With interest we read the article by Gustavsson and colleagues [1] on the breast cancer risk in a cohort with night work. The authors started from two facts: First, “night shift work” [2] was classified as “probably carcinogenic to humans” (Group 2A) by the International Agency for Research on Cancer [IARC]; second, the evidence in humans was considered limited because of variable results and potential bias. Since prior studies had problems regarding exposure assessment, Gustavsson et al. emphasized their very detailed registry-based data on night work. Yet, as key result the authors noted that “conclusions are limited due to a short period of follow-up and lack of information of night work before 2008”. Thus, this study perpetuates limited epidemiological evidence for the carcinogenicity of night work. Although the limited data on shift work is a drawback of this study, it is not the only limitation. We would like to discuss a conceptual problem that may have contributed to the limited conclusions and that the authors did not address.
The IARC monograph mentions chronotype and sleep 73 and 199 times, respectively [2]. Chronotype tells us when persons prefer sleep or work and activity. Potentially harmful circadian disruption (CD) [3] can occur at any time over 24 hours when activities or sleep are misaligned with the chronotype-associated biological nights [3 4] or biological days. This leads to occupational and non-occupational CD [5]. Possible effects of not c...
With interest we read the article by Gustavsson and colleagues [1] on the breast cancer risk in a cohort with night work. The authors started from two facts: First, “night shift work” [2] was classified as “probably carcinogenic to humans” (Group 2A) by the International Agency for Research on Cancer [IARC]; second, the evidence in humans was considered limited because of variable results and potential bias. Since prior studies had problems regarding exposure assessment, Gustavsson et al. emphasized their very detailed registry-based data on night work. Yet, as key result the authors noted that “conclusions are limited due to a short period of follow-up and lack of information of night work before 2008”. Thus, this study perpetuates limited epidemiological evidence for the carcinogenicity of night work. Although the limited data on shift work is a drawback of this study, it is not the only limitation. We would like to discuss a conceptual problem that may have contributed to the limited conclusions and that the authors did not address.
The IARC monograph mentions chronotype and sleep 73 and 199 times, respectively [2]. Chronotype tells us when persons prefer sleep or work and activity. Potentially harmful circadian disruption (CD) [3] can occur at any time over 24 hours when activities or sleep are misaligned with the chronotype-associated biological nights [3 4] or biological days. This leads to occupational and non-occupational CD [5]. Possible effects of not considering all contributions from such ubiquitous exposures have been exemplified: 1950 landmark data “scenarios” with workplace- and non-workplace smoking evinced that neither the magnitude nor the direction (!) of estimated cancer risks would have been correct if exposures off work had been ignored [6].
Thus, why not use a comprehensive dose concept to capture CD, as we regularly do in occupational epidemiology? We can assess cumulative CD as time-dependent long-term dose [7 8] by determining how much of each study participants’ biological night does not overlap with individual sleep time, and this would capture exposures to CD both at and off work. Scandinavian countries with their excellent databases may provide the data for time-related analytical procedures [9 10] needed for this integrated dose epidemiology.
Overall, such circadian epidemiology may help to avoid conclusions such as “Most exposure metrics showed no association with breast cancer risk” [1]. Combining the methodological rigor of occupational epidemiology with insights from chronobiology may shed light on plausible relationships between ubiquitous sources of CD and disease, including cancer.
REFERENCES
1 Gustavsson P, Bigert C, Andersson T, et al. Night work and breast cancer risk in a cohort of female healthcare employees in Stockholm, Sweden. Occup Environ Med 2023;80(7):372-76. doi: 10.1136/oemed-2022-108673
2 IARC. Carcinogenicity of night shift work. Lancet Oncol 2019;20(8):1058-59. doi: 10.1016/S1470-2045(19)30455-3
3 IARC. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Volume 98. Painting, Firefighting and Shiftwork. Lyon, France., 2010.
