—

was 100 ug/m3. There is a new WCB recommenda-
tion to lower the permissable concentration to an
average level of 20 ug/m3.

There were 105 air samples with measurable
chromium levels, the average chromium concentra-
tion in these was about 4ug/m3. The WCB permiss-
able concentration is an average exposure of 50
‘ug/m3 (for hexavalent chromium).

Grinding of tungsten carbide tips (both wet and
dry grinding) and welding of stellite tips were the
tasks most likely to lead to cobalt exposure. For
chromium, the tasks contributing most to exposure
were knife grinding, welding stellite, and brazing of
saw steel. ;

Coolant from tungsten carbide wet grinders often
had very high cobalt levels; coolant from stellite
wet grinders had much lower cobalt concentra-
tions.

2. HEALTH EFFECTS

The good news is that we did not find any work-
ers with obvious, current hard metal lung disease or
cobalt asthma. Also, we did not find an increase in
the one symptom that is most often caused by hard
metal disease: namely, becoming short of breath
when doing light work like walking up a slight hill.

However, we did find that the saw filers in these
eight mills, compared to other industrial workers,
were about twice likely to report bringing up
phlegm, about three times as likely to report cough-
ing, phlegm, and wheezing that was worse at work.
Also, saw filers doing stellite welding had about 5
times more nasal symptoms than expected.

In addition, saw filers doing tungsten carbide wet
grinding performed lower on breathing tests than
other saw filers and than other industrial workers.
The type of breathing test most affected was the
type that would become reduced in hard metal lung
disease. These saw filers (that is, the ones doing
tungsten carbide wet grinding) were about 5 times
more likely to have breathing test results in the
‘abnormal’ range than other saw filers. There was
also some additional evidence that the number of
years a filer had done this kind of work was also an
important risk factor for having an abnormal
breathing test.

SO WHAT DOES ALL THIS MEAN?

1. Cobalt and chromium exposures do occur in
B.C. sawmills and there are certain jobs where
these exposures are more likely. The exposure in
the mills we studied were ‘low’. 2

2. The nasal symptoms reported by filers doing
Stellite welding were probably associated with
chromium exposure (but other substances in the
fume may also be contributing). ‘

3. The cobalt exposure from tungsten carbide wet
grinding may be leading to early lung damage of the
type found in hard metal lung disease.
Unfortunately, we do not know for sure if the
eathi ities will develop into hard

M
a

e Researchers suggest mills consider annual moni-
toring of personal exposure for those who do specif-
ic grinding and welding work.

——

metal disease or not. We hope that further control
of cobalt exposure will reduce the risk of this
potentially serious disease.

After completion of the study, we learned of a
saw filer from a small northern sawmill who had
died of hard metal lung disease in 1988. This unfor-
tunate circumstance demonstrates that the risk for
this disease is real among saw filers. Our study
results also point in the same direction.

WHAT DO WE RECOMMEND?

As the completion of the study, we returned to
each mill and made several recommendations
regarding exposure control. these included enclos-
ing or venting of wet tungsten carbide and knife
grinding machines. In addition, for tungsten carbide
wet grinding, we suggested that more frequent
changing of the coolant may minimize cobalt expo-
sures, however, without further study, we cannot
recommend a specific change schedule.

We also suggested that mills consider annual
monitoring of personal exposure to cobalt in air for
workers doing tungsten carbide grinding (any type)
and stellite welding, and for chromium in air for
knife grinders and workers doing stellite welding.

(As a side issue, we also found that many mills
were still using lead based babbitt and cadmium
containing solder. We suggested consideration of
substitutions for these products.)

From the health testing point of view, we recom-
mended that all saw filers in the study obtain chest
xrays (as this is often useful in the diagnosis of hard
metal lung disease) and that further testing be con-
ducted that will allow us to find out if it would be
appropriate to recommend regular health screening
of all saw filers in the province.

We also recommended to the Workers’
Compensation Board that the permissable concen-
tration level for cobalt be reduced even further
below the new proposed level of 20 ug/m3.
Unfortunately, our report was not available to the
WCB in time for our results to be considered in the
newest proposed exposure levels.

SHOULD ALL SAW FILERS BE TESTED?

We do not know the answer to this question yet.
Certainly, any saw filer who has worked with
tungsten carbide and who has chest symptoms,
especially symptoms of breathlessness, should take
this article to his or her family doctor and ask for
lung testing. The testing should include breathing
tests and a chest xray to look for possible hard
metal lung disease. If the symptoms are more those
of asthma (coughing, wheezing, especially at the
end of the day or at night), than the possibility of
work-related asthma should be ruled out.

Our colleagues in Washington State have recently
proposed that all workers maintaining tungsten car-
bide tools be monitored regularly for the develop-
ment of hard metal lung disease. We agree that this
may be useful, however, neither research group
knows for sure exactly what tests would be useful
on a routine basis. This is something we hope to
study in the next few years: In the meantime, saw
filers, especially those doing stellite welding or
tungsten carbide grinding should make every effort
to protect themselves from mist and fume expo-
sures.

e Study’s authors say the WCB should reduce permissable concentration levels for cobalt, which can effect
filers. *

breathing test abnormaliti |

LUMBERWORKER/SEPTEMBER, 1993/9