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J. C. Cavallari, S. C. Fang, E. A. Eisen, J. Schwartz, R. Herrick, R. Hauser, D. C. Christiani. Harvard School of Public Health
ObjectivesAlthough recent research demonstrates associations between particulate exposures and decreased heart rate variability (HRV), it is unclear whether exposures alter the natural circadian rhythm of HRV. In a cohort of boilermaker welders, we compared the circadian variation of hourly HRV on a workday during exposure to high levels of metal‐rich particulates to a non‐workday when particulate exposures were low.
MethodsWe conducted a panel study among 36 males who were monitored by 24 h ambulatory electrocardiograms (ECG) over both a workday (exposure period) and non‐workday (control period). ECGs were analysed and the standard deviation of normal‐to‐normal beats index (SDNNi) was calculated from 5 min data and summarised hourly over the 24 h measurement. Work and non‐work periods were compared using a paired t‐test.
ResultsWelders were exposed to a mean (SD) workday PM2.5 concentration of 1.14 (0.76) mg/m3. There was conservation of the circadian rhythm of HRV on workdays, with an increase in HRV during the sleeping hours, peaking at 5 am, and a decrease in the afternoon, reaching a nadir at 1 pm. However, we observed lower hourly SDNNi on workdays as compared to non‐workdays. Furthermore, the largest difference between work and non‐work HRV was during the time that most participants reported active working. For example, at 1 pm the mean (SD) hourly SDNNi was 52.47 (20.21) ms on a non‐workday and 40.67 (15.13) ms on a workday. The difference between work and non‐work hourly SDNNi was statistically significant (p<0.05) between 8 am and 3 pm. Lower SDNNi was also observed in the hours following work and in the early morning; at 5 and 6 am the difference was statistically significant.
ConclusionAlthough the circadian variation in HRV was preserved following workday exposure, HRV was decreased as compared to a non‐workday. While the largest differences between work and non‐work HRV occurred during active working, statistically significant differences were also observed following work, suggesting a multiphase response.
Key wordsfine particles; cardiovascular; heart rate variability
M. A. Isler1, J. Mason2, P. Brassard3. 1Institut de Sante Publique du Quebec et Direction de Sante Publique Montreal; 2Centre de Sante et des Services Sociaux Jeanne Mance; 3Department of Medicine, McGill University
ObjectivesAlthough the average annual incidence rate of tuberculosis in Montreal is low (8.8 per 100000 for 1999–2005), several contact investigations have targeted clients and employees of shelters or day services for homeless people. Between 1999 and 2005, public health affiliated occupational health services offered onsite annual periodic tuberculin skin testing (TST) to employees of shelters and day services for homeless people in Montreal. Available data from this screening program were analysed to estimate risk of infection to employees from unknown contact with contagious cases of tuberculosis.
MethodsThe study was conducted on a dynamic cohort of employees who returned for periodic screening following ascertainment of negative (<10 mm in duration) two‐step baseline. Time at risk was calculated from date of the negative baseline until the date of the last valid (read) TST. Conversion of TST was defined as an induration of >10 mm and increase of >6 mm from the previous TST.
ResultsOf 870 employees who were tested at least once between 1998 and 2005, 402 were ineligible for study because of incomplete baseline testing (243), documented contact with a contagious person (29), or entry in last year of screening (130). Among the 468 remaining, overall prevalence of positive TST at baseline or first test only was 25.4% and 19.0%, respectively. An additional 157 did not return for further testing after negative baseline. Thus 192 had complete data and were studied for conversion of their TST. Incidence of conversion was 2.5 (95% CI 0.3 to 4.7)/100 person‐years. Since all workers involved at any time in a contact investigation were excluded, this rate reflects only risk from unknown exposure. Preliminary data suggest that workers from shelters with dormitories may be at higher risk than those without. However, due to lack of data concerning demographic and personal risk factors, the association with occupation cannot be adjusted for usual confounders.
ConclusionThe prevalence of positive TST and incidence of conversion is similar to that found among other high risk groups in Montreal. In an area of low incidence, these data alert to the possibility of transmission of infection from unknown cases or to exposed contacts not identified at the time of contact investigations.
Key wordstuberculosis; screening; homeless
G. F. Thomsen. Department of Occupational Medicine, SVS Hospital
ObjectivesSkin prick tests are widely used, and the results compared, but how reproducible are they? The objectives of this study are to analyse the differences in weal reactions in SPTs with two batches of allergen extracts from the same vendor.
