Who is in the near market for bicycle sharing? Identifying current, potential, and unlikely users of a public bicycle share program in Vancouver, Canada.

BACKGROUND: Public bicycle share programs in many cities are used by a small segment of the population. To better understand the market for public bicycle share, this study examined the socio-demographic and transportation characteristics of current, potential, and unlikely users of a public bicycle share program and identified specific motivators and deterrents to public bicycle share use. METHODS: We used cross-sectional data from a 2017 Vancouver public bicycle share (Mobi by Shaw Go) member survey (n = 1272) and a 2017 population-based survey of Vancouver residents (n = 792). We categorized non-users from the population survey as either potential or unlikely users based on their stated interest in using public bicycle share within the next year. We used descriptive statistics to compare the demographic and transportation characteristics of current users to non-users, and multiple logistic regression to compare the profiles of potential and unlikely users. RESULTS: Public bicycle share users in Vancouver tended to be male, employed, and have higher educations and incomes as compared to non-users, and were more likely to use active modes of transportation. The vast majority of non-users (74%) thought the public bicycle share program was a good idea for Vancouver. Of the non-users, 23% were identified as potential users. Potential users tended to be younger, have lower incomes, and were more likely to use public transit for their main mode of transportation, as compared to current and unlikely users. The most common motivators among potential users related to health benefits, not owning a bicycle, and stations near their home or destination. The deterrents among unlikely users were a preference for riding their own bicycle, perceived inconvenience compared to other modes, bad weather, and traffic. Cost was a deterrent to one-fifth of unlikely users, notable given they tended to have lower incomes than current users. CONCLUSION: Findings can help inform targeted marketing and outreach to increase public bicycle share uptake in the population.

Literature review: dermal monitoring data for pesticide exposure assessment of farm workers.

OBJECTIVE: To conduct a literature review to determine the types of information that existing dermal pesticide monitoring data could provide for future pesticide exposure assessment in occupational epidemiology. METHODS: A systematic literature search was performed on eight online databases. Two screening phases with predetermined criteria identified the qualifying literature. Standard information and dermal pesticide monitoring data were recorded and summarized from each qualifying study to assess its usefulness for future pesticide exposure assessment. RESULTS: A total of 31 farm studies qualified for review; task information was used to standardize all farm job(s) evaluated into 5 job groups: operators, applicators, mixer-loaders, field workers, and flaggers. When attempting to compare dermal exposure levels between studies, two types of variation were identified: (1) variation in study focus and reporting and 2) variation in exposure levels. The former variation type prevented exposure level comparisons between studies. Within studies, exposure levels were compared across body parts to identify that which had the highest measured exposure and to determine if results were similar in other studies that evaluated the same farm job. Using studies that measured exposure for multiple farm jobs, within study comparisons of total body exposure were performed to evaluate work factors. CONCLUSION: Future dermal pesticide exposure monitoring studies should standardize reporting procedures, as suggested in this review, to allow for more extensive dermal data comparisons. Body parts with highest measured levels of dermal exposure were identified by farm job, along with work factors to be further investigated as potential dermal pesticide exposure determinants for farm workers.

Risk Factors for Low Back Disorders in Saskatchewan Farmers: Field-based Exposure Assessment to Build a Foundation for Epidemiological Studies.

BACKGROUND: Studies of many geographical settings and agricultural commodities show that low back disorders are an important public health issue among farmers, who represent a special rural population. However, few studies have examined the impact of low back disorders on farmers' work or the strategies that they adopt to avoid associated pain and disability. OBJECTIVE: This study protocol will investigate 3 issues related to low back disorders in Saskatchewan farmers: (1) the vibration, heavy lifting, and awkward postures farmers encounter during their work that might contribute to low back disorders; (2) the impact low back disorders have on farmers in terms of their ability to work; and (3) the types of preventative measures and solutions that farmers implement to reduce the occurrence of low back pain. METHODS: To answer these questions, researchers will travel to 30 farms to make measurements of vibration, lifting, and posture during the farmers' regular work tasks. Farmers will be interviewed about any pain and/or disability using standardized interview questions. Farmers will also be asked about safety measures they have implemented at their farm, such as modified tools or equipment, to reduce the occurrence of low back disorders or pain. RESULTS: Data collection is currently underway for this study, with the intention to complete all data collection and analysis by the end of 2018. CONCLUSIONS: Occupational determinants of health such as vibration, heavy lifting, and awkward postures are important in the development and progression of low back disorders, and the results of this study will allow for cost-effective epidemiological studies of these determinants in the future. In identifying prevention strategies, this study will also facilitate future research evaluating the effectiveness of safety measures.

