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H Kromhout

Publications and source records attributed to H Kromhout.

At least 55 records · Page 3Linked to original sources
PubMed2000

Designing an international industrial hygiene database of exposures among workers in the asphalt industry.

OBJECTIVES: The objective of this project was to construct a database of exposure measurements which would be used to retrospectively assess the intensity of various exposures in an epidemiological study of cancer risk among asphalt workers. METHODS: The database was developed as a stand-alone Microsoft Access 2.0 application, which could work in each of the national centres. Exposure data included in the database comprised measurements of exposure levels, plus supplementary information on production characteristics which was analogous to that used to describe companies enrolled in the study. RESULTS AND DISCUSSION: The database has been successfully implemented in eight countries, demonstrating the flexibility and data security features adequate to the task. The database allowed retrieval and consistent coding of 38 data sets of which 34 have never been described in peer-reviewed scientific literature. We were able to collect most of the data intended. As of February 1999 the database consisted of 2007 sets of measurements from persons or locations. The measurements appeared to be free from any obvious bias. CONCLUSIONS: The methodology embodied in the creation of the database can be usefully employed to develop exposure assessment tools in epidemiological studies.

Data Collection↗
PubMed2000

Trends in levels of inhalable dust exposure, exceedance and overexposure in the European carbon black manufacturing industry.

In an attempt to investigate the relationship between exposure to carbon black and respiratory morbidity, a study of the complete carbon black manufacturing industry in Western Europe was commissioned. As part of this study, a large number of personal inhalable (n=8015) dust exposure measurements was taken during three phases of data collection between 1987 and 1995. Repeated measurements on the same worker were taken in the last two phases, which enabled the estimation of the within- and between-worker components of variance. Simultaneously, the fixed effects of phase and factory were estimated using mixed-effects analysis of variance. The results show that the personal inhalable dust exposure has reduced significantly since the first phase of the study. In addition, the interaction term between phase and factory was significant in most job categories, confirming that the reduction of exposure was not equal across all factories. When all factories were considered together, the probability that the mean exposure of a randomly selected worker (overexposure) or the probability that the exposure on a randomly selected day for a randomly selected worker (exceedance) was higher than 3.5mg m(-3), was 10% or less for all job categories in the last phase. However, when the factories were considered separately, it appeared that the probability of overexposure or exceedance was in excess of 10% for the job categories 'Fitter/Welder', 'Warehouseman' and 'Site crew' for a number of factories. Therefore, even though exposure levels of inhalable dust have dropped considerably across the whole carbon black manufacturing industry in Western Europe, further reductions in exposure levels are required in these areas to make sure that the probability of overexposure and exceedance falls below a level of 10%.

Air Pollutants, Occupational↗
PubMed2000

Trends in exposure to inhalable particulate and dermal contamination in the rubber manufacturing industry: effectiveness of control measures implemented over a nine-year period.

Exposure to inhalable particulates and dermal exposure to cyclohexane soluble matter (CSM) were evaluated in seven rubber manufacturing companies in 1988 and 1997. The identified exposure trends were used to study the effectiveness of control measures implemented over a nine-year period. Sampling and analytical methodologies were identical in both surveys. Inhalable particulate exposure was measured with a PAS6 sampling head. Dermal exposure was assessed by means of a dermal pad sampler worn at the lower wrist of the hand of preference. Changes in working organization and control measures taken after 1988 were identified based on discussions with management representatives and two walk-through surveys performed in 1994 and 1997. Exposure data were aggregated for comparison between years both at company and production function level. The mixed effect statistical procedure was used to evaluate the influence of control measures and seniority on current exposure levels. Comparison of the exposure levels between 1988 and 1997 revealed a reduction rate of 5.7 and 6.7% per year for inhalable particulate and dermal exposure, respectively. Companies and production functions with the highest exposure levels in 1988 and workers with seniority (more experience) showed a steeper decline in exposure levels. Fifty-seven control measures, mostly designed to control the levels of inhalable exposure were identified. Elimination of sources significantly reduced the inhalable particulate and dermal exposure by two-thirds of the level of 1988. Reduction of emission did not show a significant overall decrease in exposure concentrations. Control measures designed to control the levels of contaminants showed a significant reduction for both inhalable and dermal exposure, respectively 34 and 49% of the exposure level of 1988. These results indicate that efforts taken to improve work conditions in the rubber manufacturing industry in The Netherlands over this decade have been successful in reducing both inhalable particulate and dermal contamination.

