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Comparative Personal Exposures to Organic Dusts and Endotoxin
\
Pergamon PII] S9992Ð3767"87#99972Ð9
Ann[ occup[ Hyg[\ Vol[ 32\ No[ 1\ pp[ 096Ð004\ 0888 Þ 0888 British Occupational Hygiene Society Published by Elsevier Science Ltd[ All rights reserved Printed in Great Britain[ 9992Ð3767:88 ,08[99¦9[99
Comparative Personal Exposures to Organic Dusts and Endotoxin J[ C[ G[ SIMPSON\ R[ McL[ NIVEN\ C[ A[ C[ PICKERING\ L[ A[ OLDHAM\ A[ M[ FLETCHER and H[ C[ FRANCIS Department of Occupational and Environmental Medicine\ North West Lun` Centre\ Wythenshawe Hospital\ Manchester M12 8LT\ UK The aims of the study were to provide valid comparative data for personal exposures to dust and endotoxins for different occupations and to calculate comparative data for the contamination of organic dusts with endotoxin[ Nine different occupational settings were studied\ drawn from the textile\ agricultural and animal handling industries[ Samples were collected by personal sampling techniques\ using the Institute of Occupational Medicine "IOM# sampling head\ glass _bre _lters and rechargeable sampling pumps[ The dust exposures were calculated by gravimetric analysis and using the calculated volume of air sampled were expressed as mg:m2[ Endotoxin exposures were measured using a simple water extraction from the collected dusts\ followed by a quantitative turbidimetric assay[ Results were expressed as ng:m2\ using the calculated volume of air sampled[ In addition\ the levels of the contamination of dusts with endotoxin for individual industries were expressed as ng:mg of collected dust[ Two hundred and _fty nine samples\ collected from 8 different industries and across 25 different sites were analysed[ This represented a sampling rate of 14) for the total work force[ The average sampling time was 3[51 h[ For all the dusts collected\ a signi_cant correlation between the collected dust and endotoxin was seen "r 9[6 and p³9[990#[ The highest dust exposures occurred during cleaning activities "grain handling] 61[4 mg:m2#[ The individuals exposed to the highest median level of dust and endotoxin were the animal handlers "poultry handlers\ dust] 00[42 mg:m2\ endotoxin] 60\884 ng:m2#[ Weaving and mushroom cultivation had the lowest exposures for dust and endotoxins[ The mostly highly contaminated dusts "median values expressed as ng of endotoxin per mg of collected dust# were found in the animal handling "poultry] 0\929 ng:mg\ swine] 041 ng:mg# and cotton spinning "411 ng:mg# industries[ Processing of cotton and wool _bres was found to reduce the levels of contamination of dusts with endotoxin[ In the study\ valid comparative data for personal exposures to organic dusts and endotoxins have been presented[ The highest exposures were found amongst animal handlers and during cleaning activities[ The results highlight that dust exposures are greater in a number of industries than the set exposure standards[ In addition\ endotoxin exposures are found to be greater than levels at which harmful effects have been demonstrated[ Þ 0888 British Occupational Hygiene Society[ Published by Elsevier Science Ltd[ All rights reseerved[ Keywords] organic dust^ endotoxin^ dust
INTRODUCTION
It has long been appreciated that exposures to organic dusts are potentially harmful to the respiratory tract[ The hazards of grain dust exposure were _rst described in the 05th century "Rask!Andersen\ 0877#[ Organic dusts are a diverse complex mixture con!
Received 02 March 0887^ in _nal form 3 November 0887[ Author to whom correspondence should be addressed[ Tel[] ¦33"9#050!180!1721^ Fax] ¦33"9#050!180!1592[ 096
taining material derived from vegetable and animal sources[ The potential for such a dust to be hazardous to health is readily appreciable[ Occupationally related exposures are implicated in the aetiology or exacerbation of a variety of diseases] byssinosis "Rylander\ 0889#\ asthma "Chan!Yeung and Malo\ 0883#\ allergic alveolitis "Campbell\ 0821#\ chronic bronchitis "Becklake\ 0874# and the organic dust toxic syndrome "ODTS# "Rask!Andersen\ 0878#[ Endotoxins are a ubiquitous contaminant of organic dusts[ Endotoxins are lipopolysaccharides
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derived from the cell wall of gram negative bacteria[ Human inhalation exposures studies with endotoxin have shown both physiological and symptomatic responses "Rylander et al[\ 0878#[ Exposure to endo! toxin has been implicated in the aetiology of a number of diseases\ including byssinosis "Kennedy et al[\ 0876#\ ODTS "Rylander\ 0876a\ 0876b# and the severity of asthma "Michel et al[\ 0880#[ Occupational exposure limits "OEL# exist for dust exposures in Britain "HSE\ 0887#[ There are speci_c maximum exposure limits "MEL# for the grain\ cotton\ wool\ wood "soft and hard# and man!made mineral _bre industries[ No exposure standards exist for endotoxin\ although attempts have been made to identify levels of exposure where there is a perceived risk to health "Rylander\ 0886#[ These proposed exposure levels are derived from the results of both experimental and epidemiological studies[ In the epi! demiological studies\ scientists have measured and reported environmental exposures in many di}erent occupational settings[ However\ they have used di}erent methodologies for the collection\ storage\ extraction and analysis of dust samples for their endo! toxin content[ This is recognised to give signi_cantly di}erent calculated levels of exposure "09!fold in some cases# between di}erent reporting laboratories even when analysing the same dust _lters "Chun\ 0887#[ However\ the repeatability of the test for individual laboratories is found to be good "Chun\ 0887^ Niven et al[\ 0887#[ Recommendations have been made for the collection\ extraction and analysis of organic dusts for their endotoxin content "Jacobs\ 0886#[ Com! parative data across and within di}erent industries for endotoxin exposures\ carried out by a single lab! oratory during a single study clearly stating the meth! odology used\ have not previously been reported[ The aim of the current survey was to provide valid comparative data for personal exposures to dust and endotoxins across and within 8 di}erent industries[ With this information\ comparative data for the levels of contamination of dusts across and within industries were determined[ METHODS
Nine di}erent industrial settings were selected for study[ Approaches were then made to senior man! agement\ safety o.cers\ workers| representatives and occupational health and hygiene departments\ where applicable[ The nature of the survey was explained and co!operation of participants elicited[ The survey was performed over a 01 month period[ A representative sample of the work force at each site was selected to record personal inhalable dust exposures during a typical work shift[ To obtain a representative sample for each industry\ volunteers were selected at each site in all di}erent work areas and occupations in these areas[ The IOM sampling head was used to collect the dust onto Whatman 14 mm glass _bre _lter papers[ The head was worn by
operatives at the level of the left clavicle[ The _lter papers contained in the sampling cassettes were weighed pre and post collection using a Sartorius micro balance to 2 decimal places in a dedicated weighing room[ Prior to weighing\ {~y| or large par! ticles "such as feathers# were removed[ Control _lters in cassettes were also taken to each site[ This was necessary to correct for changes in weight of the _lters due to changes in water content and to look for cross! contamination with endotoxin[ Calibrated battery operated rechargeable Casella personal sampling pumps were used to draw air through the _lter[ The pump ~ow rate was set at 1 l:min at the commencement of sampling and the ~ow rate checked at the end of sampling[ Using this ~ow rate and the time of the sampling period\ the volume of air sampled could be calculated\ enabling the results to be expressed as mg of dust or ng of endotoxin per m2[ Following gravimetric analysis\ each individual _l! ter was transferred using ~amed forceps to endotoxin! free glassware\ marked with a unique identity number[ The samples were then stored below −19>C until analysis[ Throughout the analysis\ endotoxin!free products were used\ including glassware and water[ When handling volumes of 0 ml or less\ adjustable volumetric pipettes "Gilson Pipetman P# with poly! propylene pipette tips were used[ Samples were thawed at room temperature for 0 h prior to a simple water extraction technique "Gould and Olenchock\ 0876#[ 09 ml of water was added to the 09 oz "179 ml# universal containers used to store the _lters[ Samples were vortexed for 59 s\ prior to agitation on roller bars for 59 min\ and were _nally vortexed for a further 59 s[ This resulted in the dis! integration of the _lter paper[ A 3 ml aliquot of this solution was then centrifuged at 2999 ` for 04 min[ Serial dilutions were then made with 9[4 ml of the supernatant ranging from 0]09 to 0]09\999[ The maximum dilution\ within the range of the standard curve generated for the analysis\ was used in an attempt to overcome problems of inhibition and enhancement from other contaminants of the col! lected dust[ The endotoxin content was assayed using a quan! titative kinetic turbidimetric method "LAL 4999e ser! ies 1 machine Associates Cape Cod#[ The pH of the _nal solutions assayed were checked using an elec! tronic monitor[ Water negative controls were also included with each analysis[ Two di}erent batches of LAL reagent were used throughout\ lot 01!05!597!t and lot 31!022!464!t "Associates Cape Cod#[ Standard curves were generated with control standard endo! toxin E Coli 9002 lot (59 "Associates Cape Cod# and these two LAL lots[ Both curves generated had correlation coe.cients of greater than 9[889[ The endotoxin contents of the control _lters for each site were used to correct the site!speci_c mea! sured exposures[ This was both to account for the contamination of clean _lters and also possible cross!
