current man-made mineral fibers (mmmf) exposures … · current man-made mineral fibers (mmmf)...

$: Current Man-Made Mineral Fibers (MMMF) Exposures … · Current Man-Made Mineral Fibers (MMMF) Exposures ... Keywords man-made mineral ﬁbers, synthetic vitreous ﬁbers, refractory$
Journal of Occupational and Environmental Hygiene, 1: 306–318ISSN: 1545-9624 print / 1545-9632 onlineCopyright c© 2004 JOEH, LLCDOI: 10.1080/15459620490445462

Current Man-Made Mineral Fibers (MMMF) ExposuresAmong Ontario Construction Workers

Dave K. Verma,1 Dru Sahai,2 Lawrence A. Kurtz,1

and Murray M. Finkelstein1

1Program in Occupational Health and Environmental Medicine, McMaster University,Hamilton, Ontario, Canada2Construction Safety Association of Ontario, Etobicoke, Ontario, Canada

Current occupational exposures to man-made mineralfibers (MMMF), including refractory ceramic fibers (RCF),were measured as part of an exposure assessment program foran epidemiological study pertaining to cancer and mortalitypatterns of Ontario construction workers. The assessmentswere carried out at commercial and residential sites. A total of130 MMMF samples (104 personal and 26 area) was collectedand included 21 RCF (16 personal and 5 area). The sampleswere analyzed by the World Health Organization method inwhich both respirable and nonrespirable airborne fibers arecounted. The results show that Ontario construction work-ers’ full-shift exposure to MMMF (excluding RCF) is gener-ally lower than the American Conference of Governmental In-dustrial Hygienists’ (ACGIH©R ) recommended threshold limitvalue–time-weighted average (TLV©R-TWA) of 1 fibers/cc andthus should not present any significant hazard. However, ap-proximately 40% of the occupational exposures to RCF arehigher than ACGIH’s TLV-TWA of 0.2 fibers/cc and present asignificant potential hazard. Workers generally wore adequateapproved respiratory protection, especially while performingparticularly dusty tasks such as blowing, spraying, and cutting,so the actual exposure received by workers was lower than thereported values. Adequate control measures such as ventilationand respiratory protection should always be used when workinvolves RCF.

Keywords man-made mineral fibers, synthetic vitreous fibers,refractory ceramic fibers, construction, fiber counts,fiber counting rules

Address correspondence to: Dave K. Verma, Program in Occu-pational Health and Environmental Medicine, McMaster University,1200 Main Street West, Hamilton, ON, Canada L8N 3Z5; e-mail:[email protected].

INTRODUCTION

M an-made mineral fibers (MMMF) constitute a family ofman-made, glass-like fibrous products. These fibers are

noncrystalline, that is they are amorphous, unlike asbestos thathas crystalline fibers. MMMF are made from molten glass (fi-brous glass), molten rock (rock wool), molten slag (slag wool),or clay (ceramic fibers). The terms “man-made vitreous fibers”or “synthetic vitreous fibers” are often used in place of MMMF.

Health concerns about MMMF are based on the morpholog-ical and toxicological similarities it has with asbestos. Asbestosis well known to be a potent occupational carcinogen causingasbestosis, lung cancer, mesothelioma, and cancers at varioussites.(1) Epidemiological evidence for human disease from fi-brous glass is largely negative, with some association reportedfor slag and rock wool.(2–4) On the basis of epidemiological ev-idence, the U.S. Environmental Protection Agency (EPA)andthe International Agency for Research on Cancer (IARC) clas-sified mineral wool, glass wool, and special purpose glass fibersas either possible or probable human carcinogens.(5,6)

Recently IARC reevaluated the carcinogenic risk of air-borne man-made vitreous fibers.(7) Epidemiological studiespublished since a 1988 monograph review,(5) plus research onnewer developed materials, were evaluated. The IARC reviewconcluded that only the more biopersistent materials such asrefractory ceramic fiber (RCF) remain classified as possiblehuman carcinogens (Group 2B). Continuous glass filamentsand the more commonly used vitreous fiber wools such asinsulation glass wool, rock (stone) wool, and slag wool arenow considered not classifiable as to their carcinogenicity tohumans (Group 3).(7)

The American Conference of Governmental Industrial Hy-gienists (ACGIH©R )(8) has also classified various MMMF incategories ranging from classification A2—suspected humancarcinogen, A3—confirmed animal carcinogen, and A4—nonclassifiable as a human carcinogen. The recommendedthreshold limit–value-time-weighted average (TLV©R-TWA)for all MMMF except RCF is 1 fiber/cc, and 0.2 fibers/cc forRCF because it is a suspected human carcinogen.(8)

Taken as a whole, evidence suggests that the risk of lungdiseases from MMMF exposure is very low in comparison

306 Journal of Occupational and Environmental Hygiene May 2004

with asbestos. In many commercial and residential construc-tion operations such as insulating, fireproof spraying, taping,and texturing, MMMF has been substituted for asbestos toreduce the health risk and protect workers. Although the riskis much lower than with asbestos, there still remains a con-cern about MMMF exposure, thus the need to gather expo-sure data involving its use. Selikoff et al.(9) found that insula-tors had a very high rate of cancer from asbestos insulation.Verma and Middleton(10) found tapers to have high exposureto asbestos.(10) In the past, sprayed fireproofing operationsentailed spraying asbestos or asbestos-containing materials onsteel beams.(11,12) Oska et al.(13) found excessive occurrences ofmesothelioma among asbestos sprayers, and the highest cancerincidence in a cohort study of Finnish asbestos sprayers andasbestosis and silicosis patients.The authors postulated thatthis was due to the high carcinogenic potential of crocidolite,which was the main type of asbestos sprayed in Finland prior tobeing prohibited, and high airborne dust concentration encoun-tered in this operation. Since the mid-1970s, asbestos has beenreplaced with MMMF in insulation and fireproofing productsto minimize the health hazard in these operations.