Methods91 persons, aged 20–44 years, were recruited from a postal survey. 55 persons were from an a priori 20% random group. 36 were invited because they had reported asthma symptoms. SPT was performed using ECRHS procedures. 13 allergens on the right forearm, seven allergens on the left forearm. Five of the allergens were in common. Birch (10 HEP), grass (Phleum pratense) (10 HEP), cat (10 HEP), dust mite (Dermatophagoides farinae) (10 HEP) and the mold Alternaria alternate (1:20 W/V). All SPT allergen extracts were delivered from ALK Abelló, but in two series and from different production batches. After 15 min the wheal reactions were measured and transferred with transparent adhesive tape onto a record sheet. The largest diameter and the perpendicular diameter were measured twice. If there was any difference, a third measurement was made. Average diameter 3 mm was considered as a positive SPT. Mean values were compared using Student's t‐test. Agreement in positive SPT for each allergen was calculated using κ statistics.
ResultsFor two of the allergens the SPT mean values were higher on the right than left arm: grass and cat. For the rest no differences in mean value were seen. The correlation coefficients between the average diameter in the two tests varied from 0.75 for grass to 0.95 for D farinae. The number of disagreements in 91 tests varied from three in birch and D farinae to nine in cat. For all allergens disagreement was seen in both directions. κ Values were 0.91 in D farinae, 0.89 in birch, 0.81 in grass, 0.70 in Alternaria and 0.72 in cat.
ConclusionBecause the differences between the allergens varied highly, it is unlikely that the differences could be explained by study design factors. A plausible explanation is difference in the allergen extract batches. To overcome within‐study bias, it is essential to use the same allergen batch within the study. Comparisons of SPT results between studies and over time should be made cautiously.
Key wordsskin prick test; standardisation; allergy screening
C. Bigert1, M. Alderling2, M. Svartengren1, N. Plato1, U. De Faire3, P. Gustavsson1. 1Division of Occupational Medicine, Department of Public Health Sciences, Karolinska Institute; 2Department of Occupational and Environmental Health, Stockholm Centre for Public Health; 3Unit of Cardiovascular Epidemiology, Institute of Environmental Medicine, Karolinska Institute
ObjectivesAlthough associations have been found between levels of ambient airborne particles and cardiovascular disease (CVD) in the general population, little is known about possible cardiovascular effects from high exposure to particles prevailing in subway systems. This led us to investigate risk markers for CVD in employees exposed to particles in the Stockholm subway system.
MethodsSeventy‐nine workers in the Stockholm subway were investigated between November 2004 and March 2005. All were non‐smokers in the age range 25–50; 54 were men and 25 were women. Three exposure groups were delineated: 29 platform workers with high exposure to particles, 29 subway drivers with medium exposure, and 21 ticket sellers with low exposure (control group). An occupational hygienic investigation confirmed the contrast in exposure between the groups. A baseline blood sample was taken after 2 days of vacation, and a second sample after 2 working days, for analysis of levels of plasminogen activator inhibitor‐1 (PAI‐1), high‐sensitivity C‐reactive protein (hs‐CRP), interleukin‐6 (IL‐6), fibrinogen, von Willebrand factor and factor VII. We investigated changes in serum concentrations between sample 1 and sample 2, and differences in average concentrations between the groups.
ResultsThe platform workers (who were highly exposed to particles) had significantly higher plasma concentrations of PAI‐1 than the ticket sellers. Higher levels of hs‐CRP, IL‐6 and fibrinogen, although not significantly higher, were also found in the platform workers, which suggests that there may be a long‐term inflammatory effect of particle exposure. These differences remained after adjusting for body mass index (BMI). No changes between sample 1 and 2 were found that could be attributed to particle exposure.
ConclusionEmployees who were highly exposed to airborne particles in the Stockholm subway were found to have elevated levels of risk markers of CVD relative to employees with low exposure. However, the differences observed cannot be linked to particle exposure as such with full certainty.
Key wordscardiovascular; haematological effects; underground
H. Y. Chuang1, S. J. Hsieh2, H. I. Chen3. 1Department of Occupational and Environmental Medicine, Kaohsiung Medical University Hospital; 2School Of Public Health, Kaohsiung Medical University; 3Institute Of Occupational Safety and Health, Kaohsiung Medical University
ObjectivesIt is known that lead may have a negative effect on human reproductive ability and may disturb our reproductive endocrine system. We used the current lead level, index of cumulative lead (ICL) and time weighted index of cumulative blood lead (TWICL) calculated from the concentrations of blood lead from 1996 to 2006 in a group of lead workers to investigate the association between different lead indexes and the concentration of serum inhibins as well as reproductive endocrines.
