Occupational Medicine Advance Access originally published online on February 23, 2006
Occupational Medicine 2006 56(4):269-271; doi:10.1093/occmed/kqj034
© The Author 2006. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Unexpected cause of raised benzene absorption in coke oven by-product workers
Richard Colman1 and
Andrew Coleman2
1 Cowl House, Bransdale, Fadmoor, YO62 7JW, UK
2 Corus UK, Redcar, UK
Correspondence to: Richard Colman, Cowl House, Bransdale, Fadmoor, YO62 7JW, UK. Tel: +44 1751 432342; e-mail: richardcol{at}doctors.org.uk
 |
Abstract
|
|---|
Background Urinary biological monitoring for benzene (by measuring
benzene metabolites) in coke oven by-product workers produced
the unexpected result that 2 out of 10 employees had significantly
raised urinary S-phenylmercapturic acid (S-PMA). However, simultaneous
personal air sampling showed no excessive airborne exposure.
Methods Possible causes for this finding were investigated having excluded inhalation as the route of uptake. It was suspected that skin absorption via contaminated overalls was the possible mechanism and a standard frequency for overall change was introduced.
Results Changing overalls after every four shifts reduced uptake levels to less than the equivalent of 1 ppm inhaled dose for all employees.
Conclusion Skin absorption of benzene in coke oven by-product workers from contaminated overalls can be significant and therefore overalls should be changed on a regular and frequent basis.
Keywords Benzene; biological monitoring; coke oven by-product workers; overalls; risk surveillance; S-PMA
|
Introduction
|
|---|
Benzene is a by-product of the coking process and is a known
carcinogen. The Control of Substances Hazardous to Health Carcinogen
Code of Practice [
1] requires that exposure to carcinogens be
monitored (Regulation 10) and exposure for benzene be maintained
at less than the Workplace Exposure Limit (WEL) of 1 ppm 8 h
TWA. This paper concerns occupational hygiene surveillance being
carried out at two coke ovens which are part of an integrated
steel producing plant.
|
Methods
|
|---|
Coke oven by-product workers periodically undergo personal air
sampling for benzene and the opportunity was taken to measure
the actual personal uptake of benzene over the same shifts by
measuring the benzene metabolite S-phenylmercapturic acid (S-PMA)
in urine of employees. Biological monitoring is considered a
better way of assessing risk as it measures total exposure from
all sources. S-PMA is a minor but highly specific marker of
benzene exposure. It has greater specificity than any other
markers such as phenol which is unsuitable for benzene monitoring
unless at very high levels and
trans, trans-muconic acid (ttMA)
which is useful for benzene monitoring at exposures <0.5
ppm but can be interfered by sorbitol, found in soft drinks.
S-PMA has been internationally recognized as a valid biomarker
of benzene exposure and both the American Conference of Government
Industrial Hygienists and the Deutsche Foorschungs Gemeinschaft
have published biological exposure indices (BEIs) for benzene
exposure based on measuring urinary S-PMA [
2]. Personal air
sampling was carried out in accordance with the method MDHS
80 [
3], published by the Health & Safety Executive (HSE).
Diffusion tubes were attached to each team member's lapel for
a full 12 h shift although in practice this varied between 11
and 12.5 h. At the end of the shift, urine samples were collected
on the site by nursing staff and sent to the HSE laboratory
in Sheffield for analysis. Personal benzene exposure by air
sampling for all 10 workers under study at the two coke ovens
ranged from 0.07 to 0.28 ppm 8 h TWA. Allowing for a 20% measurement
error, these levels were well below the 1 ppm WEL. However,
at Plant A urinary S-PMA levels were significantly elevated
in two of the four employees suggesting some other route of
exposure. Twenty-one µmol/mol creatinine equates to 1
ppm 8 h TWA (see
Table 1). To explain these findings, some other
source of exposure was necessary and skin absorption seemed
most likely. Prior to this investigation, change of overalls
at Plant A had been a matter of personal choice. The laundry
records at Plant A showed a wide variation in the frequency
of changes. Laundry records were not kept for Plant B but were
reported to be more regular and frequent. At Plant A therefore,
regular changes of overalls after every four shifts were introduced
and benzene metabolites reassessed.
|
Results
|
|---|
Following the introduction of this measure, levels returned
to acceptable levels in all four employees (see
Table 2).
|
Discussion
|
|---|
Regular and frequent changes of overalls reduced the employees'
body load of benzene. The use of urinary S-PMA is the preferred
measure of benzene absorption. Measurement is subject to a 12%
variability and metabolism within the body is subject to individual
variation which is accounted for in the ppm equivalent value.
