Diesel exhaust (DE) is classified as a probable human carcinogen. Aims were to describe the major occupational uses of diesel engines and give an overview of personal DE exposure levels and determinants of exposure as reported in the published literature. Measurements representative of personal DE exposure were abstracted from the literature for the following agents: elemental carbon (EC), particulate matter (PM), carbon monoxide (CO), nitrogen oxide (NO), and nitrogen dioxide (NO(2)). Information on determinants of exposure was abstracted. In total, 3528 EC, 4166 PM, 581 CO, 322 NO, and 1404 NO(2) measurements were abstracted. From the 10,001 measurements, 32% represented exposure from on-road vehicles and 68% from off-road vehicles (30% mining, 15% railroad, and 22% others). Highest levels were reported for enclosed underground work sites in which heavy equipment is used: mining, mine maintenance, and construction (EC: 27-658 microg/m(3)). Intermediate exposure levels were generally reported for above-ground (semi-) enclosed areas in which smaller equipment was run: mechanics in a shop, emergency workers in fire stations, distribution workers at a dock, and workers loading/unloading inside a ferry (generally: EC<50 microg/m(3)). Lowest levels were reported for enclosed areas separated from the source, such as drivers and train crew, or outside, such as surface mining, parking attendants, vehicle testers, utility service workers, surface construction and airline ground personnel (EC<25 microg/m(3)). The other agents showed a similar pattern. Determinants of exposure reported for enclosed situations were ventilation and exhaust after treatment devices. Reported DE exposure levels were highest for underground mining and construction, intermediate for working in above-ground (semi-) enclosed areas and lowest for working outside or separated from the source. The presented data can be used as a basis for assessing occupational exposure in population-based epidemiological studies and guide future exposure assessment efforts for industrial hygiene and epidemiological studies.

Occupational exposure to diesel engine exhaust: A literature review

Rationale: Recent U.S. data suggest an increased risk of work-related asthma among health care workers, yet only a few specific determinants have been elucidated.Objectives: To evaluate associations of asthma prevalence with occupational exposures in a cross-sectional survey of health care professionals.Methods: A detailed questionnaire was mailed to a random sample (n = 5,600) of all Texas physicians, nurses, respiratory therapists, and occupational therapists with active licenses in 2003. Information on asthma symptoms and nonoccupational asthma risk factors obtained from the questionnaire was linked to occupational exposures derived through an industry-specific job-exposure matrix.Measurements: There were two a priori defined outcomes: (1) physician-diagnosed asthma with onset after entry into health care (“reported asthma”) and (2) “bronchial hyperresponsiveness–related symptoms,” defined through an 8-item symptom-based predictor.Main Results: Overall response rate was 66%. The final study population ...

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Occupational Risk Factors and Asthma among Health Care Professionals

To minimize transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the novel coronavirus responsible for coronavirus disease (COVID-19), the U.S. Centers for Disease Control and Prevention and the World Health Organization recommend wearing face masks in public. Some have expressed concern that these may affect the cardiopulmonary system by increasing the work of breathing, altering pulmonary gas exchange and increasing dyspnea, especially during physical activity. These concerns have been derived largely from studies evaluating devices intentionally designed to severely affect respiratory mechanics and gas exchange. We review the literature on the effects of various face masks and respirators on the respiratory system during physical activity using data from several models: cloth face coverings and surgical masks, N95 respirators, industrial respirators, and applied highly resistive or high-dead space respiratory loads. Overall, the available data suggest that although dyspnea may be increased and alter perceived effort with activity, the effects on work of breathing, blood gases, and other physiological parameters imposed by face masks during physical activity are small, often too small to be detected, even during very heavy exercise. There is no current evidence to support sex-based or age-based differences in the physiological responses to exercise while wearing a face mask. Although the available data suggest that negative effects of using cloth or surgical face masks during physical activity in healthy individuals are negligible and unlikely to impact exercise tolerance significantly, for some individuals with severe cardiopulmonary disease, any added resistance and/or minor changes in blood gases may evoke considerably more dyspnea and, thus, affect exercise capacity.

Face Masks and the Cardiorespiratory Response to Physical Activity in Health and Disease.