Parkinson's disease and occupation: differences in associations by case identification method suggest referral bias.

METHODS: We used a population-based sample of 403 Parkinson's disease cases and 405 controls to examine risks by occupation. Results were compared to a previous clinic-based analysis. RESULTS: With censoring of jobs held within 10 years of diagnosis, the following had significantly or strongly increased risks: social science, law and library jobs (OR = 1.8); farming and horticulture jobs (OR = 2.0); gas station jobs (OR = 2.6); and welders (OR = 3.0). The following had significantly decreased risks: management and administration jobs (OR = 0.70); and other health care jobs (OR = 0.44). CONCLUSIONS: These results were consistent with other findings for social science and farming occupations. Risks for teaching, medicine and health occupations were not elevated, unlike our previous clinic-based study. This underscores the value of population-based over clinic-based samples. Occupational studies may be particularly susceptible to referral bias because social networks may spread preferentially via jobs.

Recruitment for Occupational Research: Using Injured Workers as the Point of Entry into Workplaces.

OBJECTIVE: To investigate the feasibility, costs and sample representativeness of a recruitment method that used workers with back injuries as the point of entry into diverse working environments. METHODS: Workers' compensation claims were used to randomly sample workers from five heavy industries and to recruit their employers for ergonomic assessments of the injured worker and up to 2 co-workers. RESULTS: The final study sample included 54 workers from the workers' compensation registry and 72 co-workers. This sample of 126 workers was based on an initial random sample of 822 workers with a compensation claim, or a ratio of 1 recruited worker to approximately 7 sampled workers. The average recruitment cost was CND$262/injured worker and CND$240/participating worksite including co-workers. The sample was representative of the heavy industry workforce, and was successful in recruiting the self-employed (8.2%), workers from small employers (<20 workers, 38.7%), and workers from diverse working environments (49 worksites, 29 worksite types, and 51 occupations). CONCLUSIONS: The recruitment rate was low but the cost per participant reasonable and the sample representative of workers in small worksites. Small worksites represent a significant portion of the workforce but are typically underrepresented in occupational research despite having distinct working conditions, exposures and health risks worthy of investigation.

Anthropometry-corrected exposure modeling as a method to improve trunk posture assessment with a single inclinometer.

Measuring trunk posture in the workplace commonly involves subjective observation or self-report methods or the use of costly and time-consuming motion analysis systems (current gold standard). This work compared trunk inclination measurements using a simple data-logging inclinometer with trunk flexion measurements using a motion analysis system, and evaluated adding measures of subject anthropometry to exposure prediction models to improve the agreement between the two methods. Simulated lifting tasks (n=36) were performed by eight participants, and trunk postures were simultaneously measured with each method. There were significant differences between the two methods, with the inclinometer initially explaining 47% of the variance in the motion analysis measurements. However, adding one key anthropometric parameter (lower arm length) to the inclinometer-based trunk flexion prediction model reduced the differences between the two systems and accounted for 79% of the motion analysis method's variance. Although caution must be applied when generalizing lower-arm length as a correction factor, the overall strategy of anthropometric modeling is a novel contribution. In this lifting-based study, by accounting for subject anthropometry, a single, simple data-logging inclinometer shows promise for trunk posture measurement and may have utility in larger-scale field studies where similar types of tasks are performed.

Retrospective assessment of occupational exposure to whole-body vibration for a case-control study.

