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Beane Freeman L.E.,U.S. National Institutes of Health | Blair A.,U.S. National Institutes of Health | Lubin J.H.,U.S. National Institutes of Health | Stewart P.A.,Stewart Exposure Assessments LLC | And 2 more authors.
American Journal of Industrial Medicine | Year: 2013

Background: Formaldehyde, a widely used chemical, is considered a human carcinogen. Methods: We extended follow-up of the largest industrial cohort of workers in formaldehyde industries (n=25,619) by 10 years through 2004. Standardized mortality ratios (SMRs) and rate ratios (RRs) were calculated for deaths from solid tumors using quantitative formaldehyde exposure estimates. Results: During 998,239 person-years, 13,951 deaths occurred. With one additional death, previously observed excesses for nasopharyngeal cancer (n=10) persisted for peak, average intensity and cumulative exposure; RRs in the highest exposure categories were 7.66 (95% CI: 0.94, 62.34), P-trend=0.005, 11.54 (95% CI: 1.38, 96.81), P-trend=0.09, and 2.94 (95% CI: 0.65, 13.28), P-trend=0.06, respectively. For all cancer, solid tumors and lung cancer, SMRs among exposed workers were elevated, but internal analyses revealed no positive associations with formaldehyde exposure. Conclusions: Consistent with previous analyses of this cohort, this update continues to suggest a link between formaldehyde exposure and nasopharyngeal cancer. © 2013 Wiley Periodicals, Inc.

Bhatti P.,Fred Hutchinson Cancer Research Center | Stewart P.A.,Stewart Exposure Assessments LLC | Linet M.S.,U.S. National Cancer Institute | Blair A.,U.S. National Cancer Institute | And 2 more authors.
Occupational and Environmental Medicine | Year: 2011

Objectives: There is great interest in evaluating gene-environment interactions with chemical exposures, but exposure assessment poses a unique challenge in case-control studies. Expert assessment of detailed work history data is usually considered the best approach, but it is a laborious and time-consuming process. We set out to determine if a less intensive method of exposure assessment (a job exposure matrix (JEM)) would produce similar results to a previous analysis that found evidence of effect modification of the association between expert-assessed lead exposure and risk of brain tumours by a single nucleotide polymorphism in the ALAD gene (rs1800435). Methods: We used data from a study of 355 patients with glioma, 151 patients with meningioma and 505 controls. Logistic regression models were used to examine associations between brain tumour risk and lead exposure and effect modification by genotype. We evaluated Cohen's κ, sensitivity and specificity for the JEM compared to the expert-assessed exposure metrics. Results: Although effect estimates were imprecise and driven by a small number of cases, we found evidence of effect modification between lead exposure and ALAD genotype when using expert- but not JEM-derived lead exposure estimates. κ Values indicated only modest agreement (<0.5) for the exposure metrics, with the JEM indicating high specificity (∼0.9) but poor sensitivity (∼0.5). Disagreement between the two methods was generally due to having additional information in the detailed work history. Conclusion: These results provide preliminary evidence suggesting that high quality exposure data are likely to improve the ability to detect genetic effect modification.

Gilboa S.M.,Centers for Disease Control and Prevention | Desrosiers T.A.,University of North Carolina at Chapel Hill | Lawson C.,Centers for Disease Control and Prevention | Lupo P.J.,University of Texas Health Science Center at Houston | And 6 more authors.
Occupational and Environmental Medicine | Year: 2012

Objective: To examine the relation between congenital heart defects (CHDs) in offspring and estimated maternal occupational exposure to chlorinated solvents, aromatic solvents and Stoddard solvent during the period from 1 month before conception through the first trimester. Methods: The study population included mothers of infants with simple isolated CHDs and mothers of control infants who delivered from 1997 through 2002 and participated in the National Birth Defects Prevention Study. Two methods to assess occupational solvent exposure were employed: an expert consensus-based approach and a literature-based approach. Multiple logistic regression was used to calculate adjusted ORs and 95% CIs for the association between solvent classes and CHDs. Results: 2951 control mothers and 2047 CHD case mothers were included. Using the consensus-based approach, associations were observed for exposure to any solvent and any chlorinated solvent with perimembranous ventricular septal defects (OR 1.6, 95% CI 1.0 to 2.6 and OR 1.7, 95% CI 1.0 to 2.8, respectively). Using the literature-based approach, associations were observed for: any solvent exposure with aortic stenosis (OR 2.1, 95% CI 1.1 to 4.1) and Stoddard solvent exposure with d-transposition of the great arteries (OR 2.0, 95% CI 1.0 to 4.2), right ventricular outflow tract obstruction defects (OR 1.9, 95% CI 1.1 to 3.3) and pulmonary valve stenosis (OR 2.1, 95% CI 1.1 to 3.8). Conclusions: The authors found evidence of associations between occupational exposure to solvents and several types of CHDs. These results should be interpreted in light of the potential for misclassification of exposure.

