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John W Cherrie

Publications and source records attributed to John W Cherrie.

12 recordsLinked to original sources
PubMed2006

A new sampler to assess dermal exposure during wet working.

In the UK, approximately 30% of cases of dermatitis reported to the national surveillance scheme are associated with wet working or exposure to aqueous mixtures. There is evidence that the duration and frequency that hands are wet are key determinants of risk, but there are no objective methods to measure these exposure factors. This research aimed to develop a practical tool to measure the duration and the number of occasions hands are wet. We developed an electronic sensor that is worn on the finger, which detects wetness from evaporative cooling. The output signal is recorded in electronic memory and the frequency and duration of exposure calculated using a simple data processing algorithm. The device has been tested in a variety of environmental conditions and for a standardized wet-work task. Wetting events were detectable in all the standardized tests, with the proportion of time the hands were wet ranging from 15 to 49% (mean 30%). The electronic sensor is slightly affected by abrupt changes in air temperature and rapid air movements, but these do not seem to impose any practical limitations. This IOM Wet-Work sampler has the potential to provide reliable measurements of exposure that may be used to assess the risk of contact dermatitis.

Dermatitis, Occupational↗
PubMed2006

How important is inadvertent ingestion of hazardous substances at work?

Much is known about human exposure to workplace hazardous substances by inhalation and from skin contact, but there has been little systematic research into ingestion of hazardous substances used at work. This review attempts to identify whether inadvertent ingestion of hazardous substances is an important route of exposure in the workplace and examines possible methods that could be used to quantify ingestion exposure. A number of papers highlight jobs and substances where inadvertent ingestion may be important, typically through case reports or from a theoretical analysis. These scenarios involve exposure to some metals or metal compounds, pharmaceuticals, pesticides, some infectious agents, unsealed radioactive sources and some high molecular weight allergens. In total we estimate that about 4.5 million workers in the UK could have some regular non-trivial intake of hazardous substances by inadvertent ingestion. A conceptual analysis of inadvertent ingestion exposure highlights the role of hand-to-mouth and object-to-mouth events as the primary exposure processes. Two exposure 'compartments' are defined: the peri-oral area (i.e. the area of skin around the outside of the mouth) and the oral cavity. Several options are highlighted for exposure-related measurements, including peri-oral wipes, saliva samples, mouth-rinse samples, hand-wipes and under-nail scrapings. Further research is necessary to define which measurements may be most informative. Human behaviour has a key role in determining inadvertent ingestion exposure. For example, some people are habitual nail biters or repeatedly touch their mouth, both of which will increase the chance of ingesting contaminants on their hands. The frequency that people touch their face is dependant on the circumstances of their work and probably the degree of psychological stress they are under. A proper understanding of the importance of these factors will help in designing interventions to reduce the risks from ingesting hazardous substances at work. When making inhalation or dermal exposure measurements we recommend that details of personal behaviours should be recorded so that some estimate of ingestion risks can be inferred. It is possible that inadvertent ingestion of hazardous substances at work may become more important as employers put more emphasis on controlling inhalation and dermal exposures. Further research is necessary to ensure that risk reduction strategies for inadvertent ingestion of hazardous substances are appropriate and effective.

Deglutition↗
PubMed2005

Exposure and risks from wearing asbestos mitts.

BACKGROUND: Very high fibre inhalation exposure has been measured while people were wearing personal protective equipment manufactured from chrysotile asbestos. However, there is little data that relates specifically to wearing asbestos gloves or mitts, particularly when used in hot environments such as those found in glass manufacturing. The aim of this study was to assess the likely personal exposure to asbestos fibres when asbestos mitts were used. RESULTS: Three types of work activity were simulated in a small test room with unused mitts and artificially aged mitts. Neither pair of mitts were treated to suppress the dust emission. The measured respirable fibre exposure levels ranged from <0.06 to 0.55 fibres/ml, with no significant difference in fibre exposure between aged and unused mitts. The use of high localised ventilation to simulate convective airflows from a furnace reduced exposure levels by about a factor of five. Differences between tasks were statistically significant, with simulated "rowing" of molten glass lowest and replacement of side seals on the furnace highest. Estimated lifetime cancer risk from 20 years exposure at the upper end of the exposure range measured during the study is less than 22 per 100,000. CONCLUSION: People who wore asbestos mitts were likely to have been exposed to relatively low levels of airborne chrysotile asbestos fibres, certainly much lower than the standards that were accepted in the 1960's and 70's. The cancer risks from this type of use are likely to be very low.

