PII:
Ann. occup. Hyg., Vol. 45, No. 3, pp. 217–225, 2001
Crown Copyright  2001
Published by Elsevier Science Ltd on behalf of British Occupational Hygiene Society
All rights reserved. Printed in Great Britain.
S0003-4878(00)00054-5
0003–4878/01/$20.00
Inhalation Exposure in Secondary Aluminium
Smelting
J. HEALY†*, S. D. BRADLEY‡, C. NORTHAGE† and E. SCOBBIE‡
†Health and Safety Executive, Magdalen House, Stanley Precinct, Bootle L20 3QZ, UK; ‡Health and
Safety Laboratory, Broad Lane, Sheffield S3 7HQ, UK
Inhalation exposure at seven UK secondary aluminium smelters was investigated to quantify
the main exposures and identify their sources. The substances monitored were gases (carbon
monoxide, hydrogen sulphide and nitrogen dioxide), total inhalable dust, metals, ammonia,
polycyclic aromatic hydrocarbons (PAHs), particulate fluoride salts and acids. The results
showed that people were exposed to a range of workplace air pollutants. Personal exposure
results for total inhalable dust were between 700 and 5600 mg mⴚ3 and the maximum personal exposure result for particulate fluoride salts was 690 mg mⴚ3 (as F). The maximum
aluminium, total PAH and lead personal exposure results were 900, 19 and 18 mg mⴚ3
respectively. The average proportion of aluminium in total inhalable dust samples was 13%
and rotary furnace processes generated the most dust. Particulate fluoride salt exposure was
more widespread than hydrofluoric acid exposure. The source of the salt exposure was fluoride containing fluxes. The lead exposure source was lead solder contamination in the furnace
charge. Crown Copyright  2001 Published by Elsevier Science Ltd on behalf of British
Occupational Hygiene Society. All rights reserved
Keywords: aluminium; ammonia; fluoride; lead; PAH; secondary aluminium; inhalable dust
INTRODUCTION
Production of secondary aluminium is increasing in
the UK. Secondary production, predominantly from
old scrap, increased steadily from 200 000 t in 1988,
to 229 700 t in 1995 (Aluminium Federation, 1998).
The increase in wrought remelt production, mainly
from recycled scrap from fabrication, over the same
period rose from 310 300 to 546 500 t (Aluminium
Federation, 1998). Examples of old scrap include old
engines, window frames and road signs. This usually
goes via scrap dealers to the secondary smelter and
is likely to be contaminated. Scrap from fabrication
goes directly to the smelter and is less likely to be
contaminated. A significant incentive for recycling
aluminium is that scrap melting takes only 5% of the
energy required for primary production (Hoyle,
1995).
Langer (1998) recently suggested that workers
employed in secondary smelters may be exposed to
Received 17 April 2000; in final form 10 July 2000.
*Author to whom correspondence should be addressed. Tel.:
+44-151-9514000; fax: +44-151-9513595; e-mail: john.
[email protected]
a ‘complex of new agents’. The source of these
exposures may include the thermal degradation products of polyvinyl chloride (PVC), lubricants or petrol modifiers. These are sometimes present in the aluminium feed stock as the coating of wires in the case
of PVC and residues in car engines for lubricants and
petrol modifiers. Langer (1998) concluded that the
exposures experienced during secondary aluminium
processing only partially resemble exposures associated with primary aluminium production.
There have been few reports of exposure monitoring at secondary aluminium smelters. Inhalable dust,
metal concentrations and heat stress monitoring were
carried out at a US smelter in 1995 (Kiefer and Salisbury, 1995). The work was conducted as a response
to an employee reporting adverse health effects
including tingling in the fingers, nausea and dizziness.
More recently, Westberg and Selden (1999) reported
the preliminary results of some metal determinations
at a Swedish facility.