In June 2000, our group received a grant from the WorkplaceSafety and Insurance Board of Ontario to conduct a studyentitled, “Cancer, Mortality, and Workplace Exposures AmongOntario Construction Workers.” The objectives of this studywere to assess the cancer and mortality patterns of union con-struction workers in Ontario (approximately 125,000 workersfrom nine unions), their cancer risks, and to assess both qualita-tively and quantitatively the risks of current occupational expo-sure to chemical agents. To accomplish our quantitative assess-ment, we visited numerous construction sites and conducted arange-finding exercise using task-based exposure assessmentmethods, traditional sampling (pump and filter), and direct-reading instruments. The cumulative results of our exposuremeasurement study, including a summary of the data presentedin this article, have been reported elsewhere.(14) The objectivesof this article are to present exposure data for MMMF, includ-ing RCF, collected during this study and to compare the resultswith those published in literature.

MATERIALS AND METHODS

Workplace and Process DescriptionThe installation of MMMF products is an important and

routine operation in the construction industry. MMMF is foundin all types of construction including residential, commercial,industrial, renovation, and major structural. In general, MMMFproducts can be categorized into three classes: sprayed/blown,batt, and reinforcing. Sprayed/blown products are applied di-rectly to building surfaces using spraying or blowing tech-niques. The MMMF is usually mixed with water and someform of binding material such as cement, and then sprayedusing hydraulic or pneumatic pressure. Structural insulation orfireproofing is typically applied in this manner. Batt insulationrefers to a group of products applied in sheets, rolls, and/orpanel forms to building surfaces. The MMMF may serve as

acoustical or thermal protection and may contain fiberglass,rock wool, slag wool, and/or refractory fibers. The batt productsare usually contained in protective backings such as aluminumfoil or paper. Acoustic tiles, ceiling tiles, residential insulation,pipe insulation, duct insulation, and/or boiler wrapping aretypical of batt MMMF products. In reinforcing material suchas drywall, floor tiles, and roofing felts, MMMF helps improvestructural integrity. The loose insulating fiberglass wool is usedin residential construction in attic spaces and is installed byblowing using a pneumatic system.

In Ontario, construction workers are exposed to MMMFfrom primary and secondary sources. Construction workersdirectly involved in installation or application of MMMF ma-terials are primarily exposed to MMMF. Workers not directlyinvolved in the application of MMMF materials, but who areexposed by virtue of construction work going on nearby orwho are in the presence of MMMF in unfinished construction,are secondarily exposed.

The type of construction worker performing a certain taskis determined by the winning contractor and by union rulesregarding the substrate to be used in the construction. Somecontractors may employ one type of trade such as laborers,whereas another firm may employ another type of trade suchas cement masons. Therefore, the type of tradesperson doingthe work depends largely on the firm that wins the tender. Fur-thermore, provincial collective agreements between employers(contractors) and employees (tradespeople) list the types ofwork performed and the bounds of that work. The bounds areoften set by the major material being worked on or substrate.Different substrates, such as wood, steel, concrete, piping, orductwork, will dictate which trade is allowed to perform thework. For example, if studs against a concrete fascia are beinginsulated with batt insulation, a cement mason will perform thework. However, if drywall or wood panel is being insulated, acarpenter will insulate the wall. In both cases the same MMMFmaterial may be used (i.e., fiberglass) but the trade will bedifferent.

Table I lists the most common uses of MMMF in the Ontarioconstruction industry and the corresponding trades primarilyexposed to the materials. Various tasks sampled in this studyincluded blowing, mixing, spraying, installing, cutting, han-dling, sweeping, and wrapping MMMF. Figure 1 shows someof the typical tasks.

Sampling and AnalysisAir Sampling

The majority of samples were collected January 2000 toMay 2002. Prospective subjects were approached and informedof the nature and purpose of the study. They were asked towear air sampling equipment and advised that participationwas voluntary. Both personal and area samples were taken forfiber counts using portable personal air sampling pumps. Airsamples for fiber counts were taken using a 25-mm, 3-pieceopen-face cassette at a flow rate of 1–2 L/min. Mixed cellu-lose ester filters of 0.8-µm pore size (Millipore Corporation,

Journal of Occupational and Environmental Hygiene May 2004 307

TABLE I. Primary Uses of MMMF in the Ontario Construction Industry

MMMF Type of Worker TaskCategory MMMF Use Affected Trades Specialization

Sprayed Rock wool Thermal insulation, structuralfireproofing, acoustic insulation

Painters, cement masons,laborers

Foreman, sprayer,mixer, helper

Slag wool Thermal insulation, structuralfireproofing



Mineral wool Thermal insulation, acoustic insulation,structural fireproofing



Blown Fiberglass Thermal Insulators Sprayer, loader,helper

Batt Rock wool Moisture barrier, acoustic insulation,thermal insulation

Carpenters, cement masons Installer, helper

Fiberglass Pipe insulation, boiler lagging,duct insulation, framing insulation

Insulators, carpenters,boilermakers

Foreman, installer,helper

RCF High-heat thermal insulation,duct insulation, structural insulation

Insulators, laborers Foreman, installer,helper

Brick RCF High-heat thermal brick Bricklayers Foreman, installer,cutter, helper

Panel Rock wool Acoustic insulation, moisture barrier Insulators, cement masons Installer, helperFiberglass Duct wrap, ceiling tiles Insulators, laborers, painters Installer, helper