Journal Article↗
PubMed2005

Concepts of skin protection: considerations for the evaluation and terminology of the performance of skin protective equipment.

This article proposes a common language for better understanding processes involved in dermal exposure and skin protection. A conceptual model has been developed that systematically describes the transport of agent mass from sources, eventually resulting in "loading" of the skin surface or the skin contaminant layer. In view of a harmonized glossary of exposure terminology this is considered the exposure surface. Loading is defined as agent mass present in this layer divided by the exposure surface area. Skin protective equipment (SPE) is meant to reduce uptake, that is, an agent crosses the absorption barrier of the skin, by intervening in the processes of loading the exposure surface; however, the design of the equipment may fail to cover skin surface entirely. In addition, part of the mass intercepted by the SPE may reach the skin surface either by permeation, penetration, or by transfer when touching the contaminated exterior of the SPE. Evaluation of SPE performance has earlier focused on chemical resistance performance testing for permeation, penetration, or degradation of SPE-materials. In use-scenario practice, however, all processes will occur concurrently. Thus, SPE field performance evaluation including user-SPE interaction complementary to material testing is warranted. Results of laboratory testing for SPE-materials are reported as substance-specific breakthrough times and permeation rates. SPE field performance should be evaluated for reduction of either uptake or parameters that reflect the outcome of dermal exposure. Ideally, this should be based on the results of intervention-type workplace studies, for (e.g., assessment of exposure loading). The level of reduction can be expressed as a protection factor (ratio without/with SPE) for different parameters of dermal exposure or uptake. It is concluded that for evaluation of SPE-type performance, generic protection factors can be derived for substance-independent processes (e.g., reduction of exposure loading) but not for substance-specific reduction of uptake.

Environmental Monitoring↗
PubMed2005

The development of the EASE model.

The estimation and assessment of substance exposure (EASE) model has been under development and in use since the early 1990s. It is a general model that can be used to predict workplace exposure to any substance hazardous to health. The current EASE model (version 2.0) has been used widely in the risk assessment of new and existing chemicals by the UK Health and Safety Executive (HSE) and other regulatory agencies. EASE has also been distributed globally to over 200 users and therefore may have been used for many other purposes. Despite widespread use of the model, neither the development of its structure nor its underlying concepts and principles have been published in the open literature. Using surviving documentary evidence and discussions with key personnel, the creation and development of the model from 1992 to 2002 is described. The role of the HSE's National Exposure Database (NEDB) as the principal data source for the development of the model output exposure ranges is described. A number of problems and limitations of the model have been identified and the description of the model's development provides some explanation of their presence.

Expert Systems↗
PubMed2005

Comparison of measured dermal dust exposures with predicted exposures given by the EASE expert system.

