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PubMed1997

Cumulative lead exposure in relation to mortality and lung cancer morbidity in a cohort of primary smelter workers.

OBJECTIVES: The purpose of this study was to determine the mortality and cancer incidence of long-term lead smelter workers at a primary smelter. METHODS: A cohort of 3979 workers employed for at least 1 year during 1928-1979 and a subcohort of 1992 workers employed in lead-exposed departments (lead only workers) was formed. The expected mortality in 1955-1987 and cancer incidence in 1958-1987 were calculated relative to the county rates, specified for cause, gender, 5-year age groups, and calendar year. A cumulative blood-lead index was used for the dose-response analyses. RESULTS: The lung cancer incidence of the total cohort [standardized incidence ratio (SIR) 2.8, 95% confidence interval (95% CI) 2.1-3.8] and the group with the highest exposure (SIR 3.1, 95% CI 2.0-4.6) was high. Similar risk estimates were observed with a latency of 15 years. The workers hired before 1950 had higher lung cancer risk estimates (SIR 3.6, 95% CI 2.6-5.0) than the workers hired later (SIR 1.3, 95% CI 0.6-2.6, no latency period). The risk estimates for lung cancer were further elevated in the subcohort of lead-only workers (SIR 5.1, 95% CI 2.0-10.5 in the highest exposed subgroup; latency period of 15 years). No excesses of other malignancies were noted. CONCLUSIONS: The increased relative risks were probably mainly due to interactions between lead and other carcinogenic exposures, including arsenic. Further study is required concerning such possible interactions before a role in the induction of lung cancer can be ascribed to lead.

Aged↗
PubMed1983

Health selection among metal workers.

The objective of the present study was to determine which age and exposure categories are the most prone to health selection. Mortality and morbidity were studied on three different exposure levels, defined primarily according to the physical demands of the work: heavy level (iron foundries), medium level (manufacture of metal products), and light level (manufacture of electrical devices). The population comprised about 15,700 men employed in 1950--1976 in the three branches of the metal industry. The number of person-years of follow-up was about 215, 800. During the period 1950--1978, 1,407 deaths occurred. Occupational history, morbidity, and turnover causes were studied by means of a questionnaire sent to 3,500 current and former workers. The survival curves showed no great differences between the three exposure levels. However the heavy level had the highest degree of mortality, and the medium level the lowest. Foundry workers had the highest overall rates of disability. But, in the older age groups, the disability rates of the metal product workers were the highest. Less social selection was suggested for foundry workers than for the two other cohorts. Metal product workers seemed to be selected by both social and health factors. Young electrical workers were occupationally trained. On the other hand older workers with poor health were selected to this light level (negative health selection).

Adult↗
PubMed1999

Relationship between shift work and onset of hypertension in a cohort of manual workers.

OBJECTIVES: This study investigated the possibility of a relationship between blood pressure level and rotating 3-shift work in a prospective follow-up of workers in a zipper and aluminum sash factory in Japan. METHODS: Altogether 1551 men aged 18-49 years were followed prospectively for 5 years, and the cumulative incidence of hypertension among 3-shift workers was compared with that of day workers. A multiple logistic analysis was used for adjusting for base-line characteristics such as age, body mass index, blood pressure, and drinking habit. RESULTS: In the younger age group, the relative risk of the rotating 3-shift workers during the observational period was increased compared with that of day workers after adjustment for the confounding factors. In the older group, the cumulative incidence of hypertension was not higher for workers who had continued shift work. However, a relatively high risk of hypertension was found for workers who converted from 3-shift work to day work when compared with those who remained on shift work and day work. CONCLUSIONS: It is suggested that there is an association between 3-shift work and blood pressure.

Adolescent↗
PubMed2002

Impact of repetitive manual materials handling and psychosocial work factors on the future prevalence of chronic low-back pain among construction workers.

