Aim. oeap. Hjf., Vol. 40, No. 4, pp. 423-435, 1996
Bntirii f^ • iii»*twi«l HTDCOC Society
Crown copyright G 1996 Pobtttwci by Hawicr ft***** Ltd
AM righu rocrved. Printed in Great Britain
0001-4878/96 115.00 + 0 OO
0003-4878(95)00091-7
CHEMICAL POLLUTANTS IN^-RAY FILM PROCESSING
DEPARTMENTS
Emma Scobbie, David W. Dabill and John A. Groves
[jjealth and Safety Laboratory] Health and Safety Executive, Broad Lane,Sheffield)S3 7HQSU.KT|
{Received in final form 24 August 1995)
{A survey of X-rayfilmprocessing departments revealed the main airborne contaminants
to be sulphur dioxide and acetic acid at concentrations of about 0.1 ppm. Glutaraldehyde was not
detected either in the ambient air or in the exhaust duct from an automatic film processor.
Laboratory studies confirmed sulphur dioxide and acetic acid as the main headspace constituents
above working strength processing solutions but glutaraldehyde and butyraldehyde were also
detected. (Crown copyright © 1996 Published by Hsevier Science Ltd.
INTRODUCTION
Radiographers and darkroom technicians engaged in processing X-ray films have
reported a variety of symptoms, including sinus pains, sore eyes, blurred vision,
aching and ringing ears, chest and ear infections, weight loss, tiredness, dry skin,
inflamed nostrils, bad teste in the mouth and nausea. Surveys carried out in New
Zealand (Spicer et aJ., 1986) and Britain (Society of Radiographers, 1991) suggest
that the problem may be widespread.
Although the cause of the problem is not known, suspicion has inevitably fallen
on the chemicals used in processing the films. The chemical formulations vary
between manufacturers but the substances most commonly used include: glutaraldehyde (or a glutaraldehyde bisulphite complex), hydroquinone, a glycol
(diethylene, propylene or ethylene), acetic acid, sodium sulphite, potassium
hydroxide, phenidone in the developer and ammonium thiosulphate, acetic acid,
aluminium sulphate, sodium sulphite (or bisulphite), sulphuric acid and a glycol
ether in the fixer. The potential for such mixtures of chemicals to emit harmful
vapours has been discussed (Collier, 1986; Gordon, 1987; HSE, 1992) and strategies
to reduce the risk of exposure have been suggested (Hewitt, 1993, 1994).
The processing chemicals are supplied as concentrates which are diluted and
mixed before use. Whereas it was once common practice for dilution to be done by
hand, it is now generally done in automatic mixers which then provide a direct
supply to the X-ray film processor. The processing itself is now also automated so
that films are fed into the processor and pass through various stages including
immersion in developer, removal of surplus reagent, immersion in fixer, washing in
clean water and finally warm air drying. The processed image emerges with
minimum intervention by staff and no direct exposure to chemicals. Some processors
are provided with extraction to a waste duct to remove the chemical vapours which
could be evolved at the operating temperatures of the processors, typically 28-35°C.
423
424
E. Scobbie et al.
Although advances in processing technology have minimized exposure, there is
continuing concern about the incidence of 'darkroom disease' which is reinforced by
the lack of knowledge of what actually causes it. The purpose of this work was to
investigate the composition of the chemical vapours present in X-ray processing
areas. It was intended that this might give some insight into which species might be
responsible for the symptoms observed and also form the basis for guidelines on
exposure levels on processing areas.
The study consisted of surveys of X-ray film processing units and a laboratory
investigation of the substances evolved from the processing chemicals.
EXPERIMENTAL DETAILS
Chemicals monitored and methods of analysis
The composition of the processing formulations provided by the manufacturers
gave information on the chemicals that might be encountered in X-ray film
processing areas. Some of these arc of low vapour pressure, however, and would not
be likely to become airborne under the conditions of use in a film processor and so
were excluded from this investigation. Additional substances which are not
constituents of the formulations but which can be formed during the process were
also included. These were sulphur dioxide, formed by the decomposition of the
thiosulphate or bisulphite, hydrogen sulphide which may be released if the pH of the
process falls below pH 7, and ammonia which can be released if the pH rises above 7.
