James T. Purdham

Relationships between asthma and work exposures among non‐domestic cleaners in Ontario

BACKGROUND Cleaners have been reported to have increased risk for work-related asthma symptoms but few studies have studied non-domestic cleaners. In this study, we compared work-related asthma symptoms among cleaners and other building workers and determined associations with tasks. METHODS School and racetrack workers in Ontario, Canada, completed a questionnaire to identify the prevalence of cleaning tasks, physician-diagnosed asthma, new-onset asthma, respiratory symptoms, and work-related asthma symptoms. RESULTS Cleaners and controls had a similar prevalence of most asthma outcomes although female cleaners reported significantly more respiratory symptoms; odds ratio (OR), 2.59 confidence intervals (CI) 1.6-4.3, and work-related asthma symptoms, OR 3.90 (CI 2.1-7.4) compared with female controls with adjustment for age and smoking history. Male cleaners showed a non-significant trend to more physician-diagnosed asthma, adjusted OR 2.10 (CI 0.9-4.8) and work-related asthma symptoms, adjusted OR 1.53 (CI 0.8-3.0). The work-related asthma symptoms among men were significantly associated with waxing floors, OR 2.19 (CI 1.0-4.4); wax-stripping floors, OR 2.54 (1.2-5.2); spot-cleaning carpets, OR 2.20 (1.3-3.8); and cleaning tiles, OR 4.46 (1.0-19.3) and grout, OR 2.12 (1.1-4.0). CONCLUSIONS Female cleaners have more asthma symptoms worse at work than controls. Work-related asthma symptoms among male cleaners were associated with a number of specific cleaning tasks. Findings suggest the need for school cleaners to have reduced exposure to cleaning chemicals and need for protective strategies during performance of tasks expected to exacerbate asthma, such as wax stripping.

Leukemia in electric utility workers: The evaluation of alternative indices of exposure to 60 Hz electric and magnetic fields

BACKGROUND Epidemiological studies have inconsistently demonstrated a positive relationship between magnetic and/or electric fields and leukemia. Although exposure to both 60 Hz electric and magnetic fields can be characterized in many ways, to date, risk assessment has been performed by using only a limited number of exposure indices. METHODS The associations between adult leukemia and indices of electric and magnetic fields were explored within a nested case-control study of 31,453 Ontario electric utility workers. RESULTS The percentage of time spent above electric field thresholds of 20 and 39 V/m was predictive of leukemia risk after adjusting for duration of employment and the arithmetic mean exposure to both electric and magnetic fields (P<0.05). Duration of employment was strongly associated with an increased risk of leukemia. Those who had worked for at least 20 years, and were in the highest tertiles of percentage of time spent above 10 and 20 V/m had odds ratios of 10.17 (95% CI = 1.58-65.30) and 8.23 (95% CI = 1. 24-54.43), respectively, when compared to those in the lowest tertile. Nonsignificant elevations in risk were observed between indices of magnetic fields and leukemia. CONCLUSIONS Our results support the hypothesis that electric fields act as a promoting agent in the etiology of adult leukemia. Exposure assessment based on alternate indices of electric and magnetic fields should be incorporated into future occupational studies of cancer.

Development of models to predict dose of pesticides in professional turf applicators.

Epidemiologic studies designed to assess the chronic effects of pesticides are limited by inadequate measurements of exposures. Although cohort studies have been initiated to evaluate the effects of 2,4-dichlorophenoxyacetic acid (2,4-D) and other pesticides in professional turf applicators, they may have limited power to detect significant health risks and may be subject to bias from exposure measurement error. In this study, the doses of 2,4-D, mecoprop [2-(4-chloro-2 methylphenoxy) propionic acid, MCPP] and dicamba (3,6-dichloro-o-anisic acid) were evaluated in a group of 98 professional turf applicators from 20 companies across southwestern Ontario. During a 1-week period (Saturday to Thursday), the volume of pesticide (active ingredient) applied was only weakly related to the total dose of 2,4-D absorbed (R2=0.21). Two additional factors explained a large proportion of variation in dose: the type of spray nozzle used and the use of gloves while spraying. Individuals who used a fan-type nozzle had significantly higher doses than those who used a gun-type nozzle. Glove use was associated with significantly lower doses. Job satisfaction and current smoking influenced the dose but were not highly predictive. In the final multiple regression models predicting total absorbed dose of 2,4-D and mecoprop, approximately 63–68% of the variation was explained. The future application of these models for epidemiologic research will depend on the availability of information and records from employers, the feasibility of contacting study subjects and cost.

