes. It was reported that (Anonymous, 2002; Hussin, 2007) areasclosetotheSigwartShoubraElͲKheimaCompany(Hussin2007) airborne asbestos mean fibre counts were 0.983f/cc/0.76f/cc; 0.313f/cc/0.239f/ccand0.0732f/cc/0.183f/ccatmilling,cutting f/cc Location andstoragehalls,respectively(Table8).Thedifferencesbetween Mean SD fibre counts may be attributed to pollution mitigation measures ElWehdaElArabia 2.16a 0.16 and stronger legislative measures taken to reduce the asbestos ManshiyatElGadida 0.04 0.01 fibreemissions. ManshiyatElHorriya 0.021 0.0005 EzbetOsman 0.021 0.002 Data from other countries. Many studies have revealed that asbestosfibrecountswere1x10–4f/ccinruralareas(NRC,1984), ManshiyatAbdelMoniemRaid 0.025 0.004 1x10–4–1x10–3f/cc in urban areas (Commins, 1985) in USA and EzbetRostom 0.021 0.003 2.2x10–2,8x10–3 and 6x10–3f/cc at 300m; 700m and 1000m aP<0.01,SD=standarddeviation downwind distances of asbestos plants, respectively, in Germany (Marfels et al., 1984). In India, Ansari et al. (2007) analyzed AsbestosfibrecountsatthebordersoftheORA–Egyptfactory 15airborneasbestossamplesthatwerecollectedfromasbestos– locatedinthe10thofRamadanCity,north–eastCairoareshownin cementmanufacturingplants.Theyfoundasbestosfibrecountsat Table7.TheORA–Egyptfactoryhasbeenshutdownsincetheyear meanvaluesof0.0797f/cc,0.05 f/ccand0.078f/ccatingredient 2004. The mean counts of asbestos fibres ranged from feeding,sheetproducingandfibregodownsites,respectively.Also, 0.024to0.1389f/cc with the greatest count found in the south Ansarietal.(2010)collectedandanalyzedatotalof24airasbestos side (along the prevailing wind direction). A lot of manufactured samples at three different plants of an asbestos cement roofing cement–asbestos pipes have been exposed to the air where sheet manufacturing industry located in North India, by phase weather and wind action help release fibres and fibrils into the contrast and polarized light microscopy. They found chrysotile atmosphere. In addition, asbestos wastes were not properly asbestosfibersinaverageconcentrationsrangingbetween0.036– 0.148f/cc(ameanvalueof0.075±0.034f/cc). Table8.ThecountsofairborneasbestosfibresindifferentoccupationalsitesatSigwartCompanies SigwartElͲMaasraa SigwartShoubraElͲKhiemab,c Workplacesite Rangef/cc Meanf/cc Rangef/cc Meanf/cc Indoorworkingenvironment Preparationunit 0.38Ͳ0.4 0.68 n.m. n.m. Productionunit 0.086Ͳ 0.78 0.21 0.256Ͳ2.7 0.76/0.98c Machine 0.07Ͳ0.4 0.135 0.07Ͳ0.405 0.25 Wettinganddryingarea 0.04Ͳ0.16 0.1 n.m. n.m. Cutting n.m. n.m. 0.074Ͳ0.387 0.239/1.00c Store 0.05Ͳ0.7 0.3 0.05Ͳ0.6 0.183/0.073c Office 0.3Ͳ0.65 0.445 n.m. 0.126 Outsideworkingenvironment Entrancegate 0.04Ͳ0.232 0.102 0.04Ͳ0.18 0.007 Outsideofproductionhall 0.1Ͳ 0.23 0.16 n.m. 0.92 Disposalarea 1.8Ͳ3 2.79d 0.231Ͳ3 2.33d Nearbyresidentialarea 0.007Ͳ 0.08 0.05 0.05Ͳ1.37 n.m. a(Nasralla1996),b(Hussin2007),c(Anonymous2002),dP<0.001,n.m.:notmeasured Awad–AtmosphericPollutionResearch2(2011)445Ͳ451449
Table9.Estimatesoftheriskofmesotheliomaresultingfromlifetimeexposuretoairborneasbestosfibres
Riskofmesotheliomafrom Valueinoriginalpublication Reference 0.001f/cc (riskforfibreconcentrationindicated) 1x10Ͳ5 1x10Ͳ4 for0.001 f/cc AurandandKierski(1981) 2x10Ͳ5 1x10Ͳ4 for0.00013Ͳ0.0008 f/m3 Schneidermanetal.(1981) 3.9x10Ͳ5 1.56x10Ͳ4 for0.0004f/m3 Breslowetal. (1986) Ͳ3 a2.4x10Ͳ5 2.75x10 (females) EPA(1985) Ͳ3 1.92x10 (males)for0.01f/cc Severalstudieshavebeenperformedtocalculatetheriskof Coles,1980;Thomasetal.,1982;NeubergerandKundi,1990)have mesothelioma resulting from nonoccupational exposure to shownmesotheliomaswherenoexcesslungcancerwasseen,and asbestos fibres. Lifetime exposure to 0.0001f/cc has been the proportion of mesothelioma cases was high in populations estimated by various authors to carry differing degrees of wherenosourceofasbestosexposurecan beidentified.Hodgson mesothelioma (Table 9). In USA, Enterline (1983) estimated that and Darnton (2000) suggested that relatively brief asbestos exposure to asbestos fibre counts in the range of 0.0002– exposures may carry a low, but non–zero, risk of causing 0.0005f/ccresultedinalifetimeriskofmesotheliomaof mesothelioma. Ilgren and Browne (1991) argued against dose 4–10x10–5.Hereportedthatmesotheliomaincidencerangedfrom response mesothelioma threshold and they concluded that the 1.4x10–6to2.5x10–6 per year. Australia’s high incidence of existence of zero cases in a dose category (human or animal) mesotheliomaisrelatedtohighpastasbestosuseofallfibretypes, shouldnotbeinterpretedasazerorisk. inawidevarietyofoccupationalandenvironmentalsettings.The numberofcasesintotalisexpectedtobeabout18000by2020 