Displaying 11-20 letters out of 224 published
Re:The study of the relation between maternal occupational exposure to solvents and birth defects should include oxygenated solvents (authors' response)
We appreciate the interest of Dr. Garlantezec and colleagues in our article on the association between maternal occupational exposure to organic solvents (chlorinated, aromatic and Stoddard) and birth defects. We reported a positive association between chlorinated solvents and neural tube defects, particularly spina bifida; we did not observe an association between solvent exposure and orofacial clefts.
As noted in their comment, our exposure assessment did not include oxygenated solvents such as glycol ethers, which have been previously linked with an increased prevalence of some birth defects, including both oral clefts and neural tube defects. Garlantezec et al. suggest that our exclusion of oxygenated solvents may explain our null findings for oral clefts because women exposed to such solvents may be included in our reference group, thereby introducing bias. Though potentially a plausible explanation for our findings, we believe that bias due to the lack of assessment for oxygenated solvents is unlikely. Based on preliminary, unpublished data from an expert industrial hygienist review-based assessment for the National Birth Defects Prevention Study, only 0.4 percent of working women in our study population had any exposure to glycol ethers during pregnancy or the 3 months before conception. Because the prevalence of occupational exposure to glycol ethers in our study population is exceedingly rare, its omission would not result in a meaningful underestimate of our effect measure estimates. However, estimated exposure to other oxygenated solvents such as aliphatic alcohols, ketones, esters and aldehydes in our study population is unknown.
We agree with Dr. Garlantezec and colleagues that differences in the definition of exposure (characterized by solvent type, formulation or mixture, frequency and intensity, etc., as noted in our Discussion) may explain apparent "inconsistencies" in reported results across studies. We encourage further dialogue and research aimed at elucidating the true underlying relation between exposure to distinct classes of organic solvents and birth defects.
Conflict of Interest:
The study of the relation between maternal occupational exposure to solvents and birth defects should include oxygenated solvents
We read with interest the report by Desrosiers et al of the association between maternal occupational exposure to organic solvents and some birth defects . Their case-control study examined occupational exposure to three classes of solvents (chlorinated, aromatic and Stoddard) and found one association -- between neural tube defects (mainly spinal bifida) and maternal occupational exposure to chlorinated solvents, but no association with the other solvent classes or with oral clefts. In their discussion, the authors noted that previous findings of maternal occupational exposure to solvents and oral clefts were from European, mainly French, populations and hypothesized that the inconsistency between their results and these previous studies might be due to different exposure profiles (e.g., intensity, solvent formulation). Although this explanation is plausible, another must be discussed: differences in the definition of exposure. Our research team conducted four of the five studies with positive results cited by Desrosiers et al. All four were population based and included, in addition to the solvent classes considered by Desrosiers et al, oxygenated solvents, for example alcohols or glycol ethers. Exposure limited to only oxygenated solvents appears to be very frequent among working women: more than half of the solvent exposure group in Chevrier et al  were exposed only to that solvent class. Because previous studies found the increased risk of oral clefts to be associated principally with that specific exposure, the failure to consider this association could explain the negative findings for oral clefts. Moreover, women who were exposed only to oxygenated solvents are included in the reference ('non-exposed') group here, which would result in underestimating associations with chlorinated and petroleum solvents. For both these reasons, we think that the failure to consider oxygenated solvents led to underestimating the risk estimates for oral clefts.
1. Desrosiers, T.A., et al., Maternal occupational exposure to organic solvents during early pregnancy and risks of neural tube defects and orofacial clefts. Occup Environ Med 2012;69:7 493-499 Published Online First: 23 March 2012 doi:10.1136/oemed-2011-100245. 2. Cordier, S., et al., Maternal occupational exposure and congenital malformations. Scand J Work Environ Health, 1992. 18(1): p. 11-7. 3. Lorente, C., et al., Maternal occupational risk factors for oral clefts. Occupational Exposure and Congenital Malformation Working Group. Scand J Work Environ Health, 2000. 26(2): p. 137-45. 4. Chevrier, C., et al., Occupational exposure to organic solvent mixtures during pregnancy and the risk of non-syndromic oral clefts. Occup Environ Med, 2006. 63(9): p. 617-23. 5. Garlantezec, R., et al., Maternal occupational exposure to solvents and congenital malformations: a prospective study in the general population. Occup Environ Med, 2009. 66(7): p. 456-63.