There have been a number of recent studies
investigating the emissions of various pollutants during the secondary aluminium smelting process. Some
of the studies were laboratory-scale investigations
which quantitatively determined the species present
217
218
J. Healy et al.
in flue gases. Other investigations concentrated on the
emissions from secondary aluminium smelters. The
pollutants identified in these studies were chlorinated
organic compounds (Laue et al., 1994; Aittola et al.,
1993; Westberg and Selden, 1997), organic compounds containing chlorine and sulphur (Sinkkonen et
al., 1994) polycyclic aromatic hydrocarbons (PAHs)
(Aittola et al., 1993; Westberg and Selden, 1997;
Wei, 1996), acids (Westberg and Selden, 1997) carbon monoxide (Westberg and Selden, 1997) and
ammonia (Laue et al., 1994).
It was against this background that we carried out
an exposure survey at seven UK secondary aluminium smelters. The substances monitored were
gases, inhalable dust, metals, ammonia, PAHs, particulate fluoride salts and acids. The aims of the study
were to quantify the main exposures and identify
their sources.
MATERIALS AND METHODS
Processes and chemical exposures
Seven UK secondary aluminium smelters were surveyed between August and November 1999. The
amount of aluminium cast by the smelters was
between 80 and 700 t per week. The quality of the
scrap used varied. Details regarding the smelters are
summarised in Table 1.
Furnaces operated in the range 700–750°C. Generally, induction furnaces were used for the least contaminated scrap while relatively contaminated scrap
and dross were melted in rotary furnaces. Reverberatory furnaces were mainly used for melting pure scrap
and holding furnaces were charged with molten aluminium from other furnaces. Scrap contaminated with
iron or steel was melted in sloping hearth furnaces.
The exceptions in this study were two induction furnaces and one reverberatory furnace which were used
for melting impure scrap.
Either one or two people usually worked at the
same furnace throughout the shift. Based on observations made during the survey, fume and dust
exposures appear to be a number of short-term, relatively high exposures, interspersed with longer periods of lower exposure. The most significant fume
and dust exposures were observed during the following operations:
앫 Charging furnaces. Typically, rotary and sloping
hearth furnaces were charged once or twice per
shift and induction furnaces were charged up to
four times per shift. During melting, contaminated
scrap produces more dust and fume than pure
scrap.
앫 Scraping the walls of induction furnaces prior to
transferring to holding furnaces or casting.
앫 Skimming dross from the surface of molten aluminium prior to transferring or casting. The hot
dross continues to fume for some time. Some
smelters recover aluminium from hot dross by
applying pressure to the dross in a dross press.
앫 Slagging out rotary furnaces after molten aluminium has been transferred or cast.
앫 Elemental sodium addition. The addition of 2.5 kg
of sodium to 10 t of molten aluminium alloy in a
holding furnace was seen at one smelter only. The
operation occurred once per shift, just prior to
casting.
앫 Blowing nitrogen through molten alloys to ensure
a homogeneous melt and bring dross to the surface. This operation was mostly seen at holding
furnaces, prior to casting.
Local exhaust ventilation (LEV) was used at all
furnaces. In most cases a canopy type receptor hood
was situated above the front of the furnace, above
the charging point. Seventy-five percent of induction
furnaces had moveable LEV which was moved during
tipping and wall scraping. General ventilation was
provided in all premises by large open doors. Twentyone percent of furnaces were within a couple of
metres of these doors, which may have helped control
exposure. Respiratory protective equipment (RPE)
use was not widespread. A powered respirator was
used by two people (at different smelters) during
induction furnace wall scraping. Filtering half mask
respirators were used by two people at two smelters
for specific tasks only. The tasks were skimming
dross off a sloping hearth furnace and charging, stirring and skimming dross off a reverberatory furnace.
The maximum time RPE was used was typically less
than half an hour per shift.
Sampling and analytical methods
With the exception of site number 1, which had
approximately 10 people exposed per shift, the sites
had between three and five people exposed (Table 1).
Given the relatively small number of people exposed
at each site it was possible to obtain personal
exposure results for most of the workers. The
majority of personal sampling results in this paper
represent exposures averaged over around 5 h.
Gases
Carbon monoxide, hydrogen sulphide and nitrogen
dioxide were monitored at each smelter with a portable, direct-reading instrument. The instrument,
which sampled workplace air by diffusion, was
obtained from Neotronics (Hertfordshire UK).
