Sensitivity analyses of exposure estimates from a quantitative job-exposure matrix (SYN-JEM) for use in community-based studies.
OBJECTIVE
We describe the elaboration and sensitivity analyses of a quantitative job-exposure matrix (SYN-JEM) for respirable crystalline silica (RCS). The aim was to gain insight into the robustness of the SYN-JEM RCS estimates based on critical decisions taken in the elaboration process.


METHODS
SYN-JEM for RCS exposure consists of three axes (job, region, and year) based on estimates derived from a previously developed statistical model. To elaborate SYN-JEM, several decisions were taken: i.e. the application of (i) a single time trend; (ii) region-specific adjustments in RCS exposure; and (iii) a prior job-specific exposure level (by the semi-quantitative DOM-JEM), with an override of 0 mg/m(3) for jobs a priori defined as non-exposed. Furthermore, we assumed that exposure levels reached a ceiling in 1960 and remained constant prior to this date. We applied SYN-JEM to the occupational histories of subjects from a large international pooled community-based case-control study. Cumulative exposure levels derived with SYN-JEM were compared with those from alternative models, described by Pearson correlation ((Rp)) and differences in unit of exposure (mg/m(3)-year). Alternative models concerned changes in application of job- and region-specific estimates and exposure ceiling, and omitting the a priori exposure ranking.


RESULTS
Cumulative exposure levels for the study subjects ranged from 0.01 to 60 mg/m(3)-years, with a median of 1.76 mg/m(3)-years. Exposure levels derived from SYN-JEM and alternative models were overall highly correlated (R(p) > 0.90), although somewhat lower when omitting the region estimate ((Rp) = 0.80) or not taking into account the assigned semi-quantitative exposure level (R(p) = 0.65). Modification of the time trend (i.e. exposure ceiling at 1950 or 1970, or assuming a decline before 1960) caused the largest changes in absolute exposure levels (26-33% difference), but without changing the relative ranking ((Rp) = 0.99).


CONCLUSIONS
Exposure estimates derived from SYN-JEM appeared to be plausible compared with (historical) levels described in the literature. Decisions taken in the development of SYN-JEM did not critically change the cumulative exposure levels. The influence of region-specific estimates needs to be explored in future risk analyses.
Environmental Epidemiology Division, Institute for Risk Assessment Sciences, Utrecht University, 3584 CK Utrecht, The Netherlands.
Susan
S
Peters
Hans
H
Kromhout
Lützen
L
Portengen
Ann
A
Olsson
Benjamin
B
Kendzia
Raymond
R
Vincent
Barbara
B
Savary
Jérôme
J
Lavoué
Domenico
D
Cavallo
Andrea
A
Cattaneo
Dario
D
Mirabelli
Nils
N
Plato
Joelle
J
Fevotte
Beate
B
Pesch
Thomas
T
Brüning
Kurt
K
Straif
Roel
R
Vermeulen
D000395:Air Pollutants, Occupational / Q000032:analysis*; D002170:Canada / Q000453:epidemiology; D016022:Case-Control Studies; D005060:Europe / Q000453:epidemiology; D005602:France / Q000453:epidemiology; D005858:Germany / Q000453:epidemiology; D006801:Humans; D007221:Industry; D019570:Inhalation Exposure / Q000032:analysis; D016273:Occupational Exposure / Q000032:analysis; D009790:Occupations / Q000145:classification*; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods*; D012822:Silicon Dioxide / Q000032:analysis*; D018709:Statistics, Nonparametric; D006113:United Kingdom / Q000453:epidemiology
D000395:Air Pollutants, Occupational; D012822:Silicon Dioxide