Numerous studies have documented that perception of adverse
psychosocial factors at work is related to major depression, but we still
do not know if this reflects causal characteristics of the working
environment, personal characteristics of the individual worker, trivial
associations, common method variance or other types of reporting bias
because most studies have relied on self-reported exposure information
(1)....
Numerous studies have documented that perception of adverse
psychosocial factors at work is related to major depression, but we still
do not know if this reflects causal characteristics of the working
environment, personal characteristics of the individual worker, trivial
associations, common method variance or other types of reporting bias
because most studies have relied on self-reported exposure information
(1).
Waldenström et al recently published a paper indicating a strong
association between hindrances and time pressure at work and depression
(2). This finding is important because assessment of psychosocial work
factors relied on external work content analysis, and therefore is
expected to be more objective and with a higher potential to guide
preventive measures by change of the environment rather than the
individuals’ psychological processing. We are concerned, however, whether
the new findings can be interpreted this way because Waldenström et al
previously reported that measures of psychological work characteristics
obtained by external work content analysis did not differ systematically
from measures based on self-reports in either distressed or non-distressed
individuals (3). This seems to indicate that the exposure information in
the Waldenström et al study was not independent of the individual worker’s
perception and appraisal of his or her working conditions and that the
risk estimates of depression may have been biased toward too high values.
External assessment relying on worker interviews may perhaps not be the
way forward to obtain unbiased psychosocial exposure data, even if study
participants are asked to be concrete and provide examples as they did in
the present study, as long as the information essentially is self-reported
and analyzed on an individual level. Aggregated, average exposure measures
obtained among colleagues with common working conditions, as suggested by
Frese and Zapf, have recently been introduced in risk factor studies of
depression and may be an alternative way forward (4;5).
REFERENCES
1. Bonde JP. Psychosocial factors at work and risk of depression: a
systematic review of the epidemiological evidence. Occup Environ Med 2008.
2. Waldenstrom K, Ahlberg G, Bergman P, Forsell Y, Stoetzer U,
Waldenstrom M et al. Externally assessed psychosocial work characteristics
and diagnoses of anxiety and depression. Occup Environ Med 2008; 65(2):90-
96.
3. Waldenstrom K, Lundberg I, Waldenstrom M, Harenstam A. Does
psychological distress influence reporting of demands and control at work?
Occup Environ Med 2003; 60(11):887-891.
4. Frese M, Zapf D. Methodological issues in the study of work
stress: Objective vs. subjective measurement of work stress and the
question of longitudinal studies. In: Cooper CL, Payne R, editors. Causes,
coping and consequences of stress at work. John Wiley & Sons Ltd.;
1988. 375-411.
5. Kouvonen A, Oksanen T, Vahtera J, Stafford M, Wilkinson R,
Schneider J et al. Low workplace social capital as a predictor of
depression: the Finnish Public Sector Study. Am J Epidemiol 2008;
167(10):1143-1151.
The letter from Drs Huff and Infante1 provides an opportunity to correct some misperceptions that have developed about the IARC Monographs. First, Huff and Infante call on IARC to make “appropriate adjustments” and “properly amend” the summaries for formaldehyde and other Monographs. It is important to understand that IARC does not change summaries, which are developed by independent Working Groups of scientists who conducted th...
The letter from Drs Huff and Infante1 provides an opportunity to correct some misperceptions that have developed about the IARC Monographs. First, Huff and Infante call on IARC to make “appropriate adjustments” and “properly amend” the summaries for formaldehyde and other Monographs. It is important to understand that IARC does not change summaries, which are developed by independent Working Groups of scientists who conducted the original research. This principle is meant to ensure confidence that IARC evaluations are free from the pressures that interested parties often use to influence public agencies.
A second point concerns the temporal relationship between the formaldehyde Monograph and IARC’s amended guidelines (the Preamble). The formaldehyde Working Group met and developed its conclusions in June 2004. The Preamble amendment process2 began in March 2005 and IARC posted the draft Preamble on its website for public comment from August to October 2005. Huff and Infante find fault that I wrote, “During 2005 IARC is updating the Preamble . . .”3 This statement appears in the proceedings of a September 2005 conference where I encouraged participants to examine the draft Preamble while the comment period was still open.