Inhalable dust
Quartz membrane filters held in Institute of Occupational Medicine (IOM) samplers were used to sample personal and static total inhalable dust at a flow
rate of 2 min⫺1. Sampling and analysis were carried
out according to Methods for the Determination of
Hazardous Substances (MDHS) 14/2 (HSE, 1997a).
0
2
0
0
0
2
2
3
4
5
6
7
0
2
0
1
0
0
1
Sloping
hearth
0
1
3
0
0
2
2
Induction
0
0
0
1
2
1
0
Reverberatory
No. furnaces
1
2
0
2
0
2
2
Holding
Rotary furnace—oil contaminated swarf
Sloping hearth furnace—scrap with a high (typically
20%) iron content.
Induction furnaces—car wheels, dried swarf and ingots.
Holding furnaces—-molten aluminium from rotary and
induction furnaces.
Induction furnaces and reverberatory furnace—mostly
clean with some surface lacquer.
Holding furnaces—molten aluminium from induction
and reverberatory furnaces.
Rotary furnaces—-mostly aluminium drossa
Reverberatory furnace—cast aluminium sows from
rotary furnaces
Sloping hearth furnace—scrap with a high iron content
Reverberatory furnace—-scrap contaminated with plastic
Holding furnaces—molten aluminium from reverberatory
furnace
Induction furnaces—swarf cans and engine radiators.
Also some foil and ingots.
Sloping hearth furnaces—contaminated scrap including
window frames, sign posts and lamp posts
Induction furnace—charge less contaminated than
sloping hearth furnace charge; mainly engine blocks.
Rotary furnaces—fragmented drossa accounts for 80% of
the charge.
Typical scrap quality
40
20
4
20
4
4
20
40
4
3
100
80
Approximate
amount of
aluminium cast
(tonnes per day)
5
10
Approximate no.
exposed per shift
Dross forms on the surface of molten aluminium and consists of aluminium oxide and entrained aluminium. It also contains smaller amounts of aluminium nitride, aluminium carbide
and magnesium oxide (Stanley and Haupin, 1992).
a
1
Rotary
1
Site code
number
Table 1. Secondary aluminium smelter furnace details
Inhalation exposure in secondary aluminium smelting
219
220
J. Healy et al.
Metals
The metals determined were chromium, manganese, iron, cobalt, nickel, copper, zinc, lead and aluminium. Quartz filters used for sampling inhalable
dust were cut in half after weighing. Metals and nonvolatile PAHs were estimated from the resulting
samples. Each metals sample was digested in a microwave oven at 30 bar and 210°C in hydrofluoric acid
(1 ml) hydrochloric acid (2 ml) and nitric acid (2 ml).
After cooling, the solution was diluted to 20 ml and
analysed using inductively coupled plasma mass
spectrometry. Aluminium was determined using
inductively coupled plasma atomic emission spectrometry.
Acids
Air was drawn through sorbent tubes containing
washed silica gel (SKC Ltd, Dorset UK) at 200 ml
min⫺1. National Institute of Occupational Safety and
Health method 7903 (NIOSH, 1994) was followed for
desorption and analysis by ion chromatography.
Particulate fluoride salts
MDHS 35/2 (HSE, 1998a) was followed for fluoride salt sampling onto mixed cellulose ester membrane filters at a flow rate of 200 ml min⫺1 with subsequent analysis by fluoride ion-selective electrode.
RESULTS
Ammonia
Sorbent tubes containing carbon beads impregnated
with sulphuric acid (SKC Ltd, Dorset UK) were used
for sampling ammonia in air at a flow rate of 200 ml
min⫺1. Desorption and analysis using ion chromatography were carried out according to Occupational
Health and Safety Administration Method ID 188
(OSHA, 1991).
PAHs
PAHs were sampled at a flow rate of 2 min⫺1 onto
quartz membrane filters mounted in IOM samplers
backed up with sorbent tubes containing XAD-2
resin. Non-volatile PAHs were trapped by the filter
and volatile PAHs were trapped on the sorbent tube.
