Paternal Employment Research Articles

PARENTAL OCCUPATION AND INTRACRANIAL NEOPLASMS OF CHILDHOOD: RESULTS OF A CASE-CONTROL INTERVIEW STUDY

In 1983-1984, the authors conducted a case-control study of environmental factors and childhood brain tumor risk. Cases (n = 110) were identified through the tumor registry of a pediatric hospital and matched controls (n = 193) through random digit dialing. In addition to parental occupational histories, telephone interviews elicited information about potential confounders and hypothesized risk factors for childhood brain tumors. Relying primarily on the Hoar et al. (J Occup Med 1980;22:722-6) job-exposure matrix, the authors examined parental employment characteristics in relation to the relevant developmental periods. Paternal employment in several industries (agriculture, construction, metal, and food and tobacco) and in several occupations (agriculture, benchwork, and transportation) was associated with excess risk. The range of notably elevated odds ratios was 2.0-3.3, with all confidence intervals including 1.0 except one. Elevated but unstable odds ratios were also found for both paternal and maternal employment in jobs "clustered" together because of common exposures. For both approaches to exposure classification, the greatest excess risks were consistently demonstrated for parental jobs held in the preconception period. Job-exposure matrix analyses indicated that case fathers were more likely than control fathers to have had jobs linked with aromatic amino and aromatic nitro compounds (range of notably elevated (and unstable) odds ratios, 3.4-4.4), but here the greatest excess risks were exhibited in the postnatal period. Few associations emerged for maternal employment characteristics, although this is probably explained by the relatively small number of women employed in jobs outside the home.

Adolescents and Maternal Employment

Labor statistics show that mothers of adolescents are more likely to work than are those of children in any other age group, and, therefore, represent an important sample to address. The present study had two purposes. First, the effects of maternal employment on adolescent functioning were examined in a sample of 63 young adolescents. Results showed that maternal employment was not related to any of the areas assessed, suggesting that maternal employment may not have a harmful effect on adolescent adjustment. Second, the relationship of prestige ratings of either maternal or paternal employment to adolescent functioning was examined ia a sample of 96 young adolescents. Maternal prestige ratings were not significantly related to any dependent measures, yet prestige ratings of paternal employment were significantly related to at least one measure in most areas of adolescent functioning. Multiple regression analyses demonstrated that only the paternal rating served to predict adolescent functioning, particularly for male adolescents.

PATERNAL OCCUPATIONAL EXPOSURE TO ELECTROMAGNETIC FIELDS AND NEUROBLASTOMA IN OFFSPRING

Investigators in Texas have reported an association between paternal employment in jobs linked with exposure to electromagnetic fields and risk of neuroblastoma in offspring. In an attempt to replicate this finding, the authors conducted a case-control study in Ohio. A total of 101 incident cases of neuroblastoma were identified through the Columbus (Ohio) Children's Hospital Tumor Registry. All cases were born sometime during the period 1942-1967. From a statewide roster of birth certificates, four controls were selected for each case, with individual matching on the case's year of birth, race, and sex, and the mother's county of residence at the time of the (index) child's birth. Multiple definitions were employed to infer the potential for paternal occupational exposure to electromagnetic fields from the industry/occupation statements on the birth certificates. Case-control comparisons revealed adjusted odds ratios ranging in magnitude from 0.5 to 1.9. For two of the exposure definitions employed--both of which are similar to one used by the Texas investigators--the corresponding odds ratios were modestly elevated (odds ratios = 1.6 and 1.9). Notably, the magnitude of these odds ratios is not inconsistent with the Texas findings, where the exposure definition referred to yielded an odds ratio of 2.1. Because the point estimates in this study are imprecise, and because the biologic plausibility of the association is uncertain, the results reported here must be interpreted cautiously. However, the apparent consistency between two independent studies suggests that future evaluation of the association is warranted.

NEUROBLASTOMA AND PARENTAL OCCUPATION

A matched case-control study of neuroblastoma investigated parental occupational risk factors. Cases diagnosed in 1970-1979 were identified through tumor registries in the Greater Philadelphia area. Controls were selected by random digit dialing and were matched to cases on race, birth date, and telephone exchange. Parents of 104 matched pairs were interviewed by telephone. In contrast to results of a previous study, no significant associations were noted for paternal employment in a job cluster of occupations in electricity, electronics, insulation, utility, and printing; in jobs with electromagnetic field exposure; or in jobs as workers in electronics. Six cases and one control, however, had a father or mother who worked in electrical or electronic products assembly.

