Quantum limits of position-sensitive photodiodes

The split photodiode and the lateral effect photodiode are two popular detectors for measuring beam displacement. For small displacements of a Gaussian beam, which is the case of interest here, they are often seen as equivalent and used interchangeably, giving a signal proportional to the displacement. We show theoretically and experimentally that in the limit of low technical noise, where the signal to noise ratio is dominated by the shot noise of the light, the lateral effect photodiode produces a better signal to noise ratio than the split photodiode, owing to its optimum spatial detector response. This quantum advantage can be practically exploited in spite of the intrinsic thermal noise of the lateral effect photodiode.

A behaviour change package to prevent hand dermatitis in nurses working in the National Health Service: results of a cluster randomized controlled trial

BACKGROUND

Occupational hand dermatitis poses a serious risk for nurses.

OBJECTIVES

To evaluate the clinical and cost-effectiveness of a complex intervention in reducing the prevalence of hand dermatitis in nurses METHODS: This was a cluster randomized controlled trial conducted at 35 hospital trusts, health boards or universities in the UK. Participants were (i) first-year student nurses with a history of atopic conditions or (ii) intensive care unit (ICU) nurses. Participants at intervention sites received access to a behavioural change programme plus moisturizing creams. Participants at control sites received usual care. The primary outcome was the change of prevalent dermatitis at follow-up (adjusted for baseline dermatitis) in the intervention vs. the control group. Randomization was blinded to everyone bar the trials unit to ensure allocation concealment. The trial was registered on the ISRCTN registry: ISRCTN53303171.

RESULTS

Fourteen sites were allocated to the intervention arm and 21 to the control arm. In total 2040 (69·5%) nurses consented to participate and were included in the intention-to-treat analysis. The baseline questionnaire was completed by 1727 (84·7%) participants. Overall, 789 (91·6%) ICU nurses and 938 (84·0%) student nurses returned completed questionnaires. Of these, 994 (57·6%) had photographs taken at baseline and follow-up (12-15 months). When adjusted for baseline prevalence of dermatitis and follow-up interval, the odds ratios (95% confidence intervals) for hand dermatitis at follow-up in the intervention group relative to the controls were 0·72 (0·33-1·55) and 0·62 (0·35-1·10) for student and ICU nurses, respectively. No harms were reported.

CONCLUSIONS

There was insufficient evidence to conclude whether our intervention was effective in reducing hand dermatitis in our populations. Linked Comment: Brans. Br J Dermatol 2020; 183:411-412.

Stomach cancer and occupational exposure to asbestos: a meta-analysis of occupational cohort studies

Background:

A recent Monographs Working Group of the International Agency for Research on Cancer concluded that there is limited evidence for a causal association between exposure to asbestos and stomach cancer.

Methods:

We performed a meta-analysis to quantitatively evaluate this association. Random effects models were used to summarise the relative risks across studies. Sources of heterogeneity were explored through subgroup analyses and meta-regression.

Results:

We identified 40 mortality cohort studies from 37 separate papers, and cancer incidence data were extracted for 15 separate cohorts from 14 papers. The overall meta-SMR for stomach cancer for total cohort was 1.15 (95% confidence interval 1.03–1.27), with heterogeneous results across studies. Statistically significant excesses were observed in North America and Australia but not in Europe, and for generic asbestos workers and insulators. Meta-SMRs were larger for cohorts reporting a SMR for lung cancer above 2 and cohort sizes below 1000.

Conclusions:

Our results support the conclusion by IARC that exposure to asbestos is associated with a moderate increased risk of stomach cancer.

Acute myeloid and chronic lymphoid leukaemias and exposure to low-level benzene among petroleum workers

BACKGROUND

High benzene exposure causes acute myeloid leukaemia (AML). Three petroleum case-control studies identified 60 cases (241 matched controls) for AML and 80 cases (345 matched controls) for chronic lymphoid leukaemia (CLL).

METHODS

Cases were classified and scored regarding uncertainty by two haematologists using available diagnostic information. Blinded quantitative benzene exposure assessment used work histories and exposure measurements adjusted for era-specific circumstances. Statistical analyses included conditional logistic regression and penalised smoothing splines.

RESULTS

Benzene exposures were much lower than previous studies. Categorical analyses showed increased ORs for AML with several exposure metrics, although patterns were unclear; neither continuous exposure metrics nor spline analyses gave increased risks. ORs were highest in terminal workers, particularly for Tanker Drivers. No relationship was found between benzene exposure and risk of CLL, although the Australian study showed increased risks in refinery workers.