4 Erren TC, Gross JV, Fritschi L. Focusing on the biological night: towards an epidemiological measure of circadian disruption. Occup Environ Med 2017;74(3):159-60. doi: 10.1136/oemed-2016-104056
5 Erren TC, Lewis P. Hypothesis: ubiquitous circadian disruption can cause cancer. Eur J Epidemiol 2019;34(1):1-4. doi: 10.1007/s10654-018-0469-6
6 Erren TC, Lewis P, Morfeld P. The riddle of shiftwork and disturbed chronobiology: a case study of landmark smoking data demonstrates fallacies of not considering the ubiquity of an exposure. J Occup Med Toxicol 2020;15:10. doi: 10.1186/s12995-020-00263-2
7 Erren TC, Morfeld P. Shift work and cancer research: a thought experiment into a potential chronobiological fallacy of past and perspectives for future epidemiological studies. Neuro Endocrinol Lett 2013;34(4):282-6.
8 Morfeld P, Erren, T.C. Shift Work, Chronotype, and Cancer Risk-Letter. Cancer Epidemiology, Biomarkers & Prevention 2019
9 Rothman KJ, Greenland, S., Lash, T.L. Modern epidemiology 3rd ed.: Philadelphia: Lippincott Williams & Wilkins 2008.
10 Robins J. The control of confounding by intermediate variables. Statistics in medicine 1989;8(6):679-701. doi: 10.1002/sim.4780080608
The paper by Go et al (Occup Environ Med 2023;80425-30) is an important reminder of the problem of quartz in coal mine dusts and of its association with early development of pneumoconiosis, often associated with unusual radiological patterns. The UK work which they kindly cite brought to light a problem for regulation of the quartz in coal mine dust – that in many cases quartz concentrations greater than 0.1mg/m3 in mine environments seemed not to be associated with development of silicosis. Experimentally, the toxicity of quartz is reduced when it is associated, as is usual in coal mines, with a high concentration of other silicates, which occlude the crystal surface. This led to the pragmatic solution of ignoring quartz if it constituted less than 10% of the total mine dust concentration (which then was regulated as less than 5mg/m3).
These difficulties in setting and monitoring compliance with a quartz standard in coal mines are obsolete in UK as long as mines remain closed. However, while mining continues elsewhere it is important to recognise that miners know when they are cutting rock and so do their employers. When this is happening it should be recognised that they are at risk of silicosis and, as the authors show, the implications are far more serious for their health than those from coal alone; any early radiological evidence is usually too late for the miners and extra action to increase their safety needs to be required of the employer in these circumstan...
The paper by Go et al (Occup Environ Med 2023;80425-30) is an important reminder of the problem of quartz in coal mine dusts and of its association with early development of pneumoconiosis, often associated with unusual radiological patterns. The UK work which they kindly cite brought to light a problem for regulation of the quartz in coal mine dust – that in many cases quartz concentrations greater than 0.1mg/m3 in mine environments seemed not to be associated with development of silicosis. Experimentally, the toxicity of quartz is reduced when it is associated, as is usual in coal mines, with a high concentration of other silicates, which occlude the crystal surface. This led to the pragmatic solution of ignoring quartz if it constituted less than 10% of the total mine dust concentration (which then was regulated as less than 5mg/m3).
These difficulties in setting and monitoring compliance with a quartz standard in coal mines are obsolete in UK as long as mines remain closed. However, while mining continues elsewhere it is important to recognise that miners know when they are cutting rock and so do their employers. When this is happening it should be recognised that they are at risk of silicosis and, as the authors show, the implications are far more serious for their health than those from coal alone; any early radiological evidence is usually too late for the miners and extra action to increase their safety needs to be required of the employer in these circumstances.
Anthony Seaton
This study reports an alarming prevalence of silicosis in Victoria, Australia at 28.2% among workers in the stone benchtop industry (SBI). [1] That prevalence is higher than reported in SBI workers in another Australian state of Queensland (22.7%). [4] The Victorian silicosis screening program reported respiratory function tests and chest x-rays to be of limited value in screening this high-risk population which has significant implications for health and safety policy. It also calls into question the adequacy of current screening programs in other Australian States and Territories.
In the adjoining state of New South Wales (NSW), Australia, there has been an obligation on the health and safety regulator (SafeWork NSW) to maintain a Dust Diseases Register and to provide a report on the Register at the end of each financial year since October 2020. This information is provided and published in the NSW Dust Disease Register Annual Report. However, no information is provided on the total number of workers screened (or the denominator) to enable understanding of the incidence and prevalence of silicosis in NSW.
