Powered air-purifying respirators (PAPRs) generate internal noise from the blower and result in turbulent airflow. Internal noise may reduce speech clarity and increase listening effort during critical tasks. This study examined how PAPR brand and user configuration factors affected internal noise levels. A total of 1,200 internal PAPR noise measurements were recorded on a manikin across multiple experimental conditions: two PAPR brands, five manikin sizes, hair or shroud attached (Yes/No), and both hair and shroud attached. The generalized linear mixed model with a rank-based nonparametric test was used to analyze the bivariate association between variables, given the abnormal distribution of the mean noise data. The use of the active 3M PAPR on a small manikin produced the highest mean noise level [70.7 dBA; 95% confidence interval (CI): 70.31 to 71.16] at baseline (i.e., without hair or shroud), while use on a medium manikin had the lowest (57.3 dBA; CI: 56.87 to 57.72). The 3M PAPR was significantly louder (Mean difference: 4.1 dBA; CI: 3.44 to 4.72) than the MAXAIR at baseline, though after adjusting for PAPR brand and manikin size, and considering hair and shroud individually, MAXAIR was slightly but significantly louder (Mean difference: 0.5 dBA; CI: 0.20 to 0. 90). The presence of hair was associated with a significant reduction (Mean reduction: 2.31 dBA; CI: 0. 98 to 3.65) in internal noise levels after adjusting for PAPR brand and manikin. Use of a shroud alone had a small, nonsignificant effect (Mean difference: 0.78 dBA; CI: -0.55 to 2.11) on noise levels. However, the combined effect of hair and a shroud, when comparing "Both vs. None," resulted in a lower noise level (Mean difference: 3.08 dBA; CI: -0.01 to 6.17), although this reduction was not statistically significant (p = 0.101). These findings suggest the need to focus on blower and airflow design, along with considering acoustic dampening near the ears, to improve communication during use.
Foot marches are a common occupational task for service members and require walking long distances while carrying heavy occupational loads (e.g., 25 kg fighting load). The physical exertion associated with foot marches may induce sweat-related dehydration and altered thermoregulation, potentially leading to impaired performance and increased risk of exertional heat illness. Yet, many studies fail to assess hydration, even in controlled settings. The purpose of this study was to evaluate hydration and cardiorespiratory responses to a simulated, laboratory-based 9.65 km foot march and examine relationships between participant characteristics and outcomes. Sixteen (10 male, 6 female) adults with load carriage experience performed a 9.65 km foot march at 4.82 km/h on a treadmill in a temperature-controlled (22.2 degrees C) laboratory. Participants received no fluid during the march and 1 L of water during a 1h recovery. Hydration was assessed pre-, mid-, and post-march and post-recovery via urine specific gravity (USG), nude dry mass, and perceived thirst. Heart rate and breathing rate were averaged across each half of the march. Repeated measures analysis of variances (ANOVAs), paired t-tests, and Pearson correlations (alpha = 0.05) assessed changes and associations with characteristics. Participants became mildly dehydrated (USG: p < 0.001, eta p(2) = 0.622; post-march 1.020 +/- 0.005) with 1.5 +/- 0.7% body mass loss. Heart rate (p < 0.001, eta p(2) = 0.671) and breathing rate (p < 0.001, eta p(2) = 0.788) were elevated while marching versus recovery but did not differ between march halves. Fat mass (R = 0.618, p = 0.011) and body fat percentage (R = 0.537, p = 0.032), but not aerobic fitness, were significantly correlated with USG changes. Even under controlled laboratory conditions, the fluid-restricted foot march induced mild dehydration, with greater adiposity associated with increased susceptibility. These findings underscore the need for hydration assessment, in both research and training settings, using measures such as USG, body mass change, and thirst to better manage dehydration risk and its implications for performance.
Edward B. Lewis published what is widely considered the most influential article in the history of cancer risk assessment. He was successful in changing the radiation risk assessment focus from transgenerational birth defect concerns to cancer due to his success in getting his article published in Science journal, receiving a highly laudatory editorial endorsement, and quickly becoming a prominent speaker to the U.S. Congress and the focus of a major story in Life magazine, amongst other notably rapid recognitions. However, what is generally not appreciated is that Lewis had no education and training in the complex topics of his article, with no professional knowledge of radiation, leukemia, biostatistics, epidemiology, and risk assessment. This article explores how the inexperienced Lewis benefited from the manipulation of Science by leaders in the scientific community and to avoid proper peer review. Despite the recognition of serious fundamental flaws in the Lewis article, it became embraced by the ideological leaders of the radiation genetics community who ensured the Lewis-based linear no-threshold (LNT) model for cancer risk assessment would become accepted and serve as the foundation for the adoption of the precautionary principle, which is the basis for the Environmental Protection Agency (EPA) and European Union regulatory activities, and global regulatory entities.
Work-related asthma (WRA) comprises asthma caused by chemicals in the workplace (occupational asthma, or OA) and preexisting asthma made worse by chemicals and conditions (work-exacerbated asthma, or WEA). Distinguishing these two mechanisms is extremely challenging but imperative for effective health management and regulation under global chemical regulations. The Specific Inhalation Challenge (SIC) test is considered by clinicians as the gold standard for identifying OA. However, an exposure reconstruction exercise based on the case study of methyl methacrylate, currently undergoing harmonized classification and labeling within Europe suggests that greater rigor may be needed when conducting these tests if false positive results, i.e., from nonspecific irritation are to be avoided. Accurate simulation of actual workplace conditions combined with direct measurement of peak exposure levels will likely improve test specificity.
This review provides an integrated evaluation of current asbestos sampling and analytical methodologies to determine if these are appropriate for assessing exposure to naturally occurring asbestos (NOA), particularly in the high-dust environments associated with Western Australian mining operations. Asbestos exposure remains a significant occupational health concern globally, with strong evidence linking fiber inhalation to serious diseases including mesothelioma and lung cancer. Although the commercial use of asbestos has been banned in Australia since 2003, mining activities continue to intersect with geological formations that may contain NOA minerals, creating ongoing potential for occupational exposure. For occupational hygienists working in these settings, this raises a practical question: when a worker's personal air sample is collected and analyzed using standard regulatory methods, does the result reliably reflect their actual exposure to potentially hazardous fibers? The answer to this question has direct implications for risk assessment, exposure controls, and health surveillance decisions made at the operational level. Current regulatory monitoring in Australia relies primarily on the Membrane Filter Method (MFM), a morphology-based analytical approach originally developed for environments dominated by asbestos fibers, rather than the complex mixed dust conditions typical of mining operations. Known limitations of this method include reduced fiber visibility under high particulate loading and delays between sample collection and reporting of results. Critically, samples collected during the highest-dust activities, and therefore the periods of greatest potential worker exposure, are precisely those most likely to be voided due to particulate overload. This review critically evaluates the scientific, regulatory, and geological factors relevant to NOA exposure assessment in mining settings, including the relationship between fiber characteristics and disease, international developments in monitoring methodologies, and the geological occurrence of NOA in Western Australia. The findings highlight the need to reassess current monitoring practices and may inform occupational hygiene practice, regulatory decision-making, and future research directions in industries where NOA may be encountered.
