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Articles by Sean Semple
Total Records ( 6 ) for Sean Semple
  Om P. Kurmi , Sean Semple , Markus Steiner , George D. Henderson and Jon G. Ayres

Aims: To measure particulate matter (PM) exposure of people involved in domestic work (i.e. housework by a resident, not paid work) in urban and rural Nepal, with exposure to biomass smoke in the rural areas, and to examine the performance of photometric devices in collecting these data. This paper details the results of these measurements and derives calibration factors for two photometric devices compared to gravimetric measures.

Methods: Between April 2006 and February 2007, respirable dust and PM2.5 levels were measured over a 24-h period in 490 households in a range of urban and rural settings in the Kathmandu valley of Nepal. Sampling was carried out by photometric and gravimetric methods with the co-located gravimetric data used to derive a calibration factor for the photometric devices.

Results: The time-weighted average (TWA) (24 h) respirable dust levels measured by gravimetric sampler ranged from 13 to 2600 μg m-3 in the rural settings and 3 to 110 μg m-3 in the urban settings. The co-located photometric and gravimetric devices indicate that the SidePak Personal Aerosol Monitor device required a calibration factor of 0.48 and 0.51 for rural and urban data, respectively, whereas the DustTrak device required a factor of 0.31 and 0.35 for rural and urban settings to correct for the particle size and density of the biomass smoke. The photometric devices provide time history data on PM concentration levels and generally indicate two distinct peaks around a morning and early evening cooking time.

Conclusions: Those involved in domestic work in rural Nepal are exposed to average respirable dust concentrations of ~1400 μg m-3. Converted to an 8-h TWA, this equates to more than the current UK limit for respirable dust (4000 μg m-3). Homemakers, primarily women, spend a large proportion of their lives indoors in these high respirable dust concentrations and these exposures are likely to produce respiratory illness. Exposure can be controlled by the use of different fuel types and/or the use of flued stoves.