Comparative personal exposures to organic dusts and endotoxin
contamination from the _lter!holding cassette in the IOM head "complete depyrogenation by physical methods was impossible because of the nature of the component parts#[ Using the calculated volume of air sampled\ the results are expressed as ng:m2[ With the control stan! dard endotoxin and LAL lots used\ a conversion fac! tor of approximately 09 can be used to convert the results to endotoxin units[ In addition\ the con! tamination of the dusts collected with endotoxin is also presented and expressed as ng of endotoxin per mg of dust[ RESULTS
A total of nine di}erent industries were surveyed across 25 sites[ The industries were drawn from the textile industry "cotton spinning\ wool combing and weaving#\ agriculture "mushroom cultivation and picking\ saw mills\ grain handling and animal feed manufacture# and animal handling "swine con_ne! ment\ and poultry catching and shackling#[ The gre! atest number of sites visited "00# was in the animal handling industries[ In total\ 156 samples were collected[ Only 7 "2)# of _lters were spoiled\ either by dust loading or damage to the _lter paper\ these were excluded from the analysis[ This represented a sampling rate of 14[0) "across the industries# of the available population on the day of survey[ The per! centage of the population sampled at each site was dependant on the number of individuals and the diver!
sity of jobs[ The industries studied\ the number of sites for each industry and the sampling rates are displayed in Table 0[ The mean sampling times and 84) con_dence interval for each industry and for all the samples are displayed in Table 0[ The average sampling time was 3[51 h\ the lowest was found in the poultry industry "2[45 h#[ Comparative data across the industries for personal dust exposures "expressed as mg:m2#\ endo! toxin "expressed as ng:m2# and the levels of con! tamination of dust with endotoxin "expressed as ng:mg# are displayed in Tables 1Ð3\ respectively[ The data for exposures were not normally distributed and\ consequently\ the median\ range and geometric means with 84) con_dence intervals are presented[ The highest personal dust exposures recorded were found during cleaning activities in the grain "61[4 mg:m2# and wool "51 mg:m2# industries[ The highest median exposures were found in the animal handling industries "poultry] 00[4 mg:m2\ swine] 5[6 mg:m2#[ The lowest exposures were found for geo! metric mean\ median and range in the mushroom and the weaving industries[ The highest personal endotoxin exposures were measured in the poultry "60\884 ng:m2# swine "03\812 ng:m2# and cotton "5\825 ng:m2# industries[ The endotoxin exposures may be considered as the product of the dust exposures and the levels of con! tamination of the dust with endotoxin[ Not surpris! ingly\ the highest levels of dust contamination are found in the poultry "2\418 ng:mg# cotton
Table 0[ Demographic data for the industries studied Industry Mushroom Swine Grain Poultry Saw mills Cotton spinning Wool mill Animal feed Weaving Total
Nos[ of sites
Nos[ of samples
) of work force
Mean sample time "hours# 84) con_dence interval
1 00 2 7 5 1 0 0 1 25
29 16 20 22 26 20 17 5 25 148
13[5 51[7 33[8 28[2 25[5 02[6 19[0 06[5 05[7 14[0
3[29 "2[86Ð3[51# 3[61 "3[18Ð4[03# 3[11 "2[80Ð3[42# 2[45 "2[42Ð2[65# 4[19 "3[83Ð4[34# 4[11 "3[71Ð4[50# 3[73 "3[49Ð4[07# 3[41 "3[32Ð3[59# 3[76 "3[43Ð4[19# 3[51 "3[38Ð3[63#
Table 1[ Comparative personal dust exposures expressed as mg:m2 Industry Mushroom Swine Grain Poultry Saw mills Cotton mills Wool mill Animal feed Weaving
098
Median
Minimum
Maximum
Geometric mean with 84) con_dence interval
9[57 5[60 2[23 00[42 0[27 0[93 7[63 5[6 9[48
9[98 9[65 9[97 0[38 9[18 9[11 9[67 1[88 9[98
3[38 08[98 61[40 23[38 09[04 4[28 50[58 8[96 2[86
9[58 "9[49Ð9[85# 4[67 "3[17Ð6[71# 3[25 "0[98Ð6[88# 09[47 "7[27Ð02[23# 0[34 "0[97Ð0[84# 0[98 "9[71Ð0[33# 2[82 "1[42Ð5[01# 4[85 "2[84Ð7[87# 9[48 "9[30Ð9[74#
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J[ C[ G[ Simpson et al[ Table 2[ Comparative endotoxin exposures expressed as ng:m2 Industry
Median
Minimum
Maximum
Geometric mean with 84) con_dence interval
Mushroom Swine Grain Poultry Saw mills Cotton mills Wool mill Animal feed Weaving
6 520 094 00\882 05 327 85 20 6
0 59 2 644 1 55 0 5 9
029 03\812 1\136 60\884 155 5825 2934 74 49
6 "4Ð00# 559 "396Ð0\969# 004 "44Ð139# 7\320 "4\202Ð02\275# 08 "02Ð18# 343 "184Ð587# 72 "25Ð089# 29 "00Ð79# 4 "2Ð7#
Table 3[ Comparative contamination of dusts with endotoxin expressed as ng:mg of dust Industry Mushroom Swine Grain Poultry Saw mills Cotton mills Wool mill Animal feed Weaving
Median
Minimum
Maximum
Geometric mean with 84) con_dence interval
09 041 23 0929 04 411 29 3 09
0 8 0 003 0 63 0 1 0
334 0\463 088 2\418 076 1\881 149 01 45
00 "5Ð08# 003 "69Ð082# 15 "05Ð34# 686 "442Ð0\040# 02 "7Ð10# 306 "173Ð500# 10 "01Ð25# 4 "2Ð09# 7 "4Ð00#
"1\881 ng:mg# and swine "0\463 ng:mg# industries[ The lowest levels of endotoxin exposures are found in the mushroom "median] 6 ng:m2# and weaving "median] 6 ng:m2# industries[ The lowest levels of con! tamination were found in animal feed "median] 3 ng:mg# and again in the mushroom and weaving industries "median for both] 09 ng:mg#[ Industrial settin`s For the individual industries\ the comparative exposures to dust and endotoxin are discussed in the following text and\ where appropriate\ displayed in Tables 4Ð7[ The data for exposures were not normally distributed and\ consequently\ the median and the range for both the dust and the endotoxin are given[ Mushroom cultivation Two di}erent mushroom cultivation farms were studied both growing the basidiospore A`aricus\ the process can be split into 2 work areas] composting\ picking and packing[ The comparative exposures mea! sured in workers in each of these areas are displayed in Table 4[
Swine con_nement In the swine con_nement workers studied\ 00 di}erent sites were visited^ these were all involved with the breeding and multiplication of swine and 16 samples were collected from a possible 32 workers[ The workers were multi!skilled and worked in di}er! ent areas during a single shift\ making it di.cult to measure speci_c exposures associated with speci_c jobs[
Grain handlin` Two di}erent situations of grain handling were studied\ _rstly in a large port in the dock area where grain was unloaded and stored in silos and\ secondly\ in ~our mills where grain was stored in silos\ tested for quality in a laboratory and _nally milled[ Exposures for workers involved in cleaning the silos and the maintenance engineers at the docks and the di}erent work areas in ~our mills are displayed in Table 5[ The cleaning activities were performed manu! ally with brushes\ workers being provided with simple face masks as respiratory protective equipment[
Table 4[ Comparative dust "mg:m2# and endotoxin "ng:m2# exposures in mushroom cultivation Process Composting Picking Packing
Median
Dust Minimum
Maximum
Median
0[32 9[52 9[50
9[45 9[98 9[23
3[38 0[77 0[98
3 24[3 4[5
Endotoxin Minimum 9[7 4[3 1[4
Maximum 31[0 018[7 06[79
Comparative personal exposures to organic dusts and endotoxin
000
Table 5[ Comparative dust "mg:m2# and endotoxin "ng:m2# exposures in grain handling Docks Process Silo "cleaning# Maintenance
Median
Dust Minimum
Maximum
Median
Endotoxin Minimum
52[30 1[27
14[96 9[14
61[40 01[64
549 058
287 4
0\380 0\784
39 274 56
2 11 6
094 1\136 613
Maximum
Flour mills Work room Laboratory Silo Mill
2[17 3[36 24[81
2[00 2[1 3[40
3[37 18[25 25[04
Table 6[ Comparative dust "mg:m2# and endotoxin "ng:m2# exposures in the poultry workers Process Catching Shackling
Median
Dust Minimum
Maximum
Median
09[57 01[1
4[11 0[38
23[38 10[26
01\629 8\555
Endotoxin Minimum 644 0\927
Maximum 60\884 44\718
Table 7[ Comparative dust "mg:m2# and endotoxin "ng:m2# exposures in textile workers Cotton Process
Median
Dust Minimum
Maximum
Median
0[96 0[98 9[5 0[97
9[61 9[64 9[11 9[4
4[28 3[28 3[18 1[36
862 758 267 244
60 580 55 73
5\825 0\959 0776 0\540
Wool Process Sorting Carding Combing Finishing
1[92 02[07 1[75 9[85
0[6 2[58 9[81 9[67
3[60 50[58 6[1 0[2
177 583 41 4
063 80 2 0
313 2\934 391 6
Weaving Mill 0 Mill 1
9[10 0[17
9[98 9[37
0[91 2[86
0 08
9 0
3 49
Open:Blow Carding Spinning Winding
Poultry The workers studied in the poultry industry were the catching gangs "responsible for removing poultry from sheds\ often many thousands of birds during a shift# and the shacklers "responsible for hanging the captured birds by their legs on shackles prior to their slaughter#[ Both jobs are unpleasant and dirty\ with high dust and endotoxin exposures\ as displayed in Table 6[ Wood The wood workers studied handled soft woods and were involved in a variety of processes\ including debarking\ sawing and stacking[ Also included were the {saw doctors| who were responsible for the main! tenance of the saws used in the process^ some of their dust exposure must have included metal dust[ This is probably the reason why they were found to have relatively high dust exposures "median] 4[35 mg:m2\
Endotoxin Minimum
Maximum
range] 1[42Ð7[28 mg:m2#\ compared to the average shown in Table 1 across the saw mill industry as a whole[