Air Pollutants, Occupational↗
PubMed2000

Dermal exposure assessment.

Assessing dermal exposure is a complex task. Even the most commonly used methods face fundamental problems and there are large gaps in the documentation and validation of sampling methods. Still larger uncertainties exist regarding strategies for measurement. We propose a strategy based on a conceptual model and which draws on the considerable insight gained for airborne contaminants, including EN 689 for assessing exposure by inhalation. The vast amount of air sampling data has provided good insight into the statistical properties of short-term and long-term exposure levels, which is essential for designing cost-effective exposure studies. For surface and skin contaminants an understanding of the distribution types and parameter values is only beginning to emerge. Transport rates away from the skin contaminant layer determine the 'memory' of a dermal sample and measurement principles are proposed depending on these rates. It is argued that uptake is the ultimate dermal exposure metric for risk assessment and should be the basis for devising dermal occupational exposure limits.

Cost-Benefit Analysis↗
PubMed2000

Use of qualitative and quantitative fluorescence techniques to assess dermal exposure.

Fluorescent tracers provide a way of simultaneously assessing the mass of a contaminant hazardous substance on the surface of the skin of a worker and the area of skin exposed. These parameters, along with the duration of exposure and the estimated contaminant concentration in the skin contamination layer, can be used to calculate the likely uptake through the skin. Repeated assessment of the mass of tracer on a surface within a room or on the surface of the skin can also allow the net transfer of contaminant to that compartment to be estimated. Qualitative evaluation of transfer processes using fluorescent tracers can help identify important secondary sources of exposure.

Environmental Monitoring↗
PubMed2000

Identification of dermal exposure pathways in the rubber manufacturing industry.

Current existing dermal exposure assessment strategies are predominantly based on regulatory protocols. In order to develop effective and efficient strategies more data driven approaches are needed. In a recently developed conceptual model for dermal exposure, compartments, barriers and mass transport processes relevant for dermal exposure were described. We systematically applied this conceptual model to the rubber manufacturing industry to assess dermal exposure to cyclohexane soluble matter (CSM) and used quantitative data to design an exposure assessment strategy. Identification of the spatial distribution of the dermal contamination showed high CSM surface concentrations for the upper body. Moreover, because of the high correlation between dermal exposure at the wrist and calculated total body exposure (r=0.89, P<0.01) an exposure assessment strategy based on only one pad sampler was employed to estimate CSM surface concentrations in the skin contaminant layer. Qualitative and quantitative evaluation of the relevant compartments and related mass transport processes demonstrated the importance of deposition of airborne contaminants and direct transfer of contaminants from sources and surfaces to the skin contaminant layer. Interestingly, the importance of the different exposure pathways varied considerably between production functions. The use of a model driven exposure assessment strategy in the rubber manufacturing industry revealed relevant skin regions, compartments and mass transport processes and enabled development of an effective and efficient strategy for dermal exposure assessment and hazard control in this particular occupational setting.

Bias↗
PubMed2000

Weekly patterns in smoking habits and influence on urinary cotinine and mutagenicity levels: confounding effect of nonsmoking policies in the workplace.

