A task-based assessment of parental occupational exposure to organic solvents and other compounds and the risk of childhood leukemia in California

Our plain-English summary of A task-based assessment of parental occupational exposure to organic solvents and other compounds and the risk of childhood leukemia in California, by C. Metayer, G. Scelo, A.Y. Kang, et al (Environmental Research, 2016).

The study

• Authors: C. Metayer, G. Scelo, A.Y. Kang, R.B. Gunier, K. Reinier, S. Lea, J.S. Chang, S. Selvin, J. Kirsch, V. Crouse, M. Does, P. Quinlan, S.K. Hammond
• Journal: Environmental Research
• Published: 2016;151:174-183
• Cited by: 28 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Purpose: Data on parental occupational exposures and risk of childhood leukemia lack specificity. Using 19 task-based job modules, we examined the relationship between occupational exposure to organic solvents and other compounds and the risk of leukemia in children.

Methods: Latino (48%) and non-Latino (52%) children with acute lymphoblastic leukemia (ALL; n=670), acute myeloid leukemia (AML; n=104), and controls (n=1021) were enrolled in a study in California (2000-2008). Logistic regression models were used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for socio-demographic factors.

Results: Among children with non-Latino fathers, none of the exposures evaluated were associated with risks of ALL and AML. In contrast, exposure to any organic solvents in Latino fathers was associated with an increased risk of childhood ALL (OR=1.48; 95% CI: 1.01-2.16); in multivariable analyses, the OR for chlorinated hydrocarbons was 2.28 (95% CI: 0.97-5.37) while the ORs were close to one for aromatic hydrocarbons, glycol ethers, and other hydrocarbon mixtures. We also observed an increased risk of ALL with exposure to combustion exhaust/polycyclic aromatic hydrocarbons (PAHs) (ORs=1.70; 95% CI: 1.16-2.57, and 1.46; 95% CI: 0.94-2.26 with and without adjustment for chlorinated hydrocarbons, respectively). Moderately elevated risks of ALL were seen with exposure to metals, paints, and wood dust, although not statistically significant. An increased risk was reported for asbestos based on small numbers of exposed Latino fathers. No associations were reported between maternal exposures to any exposures and childhood ALL and AML.

Conclusions: Our data support associations between paternal occupational exposures to chlorinated hydrocarbons, combustion exhaust, metals, and possibly asbestos and the risk of ALL in the children of Latino fathers only.

Copyright © 2016 Elsevier Inc. All rights reserved.

In plain English

This population-based case-control study examined whether parents' workplace exposures were linked to leukemia in their children. It included 670 children with acute lymphoblastic leukemia (ALL), 104 with acute myeloid leukemia (AML) and 1,021 control children in California, enrolled from 2000 to 2008. Parents answered task-based job questionnaires, and experts rated exposures, including asbestos (fiber type not stated). Among Latino fathers, several exposures were associated with higher odds of childhood ALL, including asbestos: 10 of 294 case fathers versus 3 of 397 control fathers were exposed (odds ratio 4.65, 95% CI 1.26 to 17.16). Among all fathers, asbestos was associated with AML (odds ratio 5.51, 95% CI 2.12 to 14.37). Among non-Latino fathers, most exposures were not associated with childhood ALL. None of the mothers' exposures was significantly associated with ALL. The authors cautioned that the asbestos results rested on small numbers. They concluded that their findings support associations of chlorinated hydrocarbons, combustion exhaust, metals and possibly asbestos with ALL in children of Latino fathers. They noted possible exposure misclassification and false positives from multiple comparisons.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Population-based case-control study (California Childhood Leukemia Study), with parents' work exposures assessed through task-based job questionnaires and expert rating
• Who was studied: Children younger than 15 at diagnosis, enrolled 2000 to 2008 in 35 counties of Northern and Central California. Controls without leukemia were selected from birth certificates. Analyses of fathers' exposures included 667 ALL cases, 103 AML cases and 1,020 controls. Analyses of mothers' exposures included 670 ALL cases, 104 AML cases and 1,021 controls. About 41% of fathers and 43% of mothers were of Latino descent.
• Exposure: Parents' occupational exposures from one year before the child's birth until the child's third birthday (or diagnosis or reference date). Exposures were assessed with 19 task-based job modules and rated by experts for likelihood and intensity. Agents covered organic solvents (aromatic and chlorinated hydrocarbons, glycol ethers, other hydrocarbon mixtures), other organic compounds, combustion exhaust/PAHs, paints, disinfectants, metals/welding fumes, asbestos (fiber type not specified) and wood dust.
• Main results:
  • Among Latino fathers, any exposure to organic solvents was associated with childhood ALL (OR 1.48, 95% CI 1.01 to 2.16)
  • Among Latino fathers, in a model including several organic solvents together, the OR for chlorinated hydrocarbons and ALL was 2.28 (95% CI 0.97 to 5.37)
  • Among Latino fathers, combustion exhaust/PAHs and ALL: OR 1.70 (95% CI 1.16 to 2.57) in the single-exposure model. The OR was 1.46 (95% CI 0.94 to 2.26) in a model that also included chlorinated hydrocarbons and metals.
  • Among Latino fathers, metals and ALL: OR 2.1 (95% CI 1.2 to 3.8) in the single-exposure model
  • Among Latino fathers, asbestos and ALL: 10 of 294 case fathers versus 3 of 397 control fathers were exposed, OR 4.65 (95% CI 1.26 to 17.16), based on small numbers. Among non-Latino fathers, 6 case and 11 control fathers were exposed, OR 0.92 (95% CI 0.33 to 2.54).
  • All fathers combined, asbestos and childhood AML: 7 of 103 case fathers versus 14 of 1,020 control fathers were exposed, OR 5.51 (95% CI 2.12 to 14.37), based on small numbers. Other AML results were mostly inconclusive. AML data were too sparse for analyses by ethnicity.
  • Among non-Latino fathers, most exposures were not associated with childhood ALL
  • Mothers: workplace exposures other than disinfectants were uncommon (under 10%), and no statistically significant associations with childhood ALL were seen
• The authors' conclusion: The authors concluded that their findings support associations between fathers' occupational exposures to chlorinated hydrocarbons, combustion exhaust/PAHs, metals and possibly asbestos and ALL in the children of Latino fathers. No associations were observed for non-Latino fathers. They said the asbestos finding should be interpreted with caution because of the small sample size.
• Limitations the authors state:
  • The authors said the asbestos finding rests on a small sample
  • Exposures may have been misclassified. Reasons given: self-reported job tasks, long recall intervals, variation in exposure over time, uncertain use of protective equipment, and limited intensity grading.
  • The authors could not rule out differential recall bias
  • Selection bias could not be ruled out
  • Low exposure prevalence among mothers reduced the ability to detect associations
  • Excluding children born outside California, such as immigrants, may limit how far the findings apply to Latinos
  • Exposures before and after birth were highly correlated, so timing-specific analyses could not be done
  • The job modules could not identify which chlorinated hydrocarbons fathers were exposed to
  • Multiple comparisons may have produced false positive findings

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Odds Ratio, confidence interval.

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