Textiles Three di}erent aspects of the textile industry were studied] cotton spinning "opening and blowing\ card! ing\ spinning and winding# wool scouring and comb! ing "sorting\ carding\ combing and _nishing# and weaving "0 mill handling purely synthetic _bre and 0 a mixture of cotton and man!made _bre#[ Table 7 displays the exposures measured in the di}erent work rooms for cotton spinning and wool scou! ring:combing and the di}erence between the 1 di}er! ent mills for weaving[ The highest endotoxin exposures are found in the open and blow areas in cotton spinning and carding in wool scouring and combing[ The levels of endotoxin exposure are low in
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J[ C[ G[ Simpson et al[
weaving\ paticularly in the mill handling the synthetic _bre "where the dust exposures are also very low#[ Animal feed The 5 workers studied in the animal feed industry produced food pellets from bone meal and other veg! etable waste matter[ The e}ect of processing on the contamination of the dust can be appreciated in Figs 0 and 1[ In these _gures "for the cotton and wool industries\ respec! tively#\ the median endotoxin contamination\ expre! ssed as ng:mg of dust\ are plotted for di}erent rooms found in the mills[ The values plotted are the mean personal exposures for workers in these rooms[ The
rooms on the x axis are displayed in a sequential manner\ with the _rst process room on the left and the last on the right[ The contamination of the dusts found in these rooms falls as the _bres are processed[ The correlation between the collected dust and the measured endotoxin is presented in Table 8[ In the calculation of the correlation coe.cients\ the logged values have been used[ For all the samples collected\ a highly signi_cant correlation is found "r 9[6\ p³9[990#[ The lack of signi_cance of the correlation found for the animal feed workers can be explained by the low number of individuals sampled "5#[ The other industries where no signi_cant correlation was found were mushroom\ swine and saw mills[
Fig[ 0[ Comparison of median levels of contamination of dust with endotoxin across rooms in cotton spinning[
Fig[ 1[ Comparison of median levels of contamination of dust with endotoxin across rooms in wool sorting and combing[
Comparative personal exposures to organic dusts and endotoxin Table 8[ Correlations between collected dusts and the mea! sured endotoxin Industry Mushroom Swine Grain Poultry Saw mills Cotton spinning Wool mill Animal feed Weaving Total
Correlation "r# −9[92 9[16 9[60 9[51 9[01 9[38 9[71 9[66 9[66 9[6
Signi_cance "p# p 9[75 p 9[06 p ³ 9[990 p ³ 9[990 p 9[49 p ³ 9[90 p ³ 9[990 p 9[97 p ³ 9[990 p ³ 9[990
DISCUSSION
This is the _rst study to provide comparative data for personal exposures to airborne organic dusts\ endotoxin and levels of dust contamination across di}erent industries in a single study[ Liesivuori has published data for endotoxin exposures in di}erent industries but no methodology\ no time scale over which the samples were collected\ and no description of the processes that the workers were involved in during collection were presented "Liesivuori\ 0883#[ In the current study\ the techniques used for the col! lection of the dust samples and their analysis for endo! toxin are accepted and validated[ Recently\ rec! ommendations have been made for the collection\ storage\ extraction and analysis of dusts for endotoxin "Jacobs\ 0886#[ The methods used in this study\ with the exceptions of sample storage at −19>C and sample vortexing during the extraction\ are in line with these recommendations[ The values obtained for the endo! toxin exposures should be interpreted with the fol! lowing two points in mind[ Firstly\ it is recognised that a water extraction\ whilst simple and reproducible\ is not exhaustive and the values obtained may be an underestimate of the true exposures "Chun\ 0887^ Jacobs\ 0886#[ Secondly\ and less likely\ components of the di}erent dusts collected could a}ect the rate of extraction[ The endotoxin results therefore are not absolute exposure levels but comparative and speci_c for the methodology used[ The highest dust exposures were found in the grain "61[4 mg:m2# and wool "50[6 mg:m2# industries^ both of these occurred during cleaning activities[ The high! est median exposures were seen in the animal handling industries "01[7 mg:m2 poultry# and the lowest in weaving "9[5 mg:m2#[ The measured personal dust exposures in animal and grain handling\ wood\ cotton and wool industries are broadly similar to those found by other inves! tigators "Rylander et al[\ 0876^ Hurst and Dosman\ 0889^ Halpin et al[\ 0883^ Sigsgaard et al[\ 0881^ Love et al[\ 0877#[ Detailed comparisons are not valid but the broad agreement supports the proposition that the samples collected are representative for the individuals working in these industries[
002
Data exist to support the hypothesis that higher dust exposures in the wood\ grain\ swine\ wool and cotton spinning industries result in greater respiratory morbidity "Enarson and Chan!Yeung\ 0889^ Hurst and Dosman\ 0889^ Donham\ 0889^ Love et al[\ 0877^ Rylander\ 0889#[ As a re~ection of this in the UK\ occupational exposure limits "OEL# exist for dust exposures EH39:87 "HSE\ 0887#] a maximum exposure limit "MEL# for grain] 09 mg:m2\ wood dust "hard and soft#] 4 mg:m2\ man!made mineral _bre] 4 mg:m2\ cotton] 1[4 mg:m2 and wool process dust] 09 mg:m2[ In addition\ in Britain\ the Control of Sub! stances Hazardous to Health Regulations apply to any other dust if the 7 h time!weighted!average exposure exceeds 09 mg:m2[ From the results of this study\ it can be appreciated that exposures are exceeding these values[ The weaving and mushroom cultivation indus! tries are the only ones to have no measured exposure greater than occupational exposure limits[ However\ no calculations for respiratory protection equipment have been used in this study[ Endotoxin exposures are related to two factors\ the level of dust contamination and the level of dust exposure[ The lowest exposures were seen in the weav! ing industry "median] 6 ng:m2#\ where the dust exposures were low and the contamination of the dust with endotoxin was low "median] 09 ng:mg#[ Conversely\ high exposures were seen in animal hand! ling "poultry median] 00\882 ng:m2\ peak] 60\884 ng:m2# and cotton spinning "median] 327 ng:m2#\ where highly contaminated dusts "poultry median] 0\929 ng:mg\ cotton median] 411 ng:mg# were found and workers have high personal exposures to dust[ Deleterious e}ects from endotoxin have been reported with occupational exposures as low as 8 and 04 ng:m2 "Castellan et al[\ 0876^ Milton et al[\ 0883# and experimental exposures of 19 mg for isolated "Michel et al[\ 0878# and 29 mcg for cell!bound endo! toxin "Rylander\ 0876a\ 0876b#[ Even allowing for di}erences in methodology\ the results from the cur! rent survey would suggest that signi_cant exposures are occurring[ At the present time\ no speci_c exposure limits for endotoxin exist\ although the Committee on organic dusts of the ICOH has completed work on an endotoxin criteria document "Rylander\ 0886#[ It concludes that the following environmental endotoxin exposures are levels at which no e}ect is seen for the following conditions^ toxic pneumonitis] 199 ng:m2\ systemic e}ects] 099 ng:m2 and 09 ng:m2 for increased airways in~ammation[ By implication\ levels higher than these are potentially harmful[ These levels are a little di}erent from those highlighted by Olenchok in his review of the health e}ects of endotoxins "Olen! chock\ 0883#\ where the following levels of exposure were associated with di}erent e}ects] organic dust toxic syndrome\ 0999 to 1999 ng:m2\ acute bron! choconstriction\ 099 to 199 ng:m2\ and mucous mem! brane irritation at 19 to 49 ng:m2[ Individuals may also be more or less susceptible to the e}ects of endotoxin\ perhaps depending upon atopy\ smoking habits or
003
J[ C[ G[ Simpson et al[
other\ as yet\ unidenti_ed factors[ Applying these exposure limits to the current study population would mean that only the mushroom and the weaving indus! try would have median or mean levels for their work! forces lower than a no!e}ect level[ Even in these indus! tries\ pickers in mushroom cultivation and workers weaving man made _bre and cotton may have average exposures higher than a no!e}ect limit[ Most workers in swine con_nement\ poultry handling and cotton spinning\ and some in grain handling "maintenance workers and silo operators and cleaners# and wool scouring and combing "sorting and carding# will have exposures consistently over 099 ng:m2\ and often over 0999 ng:m2[ The introduction of exposure limits will be di.cult[ Having accepted that the calculated exposure limits are correct and valid using the data currently available from experimental and\ more importantly\ epi! demiological studies\ problems still exist[ Firstly\ a standard methodology\ used by all analysing lab! oratories\ shown to give identical results in each setting\ would need to be developed[ The current situ! ation is far from this "Chun\ 0887#[ Perhaps\ more importantly\ endotoxin as well as having a direct e}ect\ may be acting in a facilitatory role\ allowing other agents to have a greater e}ect\ similar to the interaction seen between the non!speci_c irritant ozone and subsequent allergen challenge "Mol_no et al[\ 0880#[ This