CONCLUSION

Overall, this study does not persuasively demonstrate a risk between benzene and AML. A previously reported strong relationship between myelodysplastic syndrome (MDS) (potentially previously reported as AML) at our study's low benzene levels suggests that MDS may be the more relevant health risk for lower exposure. Higher CLL risks in refinery workers may be due to more diverse exposures than benzene alone.

Ensuring comparability of benzene exposure estimates across three nested case-control studies in the petroleum industry in support of a pooled epidemiological analysis

BACKGROUND

Three case-control studies each nested within a cohort of petroleum workers assessed exposure to benzene in relation to risk of haematopoietic cancers. These studies have each been updated and the cases will be pooled to derive a more powerful study. The benzene exposure of new leukemia cases and controls was estimated in accordance with each respective study's original methods. An essential component of the process of pooling the data was comparison and rationalisation of the exposure estimates to ensure accuracy and consistency of approach. This paper describes this process and presents comparative estimates before and after appropriate revision took place. The original petroleum industry studies, in Canada, the UK and Australia, were conducted at different points in time by different study teams, but the industry used similar technology in similar eras in each of these countries.

METHODS

A job history for each subject giving job title, dates of starting and leaving the job and location of work, was assembled. For each job or task, the average benzene exposure (Base Estimate (BE) in ppm) was derived from measurements collected at applicable worksites. Estimates of exposure intensity (workplace exposure estimates (WE)) were then calculated for each line of work history by adjusting the BEs for site- and era-specific exposure-related variables such as loading technology and percentage benzene in the product. To ensure that the exposure estimates were comparable among the studies, the WEs were allocated to generic Job Categories, e.g. Tanker Driver (by technology used e.g. bottom loading), Motor Mechanic. The WEs were stratified into eras, reflecting technological changes in the industry. The arithmetic mean (AM), geometric mean (GM) and range of the stratified WEs were calculated, by study, for each generic Job Category. These were then compared. The AMs of the WEs were regarded as substantially similar if they were within 20% in all three studies in one era or for at least two studies in two eras. If the AM of the WE group differed by more than 20%, the data were examined to see whether the difference was justified by differences in local exposure conditions, such as an enclosure versus open work area. Estimates were adjusted in the absence of justification for the difference.

RESULTS

Reconciliation of differences resulted in changes to a small number of underlying BEs, particularly the background values, also the BEs attributed to some individuals and changes to the allocation of jobs between Job Categories. Although the studies covered some differing sectors of the industry and different time periods, for 22 Job Categories there was sufficient overlap, particularly in the downstream distribution sector, to make comparisons possible. After adjustment 12 Job Categories were judged to be similar and 10 were judged to be justifiably different. Job-based peak and skin exposure estimates were applied in a uniform way across the studies and a single approach to scoring the certainty of the exposure estimates was identified.

CONCLUSIONS

The revised exposure estimates will be used in the pooled analysis to examine the risk of haematopoietic cancers and benzene exposure. This exercise provided an important quality control check on the exposure estimates and identified similarly exposed Job Categories that could be grouped for risk assessment analyses.

Meta-analysis of mortality and cancer incidence among workers in the synthetic rubber-producing industry

Production of synthetic rubber involves exposure to several potentially harmful chemicals. The authors carried out a systematic review and meta-analysis of cohort studies of workers in the rubber-producing industry. Data were obtained from computerized literature searches of several databases from their inception through December 2003. The reference lists of identified articles were inspected for further relevant articles. The authors conducted random-effects meta-analyses of log standardized mortality ratios (SMRs)/standardized incidence ratios. Heterogeneity between study results was explored through subgroup analyses and meta-regression on cohort demographic factors and study quality indicators. The authors identified 36 published articles reporting information on 31 different cohort groups. The meta-SMR was 0.86 (95% confidence interval (CI): 0.82, 0.91) for all-cause mortality (28 cohorts) and 0.94 (95% CI: 0.89, 1.01) for all malignant neoplasms (27 cohorts). Heterogeneity was observed for these endpoints and for the majority of disease-specific outcomes. Statistically significant excesses were observed for diabetes (meta-SMR=1.36, 95% CI: 1.17, 1.59) (five cohorts) and leukemia (meta-SMR=1.21, 95% CI: 1.03, 1.43) (16 cohorts), the latter particularly for persons working exclusively in nontire manufacturing (meta-SMR=1.70, 95% CI: 1.14, 2.54) (four cohorts). Excesses highlighted in previous narrative reviews were not substantiated. Interpretation of these results is complicated by substantial unexplainable heterogeneity; small excesses in specific mortality outcomes may have been disguised by the healthy worker effect.

