In their study from Massachusetts, USA, on characteristics of work
related asthma, Breton CV et al. found that individuals with work related
current asthma were 4.8 times as likely to visit the emergency room at
least once, and 2.5 times as likely to visit the doctor at least once for
worsening asthma compared to individuals with non-work related asthma (1).
Work related status of asthma was determi...
In their study from Massachusetts, USA, on characteristics of work
related asthma, Breton CV et al. found that individuals with work related
current asthma were 4.8 times as likely to visit the emergency room at
least once, and 2.5 times as likely to visit the doctor at least once for
worsening asthma compared to individuals with non-work related asthma (1).
Work related status of asthma was determined by self-report of ever having
been told by a physician that asthma was work related.
The proportion of work-related asthma in this study was 6% which is
low compared to a recent statement by the American Thoracic society (2),
and so may indicate misclassification. The authors state that the timing
of the work related diagnosis is not known. This may introduce bias in
the results because physicians often hesitate to ask patients about
exposure at work (3). In our experience (4), the question of work-
relatedness is usually not addressed until further work is in jeopardy due
to the disease. If this is the case also in Massachusetts, asthmatics with
doctors diagnosed work related disease may have a more serious disease
than those without doctors diagnosed work related disease. In part this
may explain why those with work related disease were found to visit
emergency rooms and see their doctor for worsening asthma more often.
References
1 Breton CV, Zang Z, Hunt PR, Pechter E, Davis L. Characteristics of
work related asthma: resulta from a population based survey. Occup Environ
Med 2006;63:411-415.
2 American Thoracic Society. Amerivan Thoracic Society Statement:
Occcupationa Contribution to the Burden of Airway Disease. Am J Resir Crit
Care Med 2003;167:787-797.
3 Milton DK, Solomon GM,Rosiello RA, Herrick RF. Risk and incidence
of asthma attributable to occupational exposure among HMO members. Am J
Ind Med 1998;33:1-10.
4 Leira HL, Bratt U, Slåstad S. Notified cases of occupational asthma
in Norway: exposure and consequences for health and income. Am J Ind Med
2005;48:359-364.
It is disturbing that the Interphone study group first publishes
several papers purportedly finding negative results but only now
publishes a validation study showing that the methods used to measure
exposure are so deeply flawed that it was unlikely the previously
published studies would detect an increase in risk of brain tumour in
mobile phone users(1).
It is disturbing that the Interphone study group first publishes
several papers purportedly finding negative results but only now
publishes a validation study showing that the methods used to measure
exposure are so deeply flawed that it was unlikely the previously
published studies would detect an increase in risk of brain tumour in
mobile phone users(1).
In the validation study of 672 volunteers recall of phone use over a
3-8 months period about six months later, was compared with objective data
from phone bills and use of special soft-ware modified phones. The study
found large random errors in recall which can be expected to have a “large
impact” and bias risk estimates toward a null effect. There was also a
wide variation between countries which further emphasises the randomness
of recall (and the difficulty in conducting a meta-analysis of results
from participating countries). Moreover the validation study design
minimises the errors of recall for several reasons. It largely used
"colleagues and acquaintances of the investigators". These volunteers
would have been well informed of the intent of the study and the
importance of accurately recalling mobile phone usage, and are therefore
different from the naïve subject in the actual studies whose recall would
be even more random. Also the validation study only sought recall of
mobile phone use for 3-8 months about six months later, whereas in the
actual studies recall for up to 10 years was sought which is likely to
lead to even more randomness in recall. The validation study did not
address the problem of impaired recall in the cases with brain tumours who
are likely to have their memory affected from their tumour and subsequent
surgery, radiotherapy, chemotherapy and psychological distress, let alone
the accuracy of surrogates (spouses) used in some studies.
The validation study reveals at a minimum the flawed methodology
being used in the Interphone studies which would lead to Type2 (false
negative) errors thus lessening the ability to except with confidence the
published negative papers regarding the health effects of mobile
phones(2). The late publication of a key methods paper after publication
of many results papers raises concerns about the processes within the
Interphone study group.
Yours
Dr Bruce Hocking.