Occupational whole-body vibration is often studied as a risk factor for conditions that may arise soon after exposure, but only rarely have studies examined associations with conditions arising long after occupational exposure has ceased. We aimed to develop a method of constructing previous occupational whole-body vibration exposure metrics from self-reported data collected for a case-control study of Parkinson's disease. A detailed job history and exposure interview was administered to 808 residents of British Columbia, Canada (403 people with Parkinson's disease and 405 healthy controls). Participants were prompted to report exposure to whole-body vibrating equipment. We limited the data to exposure reports deemed to be above background exposures and used the whole-body vibration literature (typically reporting on seated vector sum measurements) to assign intensity (acceleration) values to each type of equipment reported. We created four metrics of exposure (duration of exposure, most intense equipment exposure, and two dose metrics combining duration and intensity) and examined their distributions and correlations. We tested the role of age and gender in predicting whole-body vibration exposure. Thirty-six percent of participants had at least one previous occupational exposure to whole-body vibrating equipment. Because less than half of participants reported exposure, all continuous metrics exhibited positively skewed distributions, although the distribution of most intense equipment exposure was more symmetrically distributed among the exposed. The arithmetic mean of duration of exposure among those exposed was 14.0 (standard deviation, SD: 14.2) work years, while the geometric mean was 6.8 (geometric SD, GSD: 4.5). The intensity of the most intense equipment exposure (among the exposed) had an arithmetic mean of 0.9 (SD: 0.3) m·s(-2) and a geometric mean of 0.8 (GSD: 1.4). Male gender and older age were both associated with exposure, although the effect of age was attenuated after adjustment for gender. The methods developed allowed us to create continuous metrics of whole-body vibration retrospectively, displaying useful variance for epidemiologic studies.

Recruitment of healthy first-trimester pregnant women: lessons from the Chemicals, Health & Pregnancy study (CHirP).

To describe and evaluate recruitment techniques used to enroll 152 healthy pregnant women fewer than 15 weeks gestation into a prospective study of environmental chemical exposure during pregnancy. Posters, a website, online and print advertising, recruitment emails, media coverage, recruitment from clinic waiting rooms, networking within the pregnancy community and presenting a study booth at baby "trade shows" were used to advertise the study. Participants had to meet a strict set of eligibility criteria, and were asked to donate two-second-trimester blood samples, complete two questionnaires, have samples of air, dust, lint and tap water collected from their homes, and donate a cord blood sample at delivery. Over 17 months, 171 women enrolled (49% of initial contacts, and 99% of all eligible women) and 152 women completed the study (89% retention). Total recruitment costs were approximately $400 Cdn per final participant. Posters, study booth presentations and online advertising generated the most inquiries about the study. Word of mouth, referral from another study and direct email were the most cost-effective strategies. Not surprisingly, the recruited study population was less ethnically diverse, more affluent and more educated than the background population of pregnant women in Vancouver. A combination of passive and active recruitment techniques were successful for recruiting healthy women in roughly the first trimester of pregnancy (<15 weeks gestation). While a convenience sample of women is suitable for our study questions, additional strategies may be required to recruit a more representative pregnant population in future studies.

Built environment influences on healthy transportation choices: bicycling versus driving.

A growing body of evidence links the built environment to physical activity levels, health outcomes, and transportation behaviors. However, little of this research has focused on cycling, a sustainable transportation option with great potential for growth in North America. This study examines associations between decisions to bicycle (versus drive) and the built environment, with explicit consideration of three different spatial zones that may be relevant in travel behavior: trip origins, trip destinations, and along the route between. We analyzed 3,280 utilitarian bicycle and car trips in Metro Vancouver, Canada made by 1,902 adults, including both current and potential cyclists. Objective measures were developed for built environment characteristics related to the physical environment, land use patterns, the road network, and bicycle-specific facilities. Multilevel logistic regression was used to model the likelihood that a trip was made by bicycle, adjusting for trip distance and personal demographics. Separate models were constructed for each spatial zone, and a global model examined the relative influence of the three zones. In total, 31% (1,023 out of 3,280) of trips were made by bicycle. Increased odds of bicycling were associated with less hilliness; higher intersection density; less highways and arterials; presence of bicycle signage, traffic calming, and cyclist-activated traffic lights; more neighborhood commercial, educational, and industrial land uses; greater land use mix; and higher population density. Different factors were important within each spatial zone. Overall, the characteristics of routes were more influential than origin or destination characteristics. These findings indicate that the built environment has a significant influence on healthy travel decisions, and spatial context is important. Future research should explicitly consider relevant spatial zones when investigating the relationship between physical activity and urban form.