Filters were cut in half and analysed for metals and
non-volatile PAHs. PAHs sampled onto the filters and
sorbent tube were separately extracted into dichloromethane. The solutions were filtered and analysed by
gas chromatography with mass spectrometric
(selected ion monitoring) detection. Full sampling
and analysis details have been reported elsewhere
(Scobbie and Cocker, 1999).
The PAHs determined were:
naphthalene
acenaphthylene
acenaphthene
fluorene
phenanthrene
anthracene
fluoranthene
pyrene
benz(a)anthracene
chrysene
benzo(b)fluoranthene
benzo(k)fluoranthene
benzo(a)pyrene
indeno(1,2,3-c,d)pyrene
dibenz(a,h)anthracene
benzo(g,h,i)perylene
anthanthrene
Exposures
Personal exposure data obtained from seven UK
secondary aluminium smelters are summarised in
Table 2. Mean results for data sets containing results
that were less than the limit of detection (LOD) in
this and other Tables were calculated by replacing
these results with LOD/√2 (Hornung and Reed,
1990).
The ranges of area exposure results for carbon
monoxide were less than 1–43 ppm at smelter 4, less
than 1–30 ppm at smelter 5 and less than 1 ppm at
other smelters. The carbon monoxide concentration
was highest in the casting area of smelter 4. This was
adjacent to an 11 tonne holding furnace. The exposure
reached its peak and then decreased over about 4 h.
The peak result obtained at smelter 5 lasted for
around 2 min during scraping the walls of an induction furnace. Hydrogen sulphide and nitrogen dioxide
exposure results were less than their limits of detection at all smelters. The limits of detection were 0.5
ppm for hydrogen sulphide and 1 ppm for nitrogen
dioxide.
The mean inhalable dust exposure result was 4200
µg m⫺3. However, this result appears to be skewed
by a single high value of 36 000 µg m⫺3, because the
next highest result was 5600 µg m⫺3. In addition, the
high exposure result was recorded for one member of
a team of two and the other member had an exposure
result of 2300 µg m⫺3. Excluding this outlier, the
mean personal exposure result is 2600 µg m⫺3.
A scatter plot of the personal inhalable dust results
(excluding the single outlier), illustrating their distribution at each smelter, is shown in Fig. 1.
The personal inhalable dust results grouped by
furnace/process are presented in Table 3.
The number of samples in each category in Table
3 is small and so any conclusions are tentative. However, the results suggest that exposure to inhalable
dust may be lowest during casting and highest during
operations associated with rotary furnaces. Visual
observations made during the visits support this conclusion. The aluminium results follow a similar trend.
For casting and rotary furnace operations the mean
Inhalation exposure in secondary aluminium smelting
221
Table 2. Summary of personal sampling results
Pollutant
Inhalable dust
Aluminium
Ammonia
Total PAHs
Particulate fluoride salts (as
F)
Hydrofluoric acid (as F)
Hydrochloric acid
Sulphuric acid
Iron
Zinc
Lead
Chromium
Copper
Nickel
Manganese
Cobalt
No.of samples
Mean sampling time
(min)
Range of results
(µg m⫺3)
Mean result (µg m⫺3)
21
21
2
21
12
280
280
310
280
310
700–36 000
40–900
80 and 260
1–19
⬍30–690
4,200
310
170
4
225
12
12
21
21
21
21
21
21
21
21
21
310
310
310
280
280
280
280
280
280
280
280
⬍10-290a
⬍10–50a
All results ⬍50
⬍0.1–300
0.3–56
0.1–18
⬍0.6–14
0.1–9
⬍0.6–6
0.3–3
⬍0.1–0.2
31
11
⬍50
68
10
3
1
3
1
2
0.1
a
Only one result was above the limit of detection.
ters. Slightly more surprising are lead exposures. Personal aluminium and lead exposure results at the various smelters are illustrated in Fig. 2 and 3
respectively.