Estimation and Assessment of Substance Exposure (EASE) is a rule-based computer expert system used by regulatory authorities within the European Union to assist in assessing exposure for both new and existing substances. It can provide estimates of both inhalation exposure levels and dermal exposure levels to the hands and forearms. This article describes the results of a study in which measurements of workplace dermal zinc exposures were collected for an industry-wide risk assessment and also compared with the levels predicted by EASE. Measurements were obtained from subjects in seven different workplaces that were producing or working with zinc metal or zinc compounds. The work activities were grouped a priori into one of three categories used by EASE for dermal exposure assessment: 'non-dispersive use with intermittent direct handling', 'wide dispersive use with intermittent direct handling' and 'wide dispersive use with extensive direct handling'. The predicted exposure ranges for these categories are 0.1-1, 1-5 and 5-15 mg cm(-2) day(-1). Although the average measured exposure levels for each of the categories increased in line with the predictions from EASE, the model overestimated dermal exposure to the hands by a factor of approximately 50 when the mid-point of the EASE range was compared with the measured mean exposure. Furthermore, a significant additional exposure was found on other parts of the workers' bodies for which EASE does not provide any estimates. Interpretation of the dermal exposure data was complicated by the use of protective gloves, which might have limited the amount of zinc dust adhering to the workers' skin. However, observation of the work activities suggested that the pattern of glove use was such that they would not provide a consistent level of protection. This study provided an opportunity to collect a large amount of dermal zinc exposure data for risk assessment purposes and also enabled a dermal sampling method to be developed and assessed. There is no standard method for dermal dust exposure measurement, and the choice of method was a key factor in the exposure estimation process. With regard to comparison with the EASE predictions, it is possible that EASE could appear to perform more accurately if its predictions were compared with measurements obtained using surrogate skin sampling methods. However, we believe that such sampling can provide a gross overestimate of the dust on the skin surface. We suggest that further development of the EASE system is necessary to ensure that it better reflects whole-body dermal exposures to dusts.

Dermis↗
PubMed2005

The validity of the EASE expert system for inhalation exposures.

Estimation and Assessment of Substance Exposure (EASE) is a computerized expert system developed by the UK Health and Safety Executive to facilitate exposure assessments in the absence of exposure measurements. The system uses a number of rules to predict a range of likely exposures or an 'end-point' for a given work situation. The purpose of this study was to identify a number of inhalation exposure measurements covering a wide range of end-points in the EASE system to compare with the predicted exposures. Occupational exposure data sets were identified from previous research projects or from consultancy work. Available information for each set of measurements was retrieved from archive storage and reviewed to ensure that it was adequate to enable EASE (version 2) predictions to be obtained. Exposure measurements and other relevant contextual data were abstracted and entered into a computer spreadsheet. EASE predictions were then obtained for each task or job and entered into the spreadsheet. In addition, we generated a random exposure range for each data set for comparison with the EASE predictions. Finally, we produced exposure assessments for a subset of the data using a structured subjective assessment method. We were able to identify approximately 4000 inhalation exposure measurements covering 52 different scenarios and 28 EASE end-points. The data included measurements of solvent vapours, non-fibrous dusts and fibres. In 62% of the end-points the EASE predictions were generally greater than the exposure measurements and in 30% of the end-points the EASE estimates were comparable with the measurements. The random allocation of exposure ranges was, as expected, less reliable than EASE, although there were still about one-third of the cases where the randomly generated exposure ranges generally agreed with the measurements. The structured subjective assessments undertaken by a human expert produced exposure estimates in better agreement with the measurements with about two-thirds of the end-points derived from these assessments in good agreement with the data. We argue that the inhalation exposure estimates from EASE could be improved by incorporating some of the parameters included in the structured subjective assessment methodology.

Air Pollutants, Occupational↗
PubMed2004

Gloves and dermal exposure to chemicals: proposals for evaluating workplace effectiveness.

There are standardized laboratory tests for chemical protective gloves that provide estimates of breakthrough time and steady-state permeation flux. However, there is evidence to suggest that these tests may not be completely relevant to glove usage in the workplace. There is no consensus about how glove workplace effectiveness should be assessed, although a few studies have attempted to measure the effectiveness of chemical protective gloves. We have used a conceptual model of dermal exposure to help analyse how workers' skin may become exposed while wearing gloves, and propose a new glove workplace protection factor (PFgloves), which is based on the ratio of the estimated uptake of chemicals through the hands without gloves to the uptake through the hands while wearing protective gloves. Mathematical simulations demonstrate that glove protection factor is unlikely to be constant for a glove type, but will be strongly influenced by the work situation and the duration of the exposure. This has important consequences for the selection of protective gloves.