Intervention development in occupational research: an example from the printing industry

BACKGROUND

Intervention development research is an essential prerequisite of any study that attempts to determine whether specific interventions work to prevent work related injury and illness.

METHODS

Focus groups (n = 5) and direct observational studies (n = 21) of printers were used to elicit key issues that would aid the development of subsequent interventions. Transcripts from these were analysed by standard qualitative methods to identify common and related themes.

RESULTS

The views of managers differed significantly from those of print workers in a number of areas, and working practices did not always follow policy. The majority of printers did not perceive dermatitis to be a major problem, although many complained of dry hands. Other key results included: the lack of skin care policy in most companies; poor understanding of the nature, causes, and treatment of dermatitis; low priority of dermatitis within health and safety concerns; little or no provision of occupational health services, particularly skin checks; variability in provision of and access to appropriate skin protection; and lack of accessible washing facilities.

CONCLUSIONS

As a result it was decided to evaluate the implementation of four

INTERVENTIONS

provision of (1) skin checks and treatment advice; (2) gloves of the correct type and size, and use of an after-work cream; (3) information on dermatitis within the printing industry; and (4) development of best practice skin care policy.

Locally generated particulate pollution and respiratory symptoms in young children

BACKGROUND

Particulate matter <10 mum (PM(10)) from fossil fuel combustion is associated with an increased prevalence of respiratory symptoms in children and adolescents. However, the effect of PM(10) on respiratory symptoms in young children is unclear.

METHODS

The association between primary PM(10) (particles directly emitted from local sources) and the prevalence and incidence of respiratory symptoms was studied in a random sample cohort of 4400 Leicestershire children aged 1-5 years surveyed in 1998 and again in 2001. Annual exposure to primary PM(10) was calculated for the home address using the Airviro dispersion model and adjusted odds ratios (ORS) and 95% confidence intervals were calculated for each microg/m(3) increase.

RESULTS

Exposure to primary PM(10) was associated with the prevalence of cough without a cold in both 1998 and 2001, with adjusted ORs of 1.21 (1.07 to 1.38) and 1.56 (1.32 to 1.84) respectively. For night time cough the ORs were 1.06 (0.94 to 1.19) and 1.25 (1.06 to 1.47), and for current wheeze 0.99 (0.88 to 1.12) and 1.28 (1.04 to 1.58), respectively. There was also an association between primary PM(10) and new onset symptoms. The ORs for incident symptoms were 1.62 (1.31 to 2.00) for cough without a cold and 1.42 (1.02 to 1.97) for wheeze.

CONCLUSION

In young children there was a consistent association between locally generated primary PM(10) and the prevalence and incidence of cough without a cold and the incidence of wheeze which was independent of potential confounders.

Mortality in the UK industrial silica sand industry: 1. Assessment of exposure to respirable crystalline silica

AIMS

To develop a job-exposure matrix (JEM) from personal and static respirable crystalline silica (RCS) measurements in UK industrial silica sand workers.

METHODS

A total of 2429 personal and 583 static RCS dust samples were collected using cyclone samplers at seven UK quarries between 1978 and 2000. These data were combined, and analysis of variance using general linear models was used to evaluate the effect of quarry, job, and year on RCS concentrations, and facilitate the creation of five quarry and three time categories with similar exposure levels by comparing the least-square GM RCS concentrations.

RESULTS

The overall geometric mean (GM) RCS concentration was 0.09 mg/m3 (geometric standard deviation 3.9). Silica flour and dry job categories tended to have the highest RCS exposure and 13.3% of all samples exceeded the UK maximum exposure level of 0.3 mg/m3. RCS levels generally decreased over time.

CONCLUSIONS

Data have been collected and used to develop a JEM for UK industrial silica sand workers between 1978 and 2000. Although there were some limitations in the data and certain assumptions were made, the use of available data to estimate exposure quantitatively is an improvement over the use of qualitative and surrogate measures of exposure. The continual collection of dust measurements in the industry is essential to facilitate the exploration of exposure-response relations that may exist between silica and silicosis, lung cancer, and other diseases.

Mortality in the UK industrial silica sand industry: 2. A retrospective cohort study

AIMS

To evaluate the mortality experience of a cohort of employees in the UK silica sand industry exposed to respirable crystalline silica (RCS).