References
1. Vrijheid M, Cardis E, Armstrong BK, Auvinen A, Berg G, Blaasaas
KG, Brown J, Carroll M, Chetrit A, Christensen HC, Deltour I, Feychting M,
Giles GG, Hepworth SJ, Hours M, Iavarone I, Johansen C, Klaeboe L, Kurttio
P, Lagorio S, Lonn S, McKinney PA, Montestrucq L, Parslow RC, Richardson
L, Sadetzki S, Salminen T, Schuz J, Tynes T, Woodward A; Interphone Study
Group. Validation of short term recall of mobile phone use for the
Interphone study. Occup Environ Med. 2006 Apr;63(4):237-43.
2. Hocking B. Mobile phone use and risk of acoustic neuroma.
Br J Cancer. 2006 May 8;94(9):1350; author reply 1352-3.
We thank Wolf and Vana for their comments on our article "Subjective
symptoms, sleeping problems and cognitive performance in subjects living
near mobile phone base-stations" (OEM 63:307-313). We appreciate their
regret that due to methodological problems results may not be as clear-cut
as they desire.
The study of potential effects of emissions from mobile phone base-
stations is indeed fr...
We thank Wolf and Vana for their comments on our article "Subjective
symptoms, sleeping problems and cognitive performance in subjects living
near mobile phone base-stations" (OEM 63:307-313). We appreciate their
regret that due to methodological problems results may not be as clear-cut
as they desire.
The study of potential effects of emissions from mobile phone base-
stations is indeed fraught with intriguing methodological problems,
however, we admit that those raised by Wolf and Vana are not among those
we were primarily concerned about.
1. Concerning the problem of random clustering that could reduce
effective sample size via a joint influence of an unknown factor on one or
several outcome variables on all subjects within that cluster, we have
taken substantial precaution, in the statistical and material sense. We
did all analyses first by inclusion of the base-station as a random factor
(the variance component of which is equivalent to the intra-class
correlation). These analyses revealed no indication of clustering.
Furthermore, we measured in homes of participants in the urban area
volatile organic compounds and did ambient noise measurements in the rural
area. There were no differences between base-stations in these
environmental factors and no correlation between exposure to
electromagnetic fields and indoor VOC concentrations was detected.
2. Strong concerns were expressed by 8% of participants and there was
indeed a correlation with distance to the base station and, to a lesser
degree, also with exposure category (mean ratings on a scale 0 to 3 were
0.7, 0.9, and 1.3 for the exposure categories, respectively). Hence
concerns about adverse effects of base-stations is indeed a confounding
variable because, as we stated in the discussion, it was also correlated
with many symptoms. Likert type scale of concerns was area transformed
before inclusion into ANCOVA.
3. Dichotomisation of symptoms of the Zerssen Scale was done applying
the only objective cut-off, i.e. discriminating between those that did not
experience this symptom from those that did (thereby neglecting strength
of symptoms). The reasons for applying a dichotomisation were manifold,
but the most important one was to enable usage of the same method of
evaluation for all symptoms. Some symptoms were never or only rarely
categorized into the highest category and therefore applying ordinal
regression led to parameter identification problems. Scoring several
symptoms together into groups of symptoms has not found approval by
reviewers.
4. It is correct that the model of analysis must be set beforehand.
Therefore, results were given for the model as specified. However, to give
an idea about the effect of loss of power by inclusion of insignificant
covariables, following reviewers' suggestions, also the result after their
omission was presented in one case. Application of the Bonferroni or
Bonferroni-Holm method is up to the reader. He/she should only be aware
that this method is utterly conservative and will substantially increase
type II error in the case of correlations between dependent variables
(which is the rule for symptoms, performance variables, and sleep quality
indices). In exploratory studies that cannot start from evidence based
hypotheses such correction will render even much bigger trials practically
powerless and is therefore not recommended.
5. We have clearly stated that we did not apply correction for
multiple testing. We have therefore employed caution in interpretation of
results. Based on our study future investigations can be planned and
evaluated more rigorously. But awaiting more and better evidence should
not prevent us from recommending a minimisation strategy for the siting of
mobile phone base-stations. How to implement such strategies without
evoking the problem Prof. Coggon pointed to in his commentary, that
precautionary measures might distort risk perception thereby potentially
inducing reduced wellbeing and health, could be a task most suited to
Profs. Wolf and Vana that are presiding an advisory board of the Austrian
Federal Ministry of Transport, Innovation and Technology.