Interventions for the primary prevention of occupational asthma have been reported in the medical literature, understanding the effectiveness of these efforts could help future interventions. The aim of our study was to evaluate the existing knowledge regarding the impact of controlling work exposure on the prevention of occupational asthma. We conducted systematic literature searches through April 2010 to examine if control of workplace exposures is effective for primary prevention of sensitisation and occupational asthma. The literature search for primary prevention of occupational asthma yielded 29 studies. Assessment of the available information led to the following conclusions and recommendations concerning primary prevention of occupational asthma. Exposure elimination is the strongest and preferred primary preventive approach to reduce the burden of occupational asthma. If elimination is not possible, exposure reduction is the second best option for primary prevention of occupational asthma. The evidence for the effectiveness of respirators in preventing occupational asthma is limited, and other options higher in the list of controls for occupational exposures, notably eliminating or minimising exposures at the source or in the environment, should be used preferentially. There is strong evidence to recommend not using powdered allergen-rich natural rubber latex gloves. There is weak evidence that suggests workers should minimise skin exposure to asthma-inducing agents.

https://err.ersjournals.com/content/errev/21/124/112.full.pdf

Primary prevention: exposure reduction, skin exposure and respiratory protection

The mutagenicity of organic solvent extracts from diesel exhaust particulate (DEP), first noted more than 55 years ago, initiated an avalanche of diesel exhaust (DE) health effects research that now totals more than 6000 published studies. Despite an extensive body of results, scientific debate continues regarding the nature of the lung cancer risk posed by inhalation of occupational and environmental DE, with much of the debate focused on DEP. Decades of scientific scrutiny and increasingly stringent regulation have resulted in major advances in diesel engine technologies. The changed particulate matter (PM) emissions in "New Technology Diesel Exhaust (NTDE)" from today's modern low-emission, advanced-technology on-road heavy-duty diesel engines now resemble the PM emissions in contemporary gasoline engine exhaust (GEE) and compressed natural gas engine exhaust more than those in the "traditional diesel exhaust" (TDE) characteristic of older diesel engines. Even with the continued publication of epidemiologic analyses of TDE-exposed populations, this database remains characterized by findings of small increased lung cancer risks and inconsistent evidence of exposure-response trends, both within occupational cohorts and across occupational groups considered to have markedly different exposures (e.g. truckers versus railroad shopworkers versus underground miners). The recently published National Institute for Occupational Safety and Health (NIOSH)-National Cancer Institute (NCI) epidemiologic studies of miners provide some of the strongest findings to date regarding a DE-lung cancer association, but some inconsistent exposure-response findings and possible effects of bias and exposure misclassification raise questions regarding their interpretation. Laboratory animal studies are negative for lung tumors in all species, except for rats under lifetime TDE-exposure conditions with durations and concentrations that lead to "lung overload." The species specificity of the rat lung response to overload, and its occurrence with other particle types, is now well-understood. It is thus generally accepted that the rat bioassay for inhaled particles under conditions of lung overload is not predictive of human lung cancer hazard. Overall, despite an abundance of epidemiologic and experimental data, there remain questions as to whether TDE exposure causes increased lung cancers in humans. An abundance of emissions characterization data, as well as preliminary toxicological data, support NTDE as being toxicologically distinct from TDE. Currently, neither epidemiologic data nor animal bioassay data yet exist that directly bear on NTDE carcinogenic potential. A chronic bioassay of NTDE currently in progress will provide data on whether NTDE poses a carcinogenic hazard, but based on the significant reductions in PM mass emissions and the major changes in PM composition, it has been hypothesized that NTDE has a low carcinogenic potential. When the International Agency for Research on Cancer (IARC) reevaluates DE (along with GEE and nitroarenes) in June 2012, it will be the first authoritative body to assess DE carcinogenic health hazards since the emergence of NTDE and the accumulation of data differentiating NTDE from TDE.

https://www.tandfonline.com/doi/pdf/10.3109/08958378.2012.691913

Health effects research and regulation of diesel exhaust: an historical overview focused on lung cancer risk

Carbon dioxide (CO2) rebreathing has been recognised as a concern regarding respirator use and is related to symptoms of discomfort, fatigue, dizziness, headache, muscular weakness and drowsiness. Previous investigations are limited by small sample size and have not evaluated the relationship between CO2 inhalation and phonic respiration (breathing during speech) in respiratory protective devices (RPDs). A total of 40 workers trained in the use of RPDs performed a graded exercise test on a cycle ergonometer that increased in workload every 5 min. During the third minute of each stage, participants read aloud a prepared text. Measures of mixed expired CO2 (PECO2), mixed inspired CO2 (PICO2) and respiration were monitored. The results showed that phonic respiration and low work rates contributed to significantly higher levels of CO2 rebreathing. Aiming to reduce CO2 exposure may result in improved wear time of RPDs. It is recommended that these findings be incorporated in technical specifications regarding ...