METHODS

A retrospective cohort mortality study followed all workers to 2001 with at least one year's employment at one of seven UK silica sand producing quarries between 1950 and 1986. Each worker was assigned a job category and cumulative exposure to RCS was estimated using a job-exposure matrix.

RESULTS

A total of 764 deaths were identified in 2703 cohort members. The overall mortality rate for the cohort was lower than would be expected in the general population. Mortality from circulatory and respiratory disease was also less than expected, but death due to pneumoconiosis was slightly raised (two deaths). Mortality from all cancers was slightly decreased. Mortality was not raised in any job category. Cancer mortality was raised at one quarry due to a significant increase in lung (standardised mortality rate (SMR) 162.0, 95% CI 113.5 to 224.3) and bladder (SMR 366.5, 95% CI 167.6 to 695.7) cancers. Mortality from lung cancer and other causes did not show a trend with cumulative exposure to RCS.

CONCLUSIONS

This study did not show any consistent relation between RCS exposure (in the absence of other known carcinogens) and the development of lung cancer. This contrasts with a number of studies that have shown positive findings in similar and related industries.

Estimation of the impact on children's health of environmental tobacco smoke in England and Wales

In this paper, the population attributable risk (PAR), a measure of the excess risk of disease associated with a risk factor, is calculated for some of the common adverse health effects that have been associated with exposure of children to environmental tobacco smoke (ETS): childhood lower respiratory illness, chronic middle ear disease, asthma and sudden infant death syndrome (SIDS). Published data on both risk estimates and the percentage of children exposed to ETS in the home (prevalence of ETS) have been utilised. The percentage of childhood lower respiratory illness and middle ear disease typically attributable to ETS from either parent smoking ranged from 9% for asthma prevalence and for referral for glue ear, to 25% for hospital admission for lower respiratory illness. Where data were available to calculate PARs separately for mother only smoking and father only smoking, the PARs were generally larger for mothers only smoking, due mainly to higher odds ratios for mothers only smoking. The PAR for SIDS attributable to ETS from mother only smoking was 11%. Although based on a small number of studies, the PAR for SIDS attributable to smoking of fathers only was similar to that attributable to the smoking of mothers only, largely due to the higher prevalence of households where only the father smokes. This study has shown that the impact of ETS on childhood illness can be considerable, emphasising the importance of the need to develop effective strategies for reducing the risk of ETS exposure in the home and elsewhere.

Reducing domestic exposure to environmental tobacco smoke: a review of attitudes and behaviours

This paper reviews research on attitudes and behaviours towards environmental tobacco smoke (ETS), with a special focus on child health and the indoor environment. Research needs and ways forward to encourage reductions in domestic ETS levels are discussed. Published material was identified through online literature searches (Medline, Toxline, Cancerlit, Biosis, Embase, Enviroline, Sociological Abstracts, Social Science Citation Index, Academic Index and Psychinfo). The literature search strategy employed search terms such as "passive smoking" or "environmental tobacco smoke" with "attitude" or "awareness" and other synonyms. Additional publications were identified by citation chasing and expert advice. Focusing on the UK, studies that provided survey-derived data about attitudes and behaviours in relation to ETS exposure in the indoor environment were selected for review. Published studies from other countries were also included when they provided information pertinent to this review. Most people are aware of the health risks associated with ETS exposure, and there is a high level of support for smoking restrictions in public places to protect non-smokers from ETS. However, although there is concern among both non-smoking and smoking parents about children and second-hand smoke, many people allow children to be exposed to ETS in the home. The review suggests that traditional health promotion campaigns have had only limited success in encouraging ETS risk reduction measures in the home. Because ETS is a public health priority, particularly in relation to child health, the barriers to the uptake of such measures need to be explored in detail to inform the future promotion of reductions in domestic levels of ETS.

The prevalence of occupational dermatitis in the UK printing industry

AIMS

To quantify occupational ill health resulting from dermatitis in the UK printing industry and to explore links with particular processes and activities.

METHODS

Approximately 2600 members of the Graphical, Paper and Media Union living in Nottinghamshire were sent a self completion questionnaire. A sample of respondents, both those who reported current skin problems and those who did not, were invited for a short dermatological examination.