MethodsLead workers who worked in the lead‐acid battery industry in Taiwan participated in this research. We utilised health examination data which included blood lead concentration, follicle stimulating hormone (FSH), inhibin B, luteinising hormone (LH) and testosterone (TTE) measurements and a questionnaire that included age, gender, height, weight, smoking and alcohol status. Data analysis was performed with descriptive analyses, Pearson correlations and multiple linear regressions.
ResultsThe Pearson correlation coefficients of ICL and TWICL versus inhibin B were 0.220 (p=0.003) and 0.231 (p=0.008), respectively; in a multiple linear regression model, after controlling for age, FSH and TTE, when the ICL and TWICL index increases by one unit, inhibin B will increase by 0.047 pg/ml (p=0.024) and 1.333 pg/ml (p=0.017), respectively.
ConclusionAn increasing cumulative lead index will increase the concentration of serum inhibin B in long‐term exposed male lead workers and might indirectly affect spermatogenesis.
Key wordslead; male worker; inhibin B
S. E. Chia, M. AliSafiyya. National University of Singapore
ObjectivesLead and homocysteine are both linked to cardiovascular disease. With this in mind, we evaluated the relationship between blood lead and homocysteine in persons aged 19–66 years in two Asian populations.
MethodsThis cross‐sectional study comprised 183 workers from a lead stabiliser factory in Singapore and 323 workers from a battery factory in Vietnam. Workers were occupationally exposed to lead. Blood lead was analysed using atomic absorption spectrophotometry, while plasma homocysteine was measured using high‐performance liquid chromatography.
ResultsChinese subjects had the lowest blood lead levels while the Indians had the highest. Controlling for age, sex and race, an increase of 1 μg/dl in blood lead was associated with an increase of 0.04 μmol/l in homocysteine on the log scale. Gender and ethnicity seemed to be strongly associated with the relationship between lead and homocysteine. The positive relationship between lead and homocysteine among the Vietnamese subjects was significant (Pearson's r=0.254, p<0.01). When blood lead levels were divided by quartiles, the correlation coefficient between blood lead levels in the fourth quartile and homocysteine among the Vietnamese was higher (r=0.405, p<0.01). Overall, an increase of 1 μg/dl in blood lead in all the Vietnamese subjects was associated with an increase of 0.05 μmol/l in homocysteine on the log scale. However, in the fourth quartile, the same increase was associated with an increase of 0.41 μmol/l in homocysteine on the log scale.
ConclusionBlood lead was found to be associated with homocysteine levels in this Asian sample. Although we cannot determine causality from cross‐sectional data, it is sensible to consider the probability that this relationship could explain one of the mechanisms of the impact of lead on the cardiovascular system. More studies would be needed to confirm this inference.
Key wordshomocysteine; blood lead; cross‐sectional study
A. L. Schoenfisch, J. M. Dement, R. L. Rodriguez‐Acosta. Duke University Medical Center
ObjectivesBecause of its strong association with perinatal morbidity and mortality, preterm delivery has received much attention in epidemiological literature. This cross‐sectional study explores associations between preterm birth and demographic, behavioural, clinical and occupational characteristics of women employed at a university or in one of the university's affiliated healthcare entities.
MethodsA comprehensive surveillance system linking individual‐level data from human resources, medical insurance claims, and potential job exposures was used to identify 1040 women with a single live birth between 2001 and 2004 and describe maternal characteristics during pregnancy. Clinical and behavioural variables related to pregnancy and delivery were defined using International Classification of Diseases, Ninth Revision, Clinical Modification and Current Procedural Terminology codes. Occupational characteristics included potential exposure to asbestos, blood‐borne pathogens, chemicals, infectious agents, laboratory work and radiation.
ResultsAges ranged from 20 to 45 years (mean 32). A majority of the women were white (71.1%) followed by black (18.1%), Asian/Pacific Islander (8.0%), Hispanic (2.6%) and Indian (<1%). They worked predominantly as clinical/technical staff, office support staff, faculty/research associates, and inpatient nurses. Nearly all women (>99.5%) received prenatal care. Preterm delivery occurred in 74 (7.1%) of the women. Compared to faculty/research associates, the crude prevalence odds of preterm delivery was higher for inpatient nurses (prevalence odds ratio (POR) 3.2, 95% CI 1.2 to 8.5), nurses' aides (POR 6.5, 95% CI 1.5 to 29.5) and office support staff (POR 2.7, 95% CI 1.0 to 7.0). None of the potential job exposures were significantly related to preterm delivery in univariate analyses. In multivariate analyses, the risk of preterm delivery was positively associated with several clinical conditions, including haemorrhage in early pregnancy (POR 1.7, 95% CI 0.9 to 3.0), placenta previa (POR 2.8, 95% CI 1.2 to 6.5) and cardiovascular disorder/disease (POR 2.2, 95% CI 0.9 to 5.5). Older age was associated with decreased risk of preterm delivery in univariate analyses; this association was observed only among non‐diabetic women in multivariate analyses.