Conflict of Interest:
Re:Response to "Health benefits of traffic-related air pollution reduction in different socioeconomic groups: the effect of low-emission zoning in Rome." Cesaroni et al. 69:133-139 doi:10.1136/oem.2010.063750
We thanks Barratt and colleagues for their comments. We agree that "care should be taken to validate model estimates with empirical measurements wherever possible". Barratt and colleagues cite two stations from the European Environment Agency database as located in the Railway Ring and they report increasing NO2 concentrations from 2001 to 2005. However, one station (IT0953A) is actually located in the middle of a large park within the Railway Ring, and thus reflecting urban background concentrations, while the other station is not located in the Railway Ring, making a direct validation nearly impossible. The correct code of another traffic station located within the Railway Ring is IT0828A and the annual mean NO2 concentration went from 80 ?g/m3 in 2001 to 68 ?g/m3 in 2005, which is a clear decrease supporting our work.
Moreover, official data from the Regional Environmental Agency document that in Rome there was a decrease in nitrogen dioxide (NO2) concentrations in most of the fixed monitoring stations from 2001 to 2005. Moreover, Cattani et al. have documented a decrease in both NO2 and PM concentrations, especially in sites located near traffic, over a longer period.
That NOx emission standards of the different EURO vehicle classes are much smaller than initially anticipated when the policy was formulated is discovered very recently, and was not known at the time of this study. Modelling studies are hampered by assumptions about for example emission factors which may not be correct. Policy evaluation by measurements will encounter difficulties as well, particularly by other developments unrelated to the policy (for example an increase in the proportion of diesel vehicles in the London congestion charging zone). Apart from traffic other sources of air pollution on both the local and regional scale, coupled with varying meteorological conditions could all confuse air pollution trends. Therefore, multiple time windows surrounding the policy and inclusion of sites not affected by the policy should be evaluated in a proper empirical evaluation. Since this data was not readily available at the time of this study, we performed a modelling approach, reflecting real word conditions as close as possible.
Giulia Cesaroni on behalf of all the authors
2. Cattani G, Di Menno di Bucchianico A, Dina D, et al. Evaluation of the temporal variation of air quality in Rome, Italy, from 1999 to 2008. Ann Ist Super Sanita. 2010;46:242-53.
Conflict of Interest:
It is good to see some scientific rigour applied in this important area. It is interesting to note however that there is no definition of occupational dermatitis. It is a reportable and prescribed disease in the UK, and can cause major impact on workers who suffer from it, but the question is whether healthcare workers who have perhaps a period of dry skin managed with ease, should be regarded has suffering from an occupational disease. The answer to such a question is important to the context of this paper and to the subject as a whole. The title of the paper is on 'management' therefore relates to those who have the condition, but there are of course in addition, major issues of risk reduction and control, which must run in parallel. While the paper makes mention of sensitisation in its background section, this important group does not feature in the review. In its later sections the term occupational dermatitis, is often reduced just to 'dermatitis'. Does this mean that the recommendations apply equally to workers with non occupational skin problems, such as psoriasis or eczema, both in the pre-employment and in service situations?
Conflict of Interest:
Response to "Health benefits of traffic-related air pollution reduction in different socioeconomic groups: the effect of low-emission zoning in Rome." Cesaroni et al. 69:133-139 doi:10.1136/oem.2010.063750Dear Editor,
Cesaroni et al make an assessment of the health benefits of a traffic management scheme in Rome based on changes in vehicle emissions and associated chronic risk factors(1). The authors estimate that a combination of the policy intervention and unrelated fleet changes caused a 38% reduction in the annual mean exposure of NO2 and a 29% reduction of PM10 within the 'railway ring' restricted zone between 2001 and 2005. The majority of this decrease was unrelated to the intervention, however, NO2 reductions specifically driven by the policy, were translated to 1387 years of life gained per 100,000 residents.