OBJECTIVES: This study investigated the influence of manual stone and brick handling and psychosocial work factors on the risk of chronic low-back pain and describes the impact in terms of risk advancement period. METHODS: The Hamburg Construction Worker Study included a longitudinal study among 488 male construction workers. Adjusted prevalence ratios (PR) of chronic low-back pain (>3 months during the last 12 months) according to self-reported worktasks in the baseline survey were estimated with the Cox proportional hazards model. RESULTS: The 1-year prevalence of chronic low-back pain was 15.4%. Workers with chronic low-back pain in the baseline survey had a higher risk of such pain during the follow-up (PR4.07,95% CI 2.18-7.59). The prevalence in association with laying large lime sandstones for >2 hours per shift (PR 1.80, 95% CI 1.04-3.14) further increased after adjustment for job category (PR 2.69, 95% CI 1.25-5.78), and it advanced the risk by a risk advancement period of 18 years (95% CI 4-39). Workers with low satisfaction with their work achievements had a higher prevalence of chronic low-back pain (PR 2.07, 95% CI 1.10-3.88). Similar risk estimates were observed in the subgroup without chronic low-back pain in the baseline survey. A strong effect of time pressure wasonly present for these workers (high: P R 6.30,95% CI 1.41-28.21). CONCLUSIONS: The results suggest that repetitive work involving bent positions and the manual manipulation of heavy stones increases the risk of future chronic low-back pain. For risk communication, the notion that a 40-year-old construction worker laying large sandstones has the same risk as an unexposed 58-year-old construction worker may be more informative.

Achievement↗
PubMed2005

Competence of maternal and child health clinic workers in detecting malnutrition in Somalia.

BACKGROUND: The MCH clinic workers in Somalia receive formal and in-service training to perform their professional duties. Their competence in the field was never examined. This study assessed their competencies in detecting malnourished children 5 years and below in Beledweyne. OBJECTIVE: To assess the competence of MCH clinic workers in detecting malnourished children. DESIGN: Cross-sectional study. METHODS: The study was conducted in 1989. We obtained data on children five years and below from the MCH clinic in Beledweyne, Somalia. We analyzed two months data. We used CASP program to calculate the Weight-for-Age index (WFA). The nutritional status determined by the MCH clinic workers and the WFA index were used to estimate the positive and negative predicted values of the MCH clinic workers' competence in detecting malnourished children. RESULTS: We studied 487 children 5 years old and below. The health workers determined that 13.5% were malnourished. The positive and negative predicted values of the MCH clinic workers' nutritional measure were 76% and 92% respectively. CONCLUSION: The MCH clinic workers showed deficiency in their competence to detect malnourished children. They misclassified 10% of the children, which was worse among the malnourished, due to incorrect plotting of the child's current weight on the growth chart.

Child Health Services↗
PubMed1985

[Employment conditions and a system of occupational health administration for disabled workers].

A survey using a questionaire was conducted to elucidate the employment conditions and a system of occupational health administration status of the disabled workers in private enterprises. The average employment rate of disabled workers was found to be higher in small-scale enterprises, than in large-scale enterprises. Also, the low employment rate was found among cases of spinal cord injuries and hemipregia. The reasons for workers becoming disabled were "private accident and illness" (59.2%) "congenital" (30.6%) and "labor accident" (10.2%). The main physical factor influencing work efficiency of disabled workers was "degree of disability" while "work morale" was found to be the most influential psychological factor. Also it was found that about 50% of private enterprises will accept the reinstatement and employment of spinal cord injury or hemipregia workers. But it will be necessary that the disabled workers are able to do the requested job. However, it is necessary for employers of disabled workers to make various efforts in overcoming situations such as, changes in organization, improvement of occupational health administration staffs and improvements in the working environment and equipment.

Absenteeism↗
PubMed1998

Alteration of diurnal rhythms of blood pressure and heart rate to workers exposed to radiofrequency electromagnetic fields.