Third, Huff and Infante demand that “ALL exposure-associated tumour sites should be identified for ALL human carcinogens.” This is, in fact, done in the critical review portion of each Monograph, which discusses all tumour sites that have been studied and identifies all sites where increased risks were observed. The full list of sites is not obvious, however, because only the major findings appear in the short summary and evaluation sections and only these shorter sections have been available online. To increase public access to this information, IARC has begun making the full text of all Monographs freely available on its website (http://monographs.iarc.fr/). In the most recent formaldehyde Monograph,4 for example, the critical review identifies statistically significant associations for cancers of the lung, nasal cavity, nasopharynx, and hypopharynx; for lymphohaematopoietic cancer including myeloid leukaemia; for uveal melanoma and cancers of the brain and central nervous system, pancreas, salivary gland, rectum, and female breast; and for all cancers combined. After considering the epidemiological evidence overall, the Working Group highlighted in the short summary the strongest of these associations: nasopharyngeal cancer, leukaemia, and sinonasal cancer. Indeed, IARC is the first public agency to highlight the strong evidence associating formaldehyde with leukaemia.
A related question is whether to take a different approach and not to identify tumour sites at all in the final evaluation. The crux of the matter is whether to regard a list of tumour sites restrictively, as a finite number of sites where carcinogenesis is possible, or expansively, as examples where strong evidence exists at the time. IARC takes the expansive view and recognizes the likelihood that an agent may also cause cancer at other sites and by other mechanisms. For example, tobacco, first identified as a cause of lung cancer in smokers, has since been established to cause cancer at more than a dozen other sites and also in nonsmokers exposed to tobacco smoke.
Finally, Huff and Infante suggest that IARC should be re-evaluating probable and possible carcinogens during 2009 rather than continue its plan5 to review known human carcinogens (IARC Group 1) in Monograph Volume 100. A key objective of IARC’s plan for this volume, developed in collaboration with an international Advisory Group,6 is to elucidate mechanisms known to cause cancer in humans. IARC expects that future Monographs will use this information to identify additional carcinogens that act through similar mechanisms. In addition, epidemiologists can use mechanistic information to identify pre-cancerous biomarkers that can be measured long before tumours can be observed. We are convinced that taking this year to bring together information about mechanisms known to cause cancer will promote earlier identification of carcinogens in the future, including new chemicals and complex exposures that have not or cannot be studied by epidemiology. This is better than waiting decades for studies to document avoidable cancers in humans and would be a great achievement for workers and public health.
VJ Cogliano
Head, IARC Monographs Programme
International Agency for Research on Cancer, Lyon, France
Competing interests: None declared
REFERENCES
1. Huff J, Infante P. Identifying cancer sites for human carcinogens in the IARC monographs. Occup Environ Med 2009;66:140.
2. Preamble amendment process. http://monographs.iarc.fr/ENG/Preamble/amendments.php (accessed January 2009).
3. Cogliano VJ. Use of carcinogenicity bioassays in the IARC Monographs. Ann N Y Acad Sci 2006:1076:592–600.
4. Formaldehyde. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol 88, Formaldehyde, 2-Butoxyethanol and 1-tert-Butoxypropan-2-ol. Lyon France: International Agency for Research on Cancer, 2006;39–325. http://monographs.iarc.fr/ENG/Monographs/PDFs/index.php (accessed January 2009).
5. Future Meetings. http://monographs.iarc.fr/ENG/Meetings/index.php (accessed January 2009).
6. Report of the Advisory Group to Plan Volume 100: A Review of Human Carcinogens. Lyon France: International Agency for Research on Cancer, 2007, IARC Int Rpt 07/001. http://monographs.iarc.fr/ENG/Publications/internrep/07-001.pdf (accessed January 2009).
Editor’s Note: When we receive letters commenting on material published in OEM, it is our policy to allow the original authors an opportunity to see those letters in advance of publication and, if they wish, to respond to them in a letter published simultaneously. We failed to do this with the letter submitted by Drs. Huff and Infante. We apologize for this error. Dr. Cogliano’s response appears on this page.