RESULTS

The overall response rate was 62%. A total of 1189 respondents were directly involved in the printing industry and categorised according to work in pre-press (25%), printing (46%), or finishing (42%) processes. A total of 490 respondents (41%) self reported having a skin complaint at some time. Prevalence was highest in males (43%) and those working in printing (49%), in particular those who cleaned rollers and cylinders or who came into contact with substances containing isocyanates on a daily basis. The most commonly affected areas reported were the fingers and webs between the fingers. Twenty six per cent of the 490 reported a current problem on the hand. Reported symptoms included itching (61%), rash (58%), and dry skin (56%). Although certain printing industry substances were thought by respondents to aggravate their condition, constant washing and friction was most often cited. Reported use of protective equipment and cleansing products was generally high, particularly by printers. Clinical examination confirmed the high self reported prevalence and also identified a substantial proportion of mild cases which were not reported. The overall prevalence of occupationally related skin complaints is estimated to be 40%.

CONCLUSIONS

A much higher prevalence of dermatitis has been identified than from routine surveillance schemes. The use of good quality records from unions with high membership facilitated access to workers across a range of company sites and printing processes. Validation of self reported symptoms through clinical examination was shown to be essential. The importance of non-chemical causes of dermatitis was highlighted. The findings point towards the need for the development of effective and acceptable risk reduction strategies, in particular to reduce water contact and friction.

Clinical examinations to validate self-completion questionnaires: dermatitis in the UK printing industry

A self-completion questionnaire sent to 2600 Nottinghamshire members of the Graphical Paper and Media Union elicited a 62% response. Forty one per cent of respondents reported suffering a skin complaint at some time and 11% had a current skin problem on the hand. This paper reports the validation stage of the study. Samples of 45 'cases' of self-reported dermatitis and 60 'controls', who reported they had never suffered a skin complaint, were clinically examined. All 45 self-reported cases were clinically confirmed as dermatitis. Occupationally related irritant contact dermatitis (ICD) was diagnosed in 20 (44%); 26 (58%) complaints were thought to be induced or exacerbated by occupation. Of the controls, 21 (35%) were also diagnosed with a skin complaint, the majority being mild, with an occupational association in 17, the majority (15) being ICD. Sixteen ICD cases were patch tested resulting in positive reactions to colophony, neomycin, nickel and potassium dichromate (2 of each). Two cases of basal cell carcinoma on the face were also identified, of which the participants were unaware. Although there was no false positive self-reporting there was a considerable number of false negatives, demonstrating the importance of clinical validation of questionnaires relating to industrial skin disease. This study has highlighted the need for improvement in skin care provision in the printing industry.

Role of ambulatory blood pressure monitoring in the assessment and prognosis of patients with borderline hypertension

The role of ambulatory blood pressure (ABP) monitoring in the assessment of mild/borderline hypertension (BHT) is unclear. The aim of this study was to test the hypothesis that measurement of ABP in borderline hypertensives differentiates patients with true mild hypertension from those with isolated clinic hypertension (raised office BP but normal ABP) and that a raised ABP identifies a subgroup who are more likely to progress to and require treatment over 1 year. Consecutive untreated patients with BHT (n = 127, 44 +/- 13 years, 45% male) were divided into two groups according to awake ABP: Group 1 (normal ABP < or = 136/86, n = 48), and Group 2 (abnormal ABP > 136/86, n = 79). Left ventricular mass index (LVMI) was greater (116 +/- 30 vs 101 +/- 25 g/m2, p < 0.01) and the proportion of patients with an increased LVMI was significantly higher (34% vs 17%, p = 0.05) in Group 2. During 1 year of follow-up, significantly more patients in Group 2 (34%) required antihypertensive treatment compared with Group 1 (8%, p = 0.01). ABP monitoring usefully discriminates between patients with true BHT and those with isolated clinic hypertension. An elevated awake ABP on initial assessment is associated with a higher LVMI and a greater likelihood of progression to moderate hypertension requiring pharmacological treatment.

Impact of private funding on access to elective hospital treatment in the regions of England and Wales. National records survey

BACKGROUND

The UK National Health Service aims to match access to health care to the level of need and to reduce inequalities in the health of sub-populations. One in ten persons have private medical insurance (PMI). This study describes the impact of private purchasing on access to hospital care in regions according to health need.

METHOD

Details of admissions to NHS hospitals in one year and waiting times were obtained from the government's Hospital Episodes Statistics, and of patients in independent hospitals through weighted time samples of records. Data were combined into two groups, state funded and privately funded patients. The prevalence of limiting longstanding illness and the proportions of individuals covered by PMI in Wales and the eight English health regions were obtained from the General Household Survey. Correlation coefficients were calculated for inter-regional relationships between measures of need, provision of resources and levels of activity.

