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epidemiological data
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP, non-guideline study, acceptable for assessment

Data source

Reference Type:

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:
Epidemiological health study of workers in an aluminium smelter
GLP compliance:

Test material

Constituent 1
Details on test material:
not applicable


Type of population:
Ethical approval:
confirmed, but no further information available
Details on study design:
In an aluminium smelter in Canada 2066 employees were studied. The subjects were divided into groups by fluoride exposure: 570 persons who spent at least 50% of their working time in the pot room were labelled “high-exposure” and 332 who spent less than 50% of working time in the pot room were labelled “medium exposure”. A group of 284 workers (e.g. welders) was labelled “mixed-exposure”. There was also an unexposed internal control group consisting of 880 office workers and an external control group of 372 railroad workers. Observations included data from haematology (haemoglobin, haematocrit, white cell count) and clinical biochemistry (total bilirubin, alkaline phosphatase, sASAT, total protein, BUN, creatinine, Ca2+ and phosphate). Airborne fluorides were measured with personal monitors. Hips were x-rayed in a subgroup of 136 workers in the high-exposure group, 41 in the medium-exposure group who had been employed in the pot room for more than 10 years, and 33 unexposed workers (internal controls).
Exposure assessment:
Details on exposure:
For each group exposure to particulate and gaseous fluoride and urinary fluoride excretion were determined. The levels of exposure (average total airborne fluoride/ gaseous fluoride/particulate fluoride in mg/m3) in each group were: control: 0.053/0.015/0.038; potroom (high): 0.48/0.20/0.28; potroom (medium): 0.12/0.057/0.062; miscellaneous: 0.46/0.054/0.41. Fluoride concentrations measured in urine of the control group (total airborne fluorides 0.053 mg/m3) were 1.2 mg/l before a shift work and 1.3 mg/l after a shift work (mean values); 1.9 mg/l (before) and 2.7 mg/l (after) in the high-exposure group (total airborne fluorides 0.48 mg/m3); 1.4 mg/l (before) and 1.8 mg/l (after) in the medium-exposure group (total airborne fluorides 0.12 mg/m3); and 1.5 mg/l (before) and 1.8 mg/l (after) in the mixed exposure group (total airborne fluorides 0.46 mg/m3). Levels of fluoride in urine were correlated to exposures.

Results and discussion

The x-ray photographs showed slight indications of increased skeletal density in a few of those who had been exposed for more than 10 years.
However, there was some disagreement among the radiologists as to how the x-ray photographs should be interpreted. The authors concluded that there were no definite cases of skeletal fluorosis among the pot room workers who were exposed to about 0.48 mg fluoride/m3 (0.2 mg/m3 for gaseous F- and 0.28 mg/m3 for fluoride dust) for at least 50% of their time at work (about 10 years) at an aluminium smelter. There were no differences between the groups with regard to occurrence of back and joint problems. Blood tests showed no indications of renal, hepatic or haematopoietic effects. Therefore, it is concluded that no overt signs of skeletal fluorosis or renal, hepatic or haematopoietic effects were observed in workers exposed to 0.48 mg (total) fluoride/m3 for up to ten years.
Confounding factors:
not reported, considered as key study under Regulation 793/93
Strengths and weaknesses:
not reported, considered as key study under Regulation 793/93

Applicant's summary and conclusion