In their publication, the authors postulate that effects upon health
and
performance cannot be ruled out despite a low exposure to high-frequency
electro-magnetic fields, effects far below the WHO threshold values.
Unfortunately, this paper has substantial methodological problems.
1. There may well have been a clustering in the choice of test-
subjects’
addresses in relation to the location...
In their publication, the authors postulate that effects upon health
and
performance cannot be ruled out despite a low exposure to high-frequency
electro-magnetic fields, effects far below the WHO threshold values.
Unfortunately, this paper has substantial methodological problems.
1. There may well have been a clustering in the choice of test-
subjects’
addresses in relation to the location of the mobile phone base stations.
For
example, in the sense that other environmental influences may have
affected
everyone in the same cluster. In this case, the independence of the people
within the cluster may no longer be given, which in turn may lead to an
overestimation of the effective sample size, and therefore to progressive
(results are too often significant) decisions. In order to control this
effect, the
Intra-Class-Correlation should have been calculated to give an impression
of
the effective sample size. In the light of the few, tightly significant
results,
such effects may have played a decisive role.
2. It still remains unclear as to whether there are a priori
differences as to
the degree of “concerns about base station“ in relation to the
expositional
groups. This was unfortunately not presented in table 1. What was the
percentage of test-persons who were concerned, and to what extend? How is
this distributed throughout the groups? In addition, the degree of concern
was measured on a ranking-scale, despite the fact that the co-variance
analysis demands an interval scaled co-variant.
3. The Zerssen Scale was evaluated dichotomously, whereby even very
slight complaints (“1“) were already registered as complaints. This then
raises
the question as to whether the named effects in the Zerssen scale would
still
be evident if one had pooled the groups 0 and 1 (no, and/or light
complaints), and the complaints-group 2 and 3. Who doesn’t sometimes
suffer of headaches, dizziness, and appetite disorders, etc? It would be
interesting to see how the complaints - before a dichotomization – were
distributed amongst the exposition-groups.
4. In Table 2, 13(!) covariance analyses were carried out, from which
the p-value of one main effect reaches tendency level (p<0.1). After the
implementation of a Bonferroni-Holm-Correction, which strictly seen should
also include the p-values inside the covariance analyses, there are no
effects
to be found whatsoever. In this case, it is then not permitted to omit the
non-
significant co-variables, even in the co-variance analysis. The model for
the
covariance analysis must always be set, a priori, before testing;
otherwise a
Type I-error-inflation will ensue. The attained significance would only
then be
credible if confirmed on the basis of a further sample.
5. If one would adjust the p-values in table 4 according to the
Bonferroni-
or Bonferroni-Holm-convention, then none of the symptoms would be
significant anymore. The same would apply to the effects shown in table 5.
To sum up: A scientifically founded evaluation would have had to have
seen
corrections according to Bonferroni-Holm (or some other). Had this
happened, there would be no significant result, and thereby no provable
effects. Certain information was not included in the tables, such as the
nature
of the dichotomization and choice of sample. This creates the impression
that
hypothesis finding and hypothesis testing were not done quite
independently
of each other, or at least, that there is little in this study to revoke
this
impression. However, the results beg a prompt replication with all
details,
hypotheses, and corresponding evaluation criteria fixed a priorily.
Thank you for the great editorial. I would like to suggest that
given your experience, especially Dr. Hoppin, it would be especially
helpful to formulate more specific proposals for introducing at the state
level, including California. The University of California, as an example,
has been largely unresponsive to requests for disclosures regarding
potential conflict of interest situations for facu...
Thank you for the great editorial. I would like to suggest that
given your experience, especially Dr. Hoppin, it would be especially
helpful to formulate more specific proposals for introducing at the state
level, including California. The University of California, as an example,
has been largely unresponsive to requests for disclosures regarding
potential conflict of interest situations for faculty, departments, and
research institutes. Circulating a proposal for endorsement by one or
more scientific societies might also foster a larger discussion of this
issue.