In addition to these specific chemicals, air samples were collected on Tenax for
analysis by GC-MS to identify other airborne materials which may have been
present; the chemicals included in the study and the analytical methods used to
quantify them are shown in Table 1.
In addition to the techniques in Table 1, on-site measurements for sulphur
dioxide and acetic acid were made using Gastec colorimetric gas detector tubes
(Detectawl, Milton Keynes, U.K.). Low humidity has been suggested as a possible
cause of some of the symptoms observed and so relative humidity and temperature
were monitored at each site. The temperature and humidity probes were connected
to a Squirrel data logger which stored the data at 5-min intervals for periods up to
3 weeks.
Surveys
Sampling visits were carried out to answer three specific questions.
(1) What are the airborne concentrations of the selected chemicals in typical
locations?
The concentrations of the selected chemicals in typical X-ray film processing
departments were established by sampling at six units in four hospitals. These units
operated both darkroom and daylight processing using several brands of chemicals;
the processing units are described briefly in Table 2. The air samples were collected
during the normal working day for periods up to 6 h. The samplers were generally
positioned as close to the film processors as possible. No personal samples were
collected.
Chemical pollutants in X-ray film processing
425
Table 1. Sampling and analytical methods
Sample
volume
Sampling medium
Substance
Aldehydes
Glutaraldehyde
Formaldehyde
Acetaldehyde
Acetic acid
Glycol ethers
Methoxyethanol
Ethoxyethanol
Butoxyethanol
Glycols
Propylene glycol
Diethylene glycol
Sulphur dioxide
Ammonia
General
DNPH-coated niters
0.01 M sodium hydroxide
Charcoal/solvent desorption
Glass-fibre filters/iilica
gel tubes
0.3 N Hydrogen peroxide
Sulphuric acid impregnated
carbon beads
Tenax tubes
0)
Analysis*
40-60
HPLC-UV
200-300
20-30
IC
GC-FID
OSHA (1980)
HSE (1983)
50-60
GC-FID
NIOSH (1984)
200-300
20-30
IC
IC
OSHA (1981)
OSHA (1991)
30-100
TD-GC-MS
Reference
Cuthbert and
Groves (1995)
—
*HPLC-UV, high-performance liquid chromatography, ultraviolet detector; IC, ion chromatography;
GC-FTD, gas chromatography, flame ionization detector; TD-GC-MS, thermal desorption, gas
chromatography, mass spectrometry.
Table 2. Description of X-ray processing areas
Area
Processor type
Mixer type
Chemicals
Fixer
Developer
1
2
3M Laser Imager
Fuji FPM
3MXPM
Fuji FPM 190
3MXAD3
Photosol XD 2
3MXAF3
Photosol XF 2
3
2 x Dupont
processors
2 x Dupont
processors
3M Laser Imager
2xKodakRP
X-OMAT
Dupont
Dupont Cronex
MD
Dupont Cronex
Rapitech 205
4
5
6
Dupont
3MXPM
Kodak
3MXAD3
Kodak RP
X-OMAT
Rapitech 205
MD
3MXAF3
Kodak RP
X-OMAT
Ventilation
Room ventilation
Processor
extraction
Processor
extraction
Processor
extraction
Room ventilation
Processor
extraction
(2) What are the airborne concentrations of the selected chemicals in locations where
problems have been reported?
It had been intended that samples were taken at locations where there had been
reports of darkroom disease, so that comparisons with typical locations where there
was no problem could be made. However, enquiries failed to reveal any problem
areas and, as a compromise, one processing unit was included in the study which had
a past history of complaints associated with film processing although there were no
recent reports of problems. At this location, the chemicals were stored under the
processor in tanks which were not airtight (all other locations used automatic mixers
with direct feed to the processor) so there was the potential for leakage of vapours
into the work area in addition to any vapours emitted by the process. In an attempt
to recreate the conditions which might have prevailed in earlier times, the room
426
E. Scobbie et al.
ventilation was switched off during sampling. Air samples were also collected from
the headspace within the tanks to estimate the contribution of the unsealed tanks to
the airborne concentrations.