Structural panel Fiberglass Drywall Carpenters, painters Drywaller, helperStructural felt Fiberglass Roofing membrane Roofers, waterproofers Foreman, roofer,

helperStructural tile Fiberglass Floor tile Floorlayers Floorlayer, helper

Bedford, Mass., or Pall Corporation, Ann Arbor, Mich.) wereused. Since it is important not to overload the filter for fibercounting, the appropriate sampling duration was determined bytrial and error to ensure that filters could be counted. Thus, thesampling time varied depending on the expected dustiness ofthe operation and location. An attempt was made to sample forthe total duration of the task or for as long as possible withoutoverloading the filter. Where possible, personal samples weretaken; otherwise, area samples that were representative of thesubject worker’s exposure were taken.

AnalysisThe evaluation of the membrane filter for fiber counting

was carried out in accordance with the World Health Organi-zation (WHO) MMMF reference method.(15) In this methodboth respirable fibers having a diameter <3 µm and a length>5 µm with an aspect ratio (length to diameter) of 3:1, andnonrespirable fibers having a diameter ≥3µm and a length>5 µm with an aspect ratio (length to diameter) of 3:1, arecounted using phase contrast microscopy at a magnification of450×. If respirable and nonrespirable fiber counts of the WHOmethod are combined, then the result would approximate thefiber counts by National Institute of Occupational Safety andHealth (NIOSH) 7400 A rule method in which all fibers >5 µmlength with an aspect ratio of 3:1 irrespective of diameter areincluded.(16) The WHO method is one of the two methods rec-

ommended in ACGIH’s documentation of TLVs of syntheticvitreous fibers.(8) The other recommended method of analysisis the NIOSH method 7400 using B rules for counting.(16)

Using NIOSH 7400 B counting rules, fibers are counted withdiameters <3 µm, length >5 µm, but with an aspect ratio(length to diameter) of 5:1. Thus, all else being equal, NIOSH7400 B rules give lower results than the WHO method sincethe WHO method includes fibers with a shorter aspect ratio.It should be noted that respirable fibers have been definedin the documentation of the TLVs(8) as those with lengths>5 µm and with an aspect ratio of 3:1. Strictly speaking, theWHO method meets the definition more closely than 7400B rules method. The 7400 B method is generally used inNorth America, while the WHO method is used in Europeand elsewhere. In earlier studies, however, the NIOSH 7400 Arule method was generally applied.

Quality ControlAppropriate quality control procedures were adhered to in

the field sampling and in the analyses of collected samples inthe analytical laboratory. During the field sampling all air sam-pling pumps were calibrated pre- and postsampling. Hygienetechnical personnel observed the sampling. McMaster Uni-versity Occupational and Environmental Health Laboratory(OEHL) performed the analysis for fiber counts. The OEHL, anAmerican Industrial Hygiene Association accredited facility,


FIGURE 1. (a) Insulator spraying fireproofing, (b) Painter mixing sprayed fireproofing, (c) Laborer demolishing building, and (d) Insulatorblowing insulation

is experienced in the analysis of fiber counting procedures andparticipates in a proficiency analysis testing program for fibercounting.

RESULTS

A total of 130 MMMF samples (104 personal, 26 area) wascollected that included 21 RCF (16 personal, 5 area) sam-

ples. Only respirable concentration results are summarized inTable II. The table shows the range of results for specific tasksby trade, along with an assessment as to whether the exposure

was primary or secondary. Residential, commercial, industrial,and demolition sites were assessed. Fifteen of the 130 MMMFsamples including 2 out of 21 RCF samples are from secondaryexposure in which workers sampled were not directly involvedin MMMF work. Most of these samples were taken whenother operations such as insulating, mixing, and spraying werebeing carried out in the vicinity at the commercial site. Avalue of half the detection limit for the method was used tocalculate the mean respirable fiber concentrations (shown inTable II) where concentrations were reported as below detec-tion limit.


TAB

LE

II.D

istr

ibu

tio

no

fR

esp

irab

leM

MM

FC

on

cen

trat

ion

byTr

ade

and

Mat

eria

lUse

d

Sam

plin

gR

espi

rabl

eF

iber

Con

cent

rati

onD

urat

ion

(min

)(f

/cc)

MM

MF

Cat

egor

yT

rade

/O

ccup

atio

nSi

teT

ype

Maj

orTa

sks

Sam

ple

Size

Typ

eM

inM

axM

ean

Med

ian

Min

Max

MM

MF

(exc

ludi

ngR

CF)

Bat

tB

rick

laye

rC

Inst

allin

g/sm

okes

ealin

g1

P—

28—

——

0.09

Car

pent

erR

,CIn

stal

ling

2P

4759

0.12

—0.

060.

18C

Smok

esea

ling

1P

—52

——

—0.

70Fo

rem

anI

Cle

anin

g/ha

ndlin

g1

P—

80—

——

0.10

IV

acuu

min

g1

P—

94—

——

0.05

Insu

lato

rI

Cut

ting

1P

—86

——

—0.

19I

Han

dlin

g2

P66

105

0.23

—0.

220.

24I,

RIn

stal

ling

7P

4197

0.19

0.17

BD

L0.

591

A—

83—

——

BD

LI

Inst

allin

g/cu

tting

/han

dlin

g9

P70

980.

290.

240.

130.

