Pleural mesothelioma and lung cancer risks in relation to occupational history and asbestos lung burden.

BACKGROUND: We have conducted a population-based study of pleural mesothelioma patients with occupational histories and measured asbestos lung burdens in occupationally exposed workers and in the general population. The relationship between lung burden and risk, particularly at environmental exposure levels, will enable future mesothelioma rates in people born after 1965 who never installed asbestos to be predicted from their asbestos lung burdens. METHODS: Following personal interview asbestos fibres longer than 5 µm were counted by transmission electron microscopy in lung samples obtained from 133 patients with mesothelioma and 262 patients with lung cancer. ORs for mesothelioma were converted to lifetime risks. RESULTS: Lifetime mesothelioma risk is approximately 0.02% per 1000 amphibole fibres per gram of dry lung tissue over a more than 100-fold range, from 1 to 4 in the most heavily exposed building workers to less than 1 in 500 in most of the population. The asbestos fibres counted were amosite (75%), crocidolite (18%), other amphiboles (5%) and chrysotile (2%). CONCLUSIONS: The approximate linearity of the dose-response together with lung burden measurements in younger people will provide reasonably reliable predictions of future mesothelioma rates in those born since 1965 whose risks cannot yet be seen in national rates. Burdens in those born more recently will indicate the continuing occupational and environmental hazards under current asbestos control regulations. Our results confirm the major contribution of amosite to UK mesothelioma incidence and the substantial contribution of non-occupational exposure, particularly in women.

Airborne Asbestos Exposures from Warm Air Heating Systems in Schools.

The aim of this study was to investigate the concentrations of airborne asbestos that can be released into classrooms of schools that have amosite-containing asbestos insulation board (AIB) in the ceiling plenum or other spaces, particularly where there is forced recirculation of air as part of a warm air heating system. Air samples were collected in three or more classrooms at each of three schools, two of which were of CLASP (Consortium of Local Authorities Special Programme) system-built design, during periods when the schools were unoccupied. Two conditions were sampled: (i) the start-up and running of the heating systems with no disturbance (the background) and (ii) running of the heating systems during simulated disturbance. The simulated disturbance was designed to exceed the level of disturbance to the AIB that would routinely take place in an occupied classroom. A total of 60 or more direct impacts that vibrated and/or flexed the encapsulated or enclosed AIB materials were applied over the sampling period. The impacts were carried out at the start of the sampling and repeated at hourly intervals but did not break or damage the AIB. The target air volume for background samples was ~3000 l of air using a static sampler sited either below or ~1 m from the heater outlet. This would allow an analytical sensitivity (AS) of 0.0001 fibres per millilitre (f ml(-1)) to be achieved, which is 1000 times lower than the EU and UK workplace control limit of 0.1 f ml(-1). Samples with lower volumes of air were also collected in case of overloading and for the shorter disturbance sampling times used at one site. The sampler filters were analysed by phase contrast microscopy (PCM) to give a rapid determination of the overall concentration of visible fibres (all types) released and/or by analytical transmission electron microscopy (TEM) to determine the concentration of asbestos fibres. Due to the low number of fibres, results were reported in terms of both the calculated concentration and the statistically relevant limits of quantification (LOQ), which are routinely applied. The PCM fibre concentrations were all below the LOQ but analytical TEM showed that few of the fibres counted in the background samples were asbestos. The background TEM asbestos concentrations for the individual samples analysed from all three schools were at or below the AS, with a pooled average below the LOQ (<0.00005 f ml(-1)). At the two CLASP schools, there was no significant increase in the airborne amosite concentration in the classrooms during simulated disturbance conditions. At the third school, four of the five classrooms sampled gave measurable concentrations of amosite by TEM during simulated disturbance conditions. The highest concentration of amosite fibres countable by PCM was 0.0043 f ml(-1) with a pooled average of 0.0019 f ml(-1). The air sampling strategy was effective and worked well and the results provide further important evidence to inform the sampling and management of asbestos in schools.

Characterisation and modification of the porous metal foams used for the EN 15051-2 dustiness rotating drum test.