An Evaluation of 24-Hour Urinary Creatinine Excretion for Use in Identification of Incomplete Urine Collections and Adjustment of Absorbed Dose of Pesticides

The accurate quantification of the absorbed dose of pesticides following occupational exposures generally requires complete 24-hour urine collections, often over extended periods of time. Difficulty in obtaining volunteer cooperation may result in incomplete urine collections. Traditionally, 24-hour urinary creatinine has been used to identify incomplete urine samples and has been used to standardize pesticide and other chemical dose estimates. More recently, the use of creatinine to standardize dose estimates has been questioned, as has its utility in the identification of incomplete urine collections. This research evaluates the use of personal observation, statistical methods, and published models to predict creatinine excretion to identify and adjust for incomplete urine collections. Based on the use of published creatinine prediction models, an evaluation of the day-to-day creatinine excretion within subjects, and personal observation, a small number of suspected urine samples were identified. Although it is likely that these samples were incomplete, correction of these urine volumes based on the published models did little to improve pesticide dose prediction. Further, results indicate that subjects who report missed urine samples may be able to estimate the missing volumes with some accuracy. In future pesticide exposure studies, the use of self-reported missed volumes may help to increase the accuracy of dose prediction when there is strong cooperation with collection procedures. A statistical model to predict creatinine excretion in professional turf applicators was developed to provide a preliminary screening for urinary completeness for future studies in which compliance with urinary collection is thought to be insufficient.

Environmental and Medical Assessment of Stevedores Employed in Ferry Operations

Abstract The exposure of stevedores employed in ferry operations to a range of diesel and gasoline exhaust constituents was assessed. The exhaust constituents quantified included total particulate, polycyclic aromatic hydrocarbons (PAH), aldehydes, oxides of nitrogen, sulfur dioxide, and carbon monoxide. In addition, acute and chronic respiratory effects of stevedores relative to a control population of port office workers were assessed. Air sampling was conducted on board the ferry on two successive evenings. The exposure of the control group to these contaminants was also measured. Total particulate was determined gravimetrically, while PAH were determined by high performance liquid chromatographic (HPLC) analysis of the cyclohexane soluble fraction of particulate material. ldehydes were collected on SEP-PAK™ C18 cartridges treated with 2,4-dinitrophenyl-hydrazine and analyzed by HPLC. Exhaust gases were determined by frequent grab sampling using detector tubes. Medical assessment of stevedores and cont...

Exposure of hospital operating room personnel to potentially harmful environmental agents.

Epidemiologic studies of risk to reproductive health arising from the operating room environment have been inconclusive and lack quantitative exposure information. This study was undertaken to quantify exposure of operating room (OR) personnel to anesthetic agents, x-radiation, methyl methacrylate, and ethylene oxide and to determine how exposure varies with different operating room factors. Exposures of anesthetists and nurses to these agents were determined in selected operating rooms over three consecutive days. Each subject was asked to wear an x-radiation dosimeter for 1 month. Exposure to anesthetic agents was found to be influenced by the age of the OR facility, type of surgical service, number of procedures carried out during the day, type of anesthetic circuitry, and method of anesthesia delivery. Anesthetists were found to have significantly greater exposures than OR nurses. Exposure of OR personnel to ethylene oxide, methyl methacrylate, and x-radiation were well within existing standards. Exposure of anesthetists and nurses to anesthetic agents, at times, was in excess of Ontario exposure guidelines, despite improvements in the control of anesthetic pollution.

Sources of Personal Exposure to Fine Particles in Toronto, Ontario, Canada

Abstract Individuals are exposed to particulate matter from both indoor and outdoor sources. The aim of this study was to compare the relative contributions of three sources of personal exposure to fine particles (PM2.5) by using chemical tracers. The study design incorporated repeated 24-hr personal exposure measurements of air pollution from 28 cardiac-compromised residents of Toronto, Ontario, Canada. Each study participant wore the Rupprecht & Patash-nick ChemPass Personal Sampling System 1 day a week for a maximum of 10 weeks. During their individual exposure measurement days the subjects reported to have spent an average of 89% of their time indoors. Particle phase elemental carbon, sulfate, and calcium personal exposure data were used in a mixed-effects model as tracers for outdoor PM2.5 from traffic-related combustion, regional, and local crustal materials, respectively. These three sources were found to contribute 13% ± 10%, 17% ± 16%, and 7% ± 6% of PM2.5 exposures. The remaining fraction of the personal PM2.5 is hypothesized to be predominantly related to indoor sources. For comparison, central site outdoor PM2.5 measurements for the same dates as personal measurements were used to construct a receptor model using the same three tracers. In this case, traffic-related combustion, regional, and local crustal materials were found to contribute 19% ± 17%, 52% ± 22%, and 10% ± 7%, respectively. Our results indicate that the three outdoor PM2.5 sources considered are statistically significant contributors to personal exposure to PM2.5. Our results also suggest that among the Toronto subjects, who spent a considerable amount of time indoors, exposure to outdoor PM2.5 includes a greater relative contribution from combustion sources compared with outdoor PM2.5 measurements where regional sources are the dominant contributor.