Thanks again for your good works.
Bruce H. Jennings, Ph.D.
Senate Environmental Quality Committee
State Capitol, room 2205
Sacramento, CA 95814
916.651.4108
It has been clear for years, based on much published research, that
symptoms in office workers are associated with a number of environmental
factors in office buildings and also, independently, with psychosocial
stressors at work. So we were surprised to see a recent article by Marmot
et al. (1) report that, in offices in the Whitehall II Study, “raised
symptom levels appear to be largely due to a...
It has been clear for years, based on much published research, that
symptoms in office workers are associated with a number of environmental
factors in office buildings and also, independently, with psychosocial
stressors at work. So we were surprised to see a recent article by Marmot
et al. (1) report that, in offices in the Whitehall II Study, “raised
symptom levels appear to be largely due to a working environment
characterized by poor psychosocial conditions”(p. 288). The article
concluded that the physical environment in the offices had a small and
unimportant influence on these symptoms. The analyses, however, had
substantial limitations that were not mentioned. Furthermore, the
conclusions were inconsistent with much of the current scientific
literature, but the discussion cited only other studies that agreed with
the findings and none of the substantial literature that disagreed. We
expand on these points below.
1) Key environmental measurements and interpretations used by Marmot
et al. (1) in the 1991-1993 data collection are no longer considered
relevant by most indoor environmental scientists. Single metrics of total
volatile organic compounds that lump all compounds together have long been
considered inappropriate for predicting human response, because irritancy
and odor vary among specific volatile organic compounds by orders of
magnitude (2). Metrics based on counts of culturable airborne fungi and
bacteria do not detect most indoor microbial matter and “provide little
information about the microbial status of an indoor environment” (3)(p.
58). Also, many of the thresholds for acceptability used by Marmot et al.
are not considered relevant for studying building-related symptoms: e.g.,
dry bulb temperature between 19-24°C; carbon dioxide (CO2) ≤500
parts per million (ppm); or any particular number for total airborne fungi
or bacteria or volatile organic compounds. In addition, the lumping
together of extreme high and low levels for many of the parameters (e.g.,
combining very hot and very cold temperatures in one category and
comparing to a broad middle range of temperatures) is inappropriate –
high and low temperature (or high and low humidity) may have quite
different, even opposite, effects. Researchers using more current or
precise metrics have reported consistent associations between building-
related symptoms in office workers and both lower ventilation rates (6, 7)
and temperatures (8, 9). There is also a substantial literature showing
that visible dampness and mold, but not traditional airborne mold counts,
are consistently associated with asthma exacerbation and respiratory
symptoms in building occupants (3, 4).
2) The authors do not report the association of passive tobacco smoke
exposure at work with symptoms, although it is included in their models as
a confounding factor (1) and was strongly correlated with increased
symptoms (p = 0.004) in prior analyses of their data (5). The current
article does not consider passive tobacco smoke exposure to be an indoor
environmental risk factor, although it reports risk estimates for other
indoor air pollutants (1).
3) The paper cites prior studies that agreed with its findings, but
is inexplicably silent about the many prior studies that have disagreed
(1). Ventilation rate (6, 7) and temperature (8, 9), both objectively
assessed indoor environmental risk factors, have been significantly and
independently associated with symptoms in multiple prior office studies.
A 1999 review of studies reported between 1986 and 1999 found that (a) in
16 studies using measured ventilation rates, 20 of 27 comparisons of
different ventilation rates found increased symptoms associated with lower
measured office ventilation rates, and (b) 9 of 18 studies using CO2
measurements as simpler but less accurate indicators of ventilation rate
also found such associations (10). Nine articles on associations between
temperature and symptoms in offices, published between 1989 and 2004, show
overall that symptom prevalence increased systematically as temperatures
increased between about 21 and 24.5 ºC, almost entirely within the
“acceptable” reference level used in Marmot et all (1, 11).
