Childhood cancer in the offspring of male sawmill workers occupationally exposed to chlorophenate fungicides.

The objective of this study was to determine whether paternal occupational exposure to chlorophenol fungicides and their dioxin contaminants is associated with childhood cancer in the offspring of sawmill workers. We used data from 23,829 British Columbian sawmill workers employed for at least 1 continuous year between 1950 and 1985 in 11 sawmills that used chlorophenates. Probabilistic linkage of the sawmill worker cohort to the provincial marriage and birth files produced an offspring cohort of 19,674 children born at least 1 year after the initiation of employment in the period 1952-1988. We then linked the offspring cohort to the British Columbia Cancer Registry. We included all malignancies in cases younger than 20 years of age that appeared on the cancer registry between 1969 and 1993. We calculated standardized incidence ratios (SIRs) using the British Columbia population as a reference. A nested case-control analysis assessed the effects of paternal cumulative exposure and windows of exposure on the risk of developing cancer in the offspring. We identified 40 cases of cancer during 259,919 person-years of follow-up. The all-cancer SIR was 1.0 [95% confidence interval (CI), 0.7-1.4]; the SIR for leukemia was 1.0 (CI, 0.5-1.8); and the SIR for brain cancer was 1.3 (CI, 0.6-2.5). The nested case-control analysis showed slightly increased risks in the highest categories of chlorophenol exposure, although none was statistically significant. Our analyses provide little evidence to support a relationship between the risk of childhood cancer and paternal occupational exposure to chlorophenate fungicides in British Columbian sawmills.

Opportunities for a broader understanding of work and health: multiple uses of an occupational cohort database.

Occupational cohort studies conducted to study cancer incidence and mortality require extensive data gathering about workers' job histories, exposures, and health outcomes. Although this process is expensive, the database created can be looked upon as a resource for broad investigations of the relationship between work and health. This paper presents the example of a retrospective cohort study which began in the traditional way, examining the link between a specific pesticide exposure and mortality and cancer incidence. The cohort register has since been used to investigate whether infertility, adverse reproductive outcomes, and childhood cancers might be associated with this exposure. It is also being used as the basis for studying other sawmill exposures including noise and wood dust as well as socioeconomic factors including job strain, job mobility, unemployment, and retraining. This approach allows both the efficient use of occupational cohorts as well as providing the opportunity for investigators to develop a more comprehensive perspective on the determinants of the health status of workers and their families.

Fertility among a cohort of male sawmill workers exposed to chlorophenate fungicides.

The purpose of this study was to determine whether exposure to chlorophenate fungicides and their dioxin contaminants is associated with male infertility among sawmill workers. The study was conducted using fertility data compiled from 26,487 sawmill workers in 14 British Columbian sawmills. Our analysis was restricted to workers who had been employed for at least 1 continuous year between 1950 and 1985 and to live-births born at least 1 year after the initiation of employment in the period 1955-1988. We assessed fertility trends by internal comparison using Mantel-Haenszel rate ratios and by calculating standardized fertility ratios using an external and an internal reference population. We identified 19,684 births in the study period. Initially, both external and internal analyses showed that sawmill workers from mills using chlorophenates had lower fertility than workers employed in mills not using chlorophenates. After controlling for time since first hire, however, we found no inverse relation between cumulative exposure to chlorophenate fungicides and fertility. Based on the results of our study, there is little evidence for a reduction in fertility among chlorophenate-exposed sawmill workers in British Columbia. The analyses indicate the importance of time since hire as a potentially strong confounder in this type of investigation.

Applying epidemiological principles to ergonomics: a checklist for incorporating sound design and interpretation of studies.

The primary purpose of this paper is to provide a checklist of scientific requirements necessary for the design of sound ergonomics studies. Ergonomics researchers will be able to use the checklist when designing a study and preparing it for publication. Practitioners can use the checklist to critically appraise study results, thereby having greater confidence when applying ergonomic recommendations to the workplace. A secondary purpose of the paper is to pilot the checklist on a sample of papers in the ergonomics literature and to assess its reliability. While there are checklists to assess the epidemiological rigour of studies, none have been adapted to address methodological issues in ergonomics. Two epidemiologists independently searched five ergonomics journals (Applied Ergonomics, Ergonomics, Human Factors, International Journal of Human-Computer Interaction and Journal of Human Ergology) for research studies on VDT use and visual function published between 1990 and 1995. Twenty-one articles were reviewed. Each paper was scored according to the checklist. Overall, the reviewers found that the articles did not consistently fulfill some of the checklist criteria. An insufficient sample size was the most serious omission. Inter-rater reliability of the checklist was excellent for 11 of 14 items on the checklist (Kappa > 0.74), good for two items (Kappa between 0.40 and 0.74) and poor for one item. As ergonomics is gaining acceptance as an integral part of occupational health and safety, individuals in this field must be cognizant of the fact that study results are being applied directly to workplace procedures and design. It is incumbent upon ergonomists to base their work on a solid research foundation. The checklist can be used as a tool to improve study designs and so ultimately has implications for improving the fit between the worker and the work environment.

Influence of breast versus formula milk on physiological gastroesophageal reflux in healthy, newborn infants.

The effect of milk type on physiological, gastroesophageal reflux (GER) was studied in 37 breast-fed and 37 formula-fed, healthy, term neonates aged 2-8 days. The neonates were randomly selected from the public maternity ward and studied for 4 h after their morning milk feed. GER was recorded by a pH microelectrode placed 6 cm above the gastroesophageal junction and analyzed in the third and fourth postprandial hours. Sleep state was accurately defined from the electroencephalogram, electrooculogram, electromyogram, breathing, and behavioral observations. Movement was recorded from a piezo-electric transducer. In active sleep, the breast-fed neonates demonstrated GER episodes of significantly shorter duration than the formula-fed neonates. The means and 95% confidence intervals (CI) were 3.0 (1.6,5.2) compared with 8.3 (5.0,13.3) min/h of active sleep respectively (p less than 0.05). This could not be explained by greater milk volume or increased movement before or during reflux in formula-fed neonates. However, the lower median pH values for GER in breast-fed neonates, 2.0 versus 2.5, were significantly different (p less than 0.05). This difference may reflect more rapid gastric emptying. The lower esophageal pH is more likely to stimulate peristalsis and thus limit the duration of reflux (shorter episodes), in the breast-fed neonates.

Impact of sleep and movement on gastro-oesophageal reflux in healthy, newborn infants.

Seventy four normal, healthy newborn babies were studied to examine the relationship between gastro-oesophageal reflux, sleep state, and movement. Multichannel pen recordings were made to determine sleep state, movement, breathing, and reflux. The mean number of reflux episodes per hour was highest in wakefulness, followed by active and indeterminate sleep. In quiet sleep reflux rarely occurred. The mean duration of reflux episodes per hour was longest in active sleep followed by wakefulness, indeterminate and quiet sleep. There was a strong positive correlation between duration of reflux and movement time for wakefulness, active and indeterminate sleep. Movement preceded 88% of all reflux episodes. Physiological reflux occurs in most newborn infants but is clinically inapparent. The results suggest that state and movement are related to the incidence and duration of reflux. Sleep state is therefore an important variable in determining normal values for reflux in infancy since developmentally the amount of sleep time lessens but quiet sleep proportionally increases.