Suicide mortality and pesticide use among Canadian farmers.

BACKGROUND: An exploratory, case-control study was used to investigate a new hypothesis about suicide among farm operators. This hypothesis suggested a biologically plausible link between exposures to certain pesticides and the occurrence of suicide among farm operators. These analyses were based on data from the Canadian Farm Operator Cohort. METHODS: Canadian male farm operators who committed suicide between 1971-1987 (n = 1,457) were compared with a frequency matched (by age and province) sample of control farm operators (n = 11,656) who were alive at the time of death of individual cases. Comparisons focused on past exposures to pesticides reported to the 1971 Canada Census of Agriculture. RESULTS: Multivariate logistic regression analyses indicated no associations between suicide and (1) acres sprayed with herbicides, (2) acres sprayed with insecticides, and (3) the costs of agricultural chemicals purchased; after controlling for important covariates. There was, however, a suggestive increase in risk for suicide associated with herbicide and insecticide spraying among a subgroup of farm operators who were most likely to be directly exposed to pesticides: OR = 1.71 (95% CI = 1.08-2.71) for 1-48 vs. 0 acres sprayed. Additional risk factors that were identified included seasonal vs. year-round farm work (OR = 1.68; 95% CI = 1.15-2.46); and high levels of paid labor on the farm (e.g., OR = 1.61; 95% CI = 1.24-2.10, for > 13 vs. 0 weeks per year). Factors that were protective included marriage (odds ratio (OR) = 0.69; 95% confidence interval (CI) = 0.58-0.81), having more than one person resident in the farm house (e.g., two vs. one person; OR = 0.62; 95% CI = 0.42-0.92); and higher levels of education (e.g., postsecondary vs. primary; OR = 0.40; 95% CI = 0.17-0.96). CONCLUSIONS: This study does not provide strong support for the main hypothesis under study, that exposure to pesticides is an important risk factor for suicide among farmers. Although secondary to the main hypothesis, a number of other risk factors for suicide were suggested. These have implications for the future study and targeting of suicide prevention programs in rural Canada.

Epidemic disease in Glasgow during the 19th century.

19th.century Glasgow was an overcrowded city containing some of the worst housing conditions in the UK. Conditions were ripe for epidemics of infectious diseases and they came in waves causing high mortality particularly among the young. Diagnostic difficulties and ineffective therapy meant that little impact was made on these diseases during the first half of the period. Smallpox was the exception-vaccination of children reduced the incidence and mortality early in the century but subsequent public complacency caused it to return within a few years. Measles and whooping cough surpassed smallpox as the major causes of infectious disease mortality as early as 1810. Epidemics were less common after the three-quarter century mark due to improved living conditions for the poor but also as a result of the assiduos application of Public Health principles.

Screening for intestinal parasites. Is a single specimen valid?

To assess the validity of a single stool or perianal swab specimen when screening for potentially pathogenic parasites, 88 residents of a centre for developmentally handicapped adults were screened by collecting on alternate days three stool samples and pinworm swabs. Both sensitivity and negative predictive values were so low that three samples were required for some parasites. The species being screened for and its underlying prevalence must be considered before collecting only one specimen to reduce laboratory costs.

Intestinal parasite control in an institution for developmentally handicapped adults.

An intestinal parasite eradication program consisting of antiparasitic drug treatment and hygiene measures was conducted at an Ontario residential facility for developmentally handicapped adults from October, 1989 to August, 1990. The prevalence of intestinal parasites in general was initially over 90% while that of pathogenic species was 59%. Six months later, overall prevalence and that of pathogenic species were reduced to 32.9% and 11%. In one subgroup, the reduction in the prevalence of pathogenic parasites was sustained for at least one year. However, the prevalence of non-pathogenic species was similar to the baseline level. Simultaneous treatment and application of hygiene measures appeared to be effective in reducing pathogenic intestinal parasites.

Industrial accident experience of one company on 8- and 12-hour shift systems.