We suggest further analyses of the Whitehall II data by Marmot et al.
to refine their findings and help resolve discordant results: a) the use
of environmental metrics based on current knowledge that symptoms in
office workers generally increase as temperatures increase above 21 or 22
ºC, as indoor CO2 increases above about 600 to 800 ppm, with presence of
passive tobacco smoke, and in buildings with air-conditioning or
humidification; b) statistical adjustment for season of study; c) the
inclusion of the additional psychosocial variables available in Whitehall
II (5); and d) separate analyses for outcomes of biologically related
symptom subgroups – rather than continuing to use the very nonspecific
“sick building syndrome” metric (for instance, lumps rash/itch together
with cold/flu) which may be sensitive to stress-related over-reporting but
insensitive to specific biologic effects.
In conclusion, substantial evidence suggests that psychosocial and
physical factors in indoor environments, as well as biological and
chemical factors, all influence the symptoms experienced by office
workers, through multiple mechanisms that we still do not understand.
Dismissing the importance of any of these indoor environmental risk
factors is not useful or, based on all that we know, justified.
Ultimately, researchers in many disciplines will be needed to help us
understand causation and prevention of this problem.
Mark J. Mendell and William J. Fisk,
Indoor Environment Department,
Lawrence Berkeley National Laboratory
Competing interests: none.
References
1. Marmot AF, Eley J, Stafford M, Stansfeld SA, Warwick E, Marmot MG.
Building health: an epidemiological study of "sick building syndrome" in
the Whitehall II study. Occup Environ Med 2006;63:283-289.
2. Molhave L, Clausen G, Berglund B, et al. Total Volatile Organic
Compounds (TVOC) in Indoor Air Quality Investigations. Indoor Air
1997;7:225-240.
3. Institute of Medicine Committee on Damp Indoor Spaces and Health. Damp
Indoor Spaces and Health. Washington, D.C.: National Academies Press,
2004.
4. Park JH, Schleiff PL, Attfield MD, Cox-Ganser JM, Kreiss K. Building-
related respiratory symptoms can be predicted with semi-quantitative
indices of exposure to dampness and mold. Indoor Air 2004;14:425-33.
5. Marmot AF, Eley J, Nguyen M, Warwick E, Marmot MG. Building health in
Whitehall: An epidemiological study of causes of SBS in 6,831 civil
servants. In: Woods JE, Grimsrud DT, Boschi N, eds. Proceedings of Healthy
Buildings/ IAQ '97. Washington, DC, 1997:483-488.
6. Stenberg B, Eriksson N, Hoog J, Sundell J, Wall S. The Sick Building
Syndrome (SBS) in office workers. A case-referent study of personal,
psychosocial and building-related risk indicators. Int J Epidemiol
1994;23:1190-7.
7. Jaakkola JJ, Miettinen P. Ventilation rate in office buildings and sick
building syndrome. Occup Environ Med 1995;52:709-14.
8. Mendell MJ, Fisk WJ, Petersen MR, et al. Indoor particles and symptoms
among office workers: results from a double-blind cross-over study.
Epidemiology 2002;13:296-304.
9. Jaakkola JJ, Heinonen OP. Sick building syndrome, sensation of dryness
and thermal comfort in relation to room temperature in an office building:
Need for individual control of temperature. Environment International
1989;15:163-168.
10. Seppanen O, Fisk WJ, Mendell MJ. Association of ventilation rates and
CO2 concentrations with health and other responses in commercial and
institutional buildings. Indoor Air 1999;9:226-252.
11. Seppanen O, Fisk WJ. Some quantitative relations between indoor
environmental quality and work performance or health. ASHRAE Research
Journal 2006;(in press).
The current research paper by Fransen et al. (2006) contributes
interesting and useful data to the emerging research area examining the
potential risk of extended working hours, unusual work patterns, and the
occurrence of a work related injury.
I am concerned, however, that readers may conclude that working
permanent night shifts carries no increased risk of work injury, despite
contrary evidence as they cited...
The current research paper by Fransen et al. (2006) contributes
interesting and useful data to the emerging research area examining the
potential risk of extended working hours, unusual work patterns, and the
occurrence of a work related injury.
I am concerned, however, that readers may conclude that working
permanent night shifts carries no increased risk of work injury, despite
contrary evidence as they cited. Highlighted in their report (including
the Abstract and Main Messages) was their conclusion that “Permanent night
work is not associated with increased risk of work injury after adjusting
for these other risk factors.”