64R

Poly

ing

3P

3995

BD

LB

DL

BD

LB

DL

Lab

orer

IR

emov

ing

4P

133

151

0.15

0.15

0.13

0.18

ISt

orin

g6

P74

126

0.09

0.08

0.05

0.13

Blo

wn

Insu

lato

rR

Blo

win

g(R

)5

P14

270.

660.

620.

460.

95C

eilin

gtil

esL

abor

erI

Cle

anin

g1

P—

15—

——

1.75

1P

—15

——

—0.

49I

Hel

ping

3P

1842

0.49

0.29

0.25

0.93

IR

emov

ing

3P

1628

0.78

0.68

0.40

1.25

3A

1642

0.66

0.40

0.32

1.26

Dry

wal

lC

arpe

nter

CC

uttin

g/in

stal

ling

3P

3092

0.15

0.10

0.10

0.26

Duc

twra

pIn

sula

tor

CC

uttin

g/w

rapp

ing

1P

—46

——

—B

DL

CPi

nnin

g3

P12

124

0.04

0.06

BD

L0.

07C

Wra

ppin

g2

P13

167

BD

L—

BD

L0.

032

A62

130

0.04

—B

DL

0.08

Pipe

wra

pIn

sula

tor

CW

rapp

ing

1P

—66

——

—0.

06Sp

raye

dfir

epro

ofB

rick

laye

rC

Seco

ndar

yex

posu

re-w

orki

ngon

wal

l2

P76

308

0.08

—0.

010.

15E

lect

rici

anC

Seco

ndar

yex

posu

re-w

orki

ngov

erhe

ad4

P37

232

0.19

0.03

BD

L0.

70In

sula

tor

ISp

rayi

ng4

P10

180.

680.

660.

351.

08L

abor

erI

Hel

ping

/load

ing/

mix

ing

2P

2535

0.31

—0.

250.

36I

Loa

ding

/mix

ing

2P

3273

0.23

—0.

110.

34C

Mix

ing

1P

—30

——

—0.

05C

Swee

ping

1P

—27

——

—0.

22I

Swee

ping

/set

up1

P—

27—

——

0.35

310

Mul

tiple

wor

kers

CSe

cond

ary

expo

sure

-wor

king

over

head

2A

263

322

0.02

—0.

020.

02Pa

inte

rC

Spra

ying

1P

—66

——

—0.

062

A15

960.

04—

0.02

0.06

CH

elpi

ngsp

ray

1P

—53

——

—0.

07Pi

pefit

ter

CSe

cond

ary

expo

sure

-wor

king

over

head

1P

—11

3—

——

0.03

Plum

ber

CSe

cond

ary

expo

sure

-wor

king

over

head

1P

—31

5—

——

0.01

Shee

tmet

alw

orke

rC

Seco

ndar

yex

posu

re-w

orki

ngov

erhe

ad1

P—

160

——

—0.

08V

ario

usE

lect

rici

anC

Seco

ndar

yex

posu

re-w

orki

ngon

wal

l1

P—

95—

——

0.06

Iron

wor

ker

DSe

cond

ary

expo

sure

-wor

king

ongr

ound

1A

—72

——

—0.

67L

abor

erD

Dem

olis

hing

stru

ctur

es2

P45

201

0.29

—B

DL

0.58

2A

2728

0.16

—0.

120.

20D

Dem

olis

hing

/ope

rate

sm

achi

nes

3A

4781

0.64

0.66

0.45

0.82

CSw

eepi

ng2

P76

131

0.63

—0.

061.

21Su

perv

isor

DD

emol

ishi

ng/s

ettin

gup

1P

—40

——

—0.

69M

ultip

lew

orke

rsD

Dem

olis

hing

/var

ious

4A

3668

0.22

0.19

0.04

0.48

RC

FB

att

Lab

orer

CFi

nish

ing

1P

—14

3—

——

0.08

CFo

ldin

g/pr

epar

atio

n2

P13

018

20.

05—

0.04

0.06

3A

9632

1B

DL

BD

LB

DL

BD

LC

Inst

allin

g2

P32

633

30.

05—

0.03

0.06

Mul

tiple

wor

kers

CSe

cond

ary

expo

sure

-bey

ond

encl

osur

e2

A87

127

0.02

—B

DL

BD

LB

rick

Bri

ckla

yer

IC

uttin

g1

P—

69—

——

1.64

IIn

stal

ling

1P

—67

——

—0.

38Fo

rem

anI

Supe

rvis

ing

1P

—63

——

—0.

28L

abor

erI

Hel

ping

1P

—58

——

—0.

59Pi

pew

rap

Insu

lato

rI

Inst

allin

g5

P56

910.

420.

400.

260.

65Sp

raye

dL

abor

erI

Dum

ping

2P

1014

0.11

—0.

100.

13

Not

es:

Site

type

:R=

resi

dent

ial;

C=

com

mer

cial

;I=

indu

stri

al;D

=de

mol

ition

.P

=pe

rson

al;A

=ar

ea;B

DL

=be

low

dete

ctio

nlim

it.

311

FIGURE 2. Boxplot of MMMF (excluding RCF) respirable fiber distribution by material used. Outliers are shown as*

Data were analyzed using the statistical packageMinitab©R (17) version 12. Figure 2 shows boxplots of the dis-tribution of the combined personal and area samples by mate-rial type for MMMF (excluding RCF). Figure 3 shows sim-ilar information for RCF. Boxplots illustrate the statisticalrange of data between the 25th and 75th percentiles, withwhiskers extending out showing the general range of all data.