(3) What is the concentration of airborne species in the processor extraction ducts?
Many of the units visited were provided with direct extract from the processing
machines or else had general room ventilation so it was to be expected that airborne
contaminants might be present at quite low concentrations, possibly below the
environmental detection limits. In one case, therefore, samples were collected directly
from the exhaust duct of a processor to provide more concentrated samples to aid in
the identification of trace components and also to provide an estimate of the
conditions that might persist in the absence of the extraction duct.
Laboratory investigations
The laboratory study had controlled conditions in which more concentrated air
samples could be collected from above the processing chemicals to allow positive
identification of mixture components.
Headspace vapours above the liquids were collected by placing 200 ml of the
working strength processing formulation in a 500 ml bottle and allowing it to come
to equilibrium at room temperature. A Tenax tube was suspended in the neck of the
container and samples were collected either by pumping at 50 ml min~' for about 20
min, or by leaving the tube for a period of hours to sample diffusively. Background
air samples were collected in parallel so that constituents in the laboratory air could
be identified and eliminated. Samples were collected using the following developer
and fixer solutions:
(a) freshly prepared working strength solutions diluted in the laboratory and
used immediately;
(b) working strength solutions prepared in the laboratory and left open to the air
to age for 13 days prior to taking the samples (the working solutions should
not be used after 14 days); and
(c) samples of processing solutions collected during sampling visits. These
working solutions were taken from the tanks feeding the processor and were
of unknown age. In some cases only small volumes of sample were available
so the collection of headspace vapours was approximately scaled down.
The Tenax tubes were analysed by thermal desorption into a GC-MS, using a BP-1
column temperature programmed at 50°C for 5 min, then rising at 5°C min" 1 to
200°C and held for 15 min.
RESULTS
Surveys of typical areas
The results of monitoring at eight typical locations are shown in Table 3. Surveys
1-4 were preliminary reconnaissance visits intended to assess the locations for later
more detailed surveys which would include quantitative measurements. Temperature
and humidity were recorded during the preliminary surveys (for periods of 3 weeks at
sites 3 and 4) together with limited measurements of airborne contaminants. On the
strength of these preliminary visits, appropriate locations for the more comprehen-
Table 3. Survey results at typical X-ray processing locations
Survey number
1
2
3*
4°
5
6
7
8
—
—
—
—
—
—
—
—
—
—
—
—
—
—
<0.001
<0.002
< 0.004
0.2
0.06
<0.06
<0.05
<0.04
<0.04
<0.02
0.2
0.08
<0.6
See text
< 0.002
< 0.003
0.01
0.2
0.06
<0.08
<0.06
<0.05
<0.05
<0.03
0.1
0.10
<0.7
See text
<0.001
< 0.002
~0.005f
—
0.03
<0.06
<0.05
<0.04
<0.04
<0.02
—
0.02
<0.5
See text
<0.001
< 0.002
~0.005f
-0.05J
24-25
40-45
Slight
19.5-20
48-51
Slight
20
30
Slight
24-25
40-45
Slight
24-26
27-30
Slight
Glutaraldehyde
Acetaldehyde
Formaldehyde
Acetk acid (GT)
Acetic acid ( I Q
Methoxyethanol
Ethoxyethanol
Butoxyethanol
Diethylene glycol
Propylene glycol
Sulphur dioxide (GT)
Sulphur dioxide (IC)
Ammonia
Tenax
<0.004
<0.007
<0.014
0.25
—
—
—
—
—
—
<0.01
—
—
ND
< 0.001
< 0.002
<0.004
0.25
—
—
—
—
—
—
0.1
—
—
ND
—
—
—
<0.05
<0.01
—
—
—
—
—
<0.01
—
—
—
Temperature (°C)
Relative humidity (%)
SmeU
21
32-33
Slight
22
29-30
Slight
24-25
45-55
Slight
All concentrations in ppm.
"Environmental conditions measured continuously over 3 weeks.
•(•Approximate concentration.
I Slight stain.
—, no sample collected.
ND, nothing detected.