Route preferences among adults in the near market for bicycling: findings of the cycling in cities study.

PURPOSE: To provide evidence about the types of transportation infrastructure that support bicycling. DESIGN: Population-based survey with pictures to depict 16 route types. SETTING: Metro Vancouver, Canada. SUBJECTS: 1402 adult current and potential cyclists, i.e., the "near market" for cycling (representing 31% of the population). MEASURES: Preference scores for each infrastructure type (scale from -1, very unlikely to use, to +1, very likely to use); current frequency of use of each infrastructure type (mean number of times/y). ANALYSES: Descriptive statistics across demographic segments; multiple linear regression. RESULTS: Most respondents were likely or very likely to choose to cycle on the following broad route categories: off-street paths (71%-85% of respondents); physically separated routes next to major roads (71%); and residential routes (48%-65%). Rural roads (21%-49%) and routes on major streets (16%-52%) were least likely to be chosen. Within the broad categories, routes with traffic calming, bike lanes, paved surfaces, and no on-street parking were preferred, resulting in increases in likelihood of choosing the route from 12% to 37%. Findings indicate a marked disparity between preferred cycling infrastructure and the route types that were currently available and commonly used. CONCLUSION: This study provides evidence for urban planners about bicycling infrastructure designs that could lead to an increase in active transportation.

The impact of hearing conservation programs on incidence of noise-induced hearing loss in Canadian workers.

BACKGROUND: Noise exposure remains one of the most ubiquitous of occupational hazards. Hearing conservation program legislation and the programs themselves were designed to lower risk of resulting occupational noise-induced hearing loss, but there has been no broad-based effort to assess the effectiveness of this policy. METHODS: The incidence of a 10-dB standard threshold shift was examined in a group of Canadian lumber mill workers, using annual audiogram series obtained from the Workers' Compensation Board of British Columbia for the period 1979-1996 and using Cox proportional hazard models. RESULTS: Mean cumulative noise exposure was 98.1 dB-years. The audiograms from 22,376 individuals, among whom there were 2,839 threshold shifts of 10 dB or greater (i.e., a "standard threshold shift"), were retained in multivariable analyses. After adjusting for potential confounders, continuous use of hearing protection, and initial hearing tests later in the study period, the risk for standard threshold shift was reduced by 30%. Risk increased sixfold, however, in those with the highest noise exposure. CONCLUSIONS: Hearing conservation programs may be effective in reducing overall incidence of hearing loss. In the absence of noise control at source, however, highly exposed workers remain at unnecessary risk.

How long is long enough? Evaluating sampling durations for low back EMG assessment.

Few ergonomic measurement tools explicitly state when and how to sample exposures. Traditional ergonomic sampling has used short, task-based or worst-case measurements, but these may misrepresent exposures, since they neglect the temporal variations throughout the workday. Understanding the representativeness of data from shorter measurement durations compared with full-shift measurements allows for optimization of measurements resources. This study compared a variety of low back electromyography (EMG) exposure metrics measured over a full-shift with the same metrics sampled over shorter durations to identify whether shorter durations provide representative measures of exposure. Portable EMG devices were used to measure low back EMG for 138 full work shifts in a range of jobs in heavy industry. Using a random start time, each full shift of data was resampled for 4 hr, 2 hr, 1 hr, 10 min, and 2 min. Exposure metrics from each duration were compared with the full shift using absolute and percent error, bias, and limits of agreement. Comparisons between one full shift and two full shifts were made for the subset of 35 workers with two measured workdays. Compared with full-shift data, bias is very low at all sampling durations. However, as sampling durations decreased from a full-shift to a few min, the absolute error, percentage error, and limits of agreement for exposure estimates show more deviation from full-day estimates. Estimates of mean and 90th percentile exposure averaged 8% error for 4-hr durations and 14% error for 2-hr durations. The errors for 4-and 2-hr measurement durations may be acceptable for many applications, particularly if the trade-off is measuring more subjects. Sampling durations of 1 hr or less seem likely to produce very large errors over all exposure metrics, particularly for the range and peak exposures. Depending on the purpose of measurement and the detail required, 4 hr or even 2 hr appears to be long enough to reasonably estimate full-shift exposure.