FIGURE 3. Boxplot of RCF respirable fiber distribution by material used

The numerical value shown at the center of each boxplot isthe median value. The width of each box is proportional to thesquare root of the number of observations in the box.

Outliers, specific data outside the statistical range, are shownas a * symbol. Outliers were predetermined automatically bythe statistical analysis package used. In the boxplot function,Minitab considers any observation 1.5 to 3 times away from


FIGURE 4. Relationship between respirable vs. nonrespirable MMMF fibers (excluding RCF)

the middle 50% of data as a possible outlier. Figures 4 and5 show the relationships between respirable fiber counts andnonrespirable fiber counts for MMMF (excluding RCF) andRCF, respectively. Only comparisons between counts whereboth results are detectible are shown. In Table III, results ofprevious studies(18–28) relating to the construction and end userwere tabulated.

DISCUSSION

C ounts for MMMF were conducted by three methods:(1) NIOSH 7400 method with A counting rules or its

predecessor P&CAM 239, (2) NIOSH 7400 with B count-ing rules, and (3) the WHO method. Studies were conductedto estimate the differences in fiber counts obtained by these

FIGURE 5. Relationship between respirable vs. nonrespirable RCF fibers


TABLE III. Summary of Respirable MMMF Concentration in Fibers/cc from Published Sources

Respirable Concentration (Fibers/cc)

Source Remarks N Class Type AM GM GSD Min Max

UK—Head and Wagg (1980)(18)

Applications in building worksDomestic loft insulation (glass fiber blanket)

Site 7Site 8

57

1 P+AP+A

0.381.02

0.300.24

0.541.76

Domestic loft insulation (loose fill mineral wool) — Site 9 6 1 P+A 8.19 0.54 20.9Fire protection of structural steel (sprayed mineral wool)

Site 10Site 11

1111

11

P+AP+A

0.820.72

0.170.16

2.572.06

Applications in industrial productsIndustrial engine exhaust insulation (mineral wool)

Plant 16Plant 17

123

11

P+AP

0.100.07

0.020.05

0.360.10

Furnace and kiln lining (mixed ceramic and mineral wool)Plant 13Plant 14Plant 15

14

13

21+21+2

PP+AP+A

1.701.032.58

1.700.390.97

—1.475.23

Finishing vacuum formed mouldings (ceramic) – Plant 16 2 2 P+A 0.65 0.62 0.67Industrial engine silencer insulation (alumina fiber) – Plant 16 3 2 P 1.07 0.57 1.72

USA—Esmen et al. (1982)*(19)

Acoustical ceiling installerDuct installation

Pipe coveringBlanket insulationWrap around

Attic insulation (fibrous glass)RooferBlowerFeeder

Attic insulation (mineral wool)RooferBlower

12

318

11

61618

923

1

111

111

11

P

PPP

PPP

PP

0.01

0.030.050.04

0.132.400.086

0.575.3

0.0018

0.00460.0120.014

0.0150.19

0

0.0410.44

0.028

0.110.0780.064

0.194.80.25

2.0320.0

FeederBuilding insulation installerAircraft insulation (Plant A)

SewerCutterCementer

Aircraft insulation (Plant B)SewerCutterCementerIsolated jobs

931

1689

8413

11

111

1111

PP

PPP

PPPP

1.170.02

0.200.070.12

0.090.560.050.02

0.150

0.050.040.04

0.0250.38

—0.0087

3.80.085

0.590.120.20

0.182.00—

0.031Fibrous glass duct

Duct fabricatorSheet metal workerDuct installer

485

111

PPP

0.020.020.01

0.0070.00800.004

0.0490.0470.015

USA—Axten et al. (1990)*(20)

Exposure of fibrous glassBatts – InstallersLoose fill loaders – CubedMilledLoose fill installers – CubedMilled

6086188720

11111

P+AP+AP+AP+AP+A

0.240.870.561.01.8

(Continued on next page)


TABLE III. Summary of Respirable MMMF Concentration in Fibers/cc from Published Sources (Continued)



Canada—Perrault et al. (1992)(21)

Construction sitesRefractory fibers and glass wool 33 1+2 A 0.04 3.8Glass wool 17 1 A 0.01 1.9Rock wool (blown) 10 1 A 0.32 1.4Rock wool (sprayed-on) 16 1 A 0.15 1.7Refractory fibers

Site ASite BSite C

404146

222

AAA

0.640.393.51

2.61.33.4

USA—Jacob et al. (1992)(21)

Fiber concentrations associated with installation of cubed and milled blowing wool insulationPrior to installationLoader, cubedLoader, milledInstaller, cubedInstaller, milledFollowing installation

244916521538

111111

APPPPA

0.0010.120.220.370.910.001

Fiber concentrations associated with installation of batt insulationPrior to installationInstallers

153215

APA

0.0020.0590.001Following installation

USA—Lees et al. (1993)(23) (N = 401)Task length average exposure estimates by residential insulation product/occupation category

Fiberglass batts – InstallerMineral wool batts – installerFiberglass with binder loose (blowing) wool – installerFiberglass with binder loose (blowing) wool – feederFiberglass without binder loose (blowing) wool – installerFiberglass without binder loose (blowing) wool – feederMineral wool loose (blowing) wool – installerMineral wool loose (blowing) wool – installer

11111111

PPPPPPPP

0.140.170.550.187.671.741.940.31

0.120.150.440.155.980.571.160.23

2.011.731.861.892.185.412.812.20

0.020.070.170.061.320.060.320.09

0.410.392.880.67

18.49.366.160.78

8-Hour TWA exposure estimates by residential insulation product/occupation categoryFiberglass batts – installerMineral wool batts – installerFiberglass with binder loose (blowing) wool – installerFiberglass with binder loose (blowing) wool – feederFiberglass without binder loose (blowing) wool – installerFiberglass without binder loose (blowing) wool – feederMineral wool loose (blowing) wool – installerMineral wool loose (blowing) wool – installer