In Table 4, the reported point estimate (RR) and 95% confidence
interval (CI) for permanent night shift was 1.38 (0.95-2.00). I would
argue that this “mutually adjusted result” suggests a fairly strong
association between working permanent night shifts and the risk of a work
injury; however, since the number of injured cases in this cell was small
(n=69), this result is a potential Type II error and possibly
statistically underpowered result (Freiman, J.A., T.C. Chalmers, H. Smith
et al., 1978). Thus, it should have been interpreted with caution rather
than suggesting with certainty that there is no association.
Additionally, it would be of interest to see the adjusted results
when using working hours as a continuous variable, rather than a single
cut point of 40 hours, which may or may not reflect long working hours.
Again, I am grateful to the authors for publishing these important
results.
Fransen M, Wilsmore B, Winstanley J, Woodward M, Grunstein R,
Ameratunga S, Norton R Shift work and work injury in the New Zealand
Blood Donors' Health Study. Occup Environ Med 2006 May; 63(5) :352-8.
Freiman, J.A., T.C. Chalmers, H. Smith et al. The importance of beta,
the type II error and sample size in the design and interpretation of the
randomized control trial. New England Journal of Medicine 299:690-694,
1978.
We read with interest the article by Alamgir et al (1) regarding the
use of hospital discharge records in occupational health in the April
issue of Occupational and Environmental Medicine. The paper adds to the
evidence that these records represent an alternative and independent
source of information for serious work-related injuries. In their
introduction, the authors also make the point that, to...
We read with interest the article by Alamgir et al (1) regarding the
use of hospital discharge records in occupational health in the April
issue of Occupational and Environmental Medicine. The paper adds to the
evidence that these records represent an alternative and independent
source of information for serious work-related injuries. In their
introduction, the authors also make the point that, to their knowledge,
studies in Canada using this data source have not validated its use
against other available indicators.
We would like to bring to the attention of readers a previous
Canadian study conducted by us (2) in which we attempted to confirm the
diagnoses in the hospital records. In an initial study (3), we examined
the association of pneumoconiosis and cor pulmonale in Ontario using
hospital discharge data available from the Hospital Medical Records
Institute (HMRI, now the Canadian Institute for Health Information) and
the Ontario Ministry of Health (3). In the follow-up report (2), we
attempted to confirm the validity of the coding of the diagnoses of a
subset of the hospital discharges from the original study, and to identify
work exposure (occupation and industry) information available in hospital
records. We wrote to hospitals providing abstraction forms to be
completed for 521 subjects hospitalized for pneumoconiosis, cor pulmonale
or both requesting information regarding diagnoses, occupation and
industry data. We received completed abstraction forms from 151 (76%) of
the hospitals contacted, representing 720 (76%) of the 944 discharges and
421 (81%) of the 521 patients. The HMRI diagnoses were confirmed for 97%
of those with silicosis and for 96% of those with asbestosis, and there
was very good agreement between the two sources for the presence or
absence of these conditions (kappa of 0.84 and 0.86, respectively). We
also examined occupation and industry information available in the charts
for which silicosis was a diagnosis. Of the 242 charts with silicosis,
122 had occupation/ industry information that could be classified
regarding exposure to a specific dust type, and of these 89 (73%) were
classified as consistent with silica exposure.
Furthermore, as a check against a second available indicator, of 34
individuals in this data set known from the Ontario Ministry of Labour’s
Chest Clinic x-ray surveillance program of miners to have silicosis, 33
(97%) were diagnosed by the hospitals as having pneumoconiosis, and all
but two were silicosis. These findings indicated that at least for
pneumocioses (conditions that are pathognomonic of occupation), we could
confirm the diagnoses and the hospital records frequently contained
information about the responsible exposures.
Gary M Liss, MD, MS, FRCPC,
Robert A. Kusiak, MSc,
Ontario Ministry of Labour,
Toronto, ON, Canada
References
1. Alamgir H, Koehorn M, Ostry A, Tompa E, Demers P. An
evaluation of hospital discharge records as a tool for serious work
related injury surveillance. Occup Environ Med 2006; 63:290-296.
