silica dust, crystalline, in the form of quartz or cristobalite - IARC ...

IARC MONOGRAPHS – 100C
among caisson workers (who were noted to have
had higher exposures to crystalline silica dust
than non-caisson workers). The relative risk of
oesophageal cancer for caisson workers with
silicosis was reduced to 2.34 after adjusting for
smoking and alcohol drinking. No excess risk of
oesophageal cancer was observed among the noncaisson
workers with silicosis after adjustment.
2.2.4 Cancer of the kidney
In the eight reports on cancer of the kidney,
five had relative risks > 1.0 (including two significantly
elevated), and three with relative risks
≤ 1.0. The two with significantly elevated risks
provided information on exposure–response
relationships with crystalline silica exposure,
although neither formally evaluated this. In US
sand and gravel workers (McDonald et al., 2005),
a non-significant negative trend with increasing
crystalline silica exposure was observed.
However, in Vermont granite workers (Attfield
& Costello, 2004), kidney cancer SMRs increased
almost monotonically with increasing exposure
(except for the last exposure group), and the SMR
of 3.12 in the penultimate exposure group was
significantly elevated.
2.2.5 Others
There have been isolated reports of excesses
in other cancers but the evidence is, in general,
too sparse for evaluation. Elci et al. (2002)
reported an excess of cancer of the larynx in
workers potentially exposed to crystalline silica
dust, particularly for supraglottic cancer (OR,
1.8; 95%CI: 1.3–2.3), with a significant exposure–
response relationship.
2.3 Synthesis
Findings of relevance to lung cancer and
crystalline silica exposure arise from five main
industrial settings: ceramics, diatomaceous
earth, ore mining, quarries, and sand and gravel.
Of these, the industries with the least potential
for confounding are sand and gravel operations,
quarries, and diatomaceous earth facilities.
Among those industry segments, most studies
with quantitative exposures report associations
between crystalline silica exposure and lung
cancer risk. The findings are supported by studies
in these industries that lack quantitative exposures.
Results from the other industry segments
generally added support although some studies
had potential confounding from arsenic, radon,
or PAHs. In one case among Chinese tin miners,
the arsenic and crystalline silica exposures were
virtually collinear, and no adjustment could be
made for arsenic. In another (Chinese pottery
workers), adjustment for PAHs removed a significant
crystalline silica exposure effect, and in a
third, among iron and copper miners, the crystalline
silica effect disappeared after adjustment
for radon. In these, the role of crystalline silica
exposure must be regarded as unclear. Mixed
findings were reported among gold, tungsten,
and lead/zinc miners.
The strongest evidence supporting the carcinogenicity
of crystalline silica in the lung comes
from the pooled and meta-analyses. The pooled
analysis demonstrated clear exposure–response,
while all of the meta-analyses strongly confirmed
an overall effect of crystalline silica dust exposure
despite their reliance on different studies in
coming to their conclusions.
Cancers other than that of the lung have not
been as thoroughly researched. In many cases
the findings were reported in passing, in analyses
focused on lung cancer, and rarely have the data
examined exposure–response with crystalline
silica exposure or its surrogates.
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