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Ann[ occup[ Hyg[\ Vol[ 31\ No[ 7\ pp[ 446Ð452\ 0887Þ 0887 British Occupational Hygiene Society\ Pergamon Published by Elsevier Science Ltd[ All rights reserved
Printed in Great Britain[9992Ð3767:87 ,08[99¦9[99PII] S9992Ð3767"87#99950Ð0
Quartz Exposure in the Slate Industry in NorthernNorwayB[ E[ BANG� and H[ SUHR
Department of Occupational Medicine\ Re`ional Hospital of Tromso�\ P[O[ Box 05\ N!8927 Tromso�\Norway
In this study we have measured exposure levels to quartz in different parts of the slate industry in
Alta\ Northern Norway[ Full shift personal samples were collected from the breathing zones of
outdoor and indoor workers in the slate quarries and a slate factory[ The quartz content of
respirable dust was between 6 and 30)[ The slate factory had the lower quartz levels although
30) of total and 62) of respirable samples were above the Norwegian TLV for quartz[ The
average concentration of total quartz in the slate factory was 9[16 mg:m2 and the average con!
centration of respirable quartz was 9[01 mg:m2[ Outdoor in the quarries the average levels of
quartz were 9[47 and 9[02 mg:m2 for total and respirable quartz\ respectively[ From the beginning
of the last decade most of the quarry!workers have built quarry halls to protect themselves against
a cold winter climate[ Inside in these quarry halls the average levels were 0[63 mg:m2 total quartz
and 9[35 mg:m2 respirable quartz[ Assessment of historical exposure showed that 21 of totally 34
quarry workers with available exposure history had a lifetime inhaled quartz dose of more than
09 g[ There is reason to fear that silicosis will be an increasing problem among quarry workers if
efforts to reduce quartz exposure are not put into effect[ Þ 0887 British Occupational Hygiene
Society[ Published by Elsevier Science Ltd[
Keywords] quartz^ silicosis^ slate^ exposure^ Alta
INTRODUCTION
Slate rock originates from sedimentary marinedeposits that have been moulded over countless yearsby pressure and heat[ The capacity to _ssure alongcleavage planes accounts for the economic importanceof slate[ The mineral composition of the slate fromAlta\ northern Norway is 59Ð69) silica "SiO1# in theform of alpha!quartz\ the rest being potassium feld!spar\ mica and plagioclase[ After processing\ the slateproducts contain up to 72) quartz[ For comparison\the slate in North Wales\ one of the largest slate pro!ducing area in the world\ contain 29Ð39) quartz"McConnochie et al[\ 0877# and the Binota shale\ usedfor the manufacture of slate pencils\ has a silica con!tent of 58) "Jain et al[\ 0866#[
Inhalation of the crystalline form of silica is a wellknown cause of silicosis[ The association betweencrystalline silica and lung cancer is still a matter ofdebate[ This study is the _rst systematic investigationof silica exposure in the slate industry in this part ofNorway[
Received 4 September 0886^ in _nal form 05 June 0887[� Author to whom correspondence should be addressed[ Tel[]¦3666 51 63 52^ Fax] ¦3666 51 63 60[
446
The slate industry in Alta\ Norway\ consist of twomain workplaces\ the slate quarries and a slate factory[The slate factory in Alta produces various slate prod!ucts\ the main products being roof tiles\ ~oor tiles andfacade covering[ About 37 of totally 43 employers aredaily exposed to silica dust[ Protective masks are notused[ The slate factory have a general ventilationsystem[ During sawing and processing of the slate\water is used to reduce dustiness[
The slate quarry workers in Alta are self employed\organised in a cooperative society[ In 0883\ 033 quarryworkers were registered\ of which 29Ð39 worked thewhole year in the quarries[ From the beginning of thelast decade most of the quarry workers have built hallsin the quarries to protect themselves from the coldclimate in this geographic area[ Most of the work inthe quarries is thus performed indoors[ The quarry!halls have no dust reducing ventilation or wateringsystems and the use of protection equipment is limited[Only 1 of 51 workers answered that they use dust!protective masks more than 2 hours per day whenasked on a questionnaire[ None of the halls haveinstalled water in the wintertime\ and only two in thesummertime[ Some of the workers wet the work!stations with snow in the winter and water from small