We strongly believe that such statements based solely on modelled and hence theoretical decreases in pollution require validation using empirical data. Measurements from the European Environment Agency's air quality database(2) show that measured annual mean NO2 concentrations within the 'railway ring' zone actually increased between 2001 and 2005 (80 ug/m3 to 82 ug/m3 at roadside site IT0946A and 39 ug/m3 to 41 ug/m3 at background site IT0953A). It is therefore evident that the assumptions used in the analysis did not reflect real world conditions.
Similarly, in studying the impacts of the London Congestion Charging Scheme, Kelly et al, found little evidence of a beneficial effect on monitored concentrations of NO2 and PM10, despite a large and sustained reduction in vehicle numbers(3). This was attributed to the relatively small area of the zone and an increase in the proportion of the vehicle fleet using diesel engines. It is also now widely accepted that the Euro emission standards are not delivering the predicted reductions in NOX(4).
While theoretical estimations of the health benefits of policy interventions are welcome, care should be taken to validate these estimates with empirical measurements wherever possible as man and machine rarely behave as predicted.
1 Cesaroni G, Boogaard H, Jonkers S, Porta D, Badaloni C, Cattani G, Forastiere F, Hoek G. Health benefits of traffic-related air pollution reduction in different socioeconomic groups: the effect of low-emission zoning in Rome. Occup Environ Med. 2012;69(2):133-9.
2 http://www.eea.europa.eu/themes/air/airbase, accessed 08-mar-2012.
3 Kelly F.J., Anderson H.R., Armstrong B., Atkinson R, Barratt B., Beevers S.D, Derwent D., Green D., Mudway I., Wilkinson P., 2011. The Impact of the Congestion Charging Scheme on Air Quality in London. Research Report Number 155. Health Effects Institute, Boston, MA, USA. April 2011. Available from http://pubs.healtheffects.org/types.php?type=1.
4 Carslaw D.C., Beevers S.D., Westmoreland E., Williams W., Tate J., Murrells T., Stedman J., Li Y., Grice S., Kent A., Tsagatakis I., 2011. Trends in NOX and NO2 emissions and ambient measurements in the UK. Report for Defra, March 2011. Available from http://uk-air.defra.gov.uk/library/reports?report_id=645.
Conflict of Interest:
Response to "The effect of high temperatures on cause-specific mortality in England and Wales." Gasparrini et al. 69:56-61 doi:10.1136/oem.2010.059782
High temperatures and mortality - even more relevant in desert environments.
Your editorial on exposure to high ambient temperatures and mortality is timely . The Gasparrini et al. paper on ambient air temperatures and mortality in temperate England and Wales provides further support for population-level preventive measures to reduce the likelihood of adverse health effects from elevated environmental temperatures.
The risk of heat-related illness and death is especially relevant to desert environments, such as in the United Arab Emirates (UAE), where summer temperatures can often exceed 50 degrees Celsius. In recent years, the risk of morbidity and mortality from heat exposure was compounded when the holy month of Ramadan coincided with summer in the Middle East. During Ramadan, Muslims abstain from consuming fluids or food during daylight hours. Additional risk factors for these workers are prolonged day shifts, strenuous outdoor manual work and inadequate rest breaks. Muslim workers constitute a majority of the expatriate workforce in several Middle Eastern countries. Preventive measures to reduce the likelihood of morbidity and/or mortality in this group are particularly pertinent over the next few years when Ramadan will again fall during summer. In the UAE, the Health Authority of Abu Dhabi developed a "Safety in the Heat" campaign which distributed educational materials in five different languages to over 800,000 outdoor workers focusing on self-monitoring hydration status using urine colour, adequate hydration before and after fasting, and self-pacing strategies whilst performing physical activity . An environmental early warning system could be developed using a composite index of thermal stress incorporating several environmental parameters (i.e. dry bulb temperature, wet bulb temperature, wind speed and radiant heat). Another index is the Thermal Work Limit  which is a good indicator of heat stress in outdoor workers and would be a useful addendum to the Department of Health's Heatwave environmental monitoring plan .
1. Ebi KL. High temperatures and cause-specific mortality. Occup Environ Med 2012;69:3-4.
2. Gasparrini A, Armstrong B, Kovats S, Wilkinson P. The effect of high temperatures on cause-specific mortality in England and Wales. Occup Environ Med 2012;69:56-61.
