title: Father's occupational exposure to carcinogenic agents and childhood acute leukemia: a new method to assess exposure (a case-control study).
abstract: BACKGROUND
  Medical research has not been able to establish whether a father's occupational exposures are associated with the development of acute leukemia (AL) in their offspring. The studies conducted have weaknesses that have generated a misclassification of such exposure. Occupations and exposures to substances associated with childhood cancer are not very frequently encountered in the general population; thus, the reported risks are both inconsistent and inaccurate. In this study, to assess exposure we used a new method, an exposure index, which took into consideration the industrial branch, specific position, use of protective equipment, substances at work, degree of contact with such substances, and time of exposure. This index allowed us to obtain a grade, which permitted the identification of individuals according to their level of exposure to known or potentially carcinogenic agents that are not necessarily specifically identified as risk factors for leukemia. The aim of this study was to determine the association between a father's occupational exposure to carcinogenic agents and the presence of AL in their offspring.
  
  
  METHODS
  From 1999 to 2000, a case-control study was performed with 193 children who reside in Mexico City and had been diagnosed with AL. The initial sample-size calculation was 150 children per group, assessed with an expected odds ratio (OR) of three and a minimum exposure frequency of 15.8%. These children were matched by age, sex, and institution with 193 pediatric surgical patients at secondary-care hospitals. A questionnaire was used to determine each child's background and the characteristics of the father's occupation(s). In order to determine the level of exposure to carcinogenic agents, a previously validated exposure index (occupational exposure index, OEI) was used. The consistency and validity of the index were assessed by a questionnaire comparison, the sensory recognition of the work area, and an expert's opinion.
  
  
  RESULTS
  The adjusted ORs and 95% confidence intervals (CI) were 1.69 (0.98, 2.92) during the preconception period; 1.98 (1.13, 3.45) during the index pregnancy; 2.11 (1.17, 3.78) during breastfeeding period; 2.17 (1.28, 3.66) after birth; and 2.06 (1.24, 3.42) for global exposure.
  
  
  CONCLUSIONS
  This is the first study in which an OEI was used to assess a father's occupational exposure to carcinogenic agents as a risk factor for the development of childhood AL in his offspring. From our results, we conclude that children whose fathers have been exposed to a high level of carcinogenic agents seem to have a greater risk of developing acute leukemia. However, confounding factors cannot be disregarded due to an incomplete control for confounding.
authors.affiliation: Epidemiologia Clínica, Hospital de Pediatria, Centro Medico Nacional Siglo XXI, Instituto Mexicano del Seguro Social (IMSS), DF, Mexico. maria_luisa_2000_mx@yahoo.com
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Perez-Saldivar
authors.forename: Manuel Carlos
authors.initials: MC
authors.lastname: Ortega-Alvarez
authors.forename: Arturo
authors.initials: A
authors.lastname: Fajardo-Gutierrez
authors.forename: Roberto
authors.initials: R
authors.lastname: Bernaldez-Rios
authors.forename: Maria de Los Angeles
authors.initials: Mde L
authors.lastname: Del Campo-Martinez
authors.forename: Aurora
authors.initials: A
authors.lastname: Medina-Sanson
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: Palomo-Colli
authors.forename: Rogelio
authors.initials: R
authors.lastname: Paredes-Aguilera
authors.forename: Armando
authors.initials: A
authors.lastname: Martínez-Avalos
authors.forename: Victor Hugo
authors.initials: VH
authors.lastname: Borja-Aburto
authors.forename: Maria de Jesus
authors.initials: Mde J
authors.lastname: Rodriguez-Rivera
authors.forename: Victor Manuel
authors.initials: VM
authors.lastname: Vargas-Garcia
authors.forename: Jesus
authors.initials: J
authors.lastname: Zarco-Contreras
authors.forename: Janet
authors.initials: J
authors.lastname: Flores-Lujano
authors.forename: Juan Manuel
authors.initials: JM
authors.lastname: Mejia-Arangure
mesh_terms: D000208:Acute Disease / Q000453:epidemiology; D000328:Adult; D002274:Carcinogens, Environmental / Q000494:pharmacology*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005220:Fathers; D005260:Female; D006801:Humans; D007938:Leukemia / Q000139:chemically induced* / Q000453:epidemiology*; D008297:Male; D016273:Occupational Exposure; D018812:Paternal Exposure; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D002274:Carcinogens, Environmental