Two approaches were used to evaluate the performance of the reticulated metal foams used to size select and collect dust generated in the dustiness rotating drum tester according to the EN 15051-2 standard "Workplace exposure-Measurement of the dustiness of bulk materials-Rotating drum test". Firstly, the detailed performance of the metal foams was measured in a calm air chamber using a polydisperse aerosol of glass particles and assessed against the respirable conventions described in the EN 481 standard "Workplace atmospheres-Size fraction definitions for measurement of airborne particles". Secondly, the performance of the EN 15051-2 metal foam size selection for the respirable fraction was compared using the rotating drum dustiness test, with that of a cyclone set-up, using 4 polydisperse glass powders of different size distribution and dustiness potential. The research discusses further improvements to the EN 15051-2 standard and an approach to more closely match the EN 481 convention. In general, for the respirable fraction, the tests in this study demonstrated a conservative oversampling by the current EN 15051-2 metal foam set-up in comparison with the EN 481 convention. Calculations and tests showed an improved fit was achieved by reducing the inner diameter of the flanges separating the metal foams and the filter. This study also showed the importance of sealing the circumference of the metal foams when testing highly dusty powders. A direct comparison of the respirable dustiness fraction, measured by the current EN 15051-2 metal foams set-up and by a cyclone set-up, showed broad agreement. However, for extremely dusty powders, the metal foams can clog, and dust can accumulate between the 20 and 80 pores per inch foams.

Past and current asbestos exposure and future mesothelioma risks in Britain: The Inhaled Particles Study (TIPS).

Background: Occupational and environmental airborne asbestos concentrations are too low and variable for lifetime exposures to be estimated reliably, and building workers and occupants may suffer higher exposure when asbestos in older buildings is disturbed or removed. Mesothelioma risks from current asbestos exposures are therefore not known. Methods: We interviewed and measured asbestos levels in lung samples from 257 patients treated for pneumothorax and 262 with resected lung cancer, recruited in England and Wales. Average lung burdens in British birth cohorts from 1940 to 1992 were estimated for asbestos-exposed workers and the general population. Results: Regression analysis of British mesothelioma death rates and average lung burdens in birth cohorts born before 1965 suggests a lifetime mesothelioma risk of approximately 0.01% per fibre/mg of amphiboles in the lung. In those born since 1965, the average lung burden is ∼1 fibre/mg among those with no occupational exposure. Conclusions: The average lifetime mesothelioma risk caused by recent environmental asbestos exposure in Britain will be about 1 in 10 000. The risk is an order of magnitude higher in a subgroup of exposed workers and probably in occupants in the most contaminated buildings. Further data are needed to discover whether asbestos still present in buildings, particularly schools, is a persistent or decreasing hazard to workers who disturb it and to the general population, and whether environmental exposure occurs predominantly in childhood or after beginning work. Similar studies are needed in other countries to estimate continuing environmental and occupational mesothelioma hazards worldwide, including the contribution from chrysotile.

Managing Asbestos-Containing Materials in the Built Environment: Report of a Health and Safety Executive and Government Office for Science Workshop.

The duty to manage asbestos in non-domestic premises is described in the Control of Asbestos Regulations 2012. Health and Safety Executive (HSE) policy and guidance on asbestos in the built environment in Great Britain is that asbestos-containing materials (ACMs) that are in good condition and unlikely to be disturbed can be managed in place. Where ACMs are in poor condition or likely to be disturbed they should be repaired, encapsulated or, if necessary, removed. HSE and Government Office for Science hosted a stakeholder workshop to consider evidence on the management of ACMs in public buildings. Invitees attended from a range of backgrounds (including regulatory, government, academic, medical, public interest groups, and professional service providers). Participants considered the evidence, suggested nine evidence gap areas and ranked these according to preference in an anonymous vote. The top three suggested evidence gaps were: (i) the comparative risks of managing ACMs in place versus removal; (ii) improved measurement techniques at lower fibre concentrations; and (iii) building the evidence base on the effectiveness of asbestos management and safe removal. HSE will use the workshop outputs to inform its research planning. It is anticipated that a number of initiatives for shared research will be explored.