0.02
<0.06
<0.05
<0.04
<0.04
<0.02
~0.05f
0.03
<0.5
ND
428
E. Scobbie el al.
sive surveys, 5-8, were selected and the concentrations of the chemicals detected are
shown in Table 3.
Glutaraldehyde and acetaldehyde were not detected at any of the sites (analytical
detection limits are given in Table 3, for example, a value of < 0.004 ppm implies a
detection limit of 0.004 ppm). Formaldehyde was detected at 0.01 ppm on survey 6
and at close to the detection limit on surveys 7 and 8. These concentrations are
typical of those found in most work environments.
Methoxyethanol, ethoxyethanol, butoxyethanol, diethylene glycol and propylene
glycol were not detected in any of the four surveys where measurements were made,
nor was ammonia detected.
Acetic acid concentrations measured by ion chromatography (IC) ranged from
0.02 ppm (0.06 mg m~3) to 0.06 ppm (0.14 mg m~3) equivalent to about 1/500 th to
1/200 th of the OES of 10 ppm for an 8-h time-weighted average (HSE, 1995).
Although the corresponding Gastec detector tubes tended to give higher readings it
should be noted that these tubes are intended to measure much higher concentrations
(nearer the OES) and at such low levels can only be expected to provide an
approximation of the true concentration (the quoted detection limit is 0.05 ppm).
Low concentrations of sulphur dioxide were also found on all visits when
measurements were made. Typically sulphur dioxide concentrations measured by IC
were in the range 0.02 ppm (0.04 mg m~3) to 0.10 ppm (0.24 mg m~"3) equivalent to
1/100 th to 1/20 th of the Occupational Exposure Standard (OES) of 2 ppm as an 8-h
time-weighted average (HSE, 1995). The Gastec detector tubes (quoted detection
limit 0.01 ppm) again tended to give higher results than IC.
Tenax tubes analysed by GC-MS revealed no substances on surveys 1, 2 and 8
which could be attributed to X-ray film processing. On survey 5, trace levels of
tetrachloroethene, 1,2-dichlorobenzene, nonanal, decanal and dibutyl phthalate were
detected. Survey 6 revealed the presence of dibuyl phthalate and also 2,6-bis(l,ldimethylethyl)-4-methyl phenol. On survey 7 (at a different location to survey 6),
dibutyl phthalate and 2,6-bis(l,l-dimethylethyl)-4-methyl phenol were again detected
along with various alkyl benzenes. On all surveys, these substances were at trace levels
and there can be no absolute certainty that film processing was the source.
In two of the locations, temperature and humidity were monitored continuously
for a 3-week period (surveys 3 and 4). The temperature profiles depended
significantly on where the probes were located. In the first half of the trace, a
gradual rise in temperature through the day at one location when the probes were
placed on the chemical mixer was seen. In the second half of the trace, the probes
were placed on a shelf above the film drier vent. This position produced localized
temperature spikes with each cycle of the processor which raised the overall
temperature of the room so that the temperature increased from about 23.5°C at
10 a.m. to almost 26°C by mid-afternoon. The RH remained fairly constant between
50 and 53% RH.
Temperatures measured on the other surveys ranged from 19.5 to 26°C and
humidities from 27 to 55% RH.
Survey in a problem area
The results of sampling in the one-time problem area are shown in Table 4, the
samples having been collected with the room ventilation switched off to simulate
Chemical pollutants in X-ray film processing
429
Table 4. Survey in a problem area
Measurement
Amount detected
Glutaraldehyde
Acetaldehyde
Formaldehyde
Acetic acid (GT)
Acetic acid (IQ
Methoxyethanol
Ethoxyethanol
Butoxyethanol
Diethylene glycol
Propylene glycol
Sulphur dioxide (GT)
Sulphur dioxide (IQ
Ammonia
< 0.002
< 0.003
~0.005»
1.0
0.46
<0.1
<0.1
<0.02
<0.05
<0.03
0.50
0.53
<0.6
Temperature (°Q
Relative humidity (%)
Smell
24-28
38-40
Pungent
AU concentrations in ppm.