RESULTS

Limiting, longstanding illness was significantly associated with NHS resource levels, NHS hospital activity, and total hospital activity, however funded; and inversely with PMI coverage, waiting times for NHS admission and levels of privately funded activity. Waiting times for admission were positively correlated with PMI coverage.

CONCLUSIONS

Regionally, NHS resources and activity match need. Private hospital use complements lower levels of NHS service. Private consumption does not distort access according to need but in regions with lower levels of NHS activity those least deprived may make relatively more use of NHS hospitals, thus widening the health gap. Small area studies should explore this.

Assessing exposures in the United Kingdom's Armed Forces--a review of systems that collect data useful for exposure assessment

The ability to assess the exposure of individuals or groups is a critical element in any effective health surveillance system, as it provides the opportunity to identify the causes of ill health, the levels of exposure resulting in ill health and, through controlling exposures, to protect the health of Service personnel. As part of a wider programme to enhance the health surveillance capabilities of the Defence Medical Services, a project was undertaken to assess the collection and retention of data for exposure assessment in the United Kingdom's Armed Forces. The systems investigated include those for health, safety and environment policy, personnel and pay, medical records, environmental and occupational monitoring and historical records. It was found that the use of many systems for exposure assessment would be hampered by inconsistencies in the data collected, poor accessibility and linkage, and variability in the retention of the data. This paper highlights some of the problems that limit the usefulness of the record systems for exposure assessment and summarizes the principal recommendations made for enhancing the systems to better facilitate health surveillance.

The possible effects on health, comfort and safety of aircraft cabin environments

A consultation was undertaken to investigate the views and concerns of stakeholders in the aircraft industry about the possible harmful effects on personal health, comfort and safety of aircraft cabin environments. Stakeholders were identified from a variety of sources including Government agencies, the Internet, House of Lords inquiry, and suggestions of interviewees. They represented: aircraft crews, aircraft constructors and engineers, government departments and authorities, holiday/flight companies, insurance companies, non-governmental organisations, occupational health physicians, passenger representatives, and independent researchers and consultants. Eighty-seven were contacted of which 57 were interviewed over the telephone using a semi-structured questionnaire. Their concerns were transcribed into a standard format and analysed qualitatively. Key stakeholders, along with Government officials, were invited to a workshop to discuss and prioritize the issues raised during the interviews. The main concerns expressed by the participants fell into five main areas: deep vein thrombosis, air quality, infection, cosmic radiation, and jet lag and work patterns. In addition, a number of safety concerns were raised as well as comments on the provision of appropriate advice to passengers. It was generally felt that further research was required on each of these subjects, as well as an improvement in the quality, quantity and availability of information provided for passengers prior to boarding a flight.

Exposure information in European industry: implications for future occupational research

A survey has been carried out among European industry to investigate the collection and retention of records which might be used for epidemiological research. Exposure information results are reported. Approximately 1,000 questionnaires focusing on exposure information were sent to seven countries, with a 42 percent response rate. Eighty-two percent of companies reported that exposure measurements were taken to comply with legal requirements. Measurements were most often made for noise (84%), with 48% of companies measuring chemicals, 48 percent particulates but only 10 percent vibration. Measurements were most often taken for specific locations (73%), rather than for particular jobs (54%) or individual workers (50%). Eighty percent recorded location, sampling date, agents measured, and units of measurement, with about 70 percent recording job being sampled, sampling method, and duration and plant process, but less than 60 percent recording environmental conditions or worker details. Overall, only 10 percent of companies kept their exposure information forever, and 71 percent kept it for 10 years or less. Legislative requirements were most often cited as the reason for retention of records. The variation in the quantity and quality of measurements and the early destruction of records poses considerable problems for European research. Inaccuracy and misclassification of exposure limits the ability to establish causal relationships between effect and disease. Records should uniquely identify an individual worker and facilitate linkage to exposure and health effects information. Their format should be accessible, linkable, and secure. Data should be kept by an identifiable organization and there should be a secure chain of custody if a company goes out of business. Unless industry can be motivated to follow these guidelines the future of research into occupational causes of ill health, and in particular, the evaluation of exposure, will be limited.