11111111

PPPPPPPP

0.060.110.150.051.960.850.970.18

0.050.100.090.031.52—

0.520.14

2.411.453.823.062.56—

3.762.20

0.010.060.010.010.40—

0.130.07

0.170.150.350.133.23—

2.440.40

USA—Koenig and Axten (1995)(24)

Installation of Commercial and Industrial Mineral Wool ProductsInstallation of wet felted acoustical productsInstallation of molded acoustical productsInstallation of insulation products

494083

111

PPP

0.120.460.10

0.010.040.01

0.501.301.10

USA—Maxim et al. (1997)(25)

FinishingInternal 206 2 P 0.66 0.50 0.028 2.7External 375 2 P 0.99 0.37 0.009 30Combined 581 2 P 0.87 0.41 0.009 30

(Continued on next page)


TABLE III. Summary of Respirable MMMF Concentration in Fibers/cc from Published Sources (Continued)



InstallationExternal

Mixing/formingInternalExternalCombined

RemovalInternal

288

231186417

5

2

222

2

P

PPP

P

0.41

0.300.320.31

1.6

0.20

0.190.160.18

1.4

0.003

0.0070.100.007

0.66

2.51.44.14.13.2

ExternalCombined

103108

22

PP

1.21.2

0.780.80

0.0270.027

5.45.4

Korea—Kim J.H. et al. (1999)*(26)

Rock wool sprayed on building in construction industryWet processSemi-wet process

812

11

PP

0.0780.116

3.2095.061

0.0130.004

0.3340.698

Continuos filament glass fiber usersCuttingPilingGrindingOthers

15101110

1111

PPPP

0.0070.0030.0140.002

2.7304.4677.0622.450

0.0010.0010.0010.001

0.0650.0400.1260.010

USA—Breysee et al. (2001)(27)

Installers (task length average exposure estimates)Fiberglass duct boardFiberglass duct linerFiberglass duct wrapFiberglass pipe and vessel insulationMineral wool ceiling tilesFiberglass batts in prefabricated homesLoose mineral wool in prefabricated homesMineral wool building safing

67

10323910139

11111111

PPPPPPPP

0.030.320.680.040.240.190.130.16

0.030.320.350.030.220.190.110.12

1.401.173.332.541.641.331.712.21

0.020.280.170.010.080.160.060.06

0.050.422.130.210.480.260.200.32

USA—Marchant et al. (2002)(28)

Installation of mineral woolCeiling panel/tileSpray-on fireproofingInsulation batt and blanketOther insulation

33151214

1111

PPPP

0.230.080.090.11

0.020.020.040.02

0.820.420.160.40

Glass wool installationAir-handling productsAppliance insulationAutomotive insulationBlowing wool with binder – feederBlowing wool with binder – installerBlowing wool without binder – feederBlowing wool without binder – installerCavity loose fill insulationPipe insulation

1131176

1349841228

111111111

PPPPPPPPP

0.280.080.020.090.390.440.990.150.05

0.020.010.010.040.090.010.040.040.01

1.230.060.050.191.132.187.490.470.19

Insulation batts and blanketsOther

6225

11

PP

0.170.05

0.010.01

0.460.16

Glass wool retrofit/removal 6 1 P 0.26 0.03 0.74Mineral wool retrofit/removal 2 1 P 0.01 0.10 0.11

Notes: Class 1 = MMMF (excluding RCF); Class 2 = RCF; * = “A” counting rules; P = personal; A = area.


various methods.(23,25,29) As stated earlier, if both respirableand nonrespirable fiber counts as determined by the WHOmethod are added together, it should approximate the resultdetermined by NIOSH 7400 using A counting rule. The A ruleshave been shown to produce higher results (approximately 40%more based on computing A/B rules for task length or TWAexposure estimates measured by phase contrast microscopy)than counts by the B rules.(23) The NIOSH B rules methodhas also been shown to produce statistically significant lowercounts of about 27% less than by the WHO method in a studyconducted on an exchange of microscope slides prepared fromMMMF airborne samples (mainly MMMF excluding RCF).(29)

Another study conducted on 200 samples using phase con-trast optical microscopy for RCF showed the NIOSH 7400method using B rules produced only 5% less than the WHOrule for respirable fibers.(24) The difference in these two studiesis related to the materials involved indicating that RCF gener-ates proportionally more thinner fibers (aspect ratio 5:1). Theresults of these studies could be used to convert fiber counts ofvarious studies for a meta-analysis.

The aim of measuring total airborne fibers (both respirableand nonrespirable) was to provide a better index of MMMFnonrespiratory health hazards, namely skin and eye irritation,as they were often the major complaint. Total fiber measure-ment provides the necessary information and should be consid-ered as the preferred method. Results of Figure 4 for MMMF(excluding RCF) show that the airborne concentration of non-respirable fibers as a fraction of respirable fibers is about 23%.For RCF (Figure 5), the concentration of nonrespirable fibersas a fraction of respirable fibers is much less at about 8%. Thetotal fibers would be higher in MMMF (excluding RCF). Thisis useful information to estimate total airborne fibers whereonly respirable fibers are measured.

