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1.  Estimation methods with ordered exposure subject to measurement error and missingness in semi-ecological design 
Background
In epidemiological studies, it is often not possible to measure accurately exposures of participants even if their response variable can be measured without error. When there are several groups of subjects, occupational epidemiologists employ group-based strategy (GBS) for exposure assessment to reduce bias due to measurement errors: individuals of a group/job within study sample are assigned commonly to the sample mean of exposure measurements from their group in evaluating the effect of exposure on the response. Therefore, exposure is estimated on an ecological level while health outcomes are ascertained for each subject. Such study design leads to negligible bias in risk estimates when group means are estimated from ‘large’ samples. However, in many cases, only a small number of observations are available to estimate the group means, and this causes bias in the observed exposure-disease association. Also, the analysis in a semi-ecological design may involve exposure data with the majority missing and the rest observed with measurement errors and complete response data collected with ascertainment.
Methods
In workplaces groups/jobs are naturally ordered and this could be incorporated in estimation procedure by constrained estimation methods together with the expectation and maximization (EM) algorithms for regression models having measurement error and missing values. Four methods were compared by a simulation study: naive complete-case analysis, GBS, the constrained GBS (CGBS), and the constrained expectation and maximization (CEM). We illustrated the methods in the analysis of decline in lung function due to exposures to carbon black.
Results
Naive and GBS approaches were shown to be inadequate when the number of exposure measurements is too small to accurately estimate group means. The CEM method appears to be best among them when within each exposure group at least a ’moderate’ number of individuals have their exposures observed with error. However, compared with CEM, CGBS is easier to implement and has more desirable bias-reducing properties in the presence of substantial proportions of missing exposure data.
Conclusion
The CGBS approach could be useful for estimating exposure-disease association in semi-ecological studies when the true group means are ordered and the number of measured exposures in each group is small. These findings have important implication for cost-effective design of semi-ecological studies because they enable investigators to more reliably estimate exposure-disease associations with smaller exposure measurement campaign than with the analytical methods that were historically employed.
doi:10.1186/1471-2288-12-135
PMCID: PMC3552934  PMID: 22947254
Constrained estimation; EM algorithm; Group-based strategy; Isotonic regression; Measurement errors
2.  The relationship between workers’ self-reported changes in health and their attitudes towards a workplace intervention: lessons from smoke-free legislation across the UK hospitality industry 
BMC Public Health  2012;12:324.
Background
The evaluation of smoke-free legislation (SFL) in the UK examined the impacts on exposure to second-hand smoke, workers’ attitudes and changes in respiratory health. Studies that investigate changes in the health of groups of people often use self-reported symptoms. Due to the subjective nature it is of interest to determine whether workers’ attitudes towards the change in their working conditions may be linked to the change in health they report.
Methods
Bar workers were recruited before the introduction of the SFL in Scotland and England with the aim of investigating their changes to health, attitudes and exposure as a result of the SFL. They were asked about their attitudes towards SFL and the presence of respiratory and sensory symptoms both before SFL and one year later. Here we examine the possibility of a relationship between initial attitudes and changes in reported symptoms, through the use of regression analyses.
Results
There was no difference in the initial attitudes towards SFL between those working in Scotland and England. Bar workers who were educated to a higher level tended to be more positive towards SFL. Attitude towards SFL was not found to be related to change in reported symptoms for bar workers in England (Respiratory, p = 0.755; Sensory, p = 0.910). In Scotland there was suggestion of a relationship with reporting of respiratory symptoms (p = 0.042), where those who were initially more negative to SFL experienced a greater improvement in self-reported health.
Conclusions
There was no evidence that workers who were more positive towards SFL reported greater improvements in respiratory and sensory symptoms. This may not be the case in all interventions and we recommend examining subjects’ attitudes towards the proposed intervention when evaluating possible health benefits using self-reported methods.
doi:10.1186/1471-2458-12-324
PMCID: PMC3407478  PMID: 22551087
‘Self-Reported Health’; Attitudes; ‘Workplace Intervention’; ‘Public Health Intervention’
3.  An Integrated Approach to the Exposome 
Environmental Health Perspectives  2012;120(3):a103-a104.
doi:10.1289/ehp.1104719
PMCID: PMC3295361  PMID: 22381920
4.  Mobile phone use and risk of glioma in adults: case-control study 
BMJ : British Medical Journal  2006;332(7546):883-887.
Objective To investigate the risk of glioma in adults in relation to mobile phone use.
Design Population based case-control study with collection of personal interview data.
Setting Five areas of the United Kingdom.
Participants 966 people aged 18 to 69 years diagnosed with a glioma from 1 December 2000 to 29 February 2004 and 1716 controls randomly selected from general practitioner lists.
Main outcome measures Odds ratios for risk of glioma in relation to mobile phone use.