2. Liss GM, Kusiak RA, Gailitis MM. Hospital records: an
underutilized source of information regarding occupational diseases and
exposures. Am J Ind Med 1997; 31:100-106.
3. Kusiak RA, Liss GM, Gailitis MM. Cor pulmonale and
pneumoconiotic lung disease: An investigation using hospital discharge
data. Am J Ind Med 1993; 24:161-173.
In the article, "Parkinson’s disease and other basal ganglia or
movement disorders in a large nationwide cohort of Swedish welders,"1 the
authors conclude:
"This nationwide record linkage study offers no support for a relation between welding and Parkinson’s disease or other specific basal ganglia and movement disorders."
They argue that there is a need for their study, a 29 year stu...
In the article, "Parkinson’s disease and other basal ganglia or
movement disorders in a large nationwide cohort of Swedish welders,"1 the
authors conclude:
"This nationwide record linkage study offers no support for a relation between welding and Parkinson’s disease or other specific basal ganglia and movement disorders."
They argue that there is a need for their study, a 29 year study with
a large number of welders, because other studies have conjectured that low
grade exposure to manganese fumes may increase the risk for Parkinson’s
disease and other basal ganglia and movement disorders. They point out
that, unlike their study, these other studies were neither long term nor
did they include a large number of welders.
In the referenced studies cited to support their argument manganese
exposure levels were not measured. But they were measured in the subject
study and the exposure levels were at a relatively low level. According to
Table 2 of the study, the average median exposure level was roughly
0.21mg/m3 for 1974-1975 (assumed to be a representative year). This is
very close to the guidelines of the Agency for Toxic Substances and
Disease Registry - Toxicological Profile for the Manganese air quality
guideline for 2000 of 0.15 mg/m3(Recommended Air Quality Guideline for
Europe: annual average).2
Other credible studies do find a linkage where the exposure levels
are significant. A case study of 8 welders entitled, "Neurologic
manifestations in welders with pallidal MRI T1 hyperintensity" concluded
that welding without proper protection was associated with syndromes of
Parkinsonism where the welding was done with inadequate ventilation. The
symptoms included hand and postural tremor and unsteady gate.3
Neither the conclusion nor the abstract mention this qualification.
Only by reading the full article would the reader know that the airborne
manganese levels were kept at such a low level. The public often relies on
medical journal articles and the danger of misconstruing
the meaning of this article is a significant one. A report
published in the Welding Information and Knowledge Base4
interpreted the Swedish article to say:
"Study of Almost 50,000 Swedish Welders is Most Powerful To Date; Offering Support That Welders Are Not at Increased Risk for Movement Disorders."
Although the subject study is a valuable addition to the
literature of the risks of exposure to airborne manganese, the conclusion
reached is easily subject to misinterpretation. In this case,
misinterpretation poses a significant health risk.
Robert Eli
References
1. Fored CM, Fryzek JP, Brandt L, et al. Parkinson's disease and
other basal ganglia or movement disorders in a large nationwide cohort of
Swedish welders. Occupational
and Environmental Medicine 2006; 63; 135-140.
2. Agency for Toxic Substances and Disease Registry.2000.
Toxicological profile for Manganese. U.S. Department of Health and Human
Services Public Health Service
Available at:
http://www.atsdr.cdc.gov/toxprofiles/tp151.html
3. Josephs KA, Ahlskog JE, Klos KJ, et al. Neurologic manifestations
in welders with pallidal MRI T1 hyperintensity. Neurology 2005; 64:2033-2039.
This article recalls a controversy of the early 1930s, when the
authority of no less a genius than Professor JS Haldane was challenged on
behalf of South Wales coalminers by a mining mineralogist W. R. Jones, who
as a consequence was to acquire the soubriquet "Sericite". [1]
Their disease was considered by Haldane not to be attributable to the
dust to which they were exposed, as its level of c...