Results of case-control study of leukaemia and lymphoma among young people near Sellafield nuclear plant in West Cumbria.

To examine whether the observed excess of childhood leukaemia and lymphoma near the Sellafield nuclear plant is associated with established risk factors or with factors related to the plant. A case-control study. West Cumbria health district. 52 Cases of leukaemia, 22 of non-Hodgkin's lymphoma, and 23 of Hodgkin's disease occurring in people born in the area and diagnosed there in 1950-85 under the age of 25 and 1001 controls matched for sex and date of birth taken from the same birth registers as the cases. Antenatal abdominal x ray examinations, viral infections, habit factors, proximity to and employment characteristics of parents at Sellafield. Expected associations with prenatal exposure to x rays were found, but little information was available on viral illnesses. Relative risks for leukaemia and non-Hodgkin's lymphoma were higher in children born near Sellafield and in children of fathers employed at the plant, particularly those with high radiation dose recordings before their child's conception. For example, the relative risks compared with area controls were 0.17 (95% confidence interval 0.05 to 0.53) for being born further than 5 km from Sellafield 2.44 (1.04 to 5.71) for children of fathers employed at Sellafield at their conception, and 6.42 (1.57 to 26.3) for children of fathers receiving a total preconceptual ionising radiation dose of 100 mSv or more. Other factors, including exposure to x rays, maternal age, employment elsewhere, eating seafood, and playing on the beach did not explain these relationships. Focusing on Seascale, where the excess incidence has predominantly been reported, showed for the four out of five cases of leukaemia and one case of non-Hodgkin's lymphoma whose fathers were employed at Sellafield and for whom dose information was obtained that the fathers of each case had higher radiation doses before their child's conception than all their matched control fathers; the father of the other Seascale case (non-Hodgkin's lymphoma) was not employed at the plant. These results seem to explain statistically the geographical association. For Hodgkin's disease neither geographical nor employment associations with Sellafield were found. The raised incidence of leukaemia, particularly, and non-Hodgkin's lymphoma among children near Sellafield was associated with paternal employment and recorded external dose of whole body penetrating radiation during work at the plant before conception. The association can explain statistically the observed geographical excess. This result suggests an effect of ionising radiation on fathers that may be leukaemogenic in their offspring, though other, less likely, explanations are possible. There are important potential implications for radiobiology and for protection of radiation workers and their children.

BIRTH DEFECTS AMONG OFFSPRING OF FIREMEN

The authors conducted an exploratory case-control study of paternal employment as a fire fighter and the risk of birth defects among offspring. By means of a population-based registry in British Columbia, 22,192 liveborn children with birth defects were identified for the period, 1952-1973. Two comparisons were made to evaluate the risk among offspring of firemen: 1) comparison with the risk among offspring of fathers employed in other occupations using a matched (two per case) control group, and 2) comparison with the risk among offspring of policemen. Among the 20 birth defect groups studied, an association was found for paternal employment as a fire fighter (relative to all other occupations) and increased risks were observed for ventricular septal defects (odds ratio (OR) = 2.70, 95% confidence interval (Cl) 1.02-7.18) and atrial septal defects (OR = 5.91, 95% Cl 1.60-21.83) among offspring. When compared with policemen, firemen had increased risks of having a child with a ventricular septal defect (OR = 4.68, 95% Cl 1.66-13.17) and atrial septal defect (OR = 3.76, 95% Cl 1.40-10.07). Analyses using a pathogenetic classification for these heart defects yielded similar increased odds ratios for firemen.

Effect of parents' occupational exposures on risk of stillbirth, preterm delivery, and small-for-gestational-age infants.