BACKGROUND: In previous studies we found measurable effects on variability of heart rate and on blood-pressure parameters of workers exposed to radiofrequency electromagnetic fields (EMF)compared with a control population, but none of the effects could be assigned clinical significance. In general, the obtained results strongly suggested that dysregulation of the autonomic control of the circulatory system was occurring. Therefore, it seemed logical that analysis of diurnal rhythms of blood pressure and heart rate, on the basis of data from 24 h recordings, might further support the above hypothesis. OBJECTIVE: The aim of this study was to determine the course of diurnal rhythms of blood pressure and heart rate in a group of workers exposed to various intensities of radiofrequency electromagnetic fields. METHODS: In the study we used 61 healthy workers (aged 30-50 years) who had been exposed to radiofrequency EMF of 0.738-1.503 Mhz and 42 healthy workers at radio-line stations (aged 28-49 years), who had not been exposed to EMF occupationally. The work patterns of these two groups were identical (12 h day working shift, 24 h interval, 12 h night shift and then 48 h rest). During the second day of the rest period 24 h ambulatory blood pressure (ABP) was recorded. For analysis of diurnal rhythms the group of exposed workers was divided into two subgroups: group A of 38 subjects exposed to low intensities of radiofrequency EMF (20-180 V/m) and group B of 23 subjects exposed to high intensities of radiofrequency EMF (200-550 V/m). Parameters of diurnal rhythms of blood pressure and heart rate (acrophase, amplitude and mean) were calculated by performing a least-square fit of a 24 h cosinor (single cosinor analysis) at P < 0.05. RESULTS: Healthy men aged 28-49 years, working on a pattern of 12-24-12-48 h, exhibited typical, well-preserved diurnal rhythms of blood pressure and heart rate with two maxima (at about 1400 and 1700-1800 h) and one minimum (at about 0200-0400 h). For workers exposed to radiofrequency EMF we noted a significant lowering of the amplitudes of rhythms of blood pressure and heart rate (P < 0.01) and a shift of the acrophase to an earlier time (1100-1200 h; P < 0.05). These changes were more pronounced among workers exposed to high intensities of radiofrequency EMF. CONCLUSIONS: Occupational exposure to radiofrequency EMF can result in changes of the diurnal rhythms of blood pressure and heart rate with lowering of their amplitudes and a shift of the acrophase. The clinical relevance of the present finding needs to be investigated in further studies.

Adult↗
PubMed1998

[Psychological and neurobehavioral effects of aluminum on exposed workers].

OBJECTIVE: To explore neurotoxicity and the changes in psychological and neurobehavioral functions in workers exposed to aluminum. METHODS: Psychological status and neurobehavioral functions of 103 exposed workers and 64 controls were examined with Neurobehavioral Core Test Battery recommended by World Health Organization (WHO), and meanwhile, air concentrations of aluminum in the workplaces and urine levels of aluminum in the exposed workers were determined. RESULTS: Urine levels of aluminum in the exposed workers were markedly higher than those in non-exposed controls, with a statistical significance. Scores for tension, depression, anger, fatigue and confusion in the workers exposed to aluminum for more than ten years were significantly more than those in non-exposed controls. Scores of the performance of Santa Ana, digit symbol and pursuit aiming in the former were significantly lower, and no other changes in psychological and behavioral functions was found in workers exposed for less than ten years, except for their scores of pursuit aiming. CONCLUSION: Obvious changes in psychological status, neuromotor speed and their accuracy were observed in workers exposed to aluminum for a long term.

Adult↗
PubMedDate not supplied

Long-term exposure to "low levels" of manganese oxides and neurofunctional changes in ferroalloy workers.

Occupational exposure to manganese can cause early neurobehavioral effects in low- or a-symptomatic workers. A battery of neuropsychological tests was administered to a group of 61 ferroalloy male workers and 87 controls. The average (geometric mean) manganese concentrations in total dust at the plant have changed from 1981 to 1997 respectively from 1597.03 micrograms/m3 to 239 micrograms/m3 at the furnace area; from 151.53 to 255.76 micrograms/m3 at the casting area; from 167 to 54.7 micrograms/m3 at the maintenance (welding operations), yielding a current overall value of 54.25 micrograms/m3. A cumulative exposure index was calculated for each alloy worker and the average value (geometric mean) resulted to be 1204.87 micrograms/m3 x years, which divided by the average length of exposure (15.17 years), showed the concentration of 70.83 micrograms/m3 of manganese in total dust. Blood and urinary manganese geometric means resulted significantly higher in the exposed workers (9.18 micrograms/l and 1.53 micrograms/g creatinine, respectively) than in controls (5.74 micrograms/l and 0.40 microgram/g creatinine, respectively). A positive correlation was observed between the airborne manganese concentrations in total dust and blood manganese (n = 55; R = 0.36; R2 = 0.13; p = 0.0068), whereas no association resulted between cumulative exposure index and both blood manganese and urinary manganese. Higher prevalence of symptoms reporting was observed in the alloy workers concerning irritability, loss of equilibrium and rigidity. Tremor parameters including the central frequency and its dispersion, resulted to be statistically different in the exposed workers compared to the controls. Motor functions exploring the coordination of rapid and alternating movements and memory functions resulted to be impaired in the manganese workers. Dose-effect relationships were observed between the cumulative exposure index and some of the test results, whereas no relationship was found with the airborne manganese concentrations and the biological indicators of exposure. These findings are consistent with the existing knowledge of a cumulative mechanism of action of manganese, which must be carefully considered when setting safe exposure levels. In order to be protective for the entire working life, the average annual exposure level should be lower than 100 micrograms/m3.