Gloves, Protective↗
PubMed2004

Mortality among workers employed in the titanium dioxide production industry in Europe.

OBJECTIVES: To assess the risk of lung cancer mortality related to occupational exposure to titanium dioxide (TiO2). METHODS: A mortality follow-up study of 15,017 workers (14,331 men) employed in 11 factories producing TiO2 in Europe. Exposure to TiO2 dust was reconstructed for each occupational title; exposure estimates were linked with the occupational history. Observed mortality was compared with national rates, and internal comparisons were based on multivariate Cox regression analysis. RESULTS: The cohort contributed 371,067 person-years of observation (3.3% were lost to follow-up and 0.7% emigrated). 2652 cohort members died during the follow-up, yielding standardized mortality ratios (SMRs) of 0.87 (95% confidence interval [CI] 0.83-0.90) among men and 0.58 (95% CI 0.40-0.82) among women. Among men, the SMR of lung cancer was significantly increased (1.23, 95% CI 1.10-1.38); however, mortality from lung cancer did not increase with duration of employment or estimated cumulative exposure to TiO2 dust. Data on smoking were available for over one third of cohort members. In three countries, the prevalence of smokers was higher among cohort members compared to the national populations. CONCLUSIONS: The results of the study do not suggest a carcinogenic effect of TiO2 dust on the human lung.

Adolescent↗
PubMed2004

Exposure assessment for a population-based case-control study combining a job-exposure matrix with interview data.

OBJECTIVES: A system that combines the ease of use of a job-exposure matrix while taking into account job-specific data is needed. This study aimed to produce a detailed method for combining interview data with expert assessments for a large population-based case-control study of Parkinson's disease. METHOD: An interview-administered core questionnaire with a series of questions that triggers substance-specific questionnaires to gather information on key parameters is administered. Using a job-exposure matrix to generate base estimates, assessors can modify this estimate of exposure intensity using worker-specific data such as the use of control measures, reports of substance-specific acute symptoms, and the quantity of material being processed. Detailed guidance for making adjustments to exposure estimates for these modifiers is presented. RESULTS: The method has been partially validated through the use of a comparison of estimates for a separate cohort with previously validated exposure reconstructions. Agreement was high, with a Spearman's rho of 0.89 (P < 0.01). The results from a quality assurance system employed as part of the methodology show a high degree of repeatability in generated exposure values both over time (Spearman's rho 0.98, P < 0.01) and between different assessors (Spearman's rho 0.88, P < 0.01). CONCLUSIONS: The method provides detailed quantitative exposure indices for occupational epidemiology. It has particular strengths both in terms of ease and speed of use. It is hoped that it will provide a useful structure for future epidemiologic work.

Case-Control Studies↗
PubMed2003

Use of Monte Carlo simulation to investigate uncertainty in exposure modeling.

OBJECTIVES: This study used Monte Carlo (MC) simulation to examine the influence of uncertainty on an exposure model and to determine whether a difference exists between two worker groups in a ceramic fiber manufacturing plant. METHODS: Data on work practices and conditions were gathered in interviews with long-serving employees. With the use of previously developed deterministic modeling techniques and likely distributions for model parameters, MC simulations generated exposure profiles for the two job titles. RESULTS: The exposure profiles overlapped considerably, although the average estimated exposure for one job was approximately double that of the other. However, when the correlation between the model parameters in the two jobs was considered, it was concluded that there was a significant difference in the two estimates. CONCLUSIONS: Models are increasingly being used to estimate exposure. Different work situations inevitably result in different exposure estimates. However, it is difficult to determine whether such differences in estimated exposure between worker groups are simply the result of uncertainty with respect to the model parameters or whether they reflect real differences between occupational groups. This study demonstrates the value of MC simulation in helping define the uncertainty in deterministic model estimates.

Ceramics↗