Setting microbiological water quality standards for sea bathing--a critical evaluation

The World Health Organization (WHO) recently produced draft guidelines for safe recreational water environments. The microbiological standards proposed in the guidelines are expected to overestimate the degree of water quality required to provide given levels of public health protection. The WHO standards were obtained by means of a risk assessment which featured a dose-response model derived from a series of randomised controlled trials. The trials have many strengths but biases and problems with statistical analysis are likely to have led to over-estimation of the risks from bathing in the dose-response model. In addition, the WHO risk assessment failed to consider the effects of uncertainty and variability in risk estimates and sensitivity to model assumptions. Improved standards could be obtained by extending the risk assessment to examine these effects and by incorporating a suitably revised dose-response model.

Benzene in the environment: an assessment of the potential risks to the health of the population

OBJECTIVES

Benzene has long been recognised as a carcinogen and recent concern has centred on the effects of continuous exposure to low concentrations of benzene both occupationally and environmentally. This paper presents an overview of the current knowledge about human exposure to benzene in the United Kingdom population based on recently published data, summarises the known human health effects, and uses this information to provide a risk evaluation for sections of the general United Kingdom population.

METHOD

Given the minor contribution that non-inhalation sources make to the overall daily intake of benzene to humans, only exposure from inhalation has been considered when estimating the daily exposure of the general population to benzene. Exposure of adults, children, and infants to benzene has been estimated for different exposure scenarios with time-activity patterns and inhalation and absorption rates in conjunction with measured benzene concentrations for a range of relevant microenvironments. Exposures during refuelling and driving, as well as the contribution of active and passive tobacco smoke, have been considered as part of the characterisation of risk of the general population.

RESULTS

Infants (<1 years old), the average child (11 years old), and non-occupationally exposed adults, receive average daily doses in the range of 15-26, 29-50, and 75-522 microg of benzene, respectively, which correspond to average ranges to benzene in air of 3.40-5.76 microg/m(3), 3.37-5.67 microg/m(3), and 3.7-41 microg/m(3) for infants, children, and adults, respectively. Infants and children exposed to environmental tobacco smoke have concentrations of exposure to benzene comparable with those of an adult passive smoker. This is a significant source of exposure as a 1995 United Kingdom survey has shown that 47% of children aged 2-15 years live in households where at least one person smokes. The consequence of exposure to benzene in infants is more significant than for children or adults owing to their lower body weight, resulting in a higher daily intake for infants compared with children or non-smoking adults. A worst case scenario for exposure to benzene in the general population is that of an urban smoker who works adjacent to a busy road for 8 hours/day-for example, a maintenance worker-who can receive a mean daily exposure of about 820 microg (equal to an estimated exposure of 41 microg/m(3)). The major health risk associated with low concentrations of exposure to benzene has been shown to be leukaemia, in particular acute non-lymphocytic leukaemia. The lowest concentration of exposure at which an increased incidence of acute non-lymphocytic leukaemia among occupationally exposed workers has been reliably detected, has been estimated to be in the range of 32-80 mg/m(3). Although some studies have suggested that effects may occur at lower concentrations, clear estimates of risk have not been determined, partly because of the inadequacy of exposure data and the few cases.

CONCLUSIONS

Overall the evidence from human studies suggests that any risk of leukaemia at concentrations of exposure in the general population of 3.7-42 microg/m(3)-that is at concentrations three orders of magnitude less than the occupational lowest observed effect level-is likely to be exceedingly small and probably not detectable with current methods. This is also likely to be true for infants and children who may be exposed continuously to concentrations of 3.4-5.7 microg/m(3). As yet there is no evidence to suggest that continuous exposures to these environmental concentrations of benzene manifest as any other adverse health effect.

Variability of diurnal changes in ambulatory blood pressure and nocturnal dipping status in untreated hypertensive and normotensive subjects

An absent or diminished blood pressure (BP) fall during sleep (so-called "nondipping") has been associated with a higher risk of cardiovascular complications, but the long-term reproducibility of dipper status and the relationship between diurnal changes in BP and perceived sleep quality have not been previously documented in untreated hypertensive patients. Ambulatory BP (ABP) and dipping status were examined in 79 subjects (69 hypertensives and 10 normotensives) at 0, 6, and 12 months. Fifty-six percent of subjects had no change in their dipping status, the majority (53%) dipping normally on all three occasions. However, 44% of patients had variable dipping status, and normal nighttime dipping in BP was observed more often when patients perceived their sleep quality to be good during the period of ABP recording. These results highlight significant intrasubject variability in the diurnal fluctuations in ABP and dipper status, which may in part reflect day-to-day variations in sleep disturbance during ABP monitoring. Classifying hypertensive patients into dippers or nondippers on the basis of a single ABP recording is unreliable and potentially misleading.