Adult↗
PubMedDate not supplied

Focused medical surveillance: a search for subclinical movement disorders in a cohort of U.S. workers exposed to low levels of manganese dust.

Seventy-five workers with recent and/or historical exposure to manganese (Mn) at a metal producing plant in northern Mississippi were closely matched with 75 control workers who had no known history of occupational exposure to Mn. Both plants are OSHA STAR work sites and share common medical, safety, and industrial hygiene services. Airborne Mn levels were assessed for each of twelve job categories at the Mn facility by collecting 63 side-by-side full-shift personal samples of both total and respirable Mn dust. Exposures of workers currently working with Mn averaged 0.066 mg/3 respirable and 0.18 mg/3 total Mn. An assessment of major equipment and work practice changes over the past several years and estimates of the resultant relative impacts on exposure was made. Based on this information and individual employment information, each worker's cumulative exposure to respirable and total Mn was estimated for the preceding 30 days, preceding year, and for the worker's entire employment history. Both Mn and control workers were administered multiple neuropsychological tests including tests of hand-eye coordination, hand steadiness, complex reaction time, and rapidity of finger tapping. A questionnaire was used to evaluate a worker's neuropsychological status. Performance decreased significantly with increasing age in tests of hand-eye coordination, complex reaction time and finger tapping speed. No effect of Mn exposure was found on the results of the questionnaire or any neuropsychological test.

Age Factors↗
PubMedDate not supplied

[Occurrence of nonspecific symptoms of irritation in workers exposed to latex].

The study included 17 female workers employed in latex glove rubber manufacturing plants. The mean age was 42 years and the mean duration of employment 19 years. Subjects were predominantly nonsmokers. A control group of 17 nonexposed workers was also studied. Chronic respiratory symptoms and diseases as well as acute work-related symptoms were recorded for these workers. Ventilatory capacity was measured by recording maximum expiratory flow-volume (MEFV) curves on which forced vital capacity (FVC), one second forced expiratory volume (FEV1) and maximum expiratory flow at 50% and the last 25% of the vital capacity (FEF50, FEF25) were read. Skin prick tests were performed with three types of latex (original material-latex 1, extract from gloves-latex 2, and extract of latex company Epypharm-latex 3). The prevalence of chronic respiratory symptoms was greater among latex workers (varying from 5.9% for occupational asthma to 58.8% for dyspnea) than among control workers (0%). There was a high prevalence of acute work-related symptoms, particularly for eye irritation (76.5%), dryness of the nose (70.6%), throat burning (70.6%), dryness of the throat (64.7%) and cough (58.8%). Measured ventilatory capacity data in latex workers were significantly lower in comparison to control, particularly for FEF25 (75.1 +/- 19.5%). Among latex gloves making workers one had positive skin reaction to latex 3 along with the symptoms of occupational asthma. Our data indicate that employment in latex making gloves may be associated with the development of occupational asthma, in addition to frequent nonspecific respiratory findings.

Adult↗
PubMed1999

[HCV prevalence in health workers].

The risk of HBV infections in health workers and the different prevalence according to the hospital activities has been shown in a great number of papers. In order to establish the prevalence of serological HBV markers in health workers fron high complexity hospital, we have analyzed 730 inquiries refilled in the period 1994-1995 before receiving the antihepatitis B vaccine. We studied 730 health workers, 282 (38.8%) males and 447 (61.2%) females with a mean age of 40.1 years old. We found 75/730 (10.2) serums antiçHBc reactives. The found prevalence was significantly larger than the one found in blood donors. The analysis of the prevalence according to the hospital activities showed that the infirmary personnel is the only with anti-HBc prevalence significantly superior to the blood donors, and the other health workers prevalence. Differences in the anti-HBc prevalence between the physicians specialties were not found. Our results agree with other publications that clearly show that health workers are a risk group for HBV infection. However, what attracts attention in the analyzed population is that the only ones with anti-HBc prevalence significantly superior to the blood donors' and the other health workers prevalence were the nurses, suggesting that nurses are the only health workers that have risk of HBV infections.

Adolescent↗
PubMed1998

[Study on the relationship between occupational factors and work ability of middle aged workers].