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Carbon dioxide rebreathing in respiratory protective devices: influence of speech and work rate in full-face masks

This article was published in Annals of Occupational Hygiene on 07 July 2004, available at http://dx.doi.org/10.1093/annhyg/meh038

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Longitudinal study of sensitization to natural rubber latex among dental school students using powder-free gloves

Dehydration is a health risk for miners in tropical regions of Australia. However, it is not known whether dehydration poses a health risk to miners working in temperate regions of Australia. A cross-sectional study of 88 miners from two underground mines was undertaken in south-eastern New South Wales, Australia. Participants had their height, weight, waist circumference and hydration status measured and completed a self-administered questionnaire on fluid intake, access to water, and socio-demographic characteristics. Health and Safety managers were surveyed about guidelines relating to healthy work and lifestyle behaviours which impact/influence hydration. Hydration tests indicated that more than half of the miners (approximately 58%) were dehydrated (Urinary Specific Gravity (USG) >1.020) both before and after their shift, with three workers pre-shift and four workers post-shift displaying clinical dehydration (USG>1.030). Overall, 54.0% of participants were overweight and 36.8% were obese. Miners who commenced the shift with poor hydration status were 2.6 times more likely to end the shift with poor hydration, compared to those who commenced the shift with good hydration (OR 2.6, 95% CI 1.06, 6.44). Miners who had a mean USG result for the entire shift indicating dehydration were more likely to be obese (42.9%) and have a waist measurement in the high risk range for metabolic complications (40.8%) than those workers that were adequately hydrated for their entire shift (29.4% and 14.7% respectively). Some guidelines promoting healthy lifestyles and supportive work environments were in place, but there were limited guidelines on healthy weight and hydration. Dehydration, being overweight and obesity were linked issues in this cohort of miners. Strategies are needed to: adapt the workplace environment to increase water accessibility; encourage appropriate consumption of water both at work and at home; and to promote physical activity and good nutrition to maintain healthy weight.

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Hydration status of underground miners in a temperate Australian region.

Over the past 115 years the invention of a compression ignition engine by Rudolph Diesel in the 1890s has contributed significantly to the productivity of many nations, owing to the widespread use of larger diesel powered equipment in most industrial activities. The down-side in terms of occupational health has been the exposure of a large number of workers to the complex mixture of toxic, gaseous, adsorbed organics and particulate components found in the raw exhaust emissions. Although the adverse health effects of the gaseous fraction of diesel emissions have been known for sometime, only in the last two decades has research indicated that the particulate component of the diesel exhaust has the potential to induce various health effects. In addition, it is associated with nonhealth aspects such as malodour, visual and nuisance pollution. Diesel exhaust emissions were investigated >20 years by the BOHS Hygiene Standards Committee (BOHS, 1981). The Committee’s terms of reference were;

Diesel particulates--recent progress on an old issue.

Employee exposures to diesel particulate (DP) were measured under normal and abnormal mining operations at BHP Steel Collieries Tower Colliery and other underground coal mines in New South Wales coal fields. DP was measured using submicron samplers developed by the U.S. Bureau of Mines, and the results were verified using quantitative scanning electron microscopy. Personal monitoring (n = 480 full-shift samples) conducted at nine underground coal mines has indicated that the exposure of the work force ranges from less than 0.1 to 2.2 mg/m3 of DP, depending on job type and mining operation. Operations such as longwall moves and stonedusting, which generate elevated levels of dust, cause severe interference to submicron DP measurements. Based on previous knowledge that engine tune and condition affect the balance between gaseous and particulate emissions, five technologies for controlling DP were investigated in a combination of studies conducted in an above-ground simulated tunnel and in a special...

Brian Davies

Papers

Carbon dioxide rebreathing in respiratory protective devices: influence of speech and work rate in full-face masks

Longitudinal study of sensitization to natural rubber latex among dental school students using powder-free gloves

Hydration status of underground miners in a temperate Australian region.

Diesel particulates--recent progress on an old issue.

Evaluation and Control of Employee Exposure to Diesel Particulate at Several Australian Coal Mines