A desk-based “case finding” study from May 2021 in NSW estimated the average incidence (new cases) of silicosis among engineered stone workers in NSW at between 4% and 9% for the three-year reporting period, and suggested that incidence values may also be considered as the estimated prevalence within SBI workers. [3] This prevalence estimate is significant...
This study reports an alarming prevalence of silicosis in Victoria, Australia at 28.2% among workers in the stone benchtop industry (SBI). [1] That prevalence is higher than reported in SBI workers in another Australian state of Queensland (22.7%). [4] The Victorian silicosis screening program reported respiratory function tests and chest x-rays to be of limited value in screening this high-risk population which has significant implications for health and safety policy. It also calls into question the adequacy of current screening programs in other Australian States and Territories.
In the adjoining state of New South Wales (NSW), Australia, there has been an obligation on the health and safety regulator (SafeWork NSW) to maintain a Dust Diseases Register and to provide a report on the Register at the end of each financial year since October 2020. This information is provided and published in the NSW Dust Disease Register Annual Report. However, no information is provided on the total number of workers screened (or the denominator) to enable understanding of the incidence and prevalence of silicosis in NSW.
A desk-based “case finding” study from May 2021 in NSW estimated the average incidence (new cases) of silicosis among engineered stone workers in NSW at between 4% and 9% for the three-year reporting period, and suggested that incidence values may also be considered as the estimated prevalence within SBI workers. [3] This prevalence estimate is significantly lower than that reported in the neighbouring states.
In late 2022, a member of the NSW Parliament requested documents relating to information held by Insurance and Care NSW (icare) for its silicosis screening program under Standing Order 52 (SO52). [5] This resulted in information becoming publicly available, including the documents created since 1 January 2020 relating to the NSW silicosis screening program. [6] Contained in these documents was data on the number of people screened from specific industries (including engineered stone), the number of cases reported, and information on screening methods used. That information was reviewed with regard to silicosis prevalence in the NSW SBI and compared the figures with the findings of that reported in the neighbouring states of Victoria and Queensland.
The SO52 information confirmed a prevalence of silica related diseases (SRD) of only 7% in NSW SBI workers. This prevalence represents approximately 25% of that reported by adjoining states for the same period. [1] This low reported prevalence in NSW is more likely to reflect differences in respiratory surveillance methods between NSW and neighbouring states rather than a difference in SRD statistics and health protection. For example, CT scans were offered to workers as part of the NSW icare health screening program, but were only used for 18.8% of NSW workers. [6] CT scans are more sensitive in comparison to chest x rays in detecting early disease, and reliance of x-ray may have influenced the NSW results. It should also be noted that in NSW, although it is mandatory for workers in the SBI to be screened, it is not mandatory for employers to use icare services, and private contractors can be employed. This can result in a statistical bias because there is no mandatory reporting for results to the NSW silicosis registry in the absence of diagnosed disease. This is despite recommendations having been made by the Thoracic Society of Australia and New Zealand (TSANZ) in 2020; [7] and as part of the review into the Dust Diseases Scheme in 2019 to include this data, along with the standardisation of health assessment method. [8]
The findings of the Victorian screening program confirmed that relying on symptoms, spirometry screening or chest X-ray will miss many cases of silicosis and silica-related disorders, and that the prevalence of silicosis and SRDIs in the SBI in Australia is shockingly high. [1] If the prevalence in NSW is truly closer to that reported in Queensland and Victoria (between 22 and 28%), then more than 400 cases of SRDIs are expected based on the numbers of workers screened by icare. This would represent a shortfall of over 200 undiagnosed workers in NSW that may not be receiving essential care and support. It seems likely that cases in NSW are being underestimated.
Existing systems for the discovery and reporting of SRDI cases need urgent updating. More comprehensive and accurate data is urgently needed on the prevalence of SRDI’s in NSW to better inform health policy and prevention efforts; and to reduce the burden of preventable disease on these workers and their families.
References
1. Hoy, R.F., et al., Prevalence and risk factors for silicosis among a large cohort of stone benchtop industry workers. Occupational and Environmental Medicine, 2023: p. oemed-2023-108892.
2. SafeWork NSW, NSW Dust Disease Register Annual Report 2020-21. 2021.
3. Golder Associates Pty Ltd, Case Finding Study - Respirable crystalline silica exposure in the NSW manufactured stone industry. 2021.