Although,asbestosisbannedinEgypt,itisstillbeingimported (Leigh et al., 2002). Price and Ware (2004) used an age cohort formanufacturingpurposes.Allen(2006)reportedthatasbestosis model to analyze mesothelioma incidence in Surveillance, still being used in Egypt in the production of insulation boards, Epidemiology and End Results (SEER) database over the period asbestos–cement water pipes and fire resistant clothing. Abdul 1973–2000inUSA.Theirresultssuggestedthatageadjustedrates Salam (2006) described the current situation regarding asbestos amongmalesreachedapeakaroundearlytomid1990sandhave useinEgyptas“anarchy”withpeoplestillusingasbestosdespite remained relatively constant or declined somewhat since then. thefactthatitcannolongerbeused. They also reported that the age adjusted rates for females are much lower and have remained more or less constant over the 5.Conclusion period of 1973–2000. Moolgavkar et al. (2009) estimated approximately 62000 and 32000 pleural mesotheliomas among This review reinforces that geographical areas and menandwomen,respectively,overtheperiod2005–2050inUSA. occupationallocationsassociatedwithexposuretoasbestosfibre Thelargernumberofpleuralmesotheliomasamongmenreflects counts continue to drive mesothelioma. Populations living in the the continuing but declining, impact of asbestos use on pleural vicinitytoasbestossourceshaveprovedtobeexposedtohigher mesothelioma. environmentalasbestoscounts.Pleuralmesotheliomaisrelatedto asbestosfibresregardlessoftheircounts.Mesotheliomamortality 4.Discussion rate was relatively high among female subjects and chrysotile is the main cause for mesothelioma in Egypt. The improper and Exposure to asbestos fibres could cause health risks as all carelessdisposalofwastesisthemainreasonforreleasingfibresin asbestos types are toxic to macrophages in vitro and can cause highcounts.Thereisaclearneedforstrongerlegislativemeasures fibrosis and carcinoma (Ohar et al., 2004). According to some to eliminate asbestos entirely, relocate factories outside the experts only amphibole asbestos, particularly crocidolite and residentialareasandimproveindustrialhygienemeasures. amosite,causesmesothelioma.Chrysotiledoesnotcausedisease andmesotheliomaassociatedwithchrysotileexposureisprobably Acknowledgments caused by the contamination with tremolite (McDonald and McDonald, 2005). Some authors claim that chrysotile is as The author thanks to Prof. Dr. Gloria Sidhom, Professor of dangerousasamphiboleasbestosandconsiderchrysotilethemain Clinical and Chemical Pathology, Department of Clinical and causeofmesotheliomadevelopmentbecauseitaccountsforabout ChemicalPathology,MedicalSciencesDivision,NationalResearch 90%ofallexposures(SmithandWright,1996).Thepresentreview Centre, Egypt, for her help with revising the manuscript and her confirmsthatchrysotileisthemaincausesofMPMinEgyptand skillfulassistance. the risk of mesothelioma from the currently exposed concentrationsintherangeof0.0001f/ccto0.001f/cccannotbe References excluded. Thisreviewshowsthatasbestosfibrecountsdidnotexceed Abdul Salam, A., 2006. Banned material still used. The Egyptian Gazette, theEgyptianallowablecountof2f/ccfor chrysotile(EEAA,1994), June 28, page 2, http://ibasecretariat.org/lka_asb_use_middle_ exceptatthedisposalareas.Howeveratsomesamplingsitesfibre east.php. counts exceeded the urban ambient air standard 0.0001f/cc Abratt,R.P.,Vorobiof,D.A.,White,N.,2004.Asbestosandmesotheliomain according to Holland and Smith (1997). The Occupational Safety SouthAfrica.LungCancer45,S3ͲS6. and Health Administration and American Conference of ACGIH,1998.DocumentationoftheThresholdLimitValuesandBiological GovernmentalIndustrialHygienistsrequirethatworkersarenotto Exposure Indices. 6th Ed. American Conference of Governmental be exposed to more than 0.1f/cc (OSHA, 1998; ACGIH, 1998). In IndustrialHygienists.Cincinnati,OH. 1983, the EPA made the proactive statement that "exposure to Allen, L.K., 2006. Asbestos: the environmental hazard. In: Proceedings of airborneasbestosregardlessofthelevelinvolvessomehealthrisk” the International Conference Asbestos Risk Reduction and (EPA,1983). Measurement of Asbestos Fiber Concentration, Cracow, Poland, September28–29,2006. A threshold of effect has never been found for asbestos. However,severallinesofargumentalsosuggestthatanythreshold Anonymous,2002.AirborneAsbestosFibersinSigwartShoubraElKheima, formesotheliomaisataverylowlevel.Somecohorts(Rossiterand TechnicalReport,TeebenInstituteofMineralogy,Centre ofEnergyand Environment,Teeben,Cairo,November,2002. 450 Awad–AtmosphericPollutionResearch2(2011)445Ͳ451
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