The development of a new method to estimate total daily dose of pesticides in professional turf applicators following multiple and varied exposures in occupational settings

Abstract The evaluation of absorbed dose of pesticides in humans requires a knowledge of the kinetics and dynamics of the compound. In some circumstances, data that allow for the estimation of dose may be available from human volunteer studies, although often, it will be based on results from animal studies. If human metabolism data are available, estimates of dose may be more accurate, but it should be recognized that pesticide exposure in an occupational setting may differ from that in a controlled laboratory study. In this study, data from previously published studies are used to evaluate the urinary excretion of 2,4-dichlorophenoxyacetic acid (2,4-D), following single dermal applications to human volunteers. These studies are evaluated with the objective of determining the best method of predicting total absorbed dose following multiple and varied exposures in occupational settings. Further, an alternative to laboratory-controlled human volunteer studies is presented. Data from a third previously published biological monitoring study on six professional pesticide applicators over a 2-week period were used to generate estimates of the urinary excretion of the pesticide 2,4-D that would result from a single dose. The method used to estimate the urinary excretion parameters is a variation of an overlay technique used in pharmacology, and may provide information on the kinetics of other pesticides when it is not possible to conduct human studies. The generated estimates of 24-h urinary excretion of 2,4-D over a 6-day period were remarkably similar to those obtained in controlled studies. Finally, a method was developed to use the generated estimates to determine total absorbed dose of pesticides for an independent group of 95 professional pesticide applicators. This method requires information on the amount of pesticide used for 6 days prior to the collection of two, 24-h urine samples.

MCPA Permeation Through Protective Gloves

Permeation of 4-chloro-2-methylphenoxyacetic acid (MCPA) in commercial herbicide formulations through common protective glove types was evaluated to aid in the selection of appropriate skin protection. The ASTM test method F739-91 was used to measure the permeation of two undiluted formulations, one containing a salt, and the other an ester form of MCPA. The four glove types tested were natural rubber, neoprene 73, nitrile 37-145, and Viton-coated chloroprene. Triplicate tests of each combination of formulation and glove material were conducted. Permeation cells with a 0.01 M sodium hydroxide collection medium were used for the experiments. Aliquots of the collection medium were withdrawn at regular intervals and acidified, and quantification of the free acid was achieved using HPLC-UV (230 nm). There was no appreciable permeation of the salt formulation over a 24-hour test period. For the ester formulation, the following mean steady-state permeation rate (microg x cm(-2) min(-1)) and mean lag time (hours), respectively, were measured: Viton (0.06, 17.8), natural rubber (0.08, 15.4), neoprene 73 (0.21, 15.1), and nitrile (0.04, 24.2). Permeation was associated with significant swelling, averaging a nearly 30 percent increase from the pre-immersion thickness. All four glove types provide adequate protection against permeation by the salt formulation and at least eight-hour protection against the ester formulation. Given the greater permeation of the ester formulation, the salt formulation of MCPA herbicide should be used whenever possible.

Prostate Cancer and Occupational Whole-Body Vibration Exposure

Prostate cancer is common and its etiology largely unknown; therefore, it is important to explore all potential risk factors that are biologically plausible. Recent literature suggests a relationship between whole-body vibration (WBV) and prostate cancer risk. The aim of this study was to determine whether occupational WBV was a risk factor for prostate cancer. Existing data, collected on 447 incident cases and 532 population controls (or their proxies), in Montreal, Canada, were used to evaluate this question. Personal interviews collected detailed job descriptions for every job held, the tasks involved, and type of equipment used. For each job, experts assessed the intensity and daily duration of WBV exposure. Inter-rater agreement for WBV ratings was examined using the kappa statistic, with values that ranged from 0.83 to 0.94. Logistic regression models explored the relationship between WBV exposure and prostate cancer, using various combinations of intensity, daily duration, and years of exposure. Potential confounders were also examined. Occupations with WBV exposure demonstrated an increased statistically non-significant risk [odds ratio (OR) = 1.44, 95% confidence interval (CI): 0.99-2.09]. The risk for transport equipment operation, a job with WBV exposure, was significantly elevated (OR = 1.90, 95% CI: 1.07-3.39). These results, together with those of an earlier study, suggest that workers in heavy equipment and transport equipment operation may have increased risk of prostate cancer. Further investigation is warranted.