3. Joubert D, Thomsen J, Harrison O. Safety in the Heat: A Comprehensive Program for Prevention of Heat Illness Among Workers in Abu Dhabi, United Arab Emirates, Am J Public Hlth 2011;101(3):395-398.
4. Brake DJ, Bates GP. Limiting metabolic rate (Thermal Work Limit) as an Index of Thermal Stress. App Occup Environ Hyg 2002;17(3):176-186.
5. Department of Health. Heatwave: Plan for England - Protecting Health and Reducing Harm From Extreme Heat and Heatwave. London: Department of Health, 2009.
Conflict of Interest:
Analyses of cadmium and kidney function in lead workers were adjusted for lead
We thank Dr. Kawada for his interest in our manuscript entitled "Associations of low-level urine cadmium with kidney function in lead workers." As discussed in the methods and shown in the footnotes to Tables 3 and 4 in the manuscript, we adjusted for blood and tibia lead. We have presented lead analyses in this cohort in multiple past publications[2-8] so, in order to focus on the unique cadmium associations and comply with space considerations, we did not show the lead regression coefficients. Multiple linear regression was used in the analysis.
1 Weaver VM, Kim NS, Jaar BG et al. Associations of low-level urine cadmium with kidney function in lead workers. Occup Environ Med 2011;68:250-256. doi:oem.2010.056077 [pii] 10.1136/oem.2010.056077 [doi] [published Online First 2010/10/27].
2 Weaver VM, Lee BK, Ahn KD et al. Associations of lead biomarkers with renal function in Korean lead workers. Occup Environ Med 2003;60:551- 62. 2003/07/29].
3 Weaver VM, Schwartz BS, Ahn KD et al. Associations of renal function with polymorphisms in the delta-aminolevulinic acid dehydratase, vitamin D receptor, and nitric oxide synthase genes in Korean lead workers. Environ Health Perspect 2003;111:1613-9. 2003/10/07].
4 Weaver VM, Jaar BG, Schwartz BS et al. Associations among lead dose biomarkers, uric acid, and renal function in Korean lead workers. Environ Health Perspect 2005;113:36-42. 2005/01/01].
5 Weaver VM, Lee BK, Todd AC et al. Associations of patella lead and other lead biomarkers with renal function in lead workers. J Occup Environ Med 2005;47:235-43. doi:00043764-200503000-00005 [pii] [published Online First 2005/03/12].
6 Weaver VM, Schwartz BS, Jaar BG et al. Associations of uric acid with polymorphisms in the delta-aminolevulinic acid dehydratase, vitamin D receptor, and nitric oxide synthase genes in Korean lead workers. Environ Health Perspect 2005;113:1509-15. 2005/11/03].
7 Weaver VM, Lee BK, Todd AC et al. Effect modification by delta- aminolevulinic acid dehydratase, vitamin D receptor, and nitric oxide synthase gene polymorphisms on associations between patella lead and renal function in lead workers. Environ Res 2006;102:61-9. doi:S0013- 9351(06)00002-8 [pii] 10.1016/j.envres.2006.01.001 [doi] [published Online First 2006/02/21].
8 Weaver VM, Griswold M, Todd AC et al. Longitudinal associations between lead dose and renal function in lead workers. Environ Res 2009;109:101-7. doi:S0013-9351(08)00215-6 [pii] 10.1016/j.envres.2008.09.005 [doi] [published Online First 2008/11/29].
Conflict of Interest:
Response to "Does self-reported computer work add biologically relevant information beyond that of objectively recorded computer work?"
We appreciate the careful reading of our editorial  by Drs. Mikkelsen and Andersen. We regret our omission of the one published NUDATA study available at the time our editorial was submitted . That study reported significant associations between mouse usage time collected with memory resident software and both, acute neck pain and acute shoulder pain, among 2146 technical assistants. However, because i) median mouse usage time was 5.2 hours/week and median keyboard usage time was 0.9 hours/week, and ii) rates of moderate or greater musculoskeletal pain were very low among the participating computer users, we are concerned about the generalizability of the observed associations to workers with greater mouse and keyboard use.