We are writing to respond to Dr.Kalman in regard to our recent
article entitled Maternal Occupational Exposure and Risk of Spontaneous
Abortion in Veterinary Practice.
Dr. Kalman believes that he has picked up an anomaly in the
presentation of data on radiation. We would like to reassure readers of
the journal that there is no anomaly in the presentation of data and all
presented results including radiation...
We are writing to respond to Dr.Kalman in regard to our recent
article entitled Maternal Occupational Exposure and Risk of Spontaneous
Abortion in Veterinary Practice.
Dr. Kalman believes that he has picked up an anomaly in the
presentation of data on radiation. We would like to reassure readers of
the journal that there is no anomaly in the presentation of data and all
presented results including radiation are correct. The presented results
for radiation in Table 2 are the crude risks. The presented results in
abstract are derived from Table 3 which indicates adjusted relative risks.
In Table 1 the radiation exposure has been categorized into three levels
of exposures (No exposure, 1-5 films/w, >5 films/w). The crude
relative risk for radiation exposure from Table 1 indicated that taking 1
to 5 films did not have any adverse outcome which has been mentioned in
the results section, paragraph 4, column 2, page 2. Therefore, in Table 3
to estimate adjusted relative risks using logistic regression, we combined
the first two exposure categories (No exposure and 1-5 films/w) as the
reference group (less than 5 films/w) and (more than 5 films/w) as the
exposure variable. A similar grouping has been used in another study in
female veterinarians with similar results (Reference No.5). So we have
not eliminated the unexposed group from logistic regression analysis as
postulated by Dr. Kalman. Furthermore, in Table 1, if we combine the
first two exposure categories in one group (as the reference group), we
will also see an increased risk of spontaneous abortion in those who
exposed to radiation for more than 5 films per week compared with those
who performed 5 or less films including unexposed group (crudeRR:1.38,
95%CI:0.94, 2.04 ).
Dr. Kalman also raises the issue that there are no measurements
presented for the dose of radiation. Our study was a questionnaire-based
study, and unfortunately we were not funded to obtain actual measurements.
In the absence of measurements, we used the self-report of the number of X
-rays taken as a proxy for dose. In some ways, this may have been a
better measurement of the number of X-rays undertaken at the time of
pregnancy as it would be virtually impossible to obtain measurements for
what may have been a different job many years previously.
Ionising radiation at high doses is historically known to be
embryotoxic and teratogenic. Therefore, we suggest that it is always wise
to continue to inform female (and male) veterinarians of the potential
risks in this profession.
On the basis of a retrospective mortality study Mastrangelo and his
co-workers (Occup Environ Med 2008; 65: 697-700) concluded that “a high
and prolonged exposure to cotton dust and other endotoxin-containing
organic dusts was related to a lower risk of lung cancer”. The paper
looked at the cancer risk, especially on lung cancer, among cotton mill
workers by using the Standard Mortality Ratio (SMR). We believe that
meth...
On the basis of a retrospective mortality study Mastrangelo and his
co-workers (Occup Environ Med 2008; 65: 697-700) concluded that “a high
and prolonged exposure to cotton dust and other endotoxin-containing
organic dusts was related to a lower risk of lung cancer”. The paper
looked at the cancer risk, especially on lung cancer, among cotton mill
workers by using the Standard Mortality Ratio (SMR). We believe that
methodological limitation inherent in this study makes that conclusion
unpersuasive.
The proportion mortality study is utilized well to analyze the effect
of drug on the prognosis of some disease, for example, the preventive
effect of aspirin on CVD death by comparison between aspirin users and non
-users among patients. However, the mortality study is not suitable for
causal analyses of diseases because the proportion of dead cases due to
some disease, such as lung cancer in Mastrangelo’s study, has been thought
to be a deceiving measure of occurrence for the disease, when it is not an
acute fatal illness. Giving a cancer due to a causal exposure, the
proportion of survivals among all cancer cases in index cohort will depend
on cancer stage at diagnosis, the general health of patients, etc. and
could be bigger or smaller than that of dead cases, and so may be among
reference cohorts. This situation will be the key variant that determines
the deviation of results. However, it is difficult to speculate in which
direction the study results might have been biased because the magnitude
of proportion of survivors is virtually unknown.