Karami S.,U.S. National Institutes of Health | Bassig B.,U.S. National Institutes of Health | Stewart P.A.,U.S. National Institutes of Health | Stewart P.A.,Stewart Exposure Assessments LLC | And 5 more authors.
Occupational and Environmental Medicine | Year: 2013

The carcinogenic potential of trichloroethylene (TCE) continues to generate much controversy, even after the US Environmental Protection Agency raised its classification to 'carcinogenic to humans'. We conducted a meta-analysis of published cohort and case-control studies exploring occupational TCE exposure in relation to five different lymphatic and haematopoietic cancers: non-Hodgkin's lymphoma (NHL, N=24), Hodgkin's lymphoma (HL, N=13), multiple myeloma (MM, N=11), leukaemia (N=12) and chronic/small lymphocytic leukaemia (CLL/SLL, N=7). Studies published between 1950 and 2011 were identified through a PubMed Medline search. All studies included in analyses were classified as those that assessed either occupational TCE exposure specifically ('TCE-exposure' studies) or a broader classification of all chlorinated solvents ('chlorinated solvent-exposure' studies). A significantly raised summary estimate for NHL was seen for all cohort and case-control 'TCE-exposure' studies combined (N=19; relative risk (RR)=1.32, 95% CI 1.14 to 1.54; I2=25.20; p-heterogeneity=0.12) and for cohort 'TCE-exposure' studies (N=10; RR=1.52, 95% CI 1.29 to 1.79; I2=7.09; p-heterogeneity=0.63). A non-significant but raised summary estimate was seen for NHL casecontrol 'TCE-exposure' studies. No significant association with NHL risk was detected overall for any 'chlorinated solvent-exposure' studies. Summary estimates for occupational TCE exposure were not associated with risk of hL, MM, leukaemia or CLL/SLL. Our updated metaanalysis of NHL, which incorporates new analytical results from three cohort and four case-control studies, supports an association between occupational TCE exposure and NHL.

Karami S.,U.S. National Cancer Institute | Lan Q.,U.S. National Cancer Institute | Rothman N.,U.S. National Cancer Institute | Stewart P.A.,Stewart Exposure Assessments LLC | And 3 more authors.
Occupational and Environmental Medicine | Year: 2012

Objectives: Inconsistent epidemiological findings, debate over interpretation, and extrapolation of findings from animal studies to humans have produced uncertainty surrounding the carcinogenicity of trichloroethylene (TCE) exposure in occupational settings. We updated meta-analyses of published case-control and cohort studies exploring occupational TCE exposure and kidney cancer risk, incorporating new analytical results from three recently published cohort studies and a case-control study. Methods: PubMed MEDLINE was searched for studies published from 1950 to 2011 assessing occupational exposure to chlorinated solvents, degreasers or TCE. All cohort (N=15) and case-control (N=13) studies included in analyses were stratified by assessment of occupational exposure to TCE specifically and to any chlorinated solvent. Results: Significantly elevated summary estimates were observed for cohort studies (relative risk (RR) 1.26, 95% CI 1.02 to 1.56; p heterogeneity=0.65), case-control studies (OR 1.35, 95% CI 1.17 to 1.57; p heterogeneity=0.41), and cohort and case-control studies combined (RR 1.32, 95% CI 1.17 to 1.50, p heterogeneity=0.63) that specifically assessed TCE exposure after excluding outlier studies that contributed to heterogeneity. Non-significantly elevated summary estimates were generally observed for studies of workers exposed to chlorinated solvents but who were not assessed for TCE specifically. Conclusions: Regardless of study design, significant and stronger estimates were only observed in studies specifically assessing occupational exposure to TCE. Estimates were lower in studies assessing occupational exposure to chlorinated solvents. This updated meta-analysis supports an association between occupational TCE exposure and kidney cancer and provides evidence that exposure misclassification may weaken estimates assessing exposure to the broader class of chlorinated solvents.

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