Regarding differences in associations with musculoskeletal disorders (MSDs) observed across studies using self-reported estimates of computer use versus memory resident software documentation of computer use, we made no argument that one was correct and the other was incorrect. Rather, we raised the concern that these two exposure assessment methods capture different (but not totally unrelated) aspects of computer use relevant to MSD risk. The absence of perfect correlation between self-reported estimates of computer use and memory resident software documentation of computer use may be due to error in self report, differences in the kind of exposure information captured, or both. The claims of methodological objectivity and validity presented by Mikkelsen and Andersen do not address this fundamental question. We continue to believe, as noted in our editorial, that a better understanding of the attributes of work captured by self report and by computer registration software will clarify what appear to be inconsistent results reported by studies using them.
1. Gerr F, Fethke N. Ascertaining computer use in studies of musculoskeletal outcomes among computer workers: differences between self- report and computer registration software. Occup Environ Med 2011; 68: 465 -66.
2. Andersen JH, Harhoff M, Grimstrup S, et al. Computer mouse use predicts acute pain but not prolonged or chronic pain in the neck and shoulder. Occup Environ Med 2008;65 :126-31.
Conflict of Interest:
Does self-reported computer work add biologically relevant information beyond that of objectively recorded computer work?
In a recent editorial Gerr et al. discuss computer work and musculoskeletal outcomes based on self-reported exposure versus objective recordings using computer software. They state that only one small study (n=27) using objective recordings was published before a large study by Ijmker et al., published in the same issue as the editorial. They failed to consider the results of two NUDATA papers based on more than 2000 study participants, one of them published in the OEM. The results of the study of Ijmker et al. and the NUDATA studies consistently indicate that sustained or severe pain outcomes were not related to objective computer work recordings. The editorial argues that the results of the study of Ijmker et al does not invalidate the much larger literature in which self-reported computer use was associated with musculoskeletal symptoms. The main argument seems to be that objective recordings do not capture the relevant exposures, e.g. holding the hands over the keyboard without keying and that different cut points for such non-activity periods may invalidate the objective recordings. However, objective software-based computer work recordings are in very good accordance with other objective measures like video- recordings, and much better than self-reported exposure. Furthermore, within reasonable limits, different cut-off values for non-activity periods do not change these relations or computer times very much. This is consistent evidence from several studies and not from "preliminary investigations", as stated in the editorial. Finally, exposure times based on different cut off's are highly correlated, and their relation to musculoskeletal outcomes will not vary much with different cut-offs . Contrary to the editorial, we find it very unlikely that retrospective self-reports about computer use during several months should capture biologically important aspects of computer work which are not captured by a validated objective method, which prospectively collects exact computer use data on a daily basis.
1. Gerr F, Fethke N. Ascertaining computer use in studies of musculoskeletal outcomes among computer workers: differences between self- report and computer registration software. Occup Environ Med 2011; 68: 465 -66
2. IJmker S, Huysmans MA, van der Beek AJ, et al. Software-recorded and self-reported duration of computer use in relation to the onset of severe arm-wrist-hand pain and neck-shoulder pain. Occup Environ Med 2011; 68: 502-9
3. Andersen JH, Harhoff M, Grimstrup S, et al. Computer mouse use predicts acute pain but not prolonged or chronic pain in the neck and shoulder. Occup Environ Med 2008;65 :126-31.
4. Mikkelsen S, Lassen CF, Vilstrup I, et al. Does computer use affect the incidence of distal arm pain? A one-year prospective study using objective measures of computer use. Int Arch Occup Environ Health 2011 May 24 [Epub ahead of print]
Conflict of Interest:
Re:Analysis of job strain effects
We thank Dr. Mikkelsen and colleagues for their constructive comments on our paper. Our responses to their three major questions are listed below.
1) Why did we present various formulations of job strain?
The five formulations of job strain have been commonly reported in the literature. Often, authors chose one or two formulations and thus would not know if their results were consistent across different formulations. In our study, with the encouragement of an OEM peer reviewer, we presented results for all five formulations so that readers can compare the results both across different formulations and with previous job strain studies. We agree with Mikkelsen et al. that four of the five formulations of job strain we examined could be the result of the effect of job control only. As shown in Table 3, job demands was not significantly associated with IMT whereas job control was.