Based on the results of Mastrangelo’s study, We think, the conclusion
should be “a high and prolonged exposure to cotton dust and other
endotoxin-containing organic dusts was associated with a lower risk of
lung cancer mortality, and due to uncontrolled confounding other risk
factors for lung cancer death could not be ruled out as a contributor to
the association.”
Shirangi and her colleagues set out to examine the relationship
between occupational exposures and spontaneous abortion in female
veterinarians. One exposure examined, is in relation to the use of x-
rays, where the authors report in the abstract that veterinarians who
reported performing more than 5 radiographic examinations per week had a
statistically significant elevated risk of spontaneous abortion compared
with th...
Shirangi and her colleagues set out to examine the relationship
between occupational exposures and spontaneous abortion in female
veterinarians. One exposure examined, is in relation to the use of x-
rays, where the authors report in the abstract that veterinarians who
reported performing more than 5 radiographic examinations per week had a
statistically significant elevated risk of spontaneous abortion compared
with those performing 5 or less (OR 1.82, 95% CL 1.17:2.82). This leads
onto a conclusion that female veterinarians should be fully informed of
the possible reproductive effects of ionising radiation.
Looking at the text of the article, the authors reference that
spontaneous abortion has been linked to occupational exposure to
radiation, although their consideration is limited to studies of female
veterinarians and there is no mention of the large amount of occupational
data on radiation workers, or radiobiology in terms of deterministic or
stochastic effects. In relation to the study design, there is no
consideration of measured radiation dose or radiation protection practice,
with consideration limited to the crude division of 3 classes of practice:
those not exposed to x-rays at all, those indicating between one and 5
films per week, and those undertaking more than 5 films.
Interestingly, although not commented upon in the text, it appears
that there is a statistically significant reduction in relative risk from
those not exposed at all, for those undertaking one to 5 films (0.57 (0.40
to 0.79)). The risk for over 5 films is also less than that for no
exposure, although this does not reach to statistical significance. Given
a situation where it is clear that there is a higher crude risk of
spontaneous abortion amongst the unexposed than the exposed, one much
question why further analysis in terms of the logistic regression was
undertaken, and how such further analysis revealed the stated result. The
first question must be one for the authors, although the answer to the
second appears to be based on the elimination of the unexposed group from
the subsequent analysis. Table 3 indicates only 2 exposure categories,
namely 5 or less films, or over 5 films per week.
Those providing Occupational Health support to radiation workers in
the UK were in the forefront of establishing ethical standards for the
provision of prepublication information to workers on the results of
studies which they participated in. Shirangi and her colleagues do not
report their arrangements for providing such information. It is however
difficult to understand how a cohort of workers of the intelligence and
training of female veterinarians would not have picked up this apparent
anomaly in the data at worker briefing sessions.
Numerous studies have documented that perception of adverse psychosocial factors at work is related to major depression, but we still do not know if this reflects causal characteristics of the working environment, personal characteristics of the individual worker, trivial associations, common method variance or other types of reporting bias because most studies have relied on self-reported exposure information (1)....
We are writing to respond to Dr.Kalman in regard to our recent article entitled Maternal Occupational Exposure and Risk of Spontaneous Abortion in Veterinary Practice.
Dr. Kalman believes that he has picked up an anomaly in the presentation of data on radiation. We would like to reassure readers of the journal that there is no anomaly in the presentation of data and all presented results including radiation...
On the basis of a retrospective mortality study Mastrangelo and his co-workers (Occup Environ Med 2008; 65: 697-700) concluded that “a high and prolonged exposure to cotton dust and other endotoxin-containing organic dusts was related to a lower risk of lung cancer”. The paper looked at the cancer risk, especially on lung cancer, among cotton mill workers by using the Standard Mortality Ratio (SMR). We believe that meth...
Shirangi and her colleagues set out to examine the relationship between occupational exposures and spontaneous abortion in female veterinarians. One exposure examined, is in relation to the use of x- rays, where the authors report in the abstract that veterinarians who reported performing more than 5 radiographic examinations per week had a statistically significant elevated risk of spontaneous abortion compared with th...
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