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epidemiological data
Type of information:
experimental study
Adequacy of study:
key study
other: not rated acc. to Klimisch
Rationale for reliability incl. deficiencies:
other: Any kind of reliability rating is not considered to be applicable, since human studies/reports are not conducted/reported according to standardised guidelines.

Data source

Reference Type:
Respiratory health of cobalt production workers.
Linna, A. et al.
Bibliographic source:
American Journal of Industrial Medicine 44: 124-132.

Materials and methods

Study type:
cohort study (retrospective)
Endpoint addressed:
repeated dose toxicity: inhalation
Test guideline
no guideline followed
Principles of method if other than guideline:
The purpose of this study was to determine which respiratory efects and symptoms are asscociated with long-term (at least 10 years) exposure in cobalt production.
GLP compliance:
not specified

Test material

Constituent 1
Reference substance name:
cobalt and cobalt compounds
cobalt and cobalt compounds
Details on test material:
The exact test item was not decribed in the publication. On the other hand, it was stated that workers who had worked in cobalt powder or cobalt-compound production were investigated.


Type of population:
Ethical approval:
confirmed, but no further information available
Details on study design:
HYPOTHESIS TESTED: The purpose of this study was to determine which respiratory effects and symptoms are associated with long-term (at least 10 years) exposure in cobalt production.SETTING: The cobalt plant studied in this study is located in Kokkola in the western coast of Finland.STUDY POPULATION- Total population (Total no. of persons in cohort from which the subjects were drawn): 142 workers (88 of the 142 workers were still working in the cobalt plant)- Selection criteria: All the workers who had ever worked in cobalt-powder or cobalt-compound production for at least 10 years were invited to participate in the study. Persons who had worked in other metallurgic plants were excluded. Because welding can affect lung function, those who had regularly welded 6 months or more were also excluded - Total number of subjects participating in study: 110 (Of the 142 workers the following workers were excluded from the study: 2 workers had regularly welded 6 months or more; One current and 29 former workers did not wish to participate).- Sex and age: Males; 50.3 +/- 6.0 years of age;- Smoker/nonsmoker: 24.5 % were non-smoker, 41.8 % were ex-smoker and 31.8% were current smoker of the subjects participating in the study.- Total number of subjects at end of study: Thirty-seven of 54 former workers (64%) answered the questionnaire, and 25 participated in the clinical study. Thus, 85 current workers and 25 ex-workers were examined. Most of them were or had been process workers; some were or had been maintenance men and foremen. The ex-workers had left their jobs at the plant 0-15 years ago.- Other: Smoking was greater in the exposed group than in the control group. All the workers in the exposed group had been exposed to cobalt or to cobalt compounds, about 80 % to nickel and nickel compounds, about 50% to sulfur dioxide, hydrogen sulfide, and ammonia. 36 % of the workers in the exposed group had been slightly exposed to asbestos. In the 1960s and 70s, some asbestos string was used as insulation material in the roasting ovens, and the insulation was replaced several times a month.METHOD OF DATA COLLECTION- Type: Questionnaire/Pulmonary function tests/Chest X-ray- Details: A questionnaire was sent to the participants 2 weeks before health examination. Data on work history, earlier lung disease, allergies, medication, smoking habits, and current respiratory and eye symptoms were requested. Questions on work history included current and previous tasks in the cobalt plant and also previous occupations, especially those with exposure to hazardous dusts (metal industry, farming, construction work etc.). Asbestos exposure in all jobs was queried. The reasons for changing work tasks or jobs and workplaces were also requested.All questions concerning lung diseases and health symptoms were based on the Tuohilampi questionnaire that has been constructed (Susitaival, P. and Husman,T. (1996) Tuohilampi kysymyssarjat. Kyselylomakkeisto hengityselinten, ihon ja silmien yliherkkyyssairauksien väestötutkimuksia varten. [Tuohilampi questionnaire series on allergic respiratory, skin and eye disease for population studies]. Kuopio: Tuohilampi.ryhmä.) and validated for epidemiological use by a Finnish expert group (Kilpeläinen, M. Terho, EO, Helenius, H. Koskenvuo, M. (2001) Validation of a new questionnaire on asthma, allergic rhinitis, and