ConclusionThis study capitalises on a unique system already in place to capture individual‐level data from numerous sources. Risk of preterm delivery was higher among workers in occupational groups often characterised by high physical and/or psychological demands. We observed associations between preterm delivery and several previously‐indicated clinical risk factors.
Key wordsoccupational health; surveillance; preterm birth
D. Kielkowski1, B. Bello2, K. Wilson1, A. Kruger3. 1National Institute for Occupational Health; 2School of Public Health, University of the Witwatersrand; 3Faculty of Health Sciences, University of the North‐West
ObjectivesThe NIOH has established a program on women's reproductive health and a series of studies to establish baseline community prevalence of adverse pregnancy outcomes. A pilot study to test the questionnaire and investigate the feasibility and availability of blood and urine samples for measurement of POPs (lindane and DDT), mercury and lead levels was conducted. Objectives: (1) develop pre‐test reproductive questionnaire; (2) establish feasibility of time to pregnancy questions; (3) test community willingness to donate blood sample; and (4) establish domestic and agricultural pesticide use.
MethodsPopulation: African women 18–55 years old and consenting to participate and donate blood and urine samples from a rural and an urban area in the North‐West Province of South Africa. Community field workers recruited participants. The questionnaire on reproductive history and environment was administered by trained community workers. Blood and urine samples were collected by an NIOH doctor at each participant's home.
ResultsThe pilot study was successful in identifying many factors that can lead to poor quality data. Researchers were familiarised with the area studied and tested the logistics of recruiting, interviewing and sampling people on their reproductive health. We had found that people are not against providing sensitive information and are willing to provide information on their reproductive health. Specific questions within the questionnaire were not completed adequately and in some instances this was because of cultural differences in understanding the question. As result the questionnaire and methods have been refined for the main study. Despite the limitations, interesting information on the domestic use of pesticide was collected. Taking blood provided logistical difficulties and reduced participation in the study. Sample storage and transport in a warm climate in a developing country was complex. Pesticide analysis performed at the NIOH consisted of a number of complex procedures limiting its usefulness in the field in any study.
ConclusionThis pilot study has provided us with valuable information on refining our research tools. The questionnaire has been improved and we established information on levels of possible environmental exposures.
Key wordsreproductive health; pesticide, lead; validation of methods
D. Kielkowski1, B. Bello2, K. Wilson1, Z. Vundle2, A. Kruger3. 1National Institute for Occupational Health; 2School of Public Health, University of the Witwatersrand; 3Faculty of Health Sciences, University of the North‐West
ObjectivesThe reproductive health of women looking particularly at pregnancy outcomes has not been studied at a population level in South Africa. There are very few studies looking at the effect of occupational and environmental exposures on pregnancy outcomes in Africa. Our objective was to estimate baseline adverse reproductive outcomes of pregnancy in women in four communities.
MethodsStudy design: a cross‐sectional study to establish baseline community prevalence of adverse pregnancy outcomes. Population: African women 18–55 years old and consenting to participate and donate blood and urine samples from a rural and an urban area. Women have been asked questions about their whole reproductive history, maternal risk factors, occupation and pesticide exposure domestically and in agricultural activities. Blood samples and urine samples were taken to measure exposure to lead, mercury and POPs.
Results166 volunteers from four communities were asked questions about their reproductive history and detailed information on their last pregnancy in relation to environmental factors, life style and maternal risk factors. There were 323 pregnancies reported by the women. The following prevalences per 100 pregnancies were observed: spontaneous abortion 13.9 (10.2–18.6), stillbirth 1.5 (0.5–3.6) pregnancy loss 15.4 (11.5–20.4) and pre‐term delivery 13.7 (6.6–20.7). Sub‐fertility as a percentage of women who tried to become pregnant for longer than 1 year was 18.1%. Average time to pregnancy was estimated as 10.5 months but only 8.8 months for the most recent pregnancy. ANC uptake was high (83.7%). A third of participants smoke currently and 21% smoked during their last pregnancy. Women reported a high use of pesticide domestically. Biomarker results have shown marked differences within the four communities. These results have to be interpreted with caution as participation in the study was voluntary which may result in biased estimates.
ConclusionEvaluating adverse outcomes of pregnancy is important for provision of sufficient health care and to identify the major factors that play a role in these outcomes. Occupational factors are often ignored, but without good estimates of population rates and maternal factors, it is hard to evaluate the effect of occupational exposures on adverse outcomes of pregnancy within a work place.
Key wordsadverse pregnancy outcomes; occupation, pesticide; South Africa