Epidemiologic research on the effects of parental occupational exposures on fetal development has been limited. The National Natality and Fetal Mortality surveys obtained applicable data on probability samples of live births and fetal deaths which occurred in the US in 1980 among married women. Analyses were conducted for case groups of stillbirths (2,096 mothers, 3,170 fathers), preterm deliveries (less than 37 weeks completed gestation) (363 mothers, 552 fathers), and small-for-gestational-age infants (218 mothers, 371 fathers) compared with controls. Occupational exposures were defined by industry of employment and by imputed exposures based on a job-exposure linkage system. For stillbirth, maternal work in the rubber, plastics, and synthetics industry (odds ratio (OR) = 1.8, 95% confidence interval (Cl) 0.8-4.0) and lead exposure (OR = 1.6, 95% Cl 0.8-3.1), and paternal employment in the textile industry (OR = 1.9, 95% Cl 1.2-2.9), had the largest odds ratios. Preterm birth was most strongly associated with maternal lead exposure (OR = 2.3, 95% Cl 0.7-7.0), corroborating previous findings. Twofold increased risk of preterm delivery was found with paternal employment in the glass, clay, and stone; textile; and mining industries. Paternal exposures to x-rays and polyvinyl alcohol were associated with 1.5-fold increase in risk. The occupation of the mother was not associated with delivery of a small-for-gestational-age infant, in contrast to paternal employment in the art (OR = 2.6, 95% Cl 1.2-5.6) and textile industries (OR = 2.5, 95% Cl 1.3-4.7). Several toxic agents were associated with risk elevation of 1.3 or greater for fathers, most notably benzene (OR = 1.5, 95% Cl 1.1-2.3). In spite of limitations in the exposure data, the size of the exposed populations, and possible confounding, the results in this study encourage further evaluation of the effects of maternal exposure to lead and possibly solvents, as well as paternal exposure in the textile industry and to x-rays and benzene.

Childhood nervous system tumours: an assessment of risk associated with paternal occupations involving use, repair or manufacture of electrical and electronic equipment.

Parental occupational exposures to chemical carcinogens have been associated with malignancies in offspring. Recent studies have raised the issue that electromagnetic fields may play a role in carcinogenesis. We conducted a population-based case-control study testing for an association between the occurrence of a nervous system tumour in a child and paternal employment at the time of the child's birth in occupations involving potential exposure to low frequency electromagnetic fields, primarily in the electrical and electronics industries. Birth certificate data, including parental occupation information, of 499 children who died in Texas from intracranial and spinal cord tumours were compared with 998 controls randomly selected from Texas livebirths. The odds ratio for paternal employment in industries involving potential electromagnetic field exposure was 1.6 (p less than 0.07). A risk of 3.5 (p less than 0.05) was detected for fathers who were electricians. The additional presence of chemical exposures in these diverse occupations and industries must also be considered.

Paternal employment in solvent related occupations and adverse pregnancy outcomes.

Washington State birth certificates were examined for associations between adverse pregnancy outcomes and paternal employment in solvent exposed occupations. Four cohorts defined by live, singleton births to fathers usually employed as auto body shop workers, painters (construction and maintenance), printers, or fibreglass workers were compared retrospectively with both a systematically selected control cohort and a low solvent exposed, occupationally defined control cohort (paternal electricians). The effects of maternal race and medical illness were controlled by sample restriction; maternal age and gravidity by stratified analysis. There was evidence of increased risk of low birth weight for infants born to fathers employed as body shop workers (relative risk = 1.6; 95% confidence interval = 1.1-2.4) or painters (RR = 1.4; CI = 0.9-2.1) when compared with the systematically selected controls but not with the electrician controls. The excess risk appeared stronger when only term infants were analysed suggesting a mechanism of growth retardation rather than prematurity. There was no evidence of increased risk among the other exposed cohorts or for other adverse pregnancy outcomes. Several design features limit the interpretation of the findings and confirmation by other studies is needed.

Changing cognitive outcome in preterm infants with hyaline membrane disease.

One hundred seventy-four preterm survivors of hyaline membrane disease, born 1961 through 1971, were followed up for at least six years with serial psychological and neurological evaluations. This relatively mature population had a mean birth weight of 2,133 g and gestational age of 34.6 weeks. All children had consecutive preschool and school age psychological tests. The mean preschool test score was 91 (SD = 13) and the mean school age score was 101 (SD = 16). The ten-point difference between the mean preschool and school age test scores was significant. Perinatal variables and indexes of disease severity did not correlate with test scores. Higher test scores were correlated with higher paternal educational and employment levels. Improving test scores by school age may be due to test instruments that measure different cognitive skills and/or the diminishing effects of prematurity.