'Approximate concentration.
worst-case conditions. Glutaraldehyde and acetaldehyde were below the detection
limits and the formaldehyde concentration was low. The remaining chemicals (except
acetic acid and sulphur dioxide) were below the detection limits of the respective
methods of analysis. At 0.46 ppm, acetic acid was at a higher concentration than in
the typical environments (0.02-0.06 ppm, Table 2) as was sulphur dioxide at 0.5 ppm
(0.02-0.1, Table 2). Although these concentrations are well within the respective
OESs, the investigating team found the conditions in this processing area
considerably more uncomfortable than in the typical processing units.
Tenax tubes samples analysed by thermal desorption and GC-MS revealed very
low levels of propanol, methoxypropanol, methyl butanol, dimethyl formamide,
hydroxy methyl pentanone, diethylene glycol, phenol, nonanoic acid, 2-methyl
propyl phthalate and n-butylphthalate.
Headspace samples collected above the developer solution tank revealed a
glutaraldehyde concentration of 0.13 ppm along with low levels of methoxy- and
ethoxyethanol. No glycols were detected. Butyraldehyde was also detected by HPLC
but not quantified.
Tenax tube samples collected in the developer tank and analysed by GC-MS
showed the presence of butyraldehyde, acetic acid, chloroform, benzene, toluene,
glutaraldehyde, diethylene glycol, cyclohexene carbonitrile, decene, dodecene,
tetradecene and n-butylphthalate.
Tenax tubes samples collected above the fixer tank revealed sulphur dioxide,
acetic acid, cyclohexene carbonitrile, benzoic acid, 2-methylpropylphthalate and
n-butylphthalate.
Although Tenax tubes would not be recommended for sampling either sulphur
dioxide or acetic acid, analysis by mass spectrometry showed that the concentrations
of both substances in the headspace above the fixer were much higher than in the
general room environment. This indicates that higher short-term exposures to
sulphur dioxide and acetic acid might occur if operators were directly involved in
430
E. Scobbie et al.
handling the solutions. For example, at this particular site the concentrated solutions
were manually poured into the tanks beneath the processor before being diluted to
working strength with water. Such procedures are, however, becoming increasingly
uncommon as automixers become more widely used.
The temperature and humidity were ranged from 24 to 28°C and relative
humidity from 38 to 40% during the working day.
Processor exhaust duct
The results of sampling in the processor exhaust duct from a Dupont Cronex T5
processor, using Dupont Cronex mix MD developer and mix MF-Efixer,are shown
in Table 5. Once again most chemicals were reported as less than the detection limit.
Ion chromatography gave a sulphur dioxide concentration of about 0.8 ppm (2 mg
m~3) and acetic acid at about 0.8 ppm (2 mg m" 3 ). The concentrations of both these
chemicals are greater than found in the typical processing environments and also in
the problem area and suggests the possibility of localized elevated concentrations in
the absence of an exhaust duct.
Ammonia was detected for the first time in this study but at quite low levels of
0.45-1.45 ppm. Failure to detect glutaraldehyde in the exhaust duct confirms that
concentrations in the general work atmosphere are likely to be very low.
Mass spectrometry analysis of the Tenax tube samples revealed acetic acid
together with very low levels of propanol, acetaldehyde, butyraldehyde, dihydrofuran, benzene, methoxy propanol, methylpentanone and pyridine identified by
matching with library spectra. Glutaraldehyde was not detected.
Laboratory investigations
The results of analysing headspace vapours of the developers and fixers by GCMS are shown in Tables 6 and 7, respectively. Analysis was qualitative only but an
attempt has been made to classify the concentrations of the components by means of
the terms 'major', 'medium' and 'trace' according to their mass spectral abundance.
Table 5. Concentrations in an exhaust duct
Measurement
Concentration (ppm)
Glutaraldehyde
Acetaldehyde
Formaldehyde
Acetic acid (GT)
Acetic acid (IC)
Methoxyethanol
Ethoxyethanol
Butoxyethanol
Diethylene glycol
Propylene glycol
Sulphur dioxide (GT)
Sulphur dioxide (IC)
Ammonia
< 0.002
< 0.003
<0.006
1.0
(a) 0.85, (b) 0.74
<0.08
<0.07
<0.05
<0.06
<0.03
0.40
(a) 0.76, (b) 0.77
(a) 0.47, (b) 1.45
Temperature (°Q
Relative humidity (%)
24.5-25.0
39-44
All concentrations in ppm.