Lifestyle factors such as smoking have been shown to influence urinary mutagenicity. Therefore, these factors have to be considered carefully when evaluating occupational genotoxic exposures. We investigated day-to-day variability in active and passive tobacco smoke exposure by studying urinary cotinine levels and determined their influence on observed urinary mutagenicity. Urinary cotinine was assessed for 105 subjects employed in the rubber manufacturing industry in the Netherlands on Sunday, Wednesday, and Thursday. Urinary mutagenicity was measured by the Salmonella typhimurium strain YG1041 with metabolic activation for the Sunday urine sample and a pooled weekday urine sample. A sharp decrease in urinary cotinine concentration was observed during the week compared to Sunday for smokers (39%; P < 0.01) and nonsmokers (23%). Different smoking habits on Sunday resulted in higher regression coefficients for categorical proxies for smoking habits and urinary mutagenicity levels. However, regression coefficients for urinary cotinine and urinary mutagenicity were similar for the Sunday and weekday urine samples (beta = 0.29 and beta = 0.28, respectively). Consequently, these estimates were used to adjust urinary mutagenicity for tobacco smoke intake. Cotinine-adjusted urinary mutagenicity levels were comparable between smokers and nonsmokers, and a similar increase in urinary mutagenicity of 39% and 34%, respectively, was observed for both smokers and nonsmokers due to occupational genotoxic exposures or other changes in lifestyle factors. These results indicate that the introduction of nonsmoking policies in the workplace has reduced exposure to mainstream and environmental tobacco smoke, resulting in a temporal variation in lifestyle-related mutagenicity. Therefore, adequate adjustment for daily tobacco smoke exposure is a necessity when using the urinary mutagenicity assay to evaluate possible genotoxic exposures in the workplace.

Adult↗
PubMed1999

Occupational asthma in Europe and other industrialised areas: a population-based study. European Community Respiratory Health Survey Study Group.

BACKGROUND: There are no large population-based studies on occupational asthma, and few estimates of the proportion of asthma attributed to occupation, even though asthma is the most common occupational respiratory disorder in industrialised countries. METHODS: We assessed data on 15,637 people aged 20-44, randomly selected from the general population of 26 areas in 12 industrialised countries. Asthma was assessed by methacholine challenge test and by questionnaire data on respiratory symptoms and use of medication. Occupation was defined by job-titles and a job exposure matrix was constructed. FINDINGS: Highest risk of asthma, defined as bronchial hyperresponsiveness and reported asthma symptoms or medication, was shown for farmers (odds ratio 2.62 [95% CI 1.29-5.35]), painters (2.34 [1.04-5.28]), plastic workers (2.20 [0.59-8.29]), cleaners (1.97 [1.33-2.92]), spray painters (1.96 [0.72-5.34]), and agricultural workers (1.79 [1.02-3.16]). Similar risks were shown for asthma defined as reported asthma symptoms or medication. The most consistent results across countries were shown for farmers and cleaners. Excess asthma risk was associated with high exposure to biological dusts, mineral dusts, and gases and fumes. The proportion of asthma among young adults attributed to occupation was 5%-10%. INTERPRETATION: The prevalence of occupational asthma in women and in specific occupations has been underestimated. Given a mean prevalence of asthma of about 5%, about 0.2%-0.5% of young adults become asthmatics or have their asthma exacerbated because of their occupations.

Adult↗
PubMed1999

Assessment of the sensitivity of the relation between current exposure to carbon black and lung function parameters when using different grouping schemes.

BACKGROUND: Equations using variance components in exposure data to predict attenuation and standard error of exposure--response slopes have been published recently. However, to date, no comparisons have been made between results of applying these equations to a real data set with the exposure-response relations estimated directly. METHODS: Data on lung function parameters and personal inhalable and respirable dust exposure levels from the European carbon black respiratory health study were used. The predicted attenuation and standard error of the relation between current inhalable and respirable dust levels and lung function parameters (FVC and FEV(1)) were calculated for various exposure grouping schemes. These results were compared with the observed exposure-response relations. Workers were grouped by Job Category, the combination of factory and Job Category and five a posteriori created Exposure Groups. In addition, the individual approach was also used, as exposure data were available for each worker. RESULTS: The rank orders of the coefficients from the regression analyses using the different grouping schemes were similar to those predicted by the equations, although the differences were larger than predicted. When using inhalable dust exposure, the predicted standard errors of the exposure-response slopes were slightly lower than those estimated directly; for respirable dust the predicted standard errors were about a factor two to three smaller than those from the regression analyses. When considering FVC, the predicted exposure-response relations were all statistically significant, whilst the observed relation was only significant when using the five a posteriori Exposure Groups. When reviewing the relations between dust exposure and level of FEV(1), all relations were statistically significant, with the exception of the (observed) relation between respirable dust and FEV(1), when the individual approach was used. CONCLUSIONS: Using different grouping schemes for estimating exposure can have large effects on the slope and standard error of the exposure-response relation. It is, therefore, important that the effect of the different grouping schemes on the level and precision of the exposure-response slope be estimated. Despite violation of most of the assumptions when applying the equations to predict attenuation and the standard error of the exposure-response slope, the similarities in predicted and observed exposure-response relations and standard errors are indicative of the robustness of these equations. Therefore, the equations appear to be a useful tool in establishing the most efficient way of utilizing exposure measurements.