Based on the assessment of work ability index (WAI) of middle aged workers, associations between occupational factors and work ability decline of middle aged workers were examined in a case-control study. 1037 workers (age ranged from 40 to 60) were included in the study. The study group comprised 180 workers of mean age 47.71 years representing those who's work ability decreased. The control group comprised 857 workers of mean age 47.22 years representing those who's work ability was on a normal level. Results showed that some common occupation hazards such as dusts, noise, vibration, humidity, and high temperature were more frequently occurred in work environment of the study group than that of the control group. High risks were found in workers with these hazards. Another significant risk factor of work ability decline was heavy physical load. Significantly elevated risks were observed for physical load perception(OR = 2.52), repetitive work (OR = 1.36), poor work postures(OR = 1.48), and carrying heavy loads(OR = 1.59). As compared to physical loads, mental loads were not in relation to work ability decline. The information about occupational factors affecting work ability will be helpful for redesiging the work for the middle aged workers.

Adult↗
PubMed1999

Increase in signal intensities on T1-weighted magnetic resonance images in asymptomatic manganese-exposed workers.

OBJECTIVES: To clarify the clinical significance of increased signal intensities on T1 weighted magnetic resonance imaging (MRI) we performed a large-scale epidemiological study on asymptomatic manganese (Mn)-exposed workers with its focus on MRI. METHODS: We randomly selected 121 male workers out of a total of 750 workers including Mn-exposed, non-exposed manual, and non-exposed clerical workers in the factories. We studied environmental and biological monitoring, neurological examination, and MRI. RESULTS: The proportion of workers with increased signal intensities among the exposed, the non-exposed manual workers, and the non-exposed clerical workers was 46.1%, 18.8%, and 0%, respectively. Especially, 73.5% of the welders showed increased signal intensities. In no subject, were clinical signs of manganism observed. The pallidal index correlated with blood Mn concentration. CONCLUSION: Increase in signal intensities on the T1-weighted image reflect recent exposure to Mn, but not necessarily manganism. At which increase of signal intensity, the progression of manganism from Mn exposure occurs, remains to be solved.

Adult↗
PubMedDate not supplied

Prevalence of self-reported health complaints among shoe workers of small workshop exposed to organic solvents in Hebron City, West Bank: a cross-sectional survey.

The study was conducted to estimate the prevalences of neurological disorders and mucous membrane irritation complaints among workers of shoe workshops in Hebron City, in particular to measure the associations between the occurrence of symptoms indicating polyneuropathy among workers and exposure to organic solvents in the glueing tasks. A group of 103 male workers from 30 workshops, exposed to organic solvents for more than one year were recruited to the study during the years 1996-1997. A validated Swedish neuropsychiatric questionnaire which contained questions on neurological and mucous irritation symptoms was used. Prevalence ratios were used as an indicator for relative risk. The overall prevalence of painful tingling of limbs (used as indicator of polyneuropathy) was high among the workshop workers (40%) and was significantly associated with long term exposure to organic solvents in glueing tasks (PR 2.8: 95% CI 1.0-8.3). Moderate associations were seen in other tasks. Headache and mental irritability did not show any association with organic solvent exposure in the workshop tasks. Breathing difficulty showed a moderate non-significant association with long term exposure to organic solvents (72 months) in cleaning tasks (1.9,0.7-4.8), while sore eyes also showed a moderate non-significant association with exposure to organic solvents for 25-72 months in the glueing tasks. Long term exposure to n-hexane (mainly found in the glues) could be the main cause of polyneuropathy among the workers of Hebron shoe workshops. The absence of effective ventilation systems and personal protective equipment might increase the prevalence of polyneuropathy among these workers. In conclusion, glues containing high concentrations of n-hexane are still in use in many shoe workshops in Hebron City (as well as in other developing countries), and long term exposure to n-hexane in glueing compounds could result in polyneuropathy among the workers. However, in the absence of objective measurements our results must be interpreted with caution. Well planned longitudinal studies with objective measures of exposure and disease are important for future research in developing countries.

Adult↗
PubMed2000

[Concentration of serum vitamin C in workers exposed to selected physical and chemical risk factors].