Table 6. GC-MS analysis of headspace above developers
Developer
Source
Freshly mixed in laboratory
Type
Major
Components identified by GC-MS
Medium
Acetic acid methyl ester
Ethanediol monoacetate
Ethanediol diacetate
Acetic acid methyl ester
Acetic acid butyl ester
Trace
Butyraldehyde
Benzene
Glutaraldehyde
Glutaraldehyde
Benzene
Diethylene glycol monoacetate
Diethylene glycol diacetate
A
Toluene
B
Toluene
13 days after mixing in laboratory
A
B
Butyraldehyde
Butyraldehyde
Propyl dioxolane
Glutaraldehyde
Benzene
Pyridine
Quinol
Collected from survey location
A
Butyraldehyde
Toluene
Propanol
Acetic acid
Benzene
Propyl dioxolane
Styrene
Benzaldehyde
Phenol
Dihydrofuranone
Acetic acid
Butyraldehyde
Toluene
Benzene
Chloroform
Dodecene
Tetradecene
Hexadecene
Table 7. GC-MS analysis of headspace above fixers
Fixer
Source
Type
Major
Components identified by GC-MS
Medium
Trace
Freshly mixed in laboratory
A
B
Acetic acid
Acetic acid
Sulphur dioxide
Sulphur dioxide
—
Acetic acid butyl ester
Methyl pentanone
13 days after mixing in laboratory
A
B
Acetic acid
Acetic acid
Sulphur dioxide
Sulphur dioxide
_
—
Collected from survey location
A
Acetic acid
Sulphur dioxide
Acetic acid methyl ester
B
Acetic acid
Sulphur dioxide
Acetic acid methyl ester
Acetic acid ethyl ester
Styrene
Benzaldehyde
Glutaraldehyde
Acetic acid ethyl ester
Methyl pentanone
Butanoic acid
Hexanoic acid
Heptanoic acid
Benzoic acid
Cyclohexene carbonitrile
Cineole
m
s:
Chemical pollutants in X-ray film processing
433
Freshly prepared developer solutions (Table 6) revealed toluene as a major
volatile constituent accompanied by traces of glutaraldehyde and butyraldehyde. As
the solution aged over a period of 13 days, butyraldehyde emerged as the most
prominent volatile component. The developer solutions recovered from the surveys
are consistent with the laboratory prepared mixtures in that butyraldehyde and
toluene are the main volatiles suggesting that they are at an intermediate stage
between freshly prepared and 13 days old. The trace components possibly arise from
contamination of the developer during normal use in the processing machine.
The composition of the vapour phase above the fixer solutions prepared in the
laboratory does not appear to alter with age up to 13 days (Table 7). The main
components detected were sulphur dioxide and acetic acid. Once again the trace
components in the solutions recovered from the survey possibly arise as a result of
carry over from one solution to another in the processor.
CONCLUSIONS
The surveys revealed the presence of sulphur dioxide and acetic acid in typical Xray film processing environments at concentrations less than 0.1 ppm. This is
consistent with other studies where acetic acid and sulphur dioxide were measured
(Ide, 1993). These concentrations are much lower than the respective occupational
exposure limits but can give rise to a distinctive odour.
Air samples collected in the previous problem area revealed acetic acid and
sulphur dioxide concentrations of around 0.5 ppm, about 5 times higher than in the
typical locations and described by survey staff as distinctly uncomfortable. The
samples collected from the processor exhaust duct produced concentrations of acetic
acid and sulphur dioxide of around 0.8 ppm and demonstrate that the usefulness of
this extraction system in reducing the potential contamination of the work room.