  Priyamvada Paudyal , Sean Semple , Robert Niven , Gael Tavernier and Jonathan G. Ayres
  Background: Inhalation of cotton-based particulate has been associated with respiratory symptoms and overt lung disease related to endotoxin exposure in some studies. This cross-sectional study measures personal exposure to inhalable dust and endotoxin in the textile industry of Nepal. Methods: This study was conducted in four sectors (garment making, carpet making, weaving, and recycling) of the textile industry in Kathmandu, Nepal. Personal exposure to inhalable dust and airborne endotoxin was measured during a full-shift for 114 workers.  Results: Personal exposure to cotton dust was generally low [geometric mean (GM) 0.81 mg m-3) compared to the UK workplace exposure limit (WEL) (2.5 mg m-3) but with nearly 18% (n = 20) of the workers sampled exceeding the limit. Exposures were lowest in the weaving and the garment sector (GM = 0.30 mg m-3), higher in the carpet sector (GM = 1.16 mg m-3), and highest in the recycling sector (GM = 3.36 mg m-3). Endotoxin exposures were high with the overall data (GM = 2160 EU m-3) being more than 20-fold higher than the Dutch health-based guidance value of 90 EU m-3. The highest exposures were in the recycling sector (GM = 5110 EU m-3) and the weaving sector (GM = 2440 EU m-3) with lower levels in the garment sector (GM = 157 EU m-3). The highest endotoxin concentrations expressed as endotoxin units per milligram inhalable dust were found in the weaving sector (GM = 165 EU mg-1). There was a statistically significant correlation between inhalable dust concentrations and endotoxin concentrations (r = 0.37; P < 0.001) and this was particularly strong in the garment (r = 0.82; P = 0.004) and the carpet sector (r = 0.81; P < 0.001). Conclusions: Inhalable dust exposures measured in the weaving, carpet, and garment sectors were all below the UK WEL for cotton dust. A significant proportion of the measurements from the cotton recycling sector were above the UK WEL suggesting that better hygiene control measures are required. Airborne endotoxin concentrations in all sectors were found to exceed the Dutch health-based guidance limit of 90 EU m-3 and may be associated with respiratory health effects.
  Maaike J. Visser , Ali Behroozy , Maarten M. Verberk , Sean Semple and Sanja Kezic
  Occupational contact dermatitis (OCD) is an important work-related disease. A major cause of OCD is ‘wet work’: frequent contact of the skin with water, soap, detergents, or occlusive gloves. The German guidance TRGS 401 recommends that the duration of wet work (including use of occlusive gloves) should not exceed 2 h day-1 and also the frequency of hand washing or hand disinfection should be taken into account. This highlights the need for a reliable method to assess duration and frequency of wet work. Recently, a wet-work sampler has been developed by the University of Aberdeen. The sampler uses the temperature difference (ΔT) generated by evaporative cooling between two sensors: one sensor on the skin and a second one placed 2 mm above the skin. We have evaluated the use of this sampler in a healthcare setting, using direct observation as reference. Twenty-six nurses wore the sampler on the volar side of the middle finger for ~2 h during their regular daily tasks, while being observed by a researcher. Sampler results were evaluated using various threshold values for ΔT to identify wet events of the hands. The optimal ΔT to discern wet and dry skin differed considerably between individual nurses. Individual results yielded a median sensitivity of 78 and 62% and a median specificity of 79 and 68% for indicating wet skin and glove use, respectively. Overall, the sampler was moderately accurate for identifying wetness of the skin and less accurate for discerning glove use. In conclusion, agreement between observed wet work and device-reported wet events in healthcare settings was not high and further adaptations and developments may be required.
  Melanie Gorman Ng , Sean Semple , John W. Cherrie , Yvette Christopher , Christine Northage , Erik Tielemans , Violaine Veroughstraete and Martie Van Tongeren
  Occupational inadvertent ingestion exposure is ingestion exposure due to contact between the mouth and contaminated hands or objects. Although individuals are typically oblivious to their exposure by this route, it is a potentially significant source of occupational exposure for some substances. Due to the continual flux of saliva through the oral cavity and the non-specificity of biological monitoring to routes of exposure, direct measurement of exposure by the inadvertent ingestion route is challenging; predictive models may be required to assess exposure. The work described in this manuscript has been carried out as part of a project to develop a predictive model for estimating inadvertent ingestion exposure in the workplace. As inadvertent ingestion exposure mainly arises from hand-to-mouth contact, it is closely linked to dermal exposure. We present a new integrated conceptual model for dermal and inadvertent ingestion exposure that should help to increase our understanding of ingestion exposure and our ability to simultaneously estimate exposure by the dermal and ingestion routes. The conceptual model consists of eight compartments (source, air, surface contaminant layer, outer clothing contaminant layer, inner clothing contaminant layer, hands and arms layer, perioral layer, and oral cavity) and nine mass transport processes (emission, deposition, resuspension or evaporation, transfer, removal, redistribution, decontamination, penetration and/or permeation, and swallowing) that describe event-based movement of substances between compartments (e.g. emission, deposition, etc.). This conceptual model is intended to guide the development of predictive exposure models that estimate exposure from both the dermal and the inadvertent ingestion pathways. For exposure by these pathways the efficiency of transfer of materials between compartments (for example from surfaces to hands, or from hands to the mouth) are important determinants of exposure. A database of transfer efficiency data relevant for dermal and inadvertent ingestion exposure was developed, containing 534 empirically measured transfer efficiencies measured between 1980 and 2010 and reported in the peer-reviewed and grey literature. The majority of the reported transfer efficiencies (84%) relate to transfer between surfaces and hands, but the database also includes efficiencies for other transfer scenarios, including surface-to-glove, hand-to-mouth, and skin-to-skin. While the conceptual model can provide a framework for a predictive exposure assessment model, the database provides detailed information on transfer efficiencies between the various compartments. Together, the conceptual model and the database provide a basis for the development of a quantitative tool to estimate inadvertent ingestion exposure in the workplace.
  John A. S. Ross , Jennifer I. Macdiarmid , Sean Semple , Stephen J. Watt , Gill Moir and George Henderson
  Background: Prevalence of moderate to severe cognitive symptoms is markedly higher in UK professional divers who have also worked as a welder (28%) than in either divers who have not welded (18%) or offshore workers who have worked neither as a diver nor as a welder (6%).