would mean that an industry!speci_c endotoxin exposure standard would be more appro! priate than a general standard[ For the wool and cotton spinning industries "where a breakdown of exposures occurring in individual rooms is presented#\ the e}ect of processing on the contamination of dusts can be appreciated "Figs 0 and 1#[ Individuals in the earlier processes are exposed to the most highly contaminated dust[ In the cotton spinning industry\ as the waste material is removed during opening and carding\ contamination falls[ In the wool industry\ where a scouring process takes place between sorting and carding\ the fact that endo! toxin can be destroyed by heat!treatment or alkali\ demonstrated in experimental situations "Rousselle\ 0883#\ is shown in {real life|[ Finally\ the _nding of a strong and signi_cant cor! relation "r 9[6\ p³9[990# between the collected dust and measured endotoxin content should be critically appraised[ Figures 0 and 1 demonstrated that the con! tamination of dust with endotoxin changed with pro! cessing^ it would therefore be reasonable to expect the correlation between the collected dust and measured endotoxin levels to be poor[ In the wool industry\ a value of r 9[71\ p³9[990 is obtained[ This can be explained by the unequal distribution of samples taken across rooms and sites because of the diversity of jobs and numbers of employees in di}erent rooms[ Considering the cohort as a whole\ the industries where consistently high dust exposures are found also have highly contaminated dusts and\ conversely\ industries where the lowest dust exposures were found
had little contamination[ This highlights the fact that correlations between dust and endotoxin presented in this and other studies should be interpreted with caution and in conjunction with the documented vari! ation in the levels of dust contamination between rooms[ The full potential of dusts and endotoxins\ either separately or in combination\ has not yet been fully elucidated and more work in this area is required[ Until this time\ more vigorous attempts to control dust and endotoxin exposures need to be made[ A dual approach is required[ Firstly\ the requirements of employers to ensure that exposures are within the currently acceptable limits needs to be highlighted and\ where appropriate\ monitored[ Secondly\ employees need to be encouraged to wear respiratory protective equipment in situations where high exposures are possible[ To encourage this\ employees need to be educated about the potential e}ects of organic dust exposures and made aware that suitable protective equipment is readily available[
REFERENCES Becklake\ M[ R[ "0874# Chronic air~ow limitations] Its relationship to work in dusty occupations[ Chest 77"3#\ 597Ð506[ Campbell\ J[ M[ "0821# Acute symptoms following work with hay[ B[ M[ J[ 2\ 0032[ Castellan\ R[ M[\ Olenchock\ S[ A[\ Kinsley\ K[ B[ and Han! kinson\ J[ L[ "0876# Inhaled endotoxin and decreased spi! rometric values[ N[ En`l[ J[ Med[ 206\ 594Ð509[ Chan!Yeung\ M[ and Malo\ J[ L[ "0883# Aetiological agents in occupational asthma[ Eur[ Respir[ J[ 6\ 235Ð260[ Chun\ D[ T[ "0887# Preliminary report on the results of the _rst phase of a round robin endotoxin assay using cotton dust[ In Proceedin`s of the 11nd Cotton and Or`anic Dusts Research Conference Beltwide Cotton Conferences "Edited by P[ J[ Wakelyn\ R[ R[ Jacobs and R[ Rylander#\ pp[ 084Ð 087[ National Cotton Council\ Memphis\ ISBN] 9 8502397 09 01[ Donham\ K[ J[ "0889# Health e}ects from work in swine con_nement buildings[ Am[ J[ Ind[ Med[ 06\ 06Ð14[ Enarson\ D[ A[ and Chan!Yeung\ M[ "0889# Charac! terisation of health e}ects of wood dust exposures[ Am[ J[ Ind[ Med[ 06\ 22Ð27[ Gould\ M and Olenchock\ S[ "0876# Endotoxin extraction method for organic dusts[ In Proceedin`s of Endotoxin Inhalation Workshop "Edited by R[ Rylander\ R[ Burrell and Y[ Peterson#\ pp[ 193Ð194[ Swedish Work Environ! ment Fund[ Stockholm\ Sweden[ Contract 76!9767[ Haglind\ P[ and Rylander\ R[ "0876# Occupational exposure and lung function measurements among workers in swine con_nement buildings[ J[ Occ[ Med[ 18"00#\ 893Ð896[ Halpin\ D[ M[ G[\ Graneek\ B[ J[\ Lacey\ J[\ Nieuwenhuijsen\ M[ J[\ Williamson\ P[ A[ M[\ Venables\ K[ M[\ Newman Taylor\ A[ J[ "0883# Respiratory symptoms\ immu! nological responses and aeroallergen concentrations at a sawmill[ Occup Environ Med[ 40\ 054Ð061[ Health and Safety Executive "0887# Occupational Exposure Limits[ HMSO Norwich\ ISBN] 9 6065 0363 2[ Hurst\ T[ S[ and Dosman\ J[ A[ "0889# Characterisation of health e}ects of grain dust exposures[ Am[ J[ Ind[ Med[ 06\ 16Ð21[ Jacobs\ R[ R[ "0886# The endotoxin criteria document] Environmental monitoring for endotoxin aerosols[ In Pro! ceedin`s of the 10st Cotton and Or`anic Dusts Research
Comparative personal exposures to organic dusts and endotoxin Conference Beltwide Cotton Conferences "Edited by P[ J[ Wakelyn\ R[ R[ Jacobs and R[ Rylander#\ pp[ 045Ð048[ National Cotton Council\ Memphis\ ISBN] 9 8502397 09 00[ Kennedy\ S[ M[\ Christiani\ D[ C[\ Eisen\ E[ A[\ Wegman\ D[ H[\ Greaves\ I[ A[\ Olenchock\ S[ A[\ Ye\ T[!T[ and Lu\ P[!L[ "0876# Cotton dust and endotoxin exposure!response relationships in cotton textile workers[ Am[ Rev[ Respir[ Dis[ 024\ 083Ð199[ Liesivuori\ J[ "0883# Airborne endotoxin concentrations in di}erent work conditions[ Am[ J[ Ind[ Med[ 14\ 012Ð013[ Love\ R[ G[\ Smith\ T[ A[\ Gurr\ D[\ Soutar\ C[ A[\ Scar! isbrick\ D[ A[ and Seaton\ A[ "0877# Respiratory and allergic symptoms in wool textile workers[ Br[ J[ Ind[ Med[ 34\ 616Ð630[ Michel\ O[\ Duchateau\ J[ and Sergysels\ R[ "0878# E}ect of inhaled endotoxin on bronchial reactivity in asthmatic and normal subjects[ J[ Appl[ Physiol[ 55\ 0948Ð0953[ Michel\ O[\ Ginanni\ R[\ Duchateau\ J[\ Vertongen\ F[\ Le Bon\ B[ and Sergysels\ R[ "0880# Domestic endotoxin exposure and clinical severity of asthma[ Clin[ Exp[ Aller`y 10\ 330Ð337[ Milton\ D[ K[\ Kriebel\ D[\ Wypij\ D[\ Walters\ M[\ Hammond\ S[ K[ and Evans\ J[ "0883# Acute and chronic air~ow obstruction and endotoxin exposure[ Am[ Rev[ Respir[ Dis[ 038\ A288[ Mol_no\ N[ A[\ Wright\ S[ C[\ Katzi\ I[\ Tarho\ S[\ Silverman\ F[\ MaClean\ P[ A[\ Szalai\ J[ P[\ Raizenne\ M[\ Slutsky\ A[ S[ and Zamel\ N[ "0880# E}ect of low concentration of ozone on inhaled allergen responses in asthmatic subjects[ The Lancet 227\ 088Ð192[ Niven\ R[ McL[\ Fletcher\ A[ M[\ Pickering\ C[ A[ C[\ Simp! son\ J[ C[ G[\ Oldham\ L[ A[ and Bakirci\ N[ "0887# Repeat! ability of sampling for endotoxin and dust within 2 cotton textile mills[ In Proceedin`s of the 11nd Cotton and Or`anic Dusts Research Conference Beltwide Cotton Conferences "Edited by P[ J[ Wakelyn\ R[ R[ Jacobs and R[ Rylander#\ pp[ 088Ð191[ National Cotton Council\ Memphis\ ISBN] 9 8502397 09 01[
004
Olenchock\ S[ A[ "0883# Health e}ects of biological agents] the role of endotoxins[ Appl[ Occ[ Env[ Hy`[ 8"0#\ 51Ð 53[ Rask!Andersen\ A[ "0877# Pulmonary Reactions to Inha! lation of Mould Dust in Farmers With Special Reference to Fever and Alveolitis[ Doctoral thesis\ Uppsala Univer! sity[ Sweden[ Rask!Andersen\ A[ "0878# Organic dust toxic syndrome among farmers[ Brit[ J[ Ind[ Med[ 35\ 122Ð127[ Rousselle\ M[!A[ "0883# Endotoxin content of dust from heat!detoxi_ed cotton _ber[ In Proceedin`s of the 07th Cotton and Or`anic Dusts Research Conference Beltwide Cotton Conferences "Edited by P[ J[ Wakelyn\ R[ R[ Jacobs and L[ N[ Domelsmith# pp[ 251Ð253[ National Cotton Council\ Memphis\ ISBN] 9 8502397 09 7[ Rylander\ R[ "0876# Role of endotoxins in the pathogenesis of respiratory disorders[ Eur[ J[ Respir[ Dis[ Suppl[ 043\ 025Ð033[ Rylander\ R[ "0876# Toxicity of inhaled isolated and cell bound endotoxin[ In Proceedin`s of Endotoxin Inhalation Workshop "Edited by R[ Rylander\ R[ Burrell and Y[ Peterson#\ pp[ 191Ð192[ Swedish Work Environment Fund[ Stockholm\ Sweden[ Contract 76!9767[ Rylander\ R[\ Bake\ B[\ Fischer\ J[ J[ and Helander\ I[ M[ "0878# Pulmonary function and symptoms after inhalation of endotoxin[ Am[ Rev[ Respir[ Dis[ 039\ 870Ð875[ Rylander\ R[ "0889# Health e}ects of cotton dust exposures[ Am[ J[ Ind[ Med[ 06\ 28Ð34[ Rylander\ R[ "0886# The endotoxin criteria document] the risk evaluation[ In Proceedin`s of the 10st Cotton and Or`anic Dusts Research Conference Beltwide Cotton Con! ferences "Edited by P[ J[ Wakelyn\ R[ R[ Jacobs and R[ Rylander#\ pp[ 042Ð045[ National Cotton Council\ Memphis\ ISBN] 9 8502397 09 00[ Sigsgaard\ T[\ Pedersen\ O[ F[\ Juul\ S[ and Gravesen\ S[ "0881# Respiratory disorders and atopy in cotton\ wool and other textile mill workers in Denmark[ Am[ J[ Ind[ Med[ 11\ 052Ð073[
Pergamon PII] S9992Ð3767"87#99972Ð9
Ann[ occup[ Hyg[\ Vol[ 32\ No[ 1\ pp[ 096Ð004\ 0888 Þ 0888 British Occupational Hygiene Society Published by Elsevier Science Ltd[ All rights reserved Printed in Great Britain[ 9992Ð3767:88 ,08[99¦9[99