Glutaraldehyde has been suspected as being the cause of the health problems
associated with X-ray film processing units but it was not detected in this study in
the ambient air at the typical locations, in the problem area or in the exhaust
duct (environmental detection limit ~0.001 ppm). It was only detected in the
work place by sampling directly above the solution in the developer tank in the
problem area where the concentration was about 0.13 ppm. It is likely that there
was some leakage from this unsealed tank but presumably the dilution even in an
unventilated room was sufficient to produce an airborne glutaraldehyde
concentration below the detection limit. Other studies, although limited, have
reported glutaraldehyde concentrations in the range 0.003-0.006 mg m~ 3 (0.00090.002 ppm) (Leinster et al., 1993).
Butyraldehyde, a severe irritant, was detected at low concentrations in the film
processor exhaust duct and also as a main component above the developer solutions.
The laboratory studies showed that butyraldehyde becomes a more significant
component of the headspace as the solutions age and could indicate higher potential
for exposure to this aldehyde when handling waste devloper solutions.
It has been suggested that low humidity levels in X-ray processing areas could
aggravate the effects of exposure by drying out the mucous membranes of the
respiratory tract, thus increasing their susceptibility to chemical damage. Guidelines
for Radiographers in New Zealand (Gordon, 1986) recommend a relative humidity
434
E. Scobbie el al.
between 35 and 60%. Four of the locations included in the survey had relative
humidities less than 35%, the lowest being 27% but there were no indications that
this caused discomfort. Data recorded over periods of up to 3 weeks demonstrated
how the processor air drying cycle can raise the local temperature resulting in a
gradual rise in overall temperature of the room during the working period. This
drying cycle had little effect on the humidity of the room.
The study would have been more complete if comparisons had been possible
between the typical processing units and those with a known problem. Despite all
reasonable attempts, it was not possible to identify any processing units where there
was a recognized current problem which could be attributed to darkroom disease. As
a compromise, an attempt was made to recreate the conditions in a unit which was
once known to have a problem but this simply resulted in increased concentrations
of sulphur dioxide and acetic acid. If this reconstruction was in any way realistic
(and it must be accepted that it may not have been) then it seems to indicate that if
darkroom disease arose from normal day to day activities in X-ray processing units
then sulphur dioxide and acetic acid, either alone or together, must have been
involved. The argument against this hypothesis is that both these substances are
encountered at higher concentrations in other environments apparently without
causing health effects similar to darkroom disease.
An alternative explanation is that the causative agent has remained undetected in
this study or else one or more of the substances reported as not detected is capable of
exerting a health effect at concentrations substantially below the detection limits
reported here.
If the normal day to day activities are not responsible for the observed health
effects then perhaps the past systems of mixing chemicals by hand played a role.
Substantially higher concentrations of sulphur dioxide and acetic acid are present
above the chemical solutions themselves and it was only directly above the developer
that glutaraldehyde and butyraldehyde were detectable. It is likely that hand mixing
of chemicals, as was frequent in the past, could give rise to relatively high
concentrations of these substances during the short time required for dispensing and
dilution with water. The spent developer appears to be enriched in butyraldehyde but
not enough is known about the health effects of this material to be able to judge its
effect.
The issue of how to protect staff from exposures that could result in a recurrence
of the problem needs to be addressed. The causal agent is not known and cannot,
therefore, be measured directly so monitoring exposure through the use of a
surrogate has to be considered and the only options are sulphur dioxide and acetic
acid, both of which derive from the fixer. The possibility of using an indicator
contaminant such as sulphur dioxide in certain circumstances has previously been
suggested, although it may be of limited value (Hewitt, 1994). There were no
reported incidences of the disease at the typical locations included in this survey
where concentrations of 0.1 ppm or less of acetic acid and sulphur dioxide were
measured. These concentrations appeared achievable in the workplace through
adequate general ventilation and direct exhaust ventilation from processors where
possible. Direct reading gas detector tubes could be useful asfirst-lineindicators of
concentrations in the general environment but they will be operating close to their
detection limits at these low concentrations.
Chemical pollutants in X-ray film processing
435
Acknowledgements—The authors would like to thank the hospitals and staff in the Yorkshire area whose
co-operation made this study possible, and J. Healy, T. Cleary and S. Bradley for the ion chromatography
analysis.
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