4. WorkSafe Queensland. Silicosis - Workcover Screening Outcomes. . 2022 [cited 2023 23 June]; Available from: https://www.worksafe.qld.gov.au/claims-and-insurance/work-related-injuri....
5. Parliament of New South Wales, Legislative Council Minutes No. 149. 2022. Available from: https://www.parliament.nsw.gov.au/tp/files/83469/Resolution - SafeWork NSW and Insurance and Care NSW (icare) - 16 November 2022.pdf
6. Department of Premier and Cabinet, Order for Papers - Supplementary Return - SafeWork NSW and Insurance and Care NSW (icare). 2023.Available from: https://www.parliament.nsw.gov.au/tp/files/83926/SO52%20Index%20-%20Supp...(icare)%20-%2012.01.2023.pdf
7. Perret, J.L., et al., Respiratory surveillance for coal mine dust and artificial stone exposed workers in Australia and New Zealand: A position statement from the Thoracic Society of Australia and New Zealand*. Respirology, 2020. 25(11): p. 1193-1202.
8. Justice, S.C.o.L.a., 2019 Review of the Dust Diseases Scheme Silicosis in the manufactured stone industry. 2020. Available from: https://www.parliament.nsw.gov.au/lcdocs/inquiries/2538/Report%2073%20%E...
Dr. Burstyn, in his commentary (1), underscores the critical
importance of using the best exposure assessment methods possible to
minimize misclassification. We agree about the value of expert formulated
models for systematically and transparently documenting exposure
assessment1, but caution that many existing studies may not be readily
adapted to such model building. For such studies, the best alternative
exposure ass...
Dr. Burstyn, in his commentary (1), underscores the critical
importance of using the best exposure assessment methods possible to
minimize misclassification. We agree about the value of expert formulated
models for systematically and transparently documenting exposure
assessment1, but caution that many existing studies may not be readily
adapted to such model building. For such studies, the best alternative
exposure assessment methodology should be employed, such as job-exposure
matrices (JEMs) or expert assessments of self-reported work histories.
Even though the relationships between the true exposure and estimates by
expert assessment and a JEM are unknown (which is the case for most
exposure assessments) we believe that understanding the differences
between the two methods is informative, especially given the considerable
time and resources necessary to carry out an expert assessment.
As Dr. Burstyn indicates (1), neither assessment approach used in our
study (2) allows us to claim that lead definitely causes brain tumors.
However, if this is the standard for judging the success of an exposure
assessment method, most methods are failures. Although only suggestive, we
do see some evidence of an association and indicate that future studies
would benefit from the most accurate exposure assessment method available.
The intent of our analysis was to compare two widely used approaches and
to encourage epidemiologists to pursue the best exposure assessment
methods possible. We acknowledge limitations with the expert assessment
approach and strongly support the development and use of new exposure
assessment methods. However, expert assessment may be the best approach
available to an existing study and could reveal important associations
that future studies can explore in greater detail using more refined
exposure assessment techniques.
1. Burstyn I. The ghost of methods past: exposure assessment versus
job-exposure matrix studies. Occup Environ Med 2010.
2. Bhatti P, Stewart PA, Linet MS, Blair A, Inskip PD, Rajaraman P.
Comparison of occupational exposure assessment methods in a case-control
study of lead, genetic susceptibility and risk of adult brain tumours.
Occup Environ Med 2010.
Dose-dependent diagnostic efficiency and self-reporting related to a longer work history and hence to cumulative dose could explain the above-average risk of cataracts in radiologic technologists [1]. Of concern was the discrepancy between the findings for cataract history and cataract surgery, where risks for the latter were somewhat lower and generally not significant [1]. A similar pattern of significant excess relative risk (ERR) for cataract and non-significant ERR for cataract surgery has also been reported in the Mayak nuclear workers. [2,3]. This agrees with the concept of dose-dependent diagnostic efficiency with detection of mild cases not requiring surgery. Among the various groups that have been studied for radiation-associated cataract, a significant ERR for cataract surgery has been reported only in the Japanese atomic bomb survivors [4-6], where the effect of the acute exposure could indeed have taken place. More details [7].