Comparative Personal Exposures to Organic Dusts and Endotoxin J[ C[ G[ SIMPSON\ R[ McL[ NIVEN\ C[ A[ C[ PICKERING\ L[ A[ OLDHAM\ A[ M[ FLETCHER and H[ C[ FRANCIS Department of Occupational and Environmental Medicine\ North West Lun` Centre\ Wythenshawe Hospital\ Manchester M12 8LT\ UK The aims of the study were to provide valid comparative data for personal exposures to dust and endotoxins for different occupations and to calculate comparative data for the contamination of organic dusts with endotoxin[ Nine different occupational settings were studied\ drawn from the textile\ agricultural and animal handling industries[ Samples were collected by personal sampling techniques\ using the Institute of Occupational Medicine "IOM# sampling head\ glass _bre _lters and rechargeable sampling pumps[ The dust exposures were calculated by gravimetric analysis and using the calculated volume of air sampled were expressed as mg:m2[ Endotoxin exposures were measured using a simple water extraction from the collected dusts\ followed by a quantitative turbidimetric assay[ Results were expressed as ng:m2\ using the calculated volume of air sampled[ In addition\ the levels of the contamination of dusts with endotoxin for individual industries were expressed as ng:mg of collected dust[ Two hundred and _fty nine samples\ collected from 8 different industries and across 25 different sites were analysed[ This represented a sampling rate of 14) for the total work force[ The average sampling time was 3[51 h[ For all the dusts collected\ a signi_cant correlation between the collected dust and endotoxin was seen "r 9[6 and p³9[990#[ The highest dust exposures occurred during cleaning activities "grain handling] 61[4 mg:m2#[ The individuals exposed to the highest median level of dust and endotoxin were the animal handlers "poultry handlers\ dust] 00[42 mg:m2\ endotoxin] 60\884 ng:m2#[ Weaving and mushroom cultivation had the lowest exposures for dust and endotoxins[ The mostly highly contaminated dusts "median values expressed as ng of endotoxin per mg of collected dust# were found in the animal handling "poultry] 0\929 ng:mg\ swine] 041 ng:mg# and cotton spinning "411 ng:mg# industries[ Processing of cotton and wool _bres was found to reduce the levels of contamination of dusts with endotoxin[ In the study\ valid comparative data for personal exposures to organic dusts and endotoxins have been presented[ The highest exposures were found amongst animal handlers and during cleaning activities[ The results highlight that dust exposures are greater in a number of industries than the set exposure standards[ In addition\ endotoxin exposures are found to be greater than levels at which harmful effects have been demonstrated[ Þ 0888 British Occupational Hygiene Society[ Published by Elsevier Science Ltd[ All rights reseerved[ Keywords] organic dust^ endotoxin^ dust
INTRODUCTION
It has long been appreciated that exposures to organic dusts are potentially harmful to the respiratory tract[ The hazards of grain dust exposure were _rst described in the 05th century "Rask!Andersen\ 0877#[ Organic dusts are a diverse complex mixture con!
Received 02 March 0887^ in _nal form 3 November 0887[ Author to whom correspondence should be addressed[ Tel[] ¦33"9#050!180!1721^ Fax] ¦33"9#050!180!1592[ 096
taining material derived from vegetable and animal sources[ The potential for such a dust to be hazardous to health is readily appreciable[ Occupationally related exposures are implicated in the aetiology or exacerbation of a variety of diseases] byssinosis "Rylander\ 0889#\ asthma "Chan!Yeung and Malo\ 0883#\ allergic alveolitis "Campbell\ 0821#\ chronic bronchitis "Becklake\ 0874# and the organic dust toxic syndrome "ODTS# "Rask!Andersen\ 0878#[ Endotoxins are a ubiquitous contaminant of organic dusts[ Endotoxins are lipopolysaccharides
097
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derived from the cell wall of gram negative bacteria[ Human inhalation exposures studies with endotoxin have shown both physiological and symptomatic responses "Rylander et al[\ 0878#[ Exposure to endo! toxin has been implicated in the aetiology of a number of diseases\ including byssinosis "Kennedy et al[\ 0876#\ ODTS "Rylander\ 0876a\ 0876b# and the severity of asthma "Michel et al[\ 0880#[ Occupational exposure limits "OEL# exist for dust exposures in Britain "HSE\ 0887#[ There are speci_c maximum exposure limits "MEL# for the grain\ cotton\ wool\ wood "soft and hard# and man!made mineral _bre industries[ No exposure standards exist for endotoxin\ although attempts have been made to identify levels of exposure where there is a perceived risk to health "Rylander\ 0886#[ These proposed exposure levels are derived from the results of both experimental and epidemiological studies[ In the epi! demiological studies\ scientists have measured and reported environmental exposures in many di}erent occupational settings[ However\ they have used di}erent methodologies for the collection\ storage\ extraction and analysis of dust samples for their endo! toxin content[ This is recognised to give signi_cantly di}erent calculated levels of exposure "09!fold in some cases# between di}erent reporting laboratories even when analysing the same dust _lters "Chun\ 0887#[ However\ the repeatability of the test for individual laboratories is found to be good "Chun\ 0887^ Niven et al[\ 0887#[ Recommendations have been made for the collection\ extraction and analysis of organic dusts for their endotoxin content "Jacobs\ 0886#[ Com! parative data across and within di}erent industries for endotoxin exposures\ carried out by a single lab! oratory during a single study clearly stating the meth! odology used\ have not previously been reported[ The aim of the current survey was to provide valid comparative data for personal exposures to dust and endotoxins across and within 8 di}erent industries[ With this information\ comparative data for the levels of contamination of dusts across and within industries were determined[ METHODS
Nine di}erent industrial settings were selected for study[ Approaches were then made to senior man! agement\ safety o.cers\ workers| representatives and occupational health and hygiene departments\ where applicable[ The nature of the survey was explained and co!operation of participants elicited[ The survey was performed over a 01 month period[ A representative sample of the work force at each site was selected to record personal inhalable dust exposures during a typical work shift[ To obtain a representative sample for each industry\ volunteers were selected at each site in all di}erent work areas and occupations in these areas[ The IOM sampling head was used to collect the dust onto Whatman 14 mm glass _bre _lter papers[ The head was worn by
operatives at the level of the left clavicle[ The _lter papers contained in the sampling cassettes were weighed pre and post collection using a Sartorius micro balance to 2 decimal places in a dedicated weighing room[ Prior to weighing\ {~y| or large par! ticles "such as feathers# were removed[ Control _lters in cassettes were also taken to each site[ This was necessary to correct for changes in weight of the _lters due to changes in water content and to look for cross! contamination with endotoxin[ Calibrated battery operated rechargeable Casella personal sampling pumps were used to draw air through the _lter[ The pump ~ow rate was set at 1 l:min at the commencement of sampling and the ~ow rate checked at the end of sampling[ Using this ~ow rate and the time of the sampling period\ the volume of air sampled could be calculated\ enabling the results to be expressed as mg of dust or ng of endotoxin per m2[ Following gravimetric analysis\ each individual _l! ter was transferred using ~amed forceps to endotoxin! free glassware\ marked with a unique identity number[ The samples were then stored below −19>C until analysis[ Throughout the analysis\ endotoxin!free products were used\ including glassware and water[ When handling volumes of 0 ml or less\ adjustable volumetric pipettes "Gilson Pipetman P# with poly! propylene pipette tips were used[ Samples were thawed at room temperature for 0 h prior to a simple water extraction technique "Gould and Olenchock\ 0876#[ 09 ml of water was added to the 09 oz "179 ml# universal containers used to store the _lters[ Samples were vortexed for 59 s\ prior to agitation on roller bars for 59 min\ and were _nally vortexed for a further 59 s[ This resulted in the dis! integration of the _lter paper[ A 3 ml aliquot of this solution was then centrifuged at 2999 ` for 04 min[ Serial dilutions were then made with 9[4 ml of the supernatant ranging from 0]09 to 0]09\999[ The maximum dilution\ within the range of the standard curve generated for the analysis\ was used in an attempt to overcome problems of inhibition and enhancement from other contaminants of the col! lected dust[ The endotoxin content was assayed using a quan! titative kinetic turbidimetric method "LAL 4999e ser! ies 1 machine Associates Cape Cod#[ The pH of the _nal solutions assayed were checked using an elec! tronic monitor[ Water negative controls were also included with each analysis[ Two di}erent batches of LAL reagent were used throughout\ lot 01!05!597!t and lot 31!022!464!t "Associates Cape Cod#[ Standard curves were generated with control standard endo! toxin E Coli 9002 lot (59 "Associates Cape Cod# and these two LAL lots[ Both curves generated had correlation coe.cients of greater than 9[889[ The endotoxin contents of the control _lters for each site were used to correct the site!speci_c mea! sured exposures[ This was both to account for the contamination of clean _lters and also possible cross!