B[ E[ Bang and H[ Suhr447
Table 0[ Description of the quarry halls
Hall no 0 Hall no 1 Hall no 2 Hall no 3
Size ½049 m1 ½199 m1 ½229 m1 ½79 m1
Number of workers 1 2Ð5 5 0Ð2Ventilation Extractor fan Extractor fan Information missing None
Heating system Radiant heating "roof# Radiant heating "roof# Heating cables "~oor# 0 heater placed on ~oor
water tanks in the summer\ to reduce dustiness[ Theslate quarry!workers are thus much more heavilyexposed to quartz dust today than they were 09Ð04years ago when most of the work was performed out!door[
The object of the study was to]
0[ Determine exposure levels to quartz in di}erentparts of the slate industry\
1[ To demonstrate the e}ect of increased indoor workin the quarries and
2[ To quantify historical exposure of the workers bymeans of a questionnaire combined with exposuremeasurement data[
MATERIALS AND METHODS
Four di}erent halls and one outdoor workplacewere selected in the quarries[ The halls representeddi}erent locations\ di}erent sizes and di}erent num!ber of workers[ The halls are described in Table 0[ Inthe factory eight sampling sites were selected in eachof the two departments[ Total and respirable dustwere collected from similar sites[ Seasonal di}erencesin exposure levels were accounted for by sampling treedays in summer and three days in winter[
Full shift personal samples were collected in thebreathing zone on cellulose ester _lters in Nuclepore_lter holders by means of a sampling pump "Alpha 0and SKC 113 PCXR6#[ A limited number of station!ary samples were collected near the breathing zone ofthe workers at some work stations[ Total dust sampleswere collected using a three!section 26 mm closed!faceplastic _lter holder at 1 l:min"SKC part No[ 114!2#[Respirable dust was collected using an SKC metalcyclone "SKC part No[ 114!90!91#\ at 0[8 l:min tomatch the BMRC respirable dust de_nition[ Dustsamples were weighed and analyzed for quartz
Table 1[ Time spent at di}erent work tasks in the quarries[ The registration was made by the workers by_lling out a time sheet each sampling day
Winter Summer") of working hours# ") of working hours#
Cleaving 54 79Shaping slate ~akes by knocking with iron!bar 19 06Cutting products with stone!scissor 6 9Other " fetching blocks\ snow!clearing etc[# 7 2
content[ Quartz analysis by X!ray di}raction wasperformed by the Norwegian National Institute ofOccupatonal Health[
The workers kept a time sheet of their various activi!ties during the sampling periods[ These were used tocalculate percentage of time spent a each work task"Table 1#[ A total of 019 working hours were regis!trated in the winter and 015 working hours were regis!trated in the summer[
Concentrations are given as arithmetic and geo!metric means with arithmetic and geometric standarddeviations in tables[ Whenever average values arereferred to in the text\ the geometric quantities areused[
Cumulative exposure was calculated according toOhman "0867# from exposure measurement data com!bined with information on personal exposure historyreported on a questionnaire[ Task!speci_ed historicalmeasurement data was available only from the slatefactory and only back to 0889[ Lung ventilation wasestimated from task!speci_ed tables of oxygen exch!ange during work "Elgstrand et al[\ 0856^ A� strand\0889#[
RESULTS AND DISCUSSION
The study was designed to characterize the exposureto quartz dust among workers in two di}erent workplaces in the slate industry in Alta\ Northern Norway[
In the slate factory the dust concentration of per!sonal air samples was 9[76 mg total dust:m2
"GSD � 1[42\ n � 31# and 9[42 mg respirable dust:m2
"GSD � 1[01\ n � 33#[ Outdoor in the quarries thepersonal dust!exposure was 0[71 mg:m2 total dust"GSD � 0[42\ n � 4# and 9[28 mg:m2 respirable dust"GSD � 1[62\ n � 2#[ Inside in the quarry halls thetotal dust content was 4[24 mg:m2 "GSD � 0[68\
Quartz exposure in slate industry 448
Table 2[ Quartz content in personal air samples[ The quartz analysis have beenperformed on pooled samples from each individual[ SD�arithmeticstandard devi!
