232 e-Letters


    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...

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  • Coal and quartz

    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...

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  • Are we underestimating the prevalence of silicosis in the stone benchtop industry in New South Wales, Australia?

    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...

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  • RE: The ghost of methods past: exposure assessment versus job-exposure matrix studies
    Parveen Bhatti

    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...

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  • Excess additive risk of cataract incidence in radiologic technologists: alternative explanation

    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...

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  • Mental ill health in workers: observations from a few Indian populations
    Nilamadhab Kar

    Dear Editor

    The article titled mental ill health and fitness for work [1] by Glozier has focused on work related mental ill health issues and has discussed various topics like screening, safety and legal issues. However as the work environments differ considering bio-psycho-social factors and different levels of exposure, which are known to increase the vulnerability for the psychiatric disorder in the workers [2] it w...

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  • Are personal and static samples related?
    John H. Lange

    Dear Editor

    The article by Harrison and colleagues’[1] reports on a relationship between personal and static microenvironment air sampling for carbon monoxide and nitrogen dioxide and for PM10 which include the addition "of a personal cloud increment." Static sampling is also commonly referred to as area or stationary sampling.[2,3] These relationships are important because static sampling is more easily achieved th...

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  • Comments on article by Harrison et al and editorial by Cherrie
    Hans Kromhout

    Dear Editor

    The paper by Harrison et al.[1] and the accompanying editorial by Cherrie [2] address the important issue of personal exposure assessment (of air pollutants) in environmental epidemiology. After reading both papers we would like to make some comments with regard to the design, conduct and statistical analysis of the study by Harrison et al. and at the same time answer the question raised by...

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  • Response to Letter by Kromhout and van Tongeren
    Roy M. Harrison

    Dear Editor

    In commenting on our paper published recently in OEM,[1] Kromhout and van Tongeren admonish us for paying insufficient attention to the earlier literature on occupational pollutant exposures. Whilst no doubt an element of their criticism is justified, we feel that the exposure situation for the general public is sufficiently different that it should not be assumed that findings in the occupational...

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  • Reporting of occupational and environmental research
    Dana Loomis

    Rushton's recent article on the reporting of occupational and environmental research raises a number of useful points that all researchers would do well to remember when writing up epidemiological findings for publication. Without expressly intending to do so, however, the article also emphasizes the hazards of establishing formal criteria or checklists for the evaluation of scientific work. Good epi...

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