The mean of the personal and static results from
smelter 6 was 12 µg m⫺3. This is higher than the
Fig. 1. Scatter plot of personal inhalable dust results.
personal aluminium results were 60 and 490 µg m⫺3
respectively. The mean personal aluminium results
for the operations sampled at sloping hearth, induction and reverberatory/holding furnaces were in the
range 130–290 µg m⫺3. As might be expected, aluminium is the most abundant pollutant metal in the
workplace atmosphere of secondary aluminium smel-
Fig. 2. Scatter plot of personal aluminium results.
Table 3. Personal inhalable dust exposure by furnace/process
Furnace/process
No. of samples
Range of results (µg m⫺3)
Mean result (µg m⫺3)
7
4
5
3
2
2700–5600
1100–3100
1300–4100
2300–2400a
700 and 900
3700
2100
2200
2400a
800
Rotary
Sloping hearth
Induction
Reverberatory/holding
Casting
Excluding outlying result of 36 000 µg m⫺3.
a
222
J. Healy et al.
Fig. 3. Scatter plot of personal lead results.
Fig. 4. Scatter plot of personal total PAH results.
range of the same means from the other smelters,
which was between 0.1 and 6 µg m⫺3.
Only two personal ammonia samples were taken
and the results are shown in Table 2. The result of
80 µg m⫺3 was for a person who spent around 30%
of the shift pressing and moving dross. Other activities were charging relatively pure scrap into a reverberatory furnace (30% of shift) and breaks (30% of
shift). The result of 260 µg m⫺3 was for a person
who divided his time approximately equally between
induction furnace operations (charging, wall scraping
etc) and ingot stacking. A dross press was situated
about 10 m from the furnace. Static samples were also
taken at each of the smelters. The range of results
from 23 samples was less than 10–1300 µg m⫺3.
Eighty seven per cent of the results were greater than
the limit of detection. From a total of 25 personal
and static ammonia results, the results from smelter
3 exceeded all other results. There were three results
(all static samples) and their range was from 260 to
1300 µg m⫺3.
The proportion of volatile PAHs nearly always
exceeded the proportion of non-volatile PAHs in both
personal and static samples. The main PAH in all
samples was naphthalene. The personal exposure
results obtained are shown in Fig. 4.
There is one noticeably high personal total PAH
result of 19 µg m⫺3. This person worked at a (tilting)
induction furnace. During the sampling period there
were 2×10 min pouring periods, 15 min blowing with
a nitrogen/argon mixture and the rest of the time was
spent preparing and charging 3.4 t of scrap and casting. There was nothing unusual in this shift pattern
and so we are unable to account for this high result.
The next highest personal exposure result was 8 µg
m⫺3. The remaining total PAH results, either personal
or static samples, did not exhibit any discernible trend
when grouped by smelter or furnace. The range of
personal exposure results for naphthalene were from
1 to 10 µg m⫺3, with a mean of 2 µg m⫺3.
Benzo(a)pyrene personal exposure results were
between 0.01 and 0.4 µg m⫺3, with a mean of 0.1
µg m⫺3.
Twelve personal acid exposure samples were taken
and hydrofluoric, hydrochloric and sulphuric acid
concentrations were determined from each sample.
All of the sulphuric acid results and 11 out of 12
hydrofluoric and hydrochloric acid results were less
than the limit of detection. All static hydrofluoric acid
samples results (N=23) were less than the limit of
detection. Only 4 out of 23 static hydrochloric acid
samples were above the limit of detection. The range
of these results was between 40 and 1400 µg m⫺3.
Twenty three static sulphuric acid samples were
taken. Five were greater than the limit of detection
and these results were between 60 and 180 µg m⫺3.
The results of personal fluoride salt determinations
are illustrated in Fig. 5.
Personal samples were not taken at smelters 3 and
7. The results for three static samples at smelter 3
were all less than the limit of detection. The range of
Fig. 5. Scatter plot of personal particulate fluoride salt results.
Inhalation exposure in secondary aluminium smelting
results from four static samples at smelter 7 were
from less than the limit of detection to 90 µg m⫺3.