Comparative personal exposures to organic dusts and endotoxin
contamination from the _lter!holding cassette in the IOM head "complete depyrogenation by physical methods was impossible because of the nature of the component parts#[ Using the calculated volume of air sampled\ the results are expressed as ng:m2[ With the control stan! dard endotoxin and LAL lots used\ a conversion fac! tor of approximately 09 can be used to convert the results to endotoxin units[ In addition\ the con! tamination of the dusts collected with endotoxin is also presented and expressed as ng of endotoxin per mg of dust[ RESULTS
A total of nine di}erent industries were surveyed across 25 sites[ The industries were drawn from the textile industry "cotton spinning\ wool combing and weaving#\ agriculture "mushroom cultivation and picking\ saw mills\ grain handling and animal feed manufacture# and animal handling "swine con_ne! ment\ and poultry catching and shackling#[ The gre! atest number of sites visited "00# was in the animal handling industries[ In total\ 156 samples were collected[ Only 7 "2)# of _lters were spoiled\ either by dust loading or damage to the _lter paper\ these were excluded from the analysis[ This represented a sampling rate of 14[0) "across the industries# of the available population on the day of survey[ The per! centage of the population sampled at each site was dependant on the number of individuals and the diver!
sity of jobs[ The industries studied\ the number of sites for each industry and the sampling rates are displayed in Table 0[ The mean sampling times and 84) con_dence interval for each industry and for all the samples are displayed in Table 0[ The average sampling time was 3[51 h\ the lowest was found in the poultry industry "2[45 h#[ Comparative data across the industries for personal dust exposures "expressed as mg:m2#\ endo! toxin "expressed as ng:m2# and the levels of con! tamination of dust with endotoxin "expressed as ng:mg# are displayed in Tables 1Ð3\ respectively[ The data for exposures were not normally distributed and\ consequently\ the median\ range and geometric means with 84) con_dence intervals are presented[ The highest personal dust exposures recorded were found during cleaning activities in the grain "61[4 mg:m2# and wool "51 mg:m2# industries[ The highest median exposures were found in the animal handling industries "poultry] 00[4 mg:m2\ swine] 5[6 mg:m2#[ The lowest exposures were found for geo! metric mean\ median and range in the mushroom and the weaving industries[ The highest personal endotoxin exposures were measured in the poultry "60\884 ng:m2# swine "03\812 ng:m2# and cotton "5\825 ng:m2# industries[ The endotoxin exposures may be considered as the product of the dust exposures and the levels of con! tamination of the dust with endotoxin[ Not surpris! ingly\ the highest levels of dust contamination are found in the poultry "2\418 ng:mg# cotton
Table 0[ Demographic data for the industries studied Industry Mushroom Swine Grain Poultry Saw mills Cotton spinning Wool mill Animal feed Weaving Total
Nos[ of sites
Nos[ of samples
) of work force
Mean sample time "hours# 84) con_dence interval
1 00 2 7 5 1 0 0 1 25
29 16 20 22 26 20 17 5 25 148
13[5 51[7 33[8 28[2 25[5 02[6 19[0 06[5 05[7 14[0
3[29 "2[86Ð3[51# 3[61 "3[18Ð4[03# 3[11 "2[80Ð3[42# 2[45 "2[42Ð2[65# 4[19 "3[83Ð4[34# 4[11 "3[71Ð4[50# 3[73 "3[49Ð4[07# 3[41 "3[32Ð3[59# 3[76 "3[43Ð4[19# 3[51 "3[38Ð3[63#
Table 1[ Comparative personal dust exposures expressed as mg:m2 Industry Mushroom Swine Grain Poultry Saw mills Cotton mills Wool mill Animal feed Weaving
098
Median
Minimum
Maximum
Geometric mean with 84) con_dence interval
9[57 5[60 2[23 00[42 0[27 0[93 7[63 5[6 9[48
9[98 9[65 9[97 0[38 9[18 9[11 9[67 1[88 9[98
3[38 08[98 61[40 23[38 09[04 4[28 50[58 8[96 2[86
9[58 "9[49Ð9[85# 4[67 "3[17Ð6[71# 3[25 "0[98Ð6[88# 09[47 "7[27Ð02[23# 0[34 "0[97Ð0[84# 0[98 "9[71Ð0[33# 2[82 "1[42Ð5[01# 4[85 "2[84Ð7[87# 9[48 "9[30Ð9[74#
009
J[ C[ G[ Simpson et al[ Table 2[ Comparative endotoxin exposures expressed as ng:m2 Industry
Median
Minimum
Maximum
Geometric mean with 84) con_dence interval
Mushroom Swine Grain Poultry Saw mills Cotton mills Wool mill Animal feed Weaving
6 520 094 00\882 05 327 85 20 6
0 59 2 644 1 55 0 5 9
029 03\812 1\136 60\884 155 5825 2934 74 49
6 "4Ð00# 559 "396Ð0\969# 004 "44Ð139# 7\320 "4\202Ð02\275# 08 "02Ð18# 343 "184Ð587# 72 "25Ð089# 29 "00Ð79# 4 "2Ð7#
Table 3[ Comparative contamination of dusts with endotoxin expressed as ng:mg of dust Industry Mushroom Swine Grain Poultry Saw mills Cotton mills Wool mill Animal feed Weaving
Median
Minimum
Maximum
Geometric mean with 84) con_dence interval
09 041 23 0929 04 411 29 3 09
0 8 0 003 0 63 0 1 0
334 0\463 088 2\418 076 1\881 149 01 45
00 "5Ð08# 003 "69Ð082# 15 "05Ð34# 686 "442Ð0\040# 02 "7Ð10# 306 "173Ð500# 10 "01Ð25# 4 "2Ð09# 7 "4Ð00#
"1\881 ng:mg# and swine "0\463 ng:mg# industries[ The lowest levels of endotoxin exposures are found in the mushroom "median] 6 ng:m2# and weaving "median] 6 ng:m2# industries[ The lowest levels of con! tamination were found in animal feed "median] 3 ng:mg# and again in the mushroom and weaving industries "median for both] 09 ng:mg#[ Industrial settin`s For the individual industries\ the comparative exposures to dust and endotoxin are discussed in the following text and\ where appropriate\ displayed in Tables 4Ð7[ The data for exposures were not normally distributed and\ consequently\ the median and the range for both the dust and the endotoxin are given[ Mushroom cultivation Two di}erent mushroom cultivation farms were studied both growing the basidiospore A`aricus\ the process can be split into 2 work areas] composting\ picking and packing[ The comparative exposures mea! sured in workers in each of these areas are displayed in Table 4[
Swine con_nement In the swine con_nement workers studied\ 00 di}erent sites were visited^ these were all involved with the breeding and multiplication of swine and 16 samples were collected from a possible 32 workers[ The workers were multi!skilled and worked in di}er! ent areas during a single shift\ making it di.cult to measure speci_c exposures associated with speci_c jobs[
Grain handlin` Two di}erent situations of grain handling were studied\ _rstly in a large port in the dock area where grain was unloaded and stored in silos and\ secondly\ in ~our mills where grain was stored in silos\ tested for quality in a laboratory and _nally milled[ Exposures for workers involved in cleaning the silos and the maintenance engineers at the docks and the di}erent work areas in ~our mills are displayed in Table 5[ The cleaning activities were performed manu! ally with brushes\ workers being provided with simple face masks as respiratory protective equipment[
Table 4[ Comparative dust "mg:m2# and endotoxin "ng:m2# exposures in mushroom cultivation Process Composting Picking Packing
Median
Dust Minimum
Maximum
Median
0[32 9[52 9[50
9[45 9[98 9[23
3[38 0[77 0[98
3 24[3 4[5
Endotoxin Minimum 9[7 4[3 1[4
Maximum 31[0 018[7 06[79
Comparative personal exposures to organic dusts and endotoxin
000
Table 5[ Comparative dust "mg:m2# and endotoxin "ng:m2# exposures in grain handling Docks Process Silo "cleaning# Maintenance
Median
Dust Minimum
Maximum
Median
Endotoxin Minimum
52[30 1[27
14[96 9[14
61[40 01[64
549 058
287 4
0\380 0\784
39 274 56
2 11 6
094 1\136 613
Maximum
Flour mills Work room Laboratory Silo Mill
2[17 3[36 24[81
2[00 2[1 3[40
3[37 18[25 25[04
Table 6[ Comparative dust "mg:m2# and endotoxin "ng:m2# exposures in the poultry workers Process Catching Shackling
Median
Dust Minimum
Maximum
Median
09[57 01[1
4[11 0[38
23[38 10[26
01\629 8\555
Endotoxin Minimum 644 0\927
Maximum 60\884 44\718
Table 7[ Comparative dust "mg:m2# and endotoxin "ng:m2# exposures in textile workers Cotton Process
Median
Dust Minimum
Maximum
Median
0[96 0[98 9[5 0[97
9[61 9[64 9[11 9[4
4[28 3[28 3[18 1[36
862 758 267 244
60 580 55 73
5\825 0\959 0776 0\540
Wool Process Sorting Carding Combing Finishing
1[92 02[07 1[75 9[85
0[6 2[58 9[81 9[67
3[60 50[58 6[1 0[2
177 583 41 4
063 80 2 0
313 2\934 391 6
Weaving Mill 0 Mill 1
9[10 0[17
9[98 9[37
0[91 2[86
0 08
9 0
3 49
Open:Blow Carding Spinning Winding
Poultry The workers studied in the poultry industry were the catching gangs "responsible for removing poultry from sheds\ often many thousands of birds during a shift# and the shacklers "responsible for hanging the captured birds by their legs on shackles prior to their slaughter#[ Both jobs are unpleasant and dirty\ with high dust and endotoxin exposures\ as displayed in Table 6[ Wood The wood workers studied handled soft woods and were involved in a variety of processes\ including debarking\ sawing and stacking[ Also included were the {saw doctors| who were responsible for the main! tenance of the saws used in the process^ some of their dust exposure must have included metal dust[ This is probably the reason why they were found to have relatively high dust exposures "median] 4[35 mg:m2\
Endotoxin Minimum
Maximum