ation[ n�number of pooled samples[ ND�not determined
Quartz in total dust ")# Quartz in respirable dust ")#
Quarry Factory Quarry Factory
Minimum 17 10 17 6Maximum 25 26 28 30Average 21 29[5 22[3 12[2
SD ND 4[8 3[1 09[8n 1 7 4 6
n � 03# whereas the respirable dust content was0[26 mg:m2 "GSD � 1[36\ n � 06#[ The results aboveare all airborne dust[ The quartz content of the dustare given in Table 2[
In our study\ the quartz content of the respirabledust was between 6 and 30)[ This is comparable tothe quartz content of respirable dust in the slate indus!try of North Wales "02Ð21)# "Glover et al[\ 0879#and Lugo\ Spain "20[7)# "De Quiros et al[\ 0882#[ Thesilica content of the dust in the slate pencil industry inIndia are reported to be 24Ð44) "Saiyed et al[\ 0874^Saiyed and Chatterjee\ 0874#[
The Norwegian Treshold Limit Value "TLV# forquartz is 9[2 mg:m2 total dust and 9[0 mg:m2 res!pirable dust[ Personal exposure to respirable quartzdust was above the Norwegian TLV in both work!places in the slate industry[ The slate factory had thelowest quartz levels although 30) of total and 62)of respirable samples were above TLV[ The averageconcentration of total quartz in the factory was9[16 mg:m2 "GSD � 1[39\ n � 31#[ The average con!
Fig[ 0[ Quartz exposure in the slate factory[ The samples are taken as full shift personal air samples or stationary samples"�#[ The work stations are ranked in the same order as in Table 3[ The levels shown are arithmetic means[ The number in
parenthesis represents the number of individual samples[ TLV�Norwegian threshold limit value[
centration of respirable quartz was 9[01 mg:m2
"GSD � 1[91\ n � 33#[Outdoor in the quarries 72) of total dust samples
and 56) of respirable dust samples were aboveTLV for quartz[ Outdoor levels were 9[47 mg:m2
"GSD � 0[41\ n � 4# and 9[02 mg:m2 "GSD � 1[56\n � 2# of total and respirable quartz respectively[Indoor\ 099) of total dust samples and 83) of res!pirable dust samples were above TLV for quartz[Average indoor levels of total quartz was 0[63 mg:m2
"GSD � 0[67\ n � 03# and the average level of res!pirable quartz was 9[35 mg:m2 "GSD � 1[42\ n � 06#[
The highest quartz level measured in one day was5[61 mg:m2 total quartz dust in hall no 2[ The use ofheating cables in the ~oor as well as the presence ofup to 5 workers at the same time may explain thetendency of higher levels of quartz dust in the air inthis hall compared to the other "Table 0#[ The heatingcables will keep the ~oor dry and thus counteract thedust!binding e}ect of water[ In addition\ the methodand frequency of cleaning will contribute to di}er!