The MMMF (excluding RCF) exposures measured in thisOntario study are generally lower than 1 fiber/cc with meanvalues ranging from 0.04 to 0.72 fibers/cc (see Table II andFigure 2). Blowing residential insulation and sweeping hadthe highest concentration, 0.95 and 1.75 fibers/cc, respectively.Very high arithmetic mean values of 5.3 fibers/cc,(19) 7.7 fibers/cc,(23) and 8.2 fibers/cc(18) have been reported previously (seeTable III). These high values are mainly from residential blow-ing and feeding operations. In the case of RCF there wereseveral samples that exceeded the recommended TLV-TWAof 0.2 fibers/cc (see Table II and Figure 3). About 42% of allsamples (9 of 21) were above 0.2 fibers/cc, indicating thatthe RCF exposure needs to be controlled more rigorously.Exposure levels in excess of 0.2 fibers/cc have been prevalentas noted in other studies listed in Table III. All reported RCFexposures by Head and Wagg,(18) and some by Perrault et al.,(21)

are in excess of 0.2 fibers/cc. The extensive data set of Maximet al.(25) (almost 1400 samples) also shows all the mean valuesto be in excess of 0.2 fibers/cc. The exposure to RCF is thusof significant concern and needs special attention. It shouldbe noted that the actual exposure received by workers wouldbe lower than the reported values if they wore respirators. In

this study, most workers in direct contact with MMMF woreNIOSH approved N95 disposable or half-mask cartridge respi-rators, especially during dusty tasks such as mixing, spraying,and blowing insulation. The assigned protection factors forthese respirators are between 5 and 10.(30) Assuming the actualprotection in field use of about 50%, the exposure received bythe workers would be less than half of the reported exposure.Maxim et al.(31) also found that the use of respirators wassubstantially beneficial for many job categories. A high per-centage wore respirators while engaged in removal activities,which had the highest exposures. The use of respirators reducedRCF exposure for removal activities from an average of 1.84fibers/cc to 0.247 fibers/cc.(31) The exposure of 0.247 fibers/ccis, however, still above the current ACGIH TLV-TWA of 0.2fibers/cc. The actual exposure received by Ontario workers toMMMF including RCF was lower than those listed in TableII, especially for dusty tasks. The potential of nonoccupationalor para-occupational exposure to MMMF including RCF forthose who work in the vicinity, or happen to be in the area,can be estimated by area and secondary exposure. The data inTable II shows that levels for trades and bystander areas arelow, ranging from 0.01 to 0.68 fibers/cc for MMMF (excludingRCF) and below the limit of detection for RCF. It should benoted that the sample size for secondary exposure is small.Based on this data set the exposure to MMMF including RCFfor workers not directly involved should not be of any signifi-cant concern.

CONCLUSIONS

B ased on this data set and our observations it appears thatfull-shift occupational exposure to MMMF (excluding

RCF) in Ontario is generally below the ACGIH TLV-TWA of1 fibers/cc and therefore should not present a significant hazard.However, exposure to RCF could be a significant problem sinceseveral measured concentrations were in excess of the ACGIHTLV-TWA of 0.2 fibers/cc. The actual exposure received byworkers to MMMF including RCF would likely be lower thanthe measured concentration due to respirator usage. It is im-portant that workers’ RCF exposure be controlled diligentlythrough engineering control measures and use of respirators.The bystanders and other trades not directly involved, but in thevicinity of MMMF operations, generally have minimal expo-sure and therefore should not be of concern. Both respirable andnonrespirable fibers determined by the WHO method shouldbe routinely measured since the method provides added in-formation on total airborne fibers that is relevant from a skinand eye irritation hazard point-of-view. Studies of the rela-tionships between various methods of counting exist, enablingconversion of fiber counts made by different methods. Theratios of respirable and nonrespirable fibers are different forMMMF (excluding RCF) and RCF. There are a lot more non-respirable fibers as a percent of respirable fibers (about 23%) inMMMF (excluding RCF) than the RCF (about 8%) in airbornefibers.


ACKNOWLEDGMENT

W e would like to thank the Workplace Safety and In-surance Board of Ontario for their financial support.

We are grateful to all contractors, unions, and workers whoparticipated in this study. Finally, we thank Karen des Tombefor her help in the preparation of this manuscript.

REFERENCES

1. American Conference of Governmental Industrial Hygienists(ACGIH

©R): Documentation of TLV for asbestos, all forms. In Chemical

Substances TLVs©R and BEIs©R , 7th edition. Cincinnati, Ohio: ACGIH,2002.

2. Doll, R.: Symposium on MMMF, Copenhagen, October 1986: Overviewand conclusions. Ann. Occup. Hyg. 31:805–819 (1987).

3. Lippman, M.: Man-made mineral fibers (MMMF): Human exposuresand health risk assessment. Toxic Ind. Health 6:225–246 (1990).

4. Miettinen, O.S., and M.A. Rossiter: Man-made mineral fibers and lungcancer. Scand. J. Work Environ. Health 16:221–231 (1990).

5. World Health Organization (WHO): Environmental Health Criteria 77.Man-Made Mineral Fibers. Geneva: WHO, 1988.

6. Kojola, W.H., and J.B. Moran: Exposure limits for man-made mineralfibers. Position of the Building and Construction Trades Department,AFL-CIO. Appl. Occup. Environ. Hyg. 7:724–733 (1992).

7. International Agency for Research in Cancer (IARC): Man-madevitreous fibres. In IARC Monographs on the Evaluation of CarcinogenicRisk to Humans, vol. 81. Lyons, France: IARC Press, 2002.

8. American Conference of Governmental Industrial Hygienists(ACGIH): Documentation of TLV for synthetic vitreous fibers. InChemical Substances TLVs and BEIs, 7th edition. Cincinnati, Ohio:ACGIH, 2002.