Results The overall odds ratio for regular phone use was 0.94 (95% confidence interval 0.78 to 1.13). There was no relation for risk of glioma and time since first use, lifetime years of use, and cumulative number of calls and hours of use. A significant excess risk for reported phone use ipsilateral to the tumour (1.24, 1.02 to 1.52) was paralleled by a significant reduction in risk (0.75, 0.61 to 0.93) for contralateral use.
Conclusions Use of a mobile phone, either in the short or medium term, is not associated with an increased risk of glioma. This is consistent with most but not all published studies. The complementary positive and negative risks associated with ipsilateral and contralateral use of the phone in relation to the side of the tumour might be due to recall bias.
doi:10.1136/bmj.38720.687975.55
PMCID: PMC1440611  PMID: 16428250
5.  Biological monitoring of pesticide exposures in residents living near agricultural land 
BMC Public Health  2011;11:856.
Background
There is currently a lack of reliable information on the exposures of residents and bystanders to pesticides in the UK. Previous research has shown that the methods currently used for assessing pesticide exposure for regulatory purposes are appropriate for farm workers [1]. However, there were indications that the exposures of bystanders may sometimes be underestimated. The previous study did not collect data for residents. Therefore, this study aims to collect measurements to determine if the current methods and tools are appropriate for assessing pesticide exposure for residents living near agricultural fields.
Methods/design
The study will recruit owners of farms and orchards (hereafter both will be referred to as farms) that spray their agricultural crops with certain specified pesticides, and which have residential areas in close proximity to these fields. Recruited farms will be asked to provide details of their pesticide usage throughout the spray season. Informed consenting residents (adults (18 years and over) and children (aged 4-12 years)) will be asked to provide urine samples and accompanying activity diaries during the spraying season and in addition for a limited number of weeks before/after the spray season to allow background pesticide metabolite levels to be determined. Selected urine samples will be analysed for the pesticide metabolites of interest. Statistical analysis and mathematical modelling will use the laboratory results, along with the additional data collected from the farmers and residents, to determine systemic exposure levels amongst residents. Surveys will be carried out in selected areas of the United Kingdom over two years (2011 and 2012), covering two spraying seasons and the time between the spraying seasons.
Discussion
The described study protocol was implemented for the sample and data collection procedures carried out in 2011. Based on experience to date, no major changes to the protocol are anticipated for the 2012 spray season although the pesticides and regional areas for inclusion in 2012 are still to be confirmed.
doi:10.1186/1471-2458-11-856
PMCID: PMC3236113  PMID: 22074397
6.  Levels of second hand smoke in pubs and bars by deprivation and food-serving status: a cross-sectional study from North West England 
BMC Public Health  2006;6:42.
Background
The UK government proposed introducing partial smokefree legislation for England with exemptions for pubs and bars that do not prepare and serve food. We set out to test the hypothesis that pubs from more deprived areas and non food-serving pubs have higher levels of particulate air pollution.
Methods
We conducted a cross sectional study in four mainly urban areas of the North West of England. We recruited a stratified random sample of 64 pubs divided into four groups based on whether their local population was affluent or deprived (using a UK area based deprivation measure), and whether or not they served food. The timing of air quality monitoring stratified to ensure similar distribution of monitoring by day of the week and time of evening between groups. We used a portable air quality monitor to collect fine particle (PM2.5) levels over a minimum of 30 minutes in areas where smoking was allowed,, and calculated mean time-time weighted average PM2.5 levels.
Results
Mean PM2.5 was 285.5 μg/m3 (95% CI 212.7 to 358.3). Mean levels in the four groups were: affluent food-serving pubs (n = 16) 188.1 μg/m3 (95%CI 128.1 to 248.1); affluent non food-serving (n = 16) 186.8 μg/m3 (95%CI 118.9 to 254.3); deprived food-serving (n = 17) 399.4 μg/m3 (95%CI 177.7 to 621.2); and deprived non food-serving (n = 15) 365.7 μg/m3 (195.6 to 535.7). Levels were higher in pubs in deprived communities: mean 383.6 μg/m3 (95% CI 249.2 to 518.0) vs 187.4 μg/m3 (144.8 to 229.9); geometric mean 245.2 μg/m3 vs 151.2 μg/m3 (p = 0.03). There was little difference in particulate levels between food and non food-serving pubs.
Conclusion
This study adds to the evidence that the UK government’s proposals for partial smokefree legislation in England would offer the least protection to the most heavily exposed group - bar workers and customers in non food-serving pubs in deprived areas. The results suggest these proposals would work against the UK government’s stated aim to reduce health inequalities.
doi:10.1186/1471-2458-6-42
PMCID: PMC1397813  PMID: 16504071

Results 1-6 (6)