Determination of the serum vitamin C levels may yield the information on the nutritional status of workers. Increasing community awareness of the health-enhancing nutrition patterns as an element of the promotion of lifestyles conducive to health among workers may limit a negative impact of risk factors on workers' health. The aim of this study was to analyse the levels of serum vitamin C in workers exposed to selected physical (noise, electromagnetic fields) and chemical risk factors present in the work environment. Two randomised groups of male workers, one exposed to physical factors (n = 43; mean age 39.5 +/- 8.6 yr.), and the other to chemical factors (n = 40; mean age 38.3 +/- 8.0 yr.) were included in the study. The control group was composed of male workers (n = 36; mean age 40.4 +/- 10.1 yr.) exposed neither to physical nor to chemical factors. In all subjects, the serum vitamin C levels were measured using the spectrophotometric method by Kyaw. The mean serum vitamin C levels in the workers exposed to physical and chemical factors were 30.1 (mumol/l) and 30.9 (mumol/l), respectively, and their statistical significance was lower (p < 0.01) as compared with the mean serum vitamin C levels of 39.7 (mumol/l) in the control group.

Adult↗
PubMedDate not supplied

[Cardiovascular disease risk factors in product quality control workers at the AD Neoplant facility in Novi Sad].

INTRODUCTION: Monitoring the health status of the employed in the meat industry "Neoplanta", a high prevalence of cardiovascular risk factors was observed. It was also observed that workers employed in the meat industry have specific dietary habits as a result of working practice. Their hypercaloric diet is with high dietary animal fat and protein intake. This particularly refers to the group of workers in charge of the quality control of meat products who, besides regular hot meal and frequent business lunches, consume certain quantities of these products on a daily basis. A common characteristic shared by members of this group is that they very seldom or never have preventive medical examination. OBJECTIVE: The objective of this paper was to determine cardiovascular risk factors in this group of workers and to evaluate educational program effects on the prevalence of risk factors. MATERIAL AND METHODS: Cardiovascular risk factors were examined in 39 workers (28 men and 11 women) involved in the daily control of meat products and performing executive jobs of different complexity levels in the meat industry "Neoplanta". Cardiovascular risks and lipid status were examined before and after a nine-month-long educational program. Occurrence of increased risks and lipid status elements were tested, p < 0.05. RESULTS: According to obtained results hypercholesterolemia is present in 94.87%, obesity in 82.05%, positive family cardiovascular anamnesis in 74.48%, physical inactivity in 69.33%, continuous alcohol consumption in 69.23%, excessive consumption of black coffee in 61.54%, hypertension in 51.28%, "stress alleviation" with food in 46.15%, hypertriglyceridemia in 46.15% and cigarette smoking in 46.15% of examinees. Cigarette smoking, chi 2 = 1.85, alcohol consumption, chi 2 = 0.26, black coffee drinking, chi 2 = 0.22, preparation of the meals on the fat, chi 2 = 0.10 has remained unchanged after educational program. The number of patients "alleviating" stress with food, chi 2 = 5.26 and physically inactive patients, chi 2 = 1.06 has significantly increased. Body mass, chi 2 = 0.06 and hypertension, chi 2 = 1.42, has not reduced, hyperholesterolemia has remained unchanged, chi 2 = 2.22, LDL-cholesterol has decreased insignificantly, chi 2 = 0.60, while HDL-cholesterol has decreased significantly, chi 2 = 4.27. Atherosclerosis index has increased significantly, chi 2 = 4.47. Thus, poor effects of the educational program can be attributed to unchanged lifestyle habits of the examined workers. CONCLUSION: It can be concluded that cardiovascular risk factors as well as lipid status elements have not decreased in this group of workers after educational program and therefore continuous medical educational program is suggested with purpose to increase the motivation of workers.

Adult↗
PubMedDate not supplied

Worker life tables, survivorship, and longevity in colonies of Bombus (Fervidobombus) atratus (Hymenoptera: Apidae).

Survivorship curves and longevity of workers were studied in two queenright and two queenless colonies of Bombus (Fervidobombus) atratus. Survivorship curves for workers of all colonies were, in general, convex, indicating an increasing mortality rate with increasing age. The mean longevity for the workers from queenright colonies, 24.3 days and 17.6 days, was not significantly different from that in queenless colonies, 21.2 days and 20.2 days. In all colonies workers started foraging activities when aged 0-5 days, and the potential forager rates rose progressively with increasing age. Mortality rates within each age interval were significantly correlated with the foraging worker rates in all colonies. Only in two of the colonies (one queenright and one queenless) longevity was significantly correlated with worker size. The duration of brood development period seems to be one of the most important factors influencing adult worker longevity in bumble bee species.

Animals↗