The accident reports of a company were analyzed for 10 years before and after change from 8- to 12-hour shifts. Age-sex standardized ratios were calculated for each year for on- and off-the-job accidents by severity. Times of occurrence of on-the-job accidents were also examined. Overall accident rates were reduced on the 12-hour shift schedule, but statistical significance was reached only for lower accident categories. Off-the-job injuries increased on the 12-hour shift. There were significant gender differences in accident rates on 8-hour but not 12-hour shifts. A distinct circadian pattern of accident frequency was observed. We concluded that the introduction of a 12-hour shift system did not result in increased accidents.

A cross-sectional study of health complaints among 79 data entry operators using video display terminals.

This paper reports on the findings of a cross-sectional study of 79 data entry clerks employed by an Ontario-based organization in five separate offices. The study was conducted to identify factors associated with physical complaints experienced by these office workers. A large percentage of the data entry clerks reported chronic physical complaints (eyestrain, musculo-skeletal pains, headache) as well as emotional or mental stress which they felt were associated with their occupation. Poorly designed overhead lighting systems in all offices contributed to both eyestrain and headache. Duration of employment as a data entry operator within the organization was not associated with stress or physical health complaints. The presence of an adjustable workstation did not in itself guarantee any protection from these conditions. Highly significant associations between occupational stress levels and some physical complaints were observed. The presence of these associations indicated that the management of both physical and stress complaints within these office environments should be tackled simultaneously.

Increasing the understanding of industrial accidents: an analysis of potential major injury records.

Understanding the causes of industrial accidents will be limited if only incidents which produce injury are studied. We examined the records of 514 Potential Major Injury events over a 20-year period in one plant. Injuries were sustained in 228 (44%) of them; 286 (56%) could be classed as "near-miss" incidents and were not associated with injury. Human error accounted for most incidents and was a more important factor among those with less experience on the job. Overall, third party injuries resulted from only 5% of incidents but from 11% of those caused by human error. Although the number of human error incidents fell by 19.5% between the first and second 10-year periods, their relative importance increased as the company managed to reduce incidents of equipment and structural failure even more. We suggest that the term Critical Incident is the most fitting for the first of a series of events in the spectrum of accidents.

Comparison of reported workplace morbidity in 8-hour and 12-hour shifts in one plant.

A retrospective study of the minor morbidity diagnoses of 775 workers during two 10-year periods was undertaken. During the first, they worked an 8-hour rotating shift, during the second, a 12-hour shift system. Data were abstracted from well-kept medical records from the plant medical department. Illnesses and symptoms indicative of stress-related complaints were abstracted. By age-sex standardization and the calculation of morbidity ratios and confidence intervals, it was shown that the introduction of the 12-hour shift system was accompanied by a statistically significant fall in the incidence of stress-related complaints such as headaches, gastrointestinal upsets and alcohol-related complaints. No reduction was found in the incidence of other illness complaints, considered to be unrelated to stress. Similar but even more marked reduction in the incidence of stress symptoms was found in a cohort of 247 workers who had 10 years of experience in each shift system.

Immunologic studies of subjects with asthma exposed to formaldehyde and urea-formaldehyde foam insulation (UFFI) off products.

There has been concern in recent years as to the health hazards of exposure to potentially carcinogenic or immunotoxic substances in the environment. This study was done to determine the effects of exposure to urea-formaldehyde foam insulation (UFFI) off products on various hematologic and immunologic parameters in subjects with asthma: complete blood count and differential, erythrocyte sedimentation rate, lymphocyte subpopulations (E-rosetting, T3, T4, T8, B73.1, and Fc receptor positive lymphocytes and large granular lymphocytes), lymphocyte response to phytohemagglutinin and formalin-treated red blood cells (Form-RBC), serum antibody against the Thomsen-Friedenreich RBC antigen and against Form-RBC, and natural killer (NK), interferon (IFN)-boosted NK (IFN-NK), and antibody-dependent cell-mediated cytotoxicity. Four control subjects with asthma from conventionally insulated homes (control group) and 23 subjects with asthma from UFFI-insulated homes (home group) were exposed to placebo, formaldehyde, dust, and UFFI off gas at levels ordinarily found in UFFI-containing homes for four separate periods in an environmental chamber. Immunologic testing was carried out before the exposure series and 1 day after completion 7 days later as part of an investigation of respiratory and possible allergic effects of such exposure. Data from the UFFI-insulated home group were not significantly different from data of the normal conventionally insulated home control group for any of the variables studied, either before or after UFFI exposure. Paired t tests comparing data from each of the two groups before and after UFFI exposure demonstrated minimal but statistically significant increases in percent eosinophils and T8 positive cells in the UFFI-insulated home group only. Although NK, relative NK, and IFN-NK were normal in all groups, IFN-NK assays by use of a low concentration of alpha-interferon demonstrated a statistically significant decrease in NK response to IFN in both the control and UFFI-insulated home groups after UFFI exposure. These differences were not observed at optimum levels of IFN stimulation. These data indicate that long-term exposure to UFFI off products in the home apparently had no effect on the immunologic parameters studied. Short-term exposure resulted in minor immunologic changes in this subject population.