range] 1[42Ð7[28 mg:m2#\ compared to the average shown in Table 1 across the saw mill industry as a whole[
Textiles Three di}erent aspects of the textile industry were studied] cotton spinning "opening and blowing\ card! ing\ spinning and winding# wool scouring and comb! ing "sorting\ carding\ combing and _nishing# and weaving "0 mill handling purely synthetic _bre and 0 a mixture of cotton and man!made _bre#[ Table 7 displays the exposures measured in the di}erent work rooms for cotton spinning and wool scou! ring:combing and the di}erence between the 1 di}er! ent mills for weaving[ The highest endotoxin exposures are found in the open and blow areas in cotton spinning and carding in wool scouring and combing[ The levels of endotoxin exposure are low in
001
J[ C[ G[ Simpson et al[
weaving\ paticularly in the mill handling the synthetic _bre "where the dust exposures are also very low#[ Animal feed The 5 workers studied in the animal feed industry produced food pellets from bone meal and other veg! etable waste matter[ The e}ect of processing on the contamination of the dust can be appreciated in Figs 0 and 1[ In these _gures "for the cotton and wool industries\ respec! tively#\ the median endotoxin contamination\ expre! ssed as ng:mg of dust\ are plotted for di}erent rooms found in the mills[ The values plotted are the mean personal exposures for workers in these rooms[ The
rooms on the x axis are displayed in a sequential manner\ with the _rst process room on the left and the last on the right[ The contamination of the dusts found in these rooms falls as the _bres are processed[ The correlation between the collected dust and the measured endotoxin is presented in Table 8[ In the calculation of the correlation coe.cients\ the logged values have been used[ For all the samples collected\ a highly signi_cant correlation is found "r 9[6\ p³9[990#[ The lack of signi_cance of the correlation found for the animal feed workers can be explained by the low number of individuals sampled "5#[ The other industries where no signi_cant correlation was found were mushroom\ swine and saw mills[
Fig[ 0[ Comparison of median levels of contamination of dust with endotoxin across rooms in cotton spinning[
Fig[ 1[ Comparison of median levels of contamination of dust with endotoxin across rooms in wool sorting and combing[
Comparative personal exposures to organic dusts and endotoxin Table 8[ Correlations between collected dusts and the mea! sured endotoxin Industry Mushroom Swine Grain Poultry Saw mills Cotton spinning Wool mill Animal feed Weaving Total
Correlation "r# −9[92 9[16 9[60 9[51 9[01 9[38 9[71 9[66 9[66 9[6
Signi_cance "p# p 9[75 p 9[06 p ³ 9[990 p ³ 9[990 p 9[49 p ³ 9[90 p ³ 9[990 p 9[97 p ³ 9[990 p ³ 9[990
DISCUSSION
This is the _rst study to provide comparative data for personal exposures to airborne organic dusts\ endotoxin and levels of dust contamination across di}erent industries in a single study[ Liesivuori has published data for endotoxin exposures in di}erent industries but no methodology\ no time scale over which the samples were collected\ and no description of the processes that the workers were involved in during collection were presented "Liesivuori\ 0883#[ In the current study\ the techniques used for the col! lection of the dust samples and their analysis for endo! toxin are accepted and validated[ Recently\ rec! ommendations have been made for the collection\ storage\ extraction and analysis of dusts for endotoxin "Jacobs\ 0886#[ The methods used in this study\ with the exceptions of sample storage at −19>C and sample vortexing during the extraction\ are in line with these recommendations[ The values obtained for the endo! toxin exposures should be interpreted with the fol! lowing two points in mind[ Firstly\ it is recognised that a water extraction\ whilst simple and reproducible\ is not exhaustive and the values obtained may be an underestimate of the true exposures "Chun\ 0887^ Jacobs\ 0886#[ Secondly\ and less likely\ components of the di}erent dusts collected could a}ect the rate of extraction[ The endotoxin results therefore are not absolute exposure levels but comparative and speci_c for the methodology used[ The highest dust exposures were found in the grain "61[4 mg:m2# and wool "50[6 mg:m2# industries^ both of these occurred during cleaning activities[ The high! est median exposures were seen in the animal handling industries "01[7 mg:m2 poultry# and the lowest in weaving "9[5 mg:m2#[ The measured personal dust exposures in animal and grain handling\ wood\ cotton and wool industries are broadly similar to those found by other inves! tigators "Rylander et al[\ 0876^ Hurst and Dosman\ 0889^ Halpin et al[\ 0883^ Sigsgaard et al[\ 0881^ Love et al[\ 0877#[ Detailed comparisons are not valid but the broad agreement supports the proposition that the samples collected are representative for the individuals working in these industries[
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Data exist to support the hypothesis that higher dust exposures in the wood\ grain\ swine\ wool and cotton spinning industries result in greater respiratory morbidity "Enarson and Chan!Yeung\ 0889^ Hurst and Dosman\ 0889^ Donham\ 0889^ Love et al[\ 0877^ Rylander\ 0889#[ As a re~ection of this in the UK\ occupational exposure limits "OEL# exist for dust exposures EH39:87 "HSE\ 0887#] a maximum exposure limit "MEL# for grain] 09 mg:m2\ wood dust "hard and soft#] 4 mg:m2\ man!made mineral _bre] 4 mg:m2\ cotton] 1[4 mg:m2 and wool process dust] 09 mg:m2[ In addition\ in Britain\ the Control of Sub! stances Hazardous to Health Regulations apply to any other dust if the 7 h time!weighted!average exposure exceeds 09 mg:m2[ From the results of this study\ it can be appreciated that exposures are exceeding these values[ The weaving and mushroom cultivation indus! tries are the only ones to have no measured exposure greater than occupational exposure limits[ However\ no calculations for respiratory protection equipment have been used in this study[ Endotoxin exposures are related to two factors\ the level of dust contamination and the level of dust exposure[ The lowest exposures were seen in the weav! ing industry "median] 6 ng:m2#\ where the dust exposures were low and the contamination of the dust with endotoxin was low "median] 09 ng:mg#[ Conversely\ high exposures were seen in animal hand! ling "poultry median] 00\882 ng:m2\ peak] 60\884 ng:m2# and cotton spinning "median] 327 ng:m2#\ where highly contaminated dusts "poultry median] 0\929 ng:mg\ cotton median] 411 ng:mg# were found and workers have high personal exposures to dust[ Deleterious e}ects from endotoxin have been reported with occupational exposures as low as 8 and 04 ng:m2 "Castellan et al[\ 0876^ Milton et al[\ 0883# and experimental exposures of 19 mg for isolated "Michel et al[\ 0878# and 29 mcg for cell!bound endo! toxin "Rylander\ 0876a\ 0876b#[ Even allowing for di}erences in methodology\ the results from the cur! rent survey would suggest that signi_cant exposures are occurring[ At the present time\ no speci_c exposure limits for endotoxin exist\ although the Committee on organic dusts of the ICOH has completed work on an endotoxin criteria document "Rylander\ 0886#[ It concludes that the following environmental endotoxin exposures are levels at which no e}ect is seen for the following conditions^ toxic pneumonitis] 199 ng:m2\ systemic e}ects] 099 ng:m2 and 09 ng:m2 for increased airways in~ammation[ By implication\ levels higher than these are potentially harmful[ These levels are a little di}erent from those highlighted by Olenchok in his review of the health e}ects of endotoxins "Olen! chock\ 0883#\ where the following levels of exposure were associated with di}erent e}ects] organic dust toxic syndrome\ 0999 to 1999 ng:m2\ acute bron! choconstriction\ 099 to 199 ng:m2\ and mucous mem! brane irritation at 19 to 49 ng:m2[ Individuals may also be more or less susceptible to the e}ects of endotoxin\ perhaps depending upon atopy\ smoking habits or
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J[ C[ G[ Simpson et al[