Collection of data for occupational epidemiologic research--results from a survey of European industry

OBJECTIVES

This study was carried out to provide information on the development of recommendations for the harmonization of record collection and retention by European industry to aid future epidemiologic research.

METHODS

A postal survey was carried out of 500 companies, stratified by size, in each of the 7 member states of the European Union. Three questionnaires were used respectively focusing on biographic and work history information, health records, and records containing information on exposures. Each questionnaire investigated the data items collected, the data format and location, the length of retention and factors influencing the length of retention.

RESULTS

The response after 2 reminders was 39%, 42%, and 33% for the biographic, exposure, and health questionnaires, respectively. Most companies recorded surname, first names, gender, address, postal code, and date of birth, but information on children, place of birth, and nationality were less frequently recorded. Overall, 26% of the companies had an occupational health service, 56% using a contract service, but the percentages varied greatly between countries. Over 85% of the French and Spanish companies carried out routine health surveillance compared with 20% of the companies in Germany and the United Kingdom. Exposure was generally measured for noise (84%), but only 48% of the companies measured chemicals and particulates. Measurements were more common for specific locations (73%) than for particular jobs or individual workers. Approximately 70% of the records were discarded within 10 years, French companies being the most likely to retain all types of records. Legislation was cited as the strongest influence on retention policies.

CONCLUSIONS

Unless both individuals and industry are made more aware of the importance of record keeping, future occupational epidemiology in Europe will remain limited.

Patients and procedures in short-stay independent hospitals in England and Wales, 1997-1998

BACKGROUND

Private hospitals' activities are not routinely reported, so what services they provide and for whom is not known. This study describes the clientele and case-mix of independent hospitals in England and Wales in 1997-1998.

METHOD

Person, clinical and funding data were collected on samples of patients admitted to 215 of 221 independent hospitals open in 1997-1998. Sample numbers were weighted to reflect sampling duration, region, season and non-response.

RESULTS

A total of 37,434 sampled records represented 828,422 admissions: 406,843 in-patients (5 per cent fewer than in 1992-1993) and 421,580 day cases (69 per cent more); 806,509 were residents of England and Wales (up 24 per cent); 16,628 came from overseas (down 20 per cent). Numbers increased in all age groups except children; 25 per cent were 65 or over (18 per cent in 1992-1993). The commonest procedures were abortion (11 per cent), endoscopy of the gastro-intestinal tract (10 per cent) or joints (5 per cent), lens operations (5 per cent), hernia repairs (3 per cent), and other common National Health Service (NHS) elective operations. The NHS funded 84,561 patients (11 per cent of the total) including 41,942 non-abortion cases (6 per cent). A total of 540,996 (76 per cent) paid through insurance; 119,101 (17 per cent) were self-funded including 30 per cent of the over-75s. Ninety-five per cent of patients went home, 0.3 per cent died and 0.2 per cent were transferred to NHS hospitals.

CONCLUSIONS

Demand for short-stay independent hospital care is rising. The clientele is becoming older, and readier to pay out of pocket. Clinical activity is mainly surgical and similar to NHS elective surgical demand. One year's caseload equals 10 weeks' elective admissions to NHS hospitals, in that sense relieving the NHS. The scale of transfer to NHS hospitals (three per day) is small.

Reporting of occupational and environmental research: use and misuse of statistical and epidemiological methods

OBJECTIVES

To report some of the most serious omissions and errors which may occur in papers submitted to Occupational and Environmental Medicine, and to give guidelines on the essential components that should be included in papers reporting results from studies of occupational and environmental health.

METHODS

Since 1994 Occupational and Environmental Medicine has used a panel of medical statisticians to review submitted papers which have a substantial statistical content. Although some studies may have genuine errors in their design, execution, and analysis, many of the problems identified during the reviewing process are due to inadequate and incomplete reporting of essential aspects of a study. This paper outlines some of the most important errors and omissions that may occur. Observational studies are often the preferred choice of design in occupational and environmental medicine. Some of the issues relating to design, execution, and analysis which should be considered when reporting three of the most common observational study designs, cross sectional, case-control, and cohort are described. An illustration of good reporting practice is given for each. Various mathematical modelling techniques are often used in the analysis of these studies, the reporting of which causes a major problem to some authors. Suggestions for the presentation of results from modelling are made.

CONCLUSIONS

There is increasing interest in the development and application of formal "good epidemiology practices". These not only consider issues of data quality, study design, and study conduct, but through their structured approach to the documentation of the study procedures, provide the potential for more rigorous reporting of the results in the scientific literature.