DISCUSSION
Kiefer and Salisbury (1995) used a direct reading
instrument to measure carbon monoxide levels. They
found concentrations in a US smelter were less than
4 ppm, with the exception of one measurement of 14
ppm at an ingot stacking station. This exposure was
attributed to propane-powered rider operated lift
trucks. We believe that the peak carbon monoxide
results of 30 and 43 ppm at two smelters in this survey were probably due to incomplete combustion of
contaminants in the furnace charge and inadequate
ventilation.
The average proportion of aluminium present in
personal and static inhalable dust samples was 13%.
From a total of 33 results, this proportion varied
between 5 and 27%, with a standard deviation of 5%.
If it is assumed that aluminium is present as the oxide,
the average proportion of Al2O3, in the dust sampled
was 25%. The composition of the remaining 75% of
the dust is uncertain, although the metals analysis
(Table 2) suggests that other metal oxides alone cannot account for the shortfall.
The source of lead in the samples is probably lead
solder contamination in the furnace charge. The
material used for copper additions at smelter 6, where
the mean of personal and static lead results was 12
µg m⫺3, was short lengths of copper pipe with lead
soldered joints. The amount of lead contamination in
the furnace charge is probably relatively small. However, the melting point of lead is around half the melting point of aluminium and is significantly less than
the melting points of other metals determined in this
survey. Secondary aluminium smelting therefore
takes place at temperatures at which lead will become
volatile and hence the high exposure relative to the
degree of contamination.
The relatively high ammonia results at smelter 3
were attributed to a large dross storage area which
was around 50 m from the samplers. The odour of
ammonia was very strong in this storage area. The
origin of ammonia is most commonly from dross
stored outside the foundry buildings. Dross contains
aluminium nitride which liberates ammonia on contact with water. The typical range of aluminium
nitride concentration in waste drosses for recovery is
5–14% (Hymes, 2000).
The source of PAHs in this study was considered
to be the thermal degradation of organic contaminants
in the furnace charge. PAH exposure is a concern
because some PAHs are known carcinogens (HSE,
1997b). As far as we are aware, this is the first time
occupational PAH exposure results have been
reported in secondary aluminium smelters. Primary
aluminium smelters are known to produce PAHs from
preparation or consumption of carbon anodes, but this
223
process is not found in secondary smelters. As a point
for comparison, HSE recently carried out a survey of
PAH exposure in various UK industries (Scobbie and
Cocker, 1999). Median total PAH concentrations at
25 sites ranged from 2 to 880 µg m⫺3. The median
total personal PAH concentration in this study was
3 µg m⫺3, which would place secondary aluminium
smelting at the lower end of those sampled.
Twelve personal hydrofluoric acid samples were
taken. Eleven of these were less than the limit of
detection and 1 result was 290 µg m⫺3. The only
possible source of hydrofluoric acid for the single
result greater than the detection limit was from the
use of a flux containing sodium fluorosilicate, sodium
carbonate and aluminium fluoride. However, during
the monitoring period only around 500 g of the flux
was added to an induction furnace under LEV. Other
fluxes encountered during the survey were potassium
aluminium fluoride, sodium fluorosilicate, calcium
fluoride, potassium chloride, sodium chloride and potassium carbonate.
The hydrochloric and sulphuric acid personal
exposure results indicate a low level of exposure to
these acids. The highest static hydrochloric acid result
(1400 µg m⫺3) was for a rotary furnace melting dross.
Two melts of around 1.5 t were carried out during
the sampling period. Three hundred kg of flux was
used per melt. The flux was a mixture of sodium
chloride (69%), potassium chloride (29%) and calcium fluoride (2%). It was added to the furnace by
shovel over a few minutes per melt.
Ten out of 12 personal fluoride salt results were
greater than the limit of detection, which suggests that
exposure to fluoride salts is more likely than hydrofluoric acid exposure. The source of the exposures is
fluoride containing fluxes. The highest exposure
result of 690 µg m⫺3 was a result of manually tipping
around 200 kg of potassium aluminium fluoride into
the launder between an induction and a holding furnace while transferring molten aluminium alloy. The
purpose of the addition was to reduce the magnesium
concentration of the alloy. This operation lasted for
a few minutes and was conducted without LEV. RPE
was not used.