1. Little MP, Cahoon EK, Kitahara CM, Simon SL, Hamada N, Linet MS. Occupational radiation exposure and excess additive risk of cataract incidence in a cohort of US radiologic technologists. Occup Environ Med. 2020 Jan;77(1):1-8. doi: 10.1136/oemed-2019-105902.
2. Azizova TV , Hamada N , Grigoryeva ES , et al. . Risk of various types of cataracts in a cohort of Mayak workers following chronic occupational exposure to ionizing radiation. Eur J Epidemiol2018;33:1193–204.doi:10.1007/s10654-018-0450-4
3. Azizova TV , Hamad...
Dose-dependent diagnostic efficiency and self-reporting related to a longer work history and hence to cumulative dose could explain the above-average risk of cataracts in radiologic technologists [1]. Of concern was the discrepancy between the findings for cataract history and cataract surgery, where risks for the latter were somewhat lower and generally not significant [1]. A similar pattern of significant excess relative risk (ERR) for cataract and non-significant ERR for cataract surgery has also been reported in the Mayak nuclear workers. [2,3]. This agrees with the concept of dose-dependent diagnostic efficiency with detection of mild cases not requiring surgery. Among the various groups that have been studied for radiation-associated cataract, a significant ERR for cataract surgery has been reported only in the Japanese atomic bomb survivors [4-6], where the effect of the acute exposure could indeed have taken place. More details [7].
1. Little MP, Cahoon EK, Kitahara CM, Simon SL, Hamada N, Linet MS. Occupational radiation exposure and excess additive risk of cataract incidence in a cohort of US radiologic technologists. Occup Environ Med. 2020 Jan;77(1):1-8. doi: 10.1136/oemed-2019-105902.
2. Azizova TV , Hamada N , Grigoryeva ES , et al. . Risk of various types of cataracts in a cohort of Mayak workers following chronic occupational exposure to ionizing radiation. Eur J Epidemiol2018;33:1193–204.doi:10.1007/s10654-018-0450-4
3. Azizova TV , Hamada N , Bragin EV , et al . Risk of cataract removal surgery in Mayak PA workers occupationally exposed to ionizing radiation over prolonged periods. Radiat Environ Biophys2019;58:139–49.doi:10.1007/s00411-019-00787-0
4. Neriishi K , Nakashima E , Akahoshi M , et al . Radiation dose and cataract surgery incidence in atomic bomb survivors, 1986–2005. Radiology2012;265:167–74.doi:10.1148/radiol.12111947 CrossRefPubMedWeb of ScienceGoogle Scholar
5. Little MP. A review of non-cancer effects, especially circulatory and ocular diseases. Radiat Environ Biophys 2013;52:435–49. doi:10.1007/s00411-013-0484-7
6. Shore RE . Radiation and cataract risk: impact of recent epidemiologic studies on ICRP judgments. Mutation Research/Reviews in Mutation Research 2016;770:231–7.doi:10.1016/j.mrrev.2016.06.006
7. Jargin SV. Chapter 3. Overestimation of Medical Consequences of Radioactive Contaminations in the Former Soviet Union. Advances in Environmental Research. Vol. 83. Nova Science Publishers, Inc., 2021. DOI: https://doi.org/10.52305/BPZX5742
With interest we read the article by Gustavsson and colleagues [1] on the breast cancer risk in a cohort with night work. The authors started from two facts: First, “night shift work” [2] was classified as “probably carcinogenic to humans” (Group 2A) by the International Agency for Research on Cancer [IARC]; second, the evidence in humans was considered limited because of variable results and potential bias. Since prior studies had problems regarding exposure assessment, Gustavsson et al. emphasized their very detailed registry-based data on night work. Yet, as key result the authors noted that “conclusions are limited due to a short period of follow-up and lack of information of night work before 2008”. Thus, this study perpetuates limited epidemiological evidence for the carcinogenicity of night work. Although the limited data on shift work is a drawback of this study, it is not the only limitation. We would like to discuss a conceptual problem that may have contributed to the limited conclusions and that the authors did not address.