Exposure of UK industrial plumbers to asbestos, Part II: Awareness and responses of plumbers to working with asbestos during a survey in parallel with personal sampling.

Throughout the European Union, millions tonnes of asbestos were used in the manufacture of products for building and for industrial installations. Today, in the UK, it is estimated that over half a million non-domestic premises alone have asbestos-containing materials in them and it is recognized that those working in building maintenance trades continue to be at significant risk. In part II, the awareness of UK plumbers to when they are working with asbestos was investigated and compared with the monitored levels reported in part I. The plumbers were issued by post with passive samplers, activity logs to monitor a working week and a questionnaire. The activity logs were used to assess whether maintenance workers were knowingly or unknowingly exposed to airborne asbestos fibres during a course of a working week. The questionnaire was designed to gather information on their: age, employment status, current and past perception of the frequency which they work with asbestos and knowledge of the precautions that should be taken to limit exposure and risk. Approximately 20% of workers reported on the sample log that they had worked with asbestos. There was a high correlation (93%) between the sampling log replies that they were knowingly working with asbestos and measured asbestos on the passive sampler. However, some 60% of the samples had >5 microm long asbestos structures found by transmission electron microscopy (TEM) analysis suggesting that the plumbers were aware of about only one-third of their contacts with asbestos materials throughout the week. This increased to just over one half of the plumbers being aware of their contact based on the results for phase contrast microscopy (PCM) countable asbestos fibres. The results from the questionnaire found that over half of the plumbers replying thought that they disturb asbestos only once a year and 90% of them thought they would work with asbestos for<10 h year-1. Their expectations and awareness of work with asbestos were therefore far lower than found during the period of monitoring. The response to an open question on the precautions to be taken, found that 61% of plumbers would avoid disturbance and 59% would use respiratory protection if they did disturb asbestos. However, their awareness of the methods and the need to reduce their risk by control of emissions at source was very low and suggests that further awareness raising and training is needed. The survey was carried out prior to the introduction of the duty to manage and gives a useful baseline to assess the impact of regulatory initiatives.

Exposure of UK industrial plumbers to asbestos, Part I: Monitoring of exposure using personal passive samplers.

Epidemiological data suggest that there has been and may continue to be a significant risk to maintenance workers, who through their work may disturb asbestos-containing materials (ACM). The sampling and assessment of maintenance workers' exposure is a particular problem because they may not know that they are working with ACM. A strategy to monitor their true exposure has been developed and applied to one group of workers. The asbestos exposure of industrial plumbers was measured using personal passive samplers developed at the Health and Safety Laboratory (HSL). The light-weight samplers, which collect particles by electrostatic attraction, are simple to use and do not require prior knowledge that asbestos is to be disturbed as does conventional sampling. The samplers were issued by post and analysed, after return, using transmission electron microscopy (TEM). The strategy was found to be a reasonably efficient and cost-effective way to obtain data on maintenance worker's exposure to asbestos. The results of the TEM analysis of the passive samplers showed that the percentage of workers exposed to >5 microm long asbestos fibres was 62% in Round 1 and 58% in Round 2. For phase contrast microscopy equivalent (PCME) asbestos fibres, the values were 46 and 29%, respectively. The three samples with the highest numbers of fibres were followed up and were associated with plumbers working in areas which had supposedly been stripped of asbestos just prior to their starting work, suggesting that poor removal, clean-up and clearance practice presents a significant part of the risk to plumbers. Although flow rates will vary with conditions and time, an approximate average sampling rate from previous comparisons was used to calculate the concentration. This gave an average exposure to regulated PCME fibres of 0.009 f ml-1 for amphibole asbestos and 0.049 f ml-1 for chrysotile. The calculate risk based on the PCME fibre types collected and their estimated concentrations, showed that the risk from airborne amphibole fibres was approximately 6 times greater than from chrysotile fibres. If representative, the estimated lifetime risk of death from an asbestos related cancer for an exposure from age 20 for 40 years would be 68 per 100,000, which equates to an annual risk of death of the order of 10 per million.