Measuring low back injury risk factors in challenging work environments: an evaluation of cost and feasibility.

BACKGROUND: Measuring low back injury risk factors in field research presents challenges not encountered in laboratory environments. METHODS: We compared the practical application of five measurement methods (observations, interviews, electromyography (EMG), inclinometry, and vibration monitoring) for 223 worker days in 50 heavy-industry worksites in western Canada. Data collection successes, challenges, costs, and data detail were documented for each method. RESULTS: Measurement success rates varied from 42.2% (seatpan accelerometer) to 99.6% (post-shift interview) of worker days assessed. Missed days for direct monitoring equipment were primarily due to explosive environments, workplace conditions likely to damage the equipment, and malfunctions. Costs per successful measurement day were lowest for interviews (approximately 23 dollars), about 10-fold higher for observations and inclinometry, and more than 20-fold higher for EMG and vibration monitoring. CONCLUSIONS: Costs and successful field performance need to be weighed against the added data detail gained from monitoring equipment when making choices about exposure assessment techniques for epidemiological studies.

Mixed models and empirical bayes estimation for retrospective exposure assessment of dust exposures in Canadian sawmills.

OBJECTIVES: Data on job histories is commonly available from study subjects and worksites, therefore jobs are often used for assigning exposures in historical epidemiological studies. Exposure estimates are often derived by offering jobs as fixed effects in statistical models. An alternative approach would be to offer job as a random effect to obtain empirical Bayes estimates of exposure. This approach is more efficient since it weights exposure estimates according to the within-job and between-job variability and the number of measurements for each job. We assess three models for predicting historical dust exposures of sawmill workers. METHODS: Models were developed using 407 inhalable dust measurements collected from 58 jobs in four sawmills. The first model incorporated all variables as fixed effects; the second added a random term to account for correlation within workers; and the third offered random terms for worker, job and mill (hierarchical model). Empirical Bayes estimates were used to calculate job-specific exposures from the hierarchical model. RESULTS: The fixed effects and random worker mixed models performed nearly identically because there was low within-worker correlation (r = 0.26). The Bayesian exposure predictions from the hierarchical model were slightly more correlated with the observed mill-job arithmetic means than those from the models where jobs were fixed effects (0.74 versus 0.70). CONCLUSIONS: While we observed no large differences in exposure estimates by treating job as a fixed or random effect, treating job as a random effect allowed for job-specific coefficients to be estimated for every job while borrowing strength in the presence of sparse data by assuming that the job means are normally distributed around the group mean. In addition, empirical Bayes job estimates can be used for a posteriori job grouping. The use of this method for retrospective exposure assessment should continue to be examined.

Assessment of exposure in an international study on cancer risks among pulp, paper, and paper product workers.

A data management system and a department-exposure matrix (PAPDEM) was designed and constructed to facilitate exposure assessment for a large multinational study on cancer risks among pulp, paper, and paper product workers. Exposure to 25 major agents was described by prevalence, P (i.e., proportion of the exposed, classified %-range), and level, L (i.e., annual mean concentration at work, classified). Some agents could be assessed only in qualitative terms. The assessment was specific to mill, work department, agent, and time period. The results of industrial hygiene measurements, information from detailed company questionnaires, and the professional judgments of the assessment team were the cornerstones of the assessment. Validity and consistency of the assessment were aimed at by setting default values for P and L prior to the assessment, accurately defining agents and exposure classes, dividing assessment work by subindustry, working in pairs, testing interrater agreement, and finalizing the estimates in a meeting. In spite of these precautions, good agreement between different assessors was difficult to reach. Exposure to chemical agents turned out to be widespread and complex with frequent multiple exposures. A computer-assisted exposure assessment system such as PAPDEM may save time and facilitate assessment in large epidemiological studies requiring complicated exposure assessment procedures. It also provides a good documentation of exposure assignments, which may be useful in the interpretation of the results and in future updates of the study.