9. Selikoff, I.J., E.C. Hammond, and H. Seidman: Mortality experienceof insulation workers in the United States and Canada, 1943–1976. Ann.NY Acad. Sci. 330:91–116 (1979).

10. Verma, D.K., and C. Middleton: Occupation exposure to asbestosin the drywall taping process. Am. Ind. Hyg. Assoc. J. 41:264–269(1980).

11. Ritze, W.B., W.J. Nicholson, D.A. Holaday, and I.J. Selikoff: Applica-tion of sprayed inorganic fiber containing asbestos: Occupational healthhazards. Am. Ind. Hyg. Assoc. J. 33:178–191 (1972).

12. Skidmore, J.W., and J.S.P. Jones: Monitoring an asbestos spray process.Ann. Occup. Hyg. 18:151–156 (1975).

13. Oksa, P., E. Pukkala, A. Karjalainen, A. Ojajarvi, and M.S. Huusko-nen: Cancer incidence and mortality among Finnish asbestos sprayersand in asbestosis and silicosis patients. Am. J. Ind. Med. 31:693–698(1997).

14. Verma, D.K., L.A. Kurtz, D. Sahai, and M.M. Finkelstein: Currentchemical exposures among Ontario construction workers. Appl. Occup.Environ. Hyg. 18:1031–1047 (2003).

15. World Health Organization (WHO): Reference methods for measuringairborne man-made mineral fibers (MMMF). In EURO Technical Com-mittee for Monitoring and Evaluating Airborne MMMF. Copenhagen:WHO, 1985. pp 16–25.

16. National Institute for Occupational Safety and Health (NIOSH):Analytical method #7400: Asbestos and other fibers by PCM. In NIOSHManual of Analytical Methods, 4th edition (Pub. No. 94-113), M.E.Cassinelli, editor. Cincinnati, Ohio: DHEW (NIOSH), 1994.

17. Manufacturer: Minitab©R. [Computer Software.] Minitab, Inc., 1998.18. Head, I.W.H., and R.M. Wagg: A survey of occupational exposure to

man-made mineral fiber dust. Ann. Occup. Hyg. 23:235–258 (1980).19. Esmen, N.A., M.J. Sheehan, M. Corn, M. Engel, and N. Kotsko:

Exposure of employees to manmade vitreous fibers: Installation ofinsulation materials. Environ. Res. 28:386–398 (1982).

20. Axten, C.W., J.R. Bender, P.F. Auborg, T.R. Jacobs, M.R. Kalinowski,and E.J. Klotz: Exposures of end-users to airborne concentrations offibrous glass during installation of insulation products and fabricationoperations. Proceedings of the VIIth International PneumoconiosesConference, Pittsburgh, Pa.: NIOSH, 1988. pp. 1094–1097.

21. Perrault, G., C. Dion, and Y. Cloutier: Sampling and analysis of mineralfibers on construction sites. Appl. Occup. Environ. Hyg. 7:323–326 (1992).

22. Jacob, T.R., J.G. Hadley, J.R. Bender, and W. Eastes: Airborne glassfiber concentrations during installation of residential insulation. Am. Ind.Hyg. Assoc. J. 53:519–523 (1992).

23. Lees, P.S.J., P.N. Breysse, B.R. McArthur, et al.: End user exposures toman-made vitreous fibers: I. Installation of residential insulation products.Appl. Occup. Environ. Hyg. 8:1022–1030 (1993).

24. Koenig, A.R., and C.W. Axten: Exposures to airborne fiber and freecrystalline silica during installation of commercial and industrial mineralwool products. Am. Ind. Hyg. Assoc. J. 56:1016–1022 (1995).

25. Maxim, L.D., J.N. Allshouse, W.P. Kelly, T. Walters, and R. Waugh:A multiyear workplace-monitoring program for refractory ceramic fibers:Findings and conclusions. Reg. Toxicol. Pharmacol. 26:156–171 (1997).

26. Kim, J.H., H.S. Chang, K.Y. Kim, et al.: Environmental measurementsof total dust and fiber concentration in manufacturer and user of man-mademineral fibers. Ind. Health 37:322–328 (1999).

27. Breysse, P.N., P.S.J. Lees, B.C. Rooney, B.R. McArthur, M.E. Miller,and C. Robbins: End user exposures to man-made vitreous fibers: II.Fabrication and installation fabrication of commercial products. Appl.Occup. Environ. Hyg. 16:464–470 (2001).

28. Marchant, G.E., M.A. Amen, C.H. Bullock, et al.: A synthetic vitreousfiber (SVF) occupational exposure database: Implementing the SVF healthand safety partnership program. Appl. Occup. Environ. Hyg. 17:276–285(2002).

29. Breysse, P.N., J.W. Cherrie, P.S.J. Lees, and P. Brown: Comparison ofNIOSH 7400 “B” rules and WHO reference methods for the evaluation ofairborne man-made mineral fibers. Ann. Occup. Hyg. 38:527–531 (1994).

30. National Institute of Occupational Safety and Health (NIOSH):Respirator Decision Logic (Pub. No. 87-108). Cincinnati, Ohio: NIOSH,1987.

31. Maxim, L.D., J.N. Allshouse, S.H. Chen, J.C. Treadway, andD.E. Venturin: Workplace monitoring of refractory ceramic fiber in theUnited States. Reg. Toxicol. Pharmacol. 32:293–309 (2000).


current man-made mineral fibers (mmmf) exposures … · current man-made mineral fibers (mmmf)...

Documents