B[ E[ Bang and H[ Suhr459
Fig[ 1[ Quartz exposure in the slate quarry[ The samples are taken as full shift personal air samples[ The levels shown arearithmetic means[ The number in parenthesis represents the number of individual samples[ TLV�Norwegian threshold limit
value[
ences in dust!levels[ The most common cleaningmethod among quarry workers\ is sweeping of drydust\ which causes the _nest dust to whirl up and intothe breathing zone of the workers[ There is a tendencyof higher dust levels in the quarry halls in winter thanin summer\ which can be explained by the fact thatthe natural ventilation is poorer because hall!gatesand windows are kept closed in wintertime[
The dilemma of assessing the right lifetime dosefrom historical data is discussed elsewere "Stewart etal[\ 0885#[ The present study su}ers from the weaknessof limited historical measurement data[ However\ thework tasks in this industry have not changed a lotthe last 59 years[ A thorough exposure case historycombined with the available historical and presentmeasurement data was thus used to assess historicalexposure[ The data clearly are very uncertain\ but inour opinion still give a reasonable estimate when usedfor group characterizations[
Figure 2 shows the distribution of the slate workersin groups of di}erent cumulative exposure calculatedas the lifetime inhaled quartz dose[ Cumulativeexposure was calculated for those who had worked 4years or more with slate[ All the factory workers ofwhich data on exposure history existed "21# werewithin the two lower exposure groups "below 19 ginhaled quartz\ range] 1Ð08 g#[ The majority of theworkers "11# were in the lowest group "below 09 ginhaled quartz#[
Amongst the quarry workers\ the cumulativeexposure was considerably heavier[ The range of life!time exposure was 1 to 53 g inhaled quartz[ Thirty!two of a total of 34 workers with available exposurehistory\ had inhaled more than 09 g quartz[ Six wor!kers had inhaled more than 29 g quartz[ Undoubtedly\the di}erences between the two groups of workers will
increase further if e}orts to reduce quartz exposure ofthe quarry!workers are not made[
The existence of a quantitative association betweenquartz exposure and risk of silicosis is well recognised"reviewed in Hilt\ 0882#[ Increased risk of pne!umoconiosis has been shown among British coal!miners exposed to silica!concentrations of 9[0 mg:m2
"Seaton et al[\ 0870#[ One third of the slate workers inNorth Wales showed evidence of pneumoconiosis butexposure measurements were not conducted in thisstudy[ In the slate pencil industry in India the averagelevels of respirable silica in the general work environ!ment was 4[4 mg:m2 and the prevalence of silicosiswas 43[5) "Saiyed et al[\ 0874#[ The fact that notonly cumulative amount of quartz dust\ but also theintensity of exposure is an important risk factor forsilicosis "Hessel et al[\ 0877#\ further emphasize theimportance of interventions in the slate industry inAlta[
Moving the main part of the quarry slate pro!duction inside to protect the workers against a coldwinter climate\ thus have led to unintended negativeconsequences[ The 2!fold increase from outdoor toindoor level of respirable quartz may have seriousconsequences by increasing the risk of developing sili!cosis[ There is reason to fear that silicosis will be anincreasing problem among quarry workers if e}ortsto reduce quartz!exposure are not put into e}ect[
Acknowled`ements*This investigation was supported bygrants from Medical Research in Finnmark\ Alta Slate Quar!ries and RiTo�|s Research Fund[ We wish to thank workersand managers at the slate factory Stensliperiet\ workers in theslate quarries and managers in the slate workers cooperativesociety for excellent cooperation[ Thanks are also dueto Jo�rn Iversen\ Bjo�rn Lundenes and Henning Olsen atthe Alta Company Health service and Lisbeth Aasmoe at
