Re spi ra ble Crys tal line Sil ica Ex po sures

Dur ing Tuck Pointing

 De scrip tion of HAZARD

Sil i co sis is a deadly lung dis ease. Con struc tion

work ers may get sick with sil i co sis if they breathe

in too much re spi ra ble crys tal line sil ica, a fine,

sandy dust.

Sil i co sis may take 10 or more years to de velop

when work ers are ex posed daily to low con cen trations of sil ica dust. How ever, when ex po sures to

sil ica are very high, symp toms can oc cur af ter only

a few weeks to 4–5 years.

To pre vent sil i co sis, re search ers from NIOSH (the

(Na tional In sti tute for Oc cu pa tional Safety and

Health) urge con struc tion work ers to pro tect them -

selves from dust ex po sure when do ing con struc tion

work, es pe cially tuck point ing.

In tuck point ing, the worker grinds the mor tar out

from be tween the bricks—the first step to fix ing up

the out side of an older brick build ing. Mor tar dust

con tains crys tal line sil ica. Dur ing tuck point ing,

work ers hold power grind ers, dig ging the mor tar

out to a depth of an inch or less. The grind ers of ten

have wheel di am e ters of 4 to 6 inches and ro tate

at speeds as high as 12,000 rpm. The grind ing

pro cess breaks up the mor tar and turns it into

airborne dust. The ro tat ing wheel cre ates wind

that car ries this air borne dust through out the

work place. When work ers clean the mor tar joints

and their clothes, tools, and equip ment with com -

pressed air, the strong blast need lessly adds even

more dust to the air (see Fig ures 1 and 2).

HAZARD ID

HID 9

Figure 1. Tuck pointing.

Dur ing a re cent study of tuck point ing at a con -

struction site, NIOSH re search ers mea sured very

high con cen tra tions of re spi ra ble crys tal line sil ica.

At this site, the work ers’ ex po sures were up to 50

times the REL (rec om mended ex po sure limit). At

an other con struc tion site, in ves ti ga tors from OSHA

(Oc cu pa tional Safety and Health Ad min is tra tion)

found high ex po sures—up to 100 times the REL.
 Rec om men da tions for Pre ven tion

Be cause these con struc tion stud ies showed such

high con cen tra tions of re spi ra ble crys tal line sil ica, 

NIOSH is run ning more tests on com mer cial

grind ers. They want to see how much the built-in

ventilation in the grind ers cuts down on dust ex posures dur ing tuck point ing. Also, NIOSH re searchers want to find out which en gi neer ing con trols

work best dur ing this work. In the mean time, con -

struc tion work ers should fol low the rec om men dations be low to re duce their ex po sures.

Con trac tors and work ers should use good work

prac tices and re spi ra tory pro tec tion.

Good Work Prac tices

t Use a grinder that has lo cal ex haust ven ti lation when pos si ble.

t Do not use the grinder near an other worker.

Re strict some work ar eas to cut down ex posures to other work ers.

t Stand so that the dusty air will not blow on

you and other work ers.

t In poorly ven ti lated ar eas such as a court yard

or the in side cor ners of a build ing, use fans to

blow out dusty air.

t Do not use com pressed air to clean your -

self, your clothes, or your equip ment. Make 

sure the vac uum clean ers used for dust

con trol and clothes clean ing cap ture at least 

99 per cent of the small par ti cles that could

be in haled (0.3 mi crom e ter di am e ter).

Re spi ra tory Pro tec tion (Res pi ra tors)

Dur ing tuck point ing, em ploy ers need to check re -

spi ra ble crys tal line sil ica ex po sures from time to

time to see how well the safe guards are working

and if work ers need re spi ra tory pro tec tion. Be cause

ven ti lated grind ers may not con trol the dust enough,

NIOSH rec om mends the fol low ing re spi ra tory

pro tec tion:

t For ex po sures less than 1,000 times the REL

(50 mg/m

3—mil li grams per cu bic me ter), use

a sup plied-air res pi ra tor that has a half-mask.

Set the res pi ra tor on pres sure-demand or one

of the other pos i tive-pressure set tings. For

example, run a Type CE abra sive-blasting

res pi ra tor on a pos i tive-pressure set ting.

t For ex po sures less than 50 times the REL

(2.5 mg/m

3

), use (a) an air-purifying,

full-face res pi ra tor with a high-efficiency

par tic u late air fil ter or a P100 fil ter, or (b) a

pow ered, air-purifying res pi ra tor with a

tight-fitting facepiece and a high-efficiency

par tic u late air fil ter or a P100 fil ter.

t For ex po sures less than 10 times the REL

(0.5 mg/m

3

), use a half-mask, air-purifying

res pi ra tor that has a P100 fil ter.

Equip ment man u fac tur ers are en cour aged to do

the fol low ing:

t De velop ven ti lated shrouds for grind ers that

give a clear view and good dust con trol.

t De velop the min i mum ex haust vol ume

needed for ven ti lated shrouds. This ex haust

vol ume must be based on ex per i men tal and

field data.

For more in for ma tion about the health haz ards of

ex po sure to crys tal line sil ica, re spi ra tory pro tec tion 

for work ers, and the four Type CE abra sive-blast ing

res pi ra tors that NIOSH cer ti fies, or der the NIOSH

Alert Pre venting Sil i co sis and Deaths in Con struction Workers, DHHS (NIOSH) Pub li ca tion

No. 96–112. To get your free copy, call NIOSH.
 For More In for ma tion

To ob tain more free in for ma tion about this haz ard

or other oc cu pa tional safety and health is sues,

 Ac knowl edg ments

 The prin ci pal con tri bu tors to this doc u ment were

Wil liam A Heitbrink, Ph.D., CIH, and Jerome P.

Flesch, M.S., of NIOSH. Char lie Shields of OSHA

pro vided much valu able in for ma tion about tuck

point ing ex po sures. Anne Votaw, M.A., of NIOSH, 

trans lated the text into eas ier-to-read prose. Desk -

top pub lish ing was pro vided by Su san Kaelin and

Kristina Wasmund.

November 1999 DHHS (NIOSH) Publication No. 2000–113

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Public Health Service

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Call NIOSH at 1–800–35–NIOSH

(1–800–356–4674)

or visit the NIOSH Web site at

www.cdc.gov/niosh

Figure 2. Air blowing.