conjunctivitis in young adults. Allergy 56: 377 - 384.).Further the following measurements/tests were made:- lung function test- Measurement of diffusing capacity of the lungs for carbon monoxide- Full size posteroanterior chest X ray were taken (only current and former workers from the production departments were examined.)COMPARISON POPULATION- Type: Reference group: The reference group consisted of 76 plant employees (stockroom/store men and 68 white collar workers) who had worked at least 10 years without exposure in cobalt production or to other irritative agents (e.g., welding fumes) and 64 male blue-collar maintenance workers of the city of Kokkola, who had worked at least 10 years, but not in the cobalt factory, and who had not been exposed to harmful dusts or fumes (e.g., from welding).
Exposure assessment:
Details on exposure:
TYPE OF EXPOSURE: InhalationBetween 1966 and 1987, cobalt powder was produced from pyrite ore concentrate. Thereafter cobalt powder, inorganic cobalt and nickel compounds have been produced using byproducts of the metallurgic industry as a raw material (See flow sheet below, Figure 1. "Attached backgroun material). After changes in the process in 1987, workers were not exposed to sulfur dioxide anymore and exposure levels to cobalt decreased slightly.In the sulfatizing roasting, dust in the ambient air has been shown to contain 15 -20 % iron, 1 % zinc, 0.4 % cobalt, and 0.2 % nickel, whereas in theleaching building dust consisted of metal sulfides and sulfates. Cobalt and nickel were present as water-soluble sulfates. In the reduction plant and powder production facility , cobalt is mainly in the form of cobalt powder and fine powder (Roto, P. (1980) Asthma symptoms of chronic bronchitis and ventilatory capacity among cobalt and zinc producing workers. 1980. Scand. J. Work. Environ. Health 6(Suppl 1): 1 -49.). In the chemical department,the cobalt and nickel compounds hav been mainly sulfates, carbonates, oxides, and hydroxides.According to biological monitoring, exposure to cobalt has been highest in the reduction department. The highest urinary conent of cobalt has been about 16,000 nmol/L (level of unexposed persons being < 40 nmol/L). In the solution purification and chemical departments, the urinary cobalt levels have been between 300 and 2,000 nmol/L and the urinary nickel concentration has been as low as 0.06 µmol/L level of unexposed persons being < 0.06 µmol/L).Exposure to most dust and gases in the process has been regularly monitored in every job task several times yearly since 1966. Air samples have been collected by an authorized hygienist bot hfrom stationary points and with personal samplers from the workers' breathing zones. In this study, cumulative exposure was calculated for each worker using a job-exposure matrix based on ambient air measurements.The mg-years were calculated for total dust, cobalt, and nickel, and the ppm-years were used for sulfur dioxide (SO2), hydrogen sulfide (H2S) , and ammonia (NH3). In workplace documents , accurate descriptions can be found of the number of hours the worker were exposeduring their 8- hr workshifts; therefore, this factor could be taken into account in the calculations. the number of men who had been exposed to other agents was small, and therefore this exposure has not been discussed separately.
Statistical methods:
- Frequency tables were constructed which were analyzed with chi-square and Fisher's exact tests-Student's t-- Analyses of variance and covariancetest

Results and discussion

Among the exposed workers (mean cumulative exposure to cobalt 1000 µg-year), there was a significantly increased prevalence of suspected work-related asthma (15 subjects), phlegm, cough with wheezing, shortness of breath with wheezing and breathlessness on exertion than among controls. No chronic respiratory diseases, except asthma, were found among non-smoking cobalt production workers. FEV1 and the respiratory flow rates MEF25 and MEF50 were significantly lower among exposed smokers compared to smoking controls. One new case of occupational asthma (cobalt) with positive reaction in a provocation test and one case of allergic asthma were diagnosed. At concentrations lower than 100 µg Co/m³ cobalt metal or cobalt sulfate exposure increased the risk of asthma by about five times in exposed workers. However, one has to notice constrictively that all cases of cobalt asthma diagnosed referred to workplace exposure conditions where additional irritant gases like sulphur dioxide, hydrogen sulphide or ammonia were present in the ambient air in addition to cobalt.

Applicant's summary and conclusion

No chronic respiratory diseases, except asthma, were found among cobalt production workers in this study.