The 7- to 9-h half-life of S-PMA will mean that on 12 h shifts
some may be lost to measurement by metabolism if the exposure
is early in the shift. This would potentially underestimate
exposure. Any such short-lived peak airborne exposure early
on in the shift would however be trapped in the tube and included
in the overall shift average. Significant inhalation from other
sources such as petrol fumes was not specifically investigated
and cannot be excluded from contributing to the findings of
this study.
Smokers, per se exhibit higher urinary S-PMA levels than non-smokers due to the presence of benzene in cigarette smoke. Average S-PMA levels in a smoker are 
2 µmol/mol creatinine compared to 1 µmol/mol creatinine for a non-smoker. However, a heavy smoker would still be expected to have S-PMA levels about five times lower than the BEI value for a 0.5-ppm exposure (12 µmol/mol creatinine). Hence, smoking as a significant confounder is ruled out.
Numbers were small and no attempt was made at statistical analyses. However, comparison with the Plant B coke oven data, at which a more regular system of overall change was in place, adds weight to the proposal.
While we concentrated on overalls, suspicion could also be thrown on gloves. These are polyvinyl chloride based and not impermeable to penetration by benzene. A walk through the sites showed that observable tar was found on valves and surrounding areas. Attention to the use of gloves and their regular changing would seem sensible but was not looked at specifically in this study. Nor was the possibility of significant ingestion of benzene from contaminated food caused by handling with unclean hands or placing on unclean surfaces.
Quinlan et al. [4] showed that regular changes of employee's overalls and clothing beneath overalls including underpants made a significant difference to the pyrene metabolite 1-hydroxypyrene measured in the urine of coal workers exposed to polycyclic aromatic hydrocarbons in the coal liquefaction process.
It could therefore be argued that we could ask the managers to go further in attempts to reduce expose. Certainly, those with persistent higher levels could be encouraged to change their behaviour and improve personal hygiene. It is interesting that the lowest level of absorption on the first round of tests was in an individual who had been warned some months previously that his levels were on the high side and he is now changing his overalls regularly.
The implication of these findings is that coke oven by-product workers with potential exposure to benzene should change their overalls regularly. On a wider level, this paper suggests that as well as environmental monitoring for volatile solvents by a hygienist ongoing risk surveillance by biological monitoring is a useful activity and may indicate the need to consider other, perhaps unexpected, routes of uptake requiring individual attention to personal hygiene.
|
Conflicts of interest
|
|---|
None declared.
|
Acknowledgements
|
|---|
We wish to thank Kate Jones, Principle Scientist at the Health
and Safety Laboratory, Sheffield, for her help and advice.
|
References
|
|---|
- General COSHH ACOP, Carcinogens ACOP and Biological Agents ACOP. Control of Substances Hazardous to Health Regulations 1999 Approved Codes of Practice. 2002; ISBN 07176 25346.
- Aston JP, Ball RL, Pople JE, Jones K, Cocker J. Development and validation of a competitive immunoassay for urinary S-phenylmercapturic acid and its application in benzene biological monitoring. Biomarkers 2002;7:103–112.[Medline]
- Methods for Determination of Hazardous Substances 80 (MDHS 80). Volatile Organic Compounds in Air. HSE, 1995; ISBN 07176 0913 8.
- Quinlan R, Kowalczyk G, Gardiner K, Calvert I. Exposure to polycyclic aromatic hydrocarbons in coal liquefaction workers: impact of a workwear policy on excretion of urinary 1-hydroxypyrene. Occup Environ Med 1995;52:600–605.[Abstract/Free Full Text]
CiteULike 
Connotea 
Del.icio.us What's this?
Top
Abstract
Introduction