Objectives: To determine whether cognitive symptoms are related to welding fume exposure or diving.

Methods: Three age-matched groups of male workers were studied using postal questionnaire: professional divers who had worked as a welder (PDW, n = 361), professional welders who had not dived (NDW, n = 352), and offshore oil field workers who had neither dived nor welded (NDNW, n =503). Health-related quality of life was assessed by the Short Form 12 questionnaire (SF12). Cognitive symptomatology was assessed using the Cognitive Failures Questionnaire (CFQ). A single variable for welding fume exposure (mg m−3 days) was calculated, incorporating welding experience in different environments and using different welding techniques and respiratory protective equipment. The level of fume exposure during hyperbaric welding operations was measured during such work as ambient PM10 (particles of 10 μm or less). Diving exposure was assessed as the number of dives performed plus the number of days spent working during saturation diving.

Results: Questionnaires were returned by 153 PDW, 108 NDW, and 252 NDNW. SF12 scores were the same in all groups and fell within normative values. Mean (95% CI) CFQ scores were higher in PDW [40.3 (37.7-42.9)] than in both NDW [34.6 (31.6-37.7)] and NDNW [32.1 (30.4-33.9)], but the scores in no groups fell outside the normative range. The mean PM10 exposure during hyperbaric welding operations was 2.58mg m−3. The geometric mean mg m−3 days (95% CI) for welding fume exposure in NDW [33 128 (24 625-44 567) n = 85] was higher than for that in PDW [10 904 (8103-14 673) n = 112]. For PDW the geometric mean (95% CI) diving exposure was 1491 [(1192-1866) n = 94] dives and days in saturation. In the general linear model regression analyses adjusted for age, alcohol consumption, and somatization, there was no signification association of CFQ score with either welding fume exposure (F = 0.072, P = 0.79, n = 152) or diving exposure (F = 0.042, P = 0.84, n = 74).

Conclusions: In conclusion, cognitive sympomatology was not related to retrospectively assessed measures of welding fume exposure or diving experience. In addition, the levels of cognitive symptomatology, even in PDW, did not exceed normative values.

  Melanie Gorman Ng , Stan de Poot , Kaspar Schmid , Hilary Cowie , Sean Semple and Martie van Tongeren
  Background: Although dustiness and viscosity are potential determinants of dermal exposure, their effect on exposure is poorly understood. The goal of this study was to investigate the effect of dustiness and viscosity on dermal exposure by each of three dermal exposure pathways (deposition, surface contact, and immersion).

Methods: The hands of four volunteers were exposed to non-toxic substances: particulate with varying dustiness (calcium acetate, zinc oxide, and Epsom salt) and liquids of varying viscosity (three glycerol/water solutions containing 20, 50, or 85% glycerol) by each pathway. Dermal exposure was measured by a systematic wipe of the entire hand. Calcium acetate, zinc oxide, and Epsom salts were analysed on wipes by inductively coupled plasma/atomic emission spectrometry and glycerol was measured by gas chromatography with a flame ionization detector. The relationship between exposure and either dustiness or viscosity was examined using either parametric (analysis of variance) or non-parametric (Kruskal-Wallis) tests.

Results: Both viscosity and dustiness appeared to have an effect on dermal exposure. Increasing viscosity lead to higher exposures by the immersion pathway (P < 0.001) but lower exposures by the deposition pathway (although this relationship was not statistically significant: P = 0.19). Viscosity had no apparent effect on exposure from surface contact. Dustiness did not affect transfer of particulate to the skin by immersion (P = 0.403) but it did affect exposure by the surface transfer and deposition pathways. The dustiest substance (calcium acetate) transferred to skin more readily following contact with contaminated surfaces than zinc oxide or Epsom salts (P = 0.016). For the deposition pathway, the highest exposures were seen for the dustiest substance (calcium acetate) but statistical analysis was not conducted as 67% of measurements were below detection limits.

Conclusion: The results suggest that both viscosity and dustiness can affect dermal exposure. They also show that the determinants of dermal exposure can be different for each of the dermal exposure pathways.

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