other\ as yet\ unidenti_ed factors[ Applying these exposure limits to the current study population would mean that only the mushroom and the weaving indus! try would have median or mean levels for their work! forces lower than a no!e}ect level[ Even in these indus! tries\ pickers in mushroom cultivation and workers weaving man made _bre and cotton may have average exposures higher than a no!e}ect limit[ Most workers in swine con_nement\ poultry handling and cotton spinning\ and some in grain handling "maintenance workers and silo operators and cleaners# and wool scouring and combing "sorting and carding# will have exposures consistently over 099 ng:m2\ and often over 0999 ng:m2[ The introduction of exposure limits will be di.cult[ Having accepted that the calculated exposure limits are correct and valid using the data currently available from experimental and\ more importantly\ epi! demiological studies\ problems still exist[ Firstly\ a standard methodology\ used by all analysing lab! oratories\ shown to give identical results in each setting\ would need to be developed[ The current situ! ation is far from this "Chun\ 0887#[ Perhaps\ more importantly\ endotoxin as well as having a direct e}ect\ may be acting in a facilitatory role\ allowing other agents to have a greater e}ect\ similar to the interaction seen between the non!speci_c irritant ozone and subsequent allergen challenge "Mol_no et al[\ 0880#[ This would mean that an industry!speci_c endotoxin exposure standard would be more appro! priate than a general standard[ For the wool and cotton spinning industries "where a breakdown of exposures occurring in individual rooms is presented#\ the e}ect of processing on the contamination of dusts can be appreciated "Figs 0 and 1#[ Individuals in the earlier processes are exposed to the most highly contaminated dust[ In the cotton spinning industry\ as the waste material is removed during opening and carding\ contamination falls[ In the wool industry\ where a scouring process takes place between sorting and carding\ the fact that endo! toxin can be destroyed by heat!treatment or alkali\ demonstrated in experimental situations "Rousselle\ 0883#\ is shown in {real life|[ Finally\ the _nding of a strong and signi_cant cor! relation "r 9[6\ p³9[990# between the collected dust and measured endotoxin content should be critically appraised[ Figures 0 and 1 demonstrated that the con! tamination of dust with endotoxin changed with pro! cessing^ it would therefore be reasonable to expect the correlation between the collected dust and measured endotoxin levels to be poor[ In the wool industry\ a value of r 9[71\ p³9[990 is obtained[ This can be explained by the unequal distribution of samples taken across rooms and sites because of the diversity of jobs and numbers of employees in di}erent rooms[ Considering the cohort as a whole\ the industries where consistently high dust exposures are found also have highly contaminated dusts and\ conversely\ industries where the lowest dust exposures were found
had little contamination[ This highlights the fact that correlations between dust and endotoxin presented in this and other studies should be interpreted with caution and in conjunction with the documented vari! ation in the levels of dust contamination between rooms[ The full potential of dusts and endotoxins\ either separately or in combination\ has not yet been fully elucidated and more work in this area is required[ Until this time\ more vigorous attempts to control dust and endotoxin exposures need to be made[ A dual approach is required[ Firstly\ the requirements of employers to ensure that exposures are within the currently acceptable limits needs to be highlighted and\ where appropriate\ monitored[ Secondly\ employees need to be encouraged to wear respiratory protective equipment in situations where high exposures are possible[ To encourage this\ employees need to be educated about the potential e}ects of organic dust exposures and made aware that suitable protective equipment is readily available[
REFERENCES Becklake\ M[ R[ "0874# Chronic air~ow limitations] Its relationship to work in dusty occupations[ Chest 77"3#\ 597Ð506[ Campbell\ J[ M[ "0821# Acute symptoms following work with hay[ B[ M[ J[ 2\ 0032[ Castellan\ R[ M[\ Olenchock\ S[ A[\ Kinsley\ K[ B[ and Han! kinson\ J[ L[ "0876# Inhaled endotoxin and decreased spi! rometric values[ N[ En`l[ J[ Med[ 206\ 594Ð509[ Chan!Yeung\ M[ and Malo\ J[ L[ "0883# Aetiological agents in occupational asthma[ Eur[ Respir[ J[ 6\ 235Ð260[ Chun\ D[ T[ "0887# Preliminary report on the results of the _rst phase of a round robin endotoxin assay using cotton dust[ In Proceedin`s of the 11nd Cotton and Or`anic Dusts Research Conference Beltwide Cotton Conferences "Edited by P[ J[ Wakelyn\ R[ R[ Jacobs and R[ Rylander#\ pp[ 084Ð 087[ National Cotton Council\ Memphis\ ISBN] 9 8502397 09 01[ Donham\ K[ J[ "0889# Health e}ects from work in swine con_nement buildings[ Am[ J[ Ind[ Med[ 06\ 06Ð14[ Enarson\ D[ A[ and Chan!Yeung\ M[ "0889# Charac! terisation of health e}ects of wood dust exposures[ Am[ J[ Ind[ Med[ 06\ 22Ð27[ Gould\ M and Olenchock\ S[ "0876# Endotoxin extraction method for organic dusts[ In Proceedin`s of Endotoxin Inhalation Workshop "Edited by R[ Rylander\ R[ Burrell and Y[ Peterson#\ pp[ 193Ð194[ Swedish Work Environ! ment Fund[ Stockholm\ Sweden[ Contract 76!9767[ Haglind\ P[ and Rylander\ R[ "0876# Occupational exposure and lung function measurements among workers in swine con_nement buildings[ J[ Occ[ Med[ 18"00#\ 893Ð896[ Halpin\ D[ M[ G[\ Graneek\ B[ J[\ Lacey\ J[\ Nieuwenhuijsen\ M[ J[\ Williamson\ P[ A[ M[\ Venables\ K[ M[\ Newman Taylor\ A[ J[ "0883# Respiratory symptoms\ immu! nological responses and aeroallergen concentrations at a sawmill[ Occup Environ Med[ 40\ 054Ð061[ Health and Safety Executive "0887# Occupational Exposure Limits[ HMSO Norwich\ ISBN] 9 6065 0363 2[ Hurst\ T[ S[ and Dosman\ J[ A[ "0889# Characterisation of health e}ects of grain dust exposures[ Am[ J[ Ind[ Med[ 06\ 16Ð21[ Jacobs\ R[ R[ "0886# The endotoxin criteria document] Environmental monitoring for endotoxin aerosols[ In Pro! ceedin`s of the 10st Cotton and Or`anic Dusts Research
Comparative personal exposures to organic dusts and endotoxin Conference Beltwide Cotton Conferences "Edited by P[ J[ Wakelyn\ R[ R[ Jacobs and R[ Rylander#\ pp[ 045Ð048[ National Cotton Council\ Memphis\ ISBN] 9 8502397 09 00[ Kennedy\ S[ M[\ Christiani\ D[ C[\ Eisen\ E[ A[\ Wegman\ D[ H[\ Greaves\ I[ A[\ Olenchock\ S[ A[\ Ye\ T[!T[ and Lu\ P[!L[ "0876# Cotton dust and endotoxin exposure!response relationships in cotton textile workers[ Am[ Rev[ Respir[ Dis[ 024\ 083Ð199[ Liesivuori\ J[ "0883# Airborne endotoxin concentrations in di}erent work conditions[ Am[ J[ Ind[ Med[ 14\ 012Ð013[ Love\ R[ G[\ Smith\ T[ A[\ Gurr\ D[\ Soutar\ C[ A[\ Scar! isbrick\ D[ A[ and Seaton\ A[ "0877# Respiratory and allergic symptoms in wool textile workers[ Br[ J[ Ind[ Med[ 34\ 616Ð630[ Michel\ O[\ Duchateau\ J[ and Sergysels\ R[ "0878# E}ect of inhaled endotoxin on bronchial reactivity in asthmatic and normal subjects[ J[ Appl[ Physiol[ 55\ 0948Ð0953[ Michel\ O[\ Ginanni\ R[\ Duchateau\ J[\ Vertongen\ F[\ Le Bon\ B[ and Sergysels\ R[ "0880# Domestic endotoxin exposure and clinical severity of asthma[ Clin[ Exp[ Aller`y 10\ 330Ð337[ Milton\ D[ K[\ Kriebel\ D[\ Wypij\ D[\ Walters\ M[\ Hammond\ S[ K[ and Evans\ J[ "0883# Acute and chronic air~ow obstruction and endotoxin exposure[ Am[ Rev[ Respir[ Dis[ 038\ A288[ Mol_no\ N[ A[\ Wright\ S[ C[\ Katzi\ I[\ Tarho\ S[\ Silverman\ F[\ MaClean\ P[ A[\ Szalai\ J[ P[\ Raizenne\ M[\ Slutsky\ A[ S[ and Zamel\ N[ "0880# E}ect of low concentration of ozone on inhaled allergen responses in asthmatic subjects[ The Lancet 227\ 088Ð192[ Niven\ R[ McL[\ Fletcher\ A[ M[\ Pickering\ C[ A[ C[\ Simp! son\ J[ C[ G[\ Oldham\ L[ A[ and Bakirci\ N[ "0887# Repeat! ability of sampling for endotoxin and dust within 2 cotton textile mills[ In Proceedin`s of the 11nd Cotton and Or`anic Dusts Research Conference Beltwide Cotton Conferences "Edited by P[ J[ Wakelyn\ R[ R[ Jacobs and R[ Rylander#\ pp[ 088Ð191[ National Cotton Council\ Memphis\ ISBN] 9 8502397 09 01[
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Olenchock\ S[ A[ "0883# Health e}ects of biological agents] the role of endotoxins[ Appl[ Occ[ Env[ Hy`[ 8"0#\ 51Ð 53[ Rask!Andersen\ A[ "0877# Pulmonary Reactions to Inha! lation of Mould Dust in Farmers With Special Reference to Fever and Alveolitis[ Doctoral thesis\ Uppsala Univer! sity[ Sweden[ Rask!Andersen\ A[ "0878# Organic dust toxic syndrome among farmers[ Brit[ J[ Ind[ Med[ 35\ 122Ð127[ Rousselle\ M[!A[ "0883# Endotoxin content of dust from heat!detoxi_ed cotton _ber[ In Proceedin`s of the 07th Cotton and Or`anic Dusts Research Conference Beltwide Cotton Conferences "Edited by P[ J[ Wakelyn\ R[ R[ Jacobs and L[ N[ Domelsmith# pp[ 251Ð253[ National Cotton Council\ Memphis\ ISBN] 9 8502397 09 7[ Rylander\ R[ "0876# Role of endotoxins in the pathogenesis of respiratory disorders[ Eur[ J[ Respir[ Dis[ Suppl[ 043\ 025Ð033[ Rylander\ R[ "0876# Toxicity of inhaled isolated and cell bound endotoxin[ In Proceedin`s of Endotoxin Inhalation Workshop "Edited by R[ Rylander\ R[ Burrell and Y[ Peterson#\ pp[ 191Ð192[ Swedish Work Environment Fund[ Stockholm\ Sweden[ Contract 76!9767[ Rylander\ R[\ Bake\ B[\ Fischer\ J[ J[ and Helander\ I[ M[ "0878# Pulmonary function and symptoms after inhalation of endotoxin[ Am[ Rev[ Respir[ Dis[ 039\ 870Ð875[ Rylander\ R[ "0889# Health e}ects of cotton dust exposures[ Am[ J[ Ind[ Med[ 06\ 28Ð34[ Rylander\ R[ "0886# The endotoxin criteria document] the risk evaluation[ In Proceedin`s of the 10st Cotton and Or`anic Dusts Research Conference Beltwide Cotton Con! ferences "Edited by P[ J[ Wakelyn\ R[ R[ Jacobs and R[ Rylander#\ pp[ 042Ð045[ National Cotton Council\ Memphis\ ISBN] 9 8502397 09 00[ Sigsgaard\ T[\ Pedersen\ O[ F[\ Juul\ S[ and Gravesen\ S[ "0881# Respiratory disorders and atopy in cotton\ wool and other textile mill workers in Denmark[ Am[ J[ Ind[ Med[ 11\ 052Ð073[