A comparison between some metal exposure
results obtained in this study with results obtained in
Swedish (Westberg and Selden, 1999) and US (Kiefer
and Salisbury, 1995) smelters is shown in Table 4.
Comparison of this study’s results with the Swedish and US studies shows that aluminium results
appear higher in the smelters sampled in this study.
Lead results are higher than in the US study and in
the same range as the Swedish work. Manganese
exposures are approximately equivalent. However,
given the limited database of results it is not possible
to draw any firmer conclusions.
A number of the workplace air pollutants found
during this survey have occupational exposure limits
(OELs). A comparison between the highest exposure
224
J. Healy et al.
Table 4. Comparison of selected metal at different smelters
Aluminium
This study
Swedish studya
US study
Lead
Manganese
N
Range
(µg m⫺3)
Mean
(µg m⫺3)
N
Range
(µg m⫺3)
Mean
(µg m⫺3)
N
Range
(µg m⫺3)
Mean
(µg m⫺3)
21
73
8
40–860
2–540
18–371
310
ns
77
21
54
8
0.1–18
1–18
All⬍2
3
ns
⬍2
21
54
8
0.3–3
1–240
⬍0.03–5
2
2b
0.8
a
Mainly personal exposures.
Geometric mean; ns=not stated.
b
Table 5. Highest personal sampling results compared with occupational exposure limits for Great Britain (HSE, 2000)
Pollutant
Inhalable dust
Particulate fluoride salts (as F)
Hydrofluoric acid (as F)
Lead
Aluminium
Chromium
Ammonia
Nickel
8-h time weighted average occupational
exposure limit (µg m⫺3)
Highest result as a percentage of
limit value
10 000a
2500c
2500c d
150f
10 000c
500c
18 000c
500g
56b
28
12e
12
9
3
1
1
If above a concentration of 10 000 µg m⫺3, inhalable dust becomes a substance hazardous to health for the purpose of
the COSHH Regulation (HSE, 1999).
b
Excluding the result of 36 000 µg m⫺3, which is regarded as an outlier.
c
Occupational exposure standard.
d
Short-term exposure limit (15-min reference period).
e
Most results (92%) were less than the limit of detection.
f
Occupational exposure limit for the purposes of the Control of Lead at Work Regulations (HSE, 1998b).
g
Maximum exposure limit.
a
results and their OELs, as defined in Great Britain
(HSE, 2000) is presented in Table 5. With the exception of hydrofluoric acid, the comparison assumes that
the exposure results obtained in this survey (average
sampling time around 5 h) are equivalent to 8-h time
weighted average exposures. Exposure results which
are less than 1% of their OEL are excluded.
The comparison between measured exposure
results and the current statutory controls for Great
Britain shows that:
앫 Exposure up to around 10% of the OEL is possible
for lead and aluminium.
앫 Particulate fluoride salt exposure can reach nearly
30% of the OEL and
앫 Exposure to inhalable dust is nearly 60% of the
level defined in the COSHH Regulations as a
substance hazardous to health (HSE, 1999).
This paper outlines the results of air sampling at
seven secondary aluminium smelters, an area which
was not well characterised. Although none of the substances measured approached the OELs set in Great
Britain, this study indicates that the main exposures
are dust, fluoride salts, lead and aluminium. However,
we cannot exclude the possibility of other exposures.
Possible examples include cadmium (from cadmium
plated fasteners on engine blocks and heads) and
polychlorinated organic compounds (Aittola et al.,
1993). The finding of PAHs on sampling in this
industry should also be noted.
The main interactions (if any) between components
of a mixed exposure are either synergistic, additive
or independent effects (HSE, 2000). A review of the
toxicological data for each of the substances identified in this survey is required to assess if there are
any interactions. Such a review is beyond the scope
of this work.
Acknowledgements—We wish to thank the smelters for their
co-operation with this survey, Nick Williams (HSE) for preparing the figures for the manuscript and colleagues who commented on the work.
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