A case-control study of lung cancer relative to domestic radon exposure.

Public concern was expressed regarding the possibility of adverse health effects with the disposal of radioactive waste in Port Hope, Ontario. A case-control study was carried out to estimate the relative importance of domestic radon gas exposure in the causation of lung cancer in the town over a ten-year period. Twenty-seven cases met the entry criteria. Statistical analyses of results did not provide conclusive results that linked an increased risk of lung cancer and elevated domestic alpha radiation levels, when all factors were considered. However, a very strong association was demonstrated between cigarette smoking and lung cancer.

Arsenic, syphilis, and cancer of the prostate.

A study was conducted to investigate the association of cancer of the prostate with historical records of previous venereal disease and treatment with arsenical drugs. Eighty-three cancer cases were each age matched with two male controls--one with benign prostatic hypertrophy and one other non-cancer patient. Analysis from pooled data showed a statistically significant difference for syphilis infection between cases and controls at p less than 0.05; odds ratio 2.9. Matched pair analysis maintained p less than 0.05 significance for the first control group but odds ratios were 5.5 and 2.75 in respect of control groups 1 and 2. The mean age at which venereal infection was acquired was higher for syphilis than for gonorrhoea, but the mean age at diagnosis of cancer was younger for the syphilis group; there was a statistically significant difference between the mean at cancer diagnosis of those who had syphilis and those who had no record of previous venereal infection (t = 2.18, df 70, p less than 0.05). No association was demonstrated for history of treatment with arsenical drugs.

Respiratory response to formaldehyde and off-gas of urea formaldehyde foam insulation.

In 18 subjects, 9 of whom had previously complained of various nonrespiratory adverse effects from the urea formaldehyde foam insulation (UFFI) in their homes, pulmonary function was assessed before and after exposure in a laboratory. On separate occasions formaldehyde, 1 part per million (ppm), and UFFI off-gas yielding a formaldehyde concentration of 1.2 ppm, were delivered to each subject in an environmental chamber for 90 minutes and a fume hood for 30 minutes respectively. None of the measures of pulmonary function used (forced vital capacity, forced expiratory volume in 1 second or maximal midexpiratory flow rate) showed any clinically or statistically significant response to the exposure either immediately after or 8 hours after its beginning. There were no statistically significant differences between the responses of the group that had previously complained of adverse effects and of the group that had not. There was no evidence that either formaldehyde or UFFI off-gas operates as a lower airway allergen or important bronchospastic irritant in this heterogeneous population.

Formaldehyde in insulation: villain or innocent bystander?

When urea formaldehyde foam insulation (UFFI) deteriorates, it produces an off-gas mixture whose major constituent is formaldehyde. Most investigative studies of UFFI have concentrated on formaldehyde. Health concerns fall into three groups: irritant characteristics, allergenic capabilities and potential carcinogenicity. Except for the first of these, formaldehyde's hazard potential is not clear. The extent to which formaldehyde may be responsible for UFFI's evil reputation is explored in this paper but the degree to which either substance is a real threat to health still appears to open to debate.

Assessing environmental toxins by human population effects.

The impact of toxins on the health of human populations can only be accurately assessed by epidemiologic methods. The investigation of toxin-disease associations in human populations and the accurate interpretation of data are often very difficult because of the existence of multiple confounding variables and the unrepresentativeness of sample or study populations. Factors influencing the deduction of cause and effect relationship rather than simple association are discussed, as is the need for continued development of epidemiological surveillance techniques.