2) Why did we not show the main effect coefficients for job demands and control as we showed the coefficient for the multiplicative term in Table 4?
When a multiplicative term is included in a regression model, the main effects of the interacted variables have a more complex interpretation;1 that is, the coefficients represent the magnitude of effect for each variable when the other is 0. We showed the main effects of the two variables in Table 3, which represent the magnitude of each variable's effect when the other is controlled for. For the sake of brevity, we did not show the coefficients for demands and control after the multiplicative term was included in the model. This was explained in the footnote for Table 4.
3) Why did we illustrate the interaction in dichotomous terms (Figure 1) and ignored that high job demands were protective?
Figure 1 is an illustration of the interaction, which could have been constructed using the mean+1SD as "high" and the mean-1SD as "low" or other ways. We used the median split again for the sake of simplicity and also because it is a commonly used approach in the job strain literature. We do recognize that the demand-control model was only partially supported in our study; that is, job control was protective only for those who reported high job demands. Overall, job demands did not have a significant association with IMT, as shown in Table 3. The following paragraph is our discussion on this finding from an earlier draft. Unfortunately, this paragraph was excluded from the final version because of the word limit.
Contrary to the demand-control model's prediction,2 we did not find significant associations between IMT and job demands. The Cardiovascular Risk in Young Finns Study also failed to find the same significant association.3 The majority of CVD studies have found positive associations between job demands and CVD,4 but Belki? et al.4 identified five studies that reported an inverse association between psychological job demands and CVD.5-9 In the MESA cohort, of which about 30% were immigrants, the job demands scale had acceptable scale reliability among U.S.-born participants but not among immigrants (Cronbach's alpha = 0.75 for U.S.-born, ranged from 0.45 to 0.65 for immigrants, depending on the language used in data collection10). Limitations in the measure of job demands used in heterogeneous samples like ours may have limited our ability to detect associations of job demands with IMT.
1. Cohen J, Cohen P. Applied Multiple Regression: Correlation Analysis for the Behavioral Sciences. 2nd ed. Hillsdale, NJ: Lawrence Erlbaum, 1983.
2. Karasek RA. Job demands, job decision latitude, and mental strain: Implications for job redesign. Administrative Science Quarterly 1979;24:285-308.
3. Hinsta T, Kivim?ki M, Elovainio M, Vahtera J, Hintsanen M, Viikari JSA, et al. Is the association between job strain and carotid intima-media thickness attributable to pre-employment environmental and dispositional factors? The Cardiovascular Risk in Young Finns Study. Occupational and Environmental Medicine 2008;65:676-82.
4. Belki? KL, Landsbergis PA, Schnall P, Baker D. Is job strain a major source of cardiovascular disease risk? Scand. J. Work Environ. Health 2004;30(2):81-128.
5. Alterman T, Shekelle RB, Vernon SW, Burau KD. Decision latitude, psychologic demand, job strain and coronary heart disease in the Western Electric Study. American Journal of Epidemiology 1994;139:620-27.
6. Bobak M, Hertzman C, Skovoda Z, Marmot MG. Association between psychosocial factors at work and non-fatal myocardial infarction in a population based case-control study in Czech men. Epidemiology 1998;9:43- 47.
7. Hall EM, Johnson JV, Tsou TS. Women, occupation, and risk of cardiovascular morbidity and mortality. Occupational Medicine 1993;8:709- 19.
8. Johnson JV, Stewart W, Hall EM, Fredlund P, Theorell T. Long-term psychosocial work environment and cardiovascular mortality among Swedish men. American Journal of Public Health 1996;86:324-31.
9. Steenland K, Johnson JV, Nowlin S. A follow-up study of job strain and heart disease among males in the NHANES1 population. American Journal of Industrial Medicine 1997;31:256-59.
10. Fujishiro K, Landsbergis P, Diez Roux AV, Hinckley Stukovsky K, Shrager S, Baron S. Factorial invariance, scale reliability, and validity of the decision latitude and psychological demands scales for immigrant workers: The Multi-Ethnic Study of Atherosclerosis (MESA). Journal of Immigrant and Minority Health 2010;13:533-40.
Conflict of Interest:
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