Quartz
exposurein
slateindustry
450
Table 3[ Quartz levels in slate factory work sites[ The samples are taken as full shift personal air samples or as full shift stationary samples "�#[The results are given as arithmetic and geometricmeans[ Variance are given as arithmetic and geometric standard deviations\ n�number of individual samples[ ND � not determined
Quartz in total dust "mg:m2# Quartz in respirable dust "mg:m2#
Winter Summer Average "year# Winter Summer Average "year#
Arithmetic Geometric Arithmetic Geometric Arithmetic Geometric Arithmetic Geometric Arithmetic Geometric Arithmetic Geometric
Manual Mean 0[54 0[51 0[81 0[59 0[65 0[50 9[06 9[06 9[12 9[07 9[19 9[06cleaving Variance 9[28 0[15 ND ND 9[70 0[48 ND ND ND ND 9[01 0[71
0 n 2 2 1 1 4 4 1 1 1 1 3 3
Manual Mean 9[29 9[29 9[46 9[46 9[28 9[26 9[07 9[07 9[14 9[04 9[10 9[06cleaving Variance ND ND ND ND 9[05 0[34 9[92 0[04 9[14 2[54 9[04 1[03
1 n 1 1 0 0 2 2 3 3 2 2 6 6
Packing: Mean 9[02 9[02 9[28 9[25 9[15 9[11 9[06 9[04 9[91 9[91 9[03 9[09end! Variance 9[91 0[07 9[08 0[59 9[07 0[77 9[01 0[75 ND ND 9[01 1[73
cutting n 2 2 2 2 5 5 3 3 0 0 4 4
Block! Mean 9[06 9[05 9[35 9[33 9[20 9[16 9[96 9[96 9[96 9[96 9[96 9[96saw Variance ND ND ND ND 9[08 0[82 ND ND 9[92 0[48 9[91 0[30
n 1 1 1 1 3 3 1 1 2 2 4 4
Tile! Mean 9[21 9[21 9[13 9[19 9[17 9[14 9[13 9[13 9[04 9[02 9[08 9[06saw Variance 9[92 0[00 9[08 1[03 9[02 0[63 9[92 0[02 9[98 0[88 9[97 0[63
n 2 2 2 2 5 5 2 2 2 2 5 5
Flag! Mean 9[07 9[07 9[19 9[03 9[08 9[05 9[04 9[04 9[00 9[09 9[02 9[02saw Variance 9[92 0[04 9[19 1[56 9[02 0[89 9[91 0[03 9[94 0[55 9[93 0[36
n 2 2 2 2 5 5 2 2 2 2 5 5
Grinding Mean 9[08 9[08 9[04 9[01 9[06 9[04 9[05� 9[05 9[98� 9[96 9[02� 9[09Variance 9[91 0[00 9[00 1[53 9[96 0[84 9[91 0[09 9[96 1[85 9[95 1[16
n 2 2 2 2 5 5 2 2 2 2 5 5
Truck Mean 9[11� 9[11 9[11� 9[08 9[11� 9[19 9[05� 9[05 9[01� 9[98 9[03� 9[01driving Variance 9[93 0[08 9[05 1[94 9[00 0[50 ND ND 9[98 1[65 9[96 1[08
n 2 2 2 2 5 5 1 1 2 2 4 4
B[E
[Bang
andH
[Suhr451
Table 4[ Quartz exposure in quarry workplaces[ The samples are taken as full shift personal air samples[ The results are given as arithmetic and geometric means[ Variance are given as arithmeticand geometric standard deviations\ n�number of individual samples\ ND�not determined
Quartz in total dust "mg:m2# Quartz in respirable dust "mg:m2#
Winter Summer Average "year# Winter Summer Average "year#
Arithmetic Geometric Arithmetic Geometric Arithmetic Geometric Arithmetic Geometric Arithmetic Geometric Arithmetic Geometric
Hall no 0 Mean ND ND 0[59 0[48 0[59 0[48 0[9 9[87 ND ND 0[9 9[87Variance ND ND ND ND ND ND ND ND
n 1 1 1 1 1 1 1 1
Hall no 1 Mean 0[87 0[84 9[81 0[04 0[34 0[29 9[41 9[33 9[04 9[00 9[23 9[11Variance 9[35 0[15 9[22 0[41 9[57 0[69 9[26 1[90 9[03 2[10 9[21 2[08
n 2 2 2 2 5 5 2 2 2 2 5 5
Hall no 2 Mean 2[69 2[06 0[83 0[79 1[71 1[28 9[87 9[87 9[50 9[47 9[79 9[64Variance 1[52 0[82 9[85 0[48 1[90 0[70 9[04 0[06 9[13 0[37 9[16 0[36
n 2 2 2 2 5 5 2 2 2 2 5 5
Hall no 3 Mean ND ND ND ND ND ND 9[35 9[34 ND ND 9[35 9[34Variance 9[09 0[14 9[09 0[14
n 2 2 2 2
Outdoor Mean 9[56 9[56 9[50 9[45 9[51 9[47 9[12 9[05 9[0 9[0 9[08 9[02Variance ND ND 9[14 0[50 9[11 0[41 ND ND ND ND 9[08 1[56
n 0 0 3 3 4 4 1 1 0 0 2 2
Quartz exposure in slate industry 452
Fig[ 2[ Lifetime inhaled quartz dose of workers in the slate industry[ The calculations are made according to Ohman"0867#[
the Department of Clinical Pharmacology\ Tromso� forcooperation[
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