Vanadium pentoxide

Breaking, loading and unloading, crushing and grinding, and magnetic separation of

vanadium slag (about 120 g/kg vanadium pentoxide) causes formation of thick dust, with

vanadium concentrations of 30–120 mg/m

3

. About 70–72 % of the particles were reported

to have a diameter of < 2 µm and 86–96% a diameter of < 5 µm. When the slag is roasted,

free vanadium pentoxide is discharged and concentrations of vanadium in the vicinity of

the furnace have been found to range from 0.04 to 1.56 mg/m

3

. During leaching and preci-

pitation, vanadium concentrations in the air can exceed 0.5 mg/m

3

. Smelting and granu-

lation of technical-grade vanadium pentoxide are accompanied by the formation of a vana-

dium-containing aerosol. During the loading of smelting furnaces, vanadium pentoxide

concentrations in the surrounding air have been found to range from 0.15 to 0.80 mg/m

3

;

during smelting and granulation, from 0.7 to 11.7 mg/m

3

; during the crushing, unloading

and packaging of pure vanadium pentoxide, dusts are formed in the facilities and concen-

trations of 2.2–49 mg/m

3

vanadium pentoxide in air have been recorded (Roshchin, 1968;

cited by WHO, 1988).

In the production of ferrovanadium alloys, a continuous discharge of vanadium pen-

toxide occurs during the smelting process. Vanadium pentoxide concentrations in air were

reported to be 0.1–2.6 mg/m

3

in the work area of smelters and helpers, 2–124.6 mg/m

3

during charging of vanadium pentoxide in furnace, 0.07–9.43 mg/m

3

in the crane driver’s

cabin during smelting, 0.97–12.6 mg/m

3

during cutting up of ferrovanadium and 7.5–

30 mg/m

3

during furnace maintenance (Roshchin, 1968; cited by WHO, 1988).

When ductile vanadium is produced by the aluminothermic process (based on the

reduction of pure vanadium pentoxide with aluminium), a condensation aerosol of vana-

dium pentoxide is released, with 98% of the particles having a diameter of < 5 

µm and

82% a diameter of < 2

µm. Vanadium pentoxide concentrations recorded in the surroun-

ding air were 19–25.1 mg/m

3

during the preparation of the charge mixture, 64–240 mg/m

3

during placing of the burden inside the smelting chambers and 0.2–0.6 mg/m

3

in smelting

operator’s workplace (Roshchin, 1968; cited by WHO, 1988).

Usutani et al. (1979) measured vanadium pentoxide concentrations in air in a vana-

dium refinery. The highest concentrations (> 1 mg/m

3

) were detected in samples collected

during removal of vanadium pentoxide flakes from the slag (cited by WHO, 1988).

In facilities producing aluminium from bauxite, concentrations of vanadium pen-

toxide up to 2.3 mg/m

3

have been recorded in workplace air during tapping, packing and

loading (Roshchin, 1968; cited by WHO, 1988).

Workers may be exposed to vanadium pentoxide in air during the handling of catalysts

in chemical manufacturing plants. Exposure depends on the type of operations being carried

out. During the removal and replacement of the catalyst, exposure to 0.01–0.67 mg/m

3

have

been reported. Sieving of the catalyst can lead to higher exposures, and concentrations

between 0.01 and 1.9 mg/m

3

(total inhalable vanadium) have been observed. Air-fed respi-

ratory protective equipment is normally worn during catalyst removal and replacement and

sieving (WHO, 2001).

Concentrations of vanadium pentoxide in the air during vanadium catalyst production

have been reported as 1–7 mg/m

3

during grinding and unloading of vanadium pentoxide,

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3.2–7.5 mg/m

3

during loading into the bin and 0.1–1 mg/m

3

during sifting and packing

granules of contact substance (Roshchin, 1968; cited by WHO, 1988).

Hery  et al. (1992) assessed exposures to chemical pollutants during the handling

(loading and unloading of reactors, sieving of catalysts) of inorganic catalysts, including

vanadium pentoxide. Concentrations of vanadium pentoxide in air were reported to be

0.08–0.9 mg/m

3

during unloading, 1.1–230 mg/m

3

during screening and 600–1200 mg/m

3

during loading.

Hery  et al. (1994) assessed exposures during the manufacture and reprocessing of

inorganic catalysts, including vanadium pentoxide. In one of four 1-h air samples taken

in a reprocessing plant during the oven-cleaning operation, a vanadium pentoxide concen-

tration of 2.2 mg/m

3

was measured. 

Fuel oil combustion results in the formation of vanadium-containing dust, and large

amounts of dust result from operations connected with removal of ash encrustations when

cleaning boilers and the blades of gas turbines. Dust concentrations in the air inside the

boilers have been reported to range from 20 to 400 mg/m

3

, the most common range being

50–100 mg/m

3

, with the dust containing 5–17% vanadium pentoxide (Roshchin, 1968;

cited by WHO, 1988).

Occupational exposure to vanadium occurs during the cleaning of oil-fired boilers and

furnaces in oil-fired heating and power plants and ships, although workers probably spend

less than 20% of their time cleaning oil-fired boilers. Vanadium concentrations in air (total

inhalable fraction) as high as 20 mg/m

3

were recorded when these tasks were performed,

but typically were lower than 0.1 mg/m

3

. The lowest results were obtained where wet

cleaning methods were used. Respiratory protective equipment was usually worn during

boiler cleaning operations (WHO, 2001).

Williams (1952) published air sampling data on boiler-cleaning operations in the

British power industry. A vanadium concentration of 40.2 mg/m

3

was recorded in air in

the superheater chamber, while the concentration was 58.6 mg/m

3

in the combustion

chamber; 93.6% of the dust particles had a diameter of 0.15–1 

µm (cited by WHO, 1988). 

Kuzelova et al. (1977) reported dust concentrations during boiler-cleaning operations

of about 136–36 000 mg/m

3

in the workplace air, in which vanadium concentrations

ranged from 1.7 to 18.4 mg/m

3

(cited by WHO, 1988).

Barisione et al. (1993) assessed the acute exposure to vanadium pentoxide in mainte-

nance personnel working inside an oil-fired boiler at an electric power station in Italy. The

vanadium pentoxide concentration in the air in the work room was 0.28 mg/m

3

, which

exceeded exposure standards. The concentration of vanadium in the urine of the arc

welders did not correlate with vanadium pentoxide concentration in the air (see Table 2).

In 26 boilermakers overhauling an oil-powered boiler in the USA, Hauser et al. (1995a)

investigated exposure to air particulates with an aerodynamic diameter of 

≤ 10 µm (PM

10

)

and respirable vanadium-containing dust for up to 15 work days. The peak PM

10

concen-

tration (1- to 10-h TWA) ranged from 1.48 to 7.30 mg/m

3

; the peak vanadium concentration

ranged from 2.2 to 32.2 

µg/m

3

, with a mean (SD) of 20.2 (11.4)

µg/m

3

. In a later study, the

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