This article recalls a controversy of the early 1930s, when the
authority of no less a genius than Professor JS Haldane was challenged on
behalf of South Wales coalminers by a mining mineralogist W. R. Jones, who
as a consequence was to acquire the soubriquet "Sericite". [1]
Their disease was considered by Haldane not to be attributable to the
dust to which they were exposed, as its level of crystalline silica was
too low: further, it was claimed that coal mine dust reduced the risks of
tuberculosis, and promoted longevity.
Jones' hypothesis was that much of the respiratory disease incurred
in such dusty industries as coal mining, gold mining, and pottery, was
related to the cericite rather than to the crystalline silica content of
their dusts. There were fallacies in the scientific arguments on both
sides, but in the event sentiment sided with Jones, and the miners
received compensation. Algranti et al confirm that yet another non-
asbestos mineral fibre can be biologically active even when below the
length that most hygienists care to be concerned about.
References
[1] Greenberg M. 'A battle for compensation for Welsh coal miners: JS
Haldane v "Sericite" Jones, 1932-1934..' Am J Ind Med, 1997;32: 309-314.
Dear Editor,
In their study from Massachusetts, USA, on characteristics of work related asthma, Breton CV et al. found that individuals with work related current asthma were 4.8 times as likely to visit the emergency room at least once, and 2.5 times as likely to visit the doctor at least once for worsening asthma compared to individuals with non-work related asthma (1). Work related status of asthma was determi...
Dear Editor,
It is disturbing that the Interphone study group first publishes several papers purportedly finding negative results but only now publishes a validation study showing that the methods used to measure exposure are so deeply flawed that it was unlikely the previously published studies would detect an increase in risk of brain tumour in mobile phone users(1).
In the validation study of 672 vo...
Dear Editor,
We thank Wolf and Vana for their comments on our article "Subjective symptoms, sleeping problems and cognitive performance in subjects living near mobile phone base-stations" (OEM 63:307-313). We appreciate their regret that due to methodological problems results may not be as clear-cut as they desire.
The study of potential effects of emissions from mobile phone base- stations is indeed fr...
Dear Editor,
In their publication, the authors postulate that effects upon health and performance cannot be ruled out despite a low exposure to high-frequency electro-magnetic fields, effects far below the WHO threshold values. Unfortunately, this paper has substantial methodological problems.
1. There may well have been a clustering in the choice of test- subjects’ addresses in relation to the location...
Dear Authors,
Thank you for the great editorial. I would like to suggest that given your experience, especially Dr. Hoppin, it would be especially helpful to formulate more specific proposals for introducing at the state level, including California. The University of California, as an example, has been largely unresponsive to requests for disclosures regarding potential conflict of interest situations for facu...
Dear Editor,
It has been clear for years, based on much published research, that symptoms in office workers are associated with a number of environmental factors in office buildings and also, independently, with psychosocial stressors at work. So we were surprised to see a recent article by Marmot et al. (1) report that, in offices in the Whitehall II Study, “raised symptom levels appear to be largely due to a...
The current research paper by Fransen et al. (2006) contributes interesting and useful data to the emerging research area examining the potential risk of extended working hours, unusual work patterns, and the occurrence of a work related injury.
I am concerned, however, that readers may conclude that working permanent night shifts carries no increased risk of work injury, despite contrary evidence as they cited...
Dear Editor:
We read with interest the article by Alamgir et al (1) regarding the use of hospital discharge records in occupational health in the April issue of Occupational and Environmental Medicine. The paper adds to the evidence that these records represent an alternative and independent source of information for serious work-related injuries. In their introduction, the authors also make the point that, to...
Dear Editor,
In the article, "Parkinson’s disease and other basal ganglia or movement disorders in a large nationwide cohort of Swedish welders,"1 the authors conclude:
"This nationwide record linkage study offers no support for a relation between welding and Parkinson’s disease or other specific basal ganglia and movement disorders."
They argue that there is a need for their study, a 29 year stu...
Dear Editor,
This article recalls a controversy of the early 1930s, when the authority of no less a genius than Professor JS Haldane was challenged on behalf of South Wales coalminers by a mining mineralogist W. R. Jones, who as a consequence was to acquire the soubriquet "Sericite". [1]
Their disease was considered by Haldane not to be attributable to the dust to which they were exposed, as its level of c...
Pages