Show MoreThe IARC monograph mentions chronotype and sleep 73 and 199 times, respectively [2]. Chronotype tells us when persons prefer sleep or work and activity. Potentially harmful circadian disruption (CD) [3] can occur at any time over 24 hours when activities or sleep are misaligned with the chronotype-associated biological nights [3 4] or biological days. This leads to occupational and non-occupational CD [5]. Possible effects of not c...
The paper by Go et al (Occup Environ Med 2023;80425-30) is an important reminder of the problem of quartz in coal mine dusts and of its association with early development of pneumoconiosis, often associated with unusual radiological patterns. The UK work which they kindly cite brought to light a problem for regulation of the quartz in coal mine dust – that in many cases quartz concentrations greater than 0.1mg/m3 in mine environments seemed not to be associated with development of silicosis. Experimentally, the toxicity of quartz is reduced when it is associated, as is usual in coal mines, with a high concentration of other silicates, which occlude the crystal surface. This led to the pragmatic solution of ignoring quartz if it constituted less than 10% of the total mine dust concentration (which then was regulated as less than 5mg/m3).
Show MoreThese difficulties in setting and monitoring compliance with a quartz standard in coal mines are obsolete in UK as long as mines remain closed. However, while mining continues elsewhere it is important to recognise that miners know when they are cutting rock and so do their employers. When this is happening it should be recognised that they are at risk of silicosis and, as the authors show, the implications are far more serious for their health than those from coal alone; any early radiological evidence is usually too late for the miners and extra action to increase their safety needs to be required of the employer in these circumstan...
This study reports an alarming prevalence of silicosis in Victoria, Australia at 28.2% among workers in the stone benchtop industry (SBI). [1] That prevalence is higher than reported in SBI workers in another Australian state of Queensland (22.7%). [4] The Victorian silicosis screening program reported respiratory function tests and chest x-rays to be of limited value in screening this high-risk population which has significant implications for health and safety policy. It also calls into question the adequacy of current screening programs in other Australian States and Territories.
In the adjoining state of New South Wales (NSW), Australia, there has been an obligation on the health and safety regulator (SafeWork NSW) to maintain a Dust Diseases Register and to provide a report on the Register at the end of each financial year since October 2020. This information is provided and published in the NSW Dust Disease Register Annual Report. However, no information is provided on the total number of workers screened (or the denominator) to enable understanding of the incidence and prevalence of silicosis in NSW.
A desk-based “case finding” study from May 2021 in NSW estimated the average incidence (new cases) of silicosis among engineered stone workers in NSW at between 4% and 9% for the three-year reporting period, and suggested that incidence values may also be considered as the estimated prevalence within SBI workers. [3] This prevalence estimate is significant...
Show MoreDr. Burstyn, in his commentary (1), underscores the critical importance of using the best exposure assessment methods possible to minimize misclassification. We agree about the value of expert formulated models for systematically and transparently documenting exposure assessment1, but caution that many existing studies may not be readily adapted to such model building. For such studies, the best alternative exposure ass...
Dose-dependent diagnostic efficiency and self-reporting related to a longer work history and hence to cumulative dose could explain the above-average risk of cataracts in radiologic technologists [1]. Of concern was the discrepancy between the findings for cataract history and cataract surgery, where risks for the latter were somewhat lower and generally not significant [1]. A similar pattern of significant excess relative risk (ERR) for cataract and non-significant ERR for cataract surgery has also been reported in the Mayak nuclear workers. [2,3]. This agrees with the concept of dose-dependent diagnostic efficiency with detection of mild cases not requiring surgery. Among the various groups that have been studied for radiation-associated cataract, a significant ERR for cataract surgery has been reported only in the Japanese atomic bomb survivors [4-6], where the effect of the acute exposure could indeed have taken place. More details [7].
Show More1. Little MP, Cahoon EK, Kitahara CM, Simon SL, Hamada N, Linet MS. Occupational radiation exposure and excess additive risk of cataract incidence in a cohort of US radiologic technologists. Occup Environ Med. 2020 Jan;77(1):1-8. doi: 10.1136/oemed-2019-105902.
2. Azizova TV , Hamada N , Grigoryeva ES , et al. . Risk of various types of cataracts in a cohort of Mayak workers following chronic occupational exposure to ionizing radiation. Eur J Epidemiol2018;33:1193–204.doi:10.1007/s10654-018-0450-4
3. Azizova TV , Hamad...