Decision No. 1642/21
fields, oil refinery work, agricultural work, radiation exposure, and exposure to some
chemicals such as vinyl chloride, petrochemicals and lead. The only firmly established
modifiable risk factor though is ionizing radiation exposure, especially among children.
A Medline/PubMed search of "occupational risk factors for glioblastoma multiforme"
since 1997 resulted in 9 articles, several of which were reviews that concluded the only
environmental factor unequivocally associated with an increased risk of brain tumors,
including gliomas, is therapeutic x-rays. Another study of potential risk factors for
glioblastoma multiforme looked at a cohort of 8006 Japanese-American men, with nine
histologically confirmed GBM cases. A multivariate Cox proportional hazards model
demonstrated sugar intake and occupational exposure to carbon tetrachloride were
independently and significantly associated with development of GBM. The number of
disease cases is small in this study, and quantification of exposure is lacking. The results
of this study have not been replicated as yet. Another study was conducted to explore a
perceived increase in glioblastoma diagnosis at a jet engine manufacturing facility in
North Haven, Connecticut. Subjects were 212,513 workers ever employed in 1 of 8
manufacturing facilities from 1952 to 2001 and at risk from 1976 to 2004. 722 cases of
CNS neoplasms were identified mainly by tracing through 19 state cancer registries.
Standardized incidence ratios (SIRs) were computed based on state and national rates and
modeled internal relative risks (RRs). Overall deficits were found in cases for
glioblastoma (275 cases, SIR = 0.77, Cl = 0.68-0.87) and a not statistically significant
overall 8% excess in glioblastoma in North Haven (43 cases, SIR = 1.08, Cl = 0.78-1.46).
No conclusion could be made as to the cause of the excess glioblastoma cases, but non-
occupational factors and workplace factors unmeasured in the study would need to be
Bhatti and colleagues (4) looked at the possibility that lead exposure was causative in
GBM formation. Using a hospital-based case-control study, they examined the potential
carcinogenicity of lead through examination of effect modification of the association
between occupational exposure and brain tumors by single nucleotide polymorphisms in
genes with functions related to oxidative stress. Lead exposure was estimated by review
of detailed job history data for each participant. In analyses restricted to cases with
glioblastoma multiforme, RAC2 rs2239774 and two highly correlated GPX1
polymorphisms (rs1050450 and rs18006688) were found to significantly modify the
association with lead exposure (P < or = 0.05) after adjustment for multiple comparisons.
The conclusion was that the results of the study showed some evidence that lead may
cause glioblastoma multiforme and meningioma through mechanisms related to oxidative
damage, but the results need to be confirmed in other populations. Without occupational
hygiene data incorporated into the study, the results are hardly verifiable though.
[The worker] was 65 years old at time of diagnosis of glioblastoma multiforme. The
WSIB Occupational Hygiene Exposure Assessment indicates he had the potential for
exposure to epoxy resins on a routine basis for about 17.5 years at work. This exposure
was via airborne vapors and possibly via dermal contact. [The worker] was also
potentially exposed to metal fumes that possibly included cadmium, lead and copper.
Furthermore, exposures were possible to organic solvents and combustion by-products.
[The worker’s] employment history did not suggest that he worked in the nuclear
products building, or that he was exposed to arsenic. The OHCOW addendum report of
May 7, 2012 speculates about a number of exposures, including leading [sic – lead?] ,
vinyl chloride, polycyclic aromatic hydrocarbons (PAHs), and arsenic.
Of the four non-modifiable risk factors for glioblastoma multiforme, [the worker] had
three, namely male sex, age over 50 and ethnicity. He does not have proven workplace
exposure to ionizing radiation, which is the only known modifiable risk factor for GBM.
There is no evidence in the medical literature of clear-cut increased risk of glioblastoma
multiforme from exposure to epoxy resins, metal fumes, organic solvents or combustion