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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  • 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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  • Re: Occupational Asthma guidelines: a systematic quality appraisal using the AGREE II instrument. Authors' response
    Theodore Lytras

    We thank Dr. Nicholson and Prof. Cullinan for their interest in our paper,[1] and welcome the opportunity to respond to their comments and provide clarification.

    We did review the most up-to-date version of all guidelines, including the 2010 version of the BOHRF guidelines. In the "Results" section of our paper, the first column of Table 1 cites the most recent guideline versions published in the peer-reviewed...

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  • Corrections on Asthma Guidelines review
    Paul J Nicholson

    We write to correct errors in the paper Occupational asthma guidelines: a systematic quality appraisal using the AGREE II instrument 1.

    The methodology for this study states that the authors reviewed the most up to date versions of guidelines. While in their Introduction the authors cite (their reference 9) a statement from the 2010 BOHRF systematic review 2; within the Results section it is clear that they a...

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  • Lung cancer risk in coal miners: The need for further investigations
    Judith M Graber

    We thank Dr. Morfeld for his comments on our updated mortality study of the U.S. coal miners study.[1] However, we disagree with his assertion that the excess of lung cancer we observed must be attributed to smoking alone. Firstly, despite the smoking prevalence being higher in our cohort than in the U.S. population in 1970, smokers in our population were significantly less likely to be heavy smokers (> 24 cigarettes...

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  • Lung cancer excess risks after coal mine dust exposure?
    Peter Morfeld

    Dear Editor,

    I read with interest about the updated US coalminer mortality study[1]. The lung cancer SMR was slightly elevated (SMR=1.08, 95% CI: 1.00-1.18). This excess is unexceptionable because of a higher proportion of smokers at the start of follow-up in 1969/1971 (current smokers: 54%) in comparison to the US male population in 1970 (44.1%). Internal analyses showed an association of lung cancer mortality...

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  • Authors' reply to "Three interpretations of an ecological study
    Frank de Vocht

    We thank Dr Idrovo for his thoughts on our paper (1) regarding multilevel approaches to ecological studies (2). We agree with Dr Idrovo that incorporating different levels of aggregation to explore the impact of macro-determinants, or "cultural determinants", would be useful and could, in theory, illuminate important factors beyond causal hypothecation at the individual-level. In our study, however, we were unable to ful...

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  • Obliterative bronchiolitis in workers laying up fiberglass-reinforced plastics with polyester resin and methylethyl ketone peroxide catalyst.
    Yue Leon Guo

    Cullilinan et al [1] reported six obliterative bronchiolitis (OB) cases with plausible correlation with fiberglass-reinforced plastics (FRP) fabrication. Five of them were boat builders and one worked for a cooling- tower manufacturer. Due to the complexity of the FRP-related boat building processes, the exact agent(s) and process causing OB were difficult to determine. The cooling-tower manufacturing had a simpler manufact...

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