Adult↗
PubMed1999

Refinements in magnetic field exposure assignment for a case-cohort study of electrical utility workers.

This study examined the effect of refinements in exposure assignment on annual and career exposure to 60 Hz magnetic fields, using all deaths from brain cancer (145) and leukemia (164) and a random sample of 800 workers from a cohort of 138,905 men. Reassessment of 1060 job titles in the measurement database generated 20 subcategories in addition to 28 occupational categories used in the original cohort mortality study. Furthermore, previously misclassified jobs were corrected. The complete work history of each sub-cohort member was re-examined. Original and refined average annual exposures were 0.086 and 0.088 microT, respectively. The average career cumulative exposures were 1.40 and 1.44 microT-years, respectively. Spearman correlation coefficients between the original and refined methods across the companies were 0.81 for annual exposure and 0.93 for career cumulative exposure. 23% of the workers were assigned to another exposure ranking after refinement, but 85% of these moved to an adjacent group, suggesting that the differences in exposure ranking are small. The results of this study indicate that refinements have modest influence on the average annual and career exposures. However, the refinements may only change a very rough exposure assessment into one that is slightly less crude. The proportion of workers assigned to another exposure ranking indicated that nondifferential exposure misclassification in the original cohort mortality study may have occurred. Implications of these changes for the risk estimates of brain cancer and leukemia cases will to be examined.

Adult↗
PubMed1999

Uncertainty in the relation between exposure to magnetic fields and brain cancer due to assessment and assignment of exposure and analytical methods in dose-response modeling.

Incomplete scientific knowledge ensures that, in every study, uncertainty will enter the processes of exposure estimation and exposure-response modeling. In the light of the heated debate about the health effects of magnetic fields resulting from power production and usage, we undertook a sensitivity analysis to evaluate uncertainty related to key decisions in a previous study of brain cancer and occupational exposure to magnetic fields. The findings appeared to be relatively insensitive to most variations in the methods of exposure assessment, exposure assignment, and data analysis. The results can be visualized by defining bands of uncertainty about a best-bet estimate of the association based on our original study. These bands of methodological uncertainties were similar in magnitude to the conventional 95% confidence interval, but they provide a measure of the potential range of systematic bias in the results, rather than reflecting statistical variability alone. The methodology employed here can be applied to other studies, and other researchers are encouraged to conduct sensitivity analysis in order to estimate methodological uncertainty as an alternative to statistical confidence intervals.

Adult↗
PubMed1999

Conceptual model for assessment of dermal exposure.

Dermal exposure, primarily to pesticides, has been measured for almost half a century. Compared with exposure by inhalation, limited progress has been made towards standardisation of methods of measurement and development of biologically relevant exposure measures. It is suggested that the absence of a consistent terminology and a theoretical model has been an important cause of this lack of progress. Therefore, a consistent terminology based on a multicompartment model for assessment of dermal exposure is proposed that describes the transport of contaminant mass from the source of the hazardous substance to the surface of the skin. Six compartments and two barriers together with eight mass transport processes are described. With the model structure, examples are given of what some existing methods actually measure and where there are limited, or no, methods for measuring the relevant mass in a compartment or transport of mass. The importance of measuring the concentration of contaminant and not mass per area in the skin contaminant layer is stressed, as it is the concentration difference between the skin contamination layer and the perfused tissue that drives uptake. Methods for measuring uptake are currently not available. Measurement of mass, concentration, and the transport processes must be based on a theoretical model. Standardisation of methods of measurement of dermal exposure is strongly recommended.

Air Pollutants↗
PubMed1999

Assessment of occupational exposures in a general population: comparison of different methods.

OBJECTIVES: To evaluate the relative merits of job specific questionnaires and various alternative assessment methods of occupational exposures often used in general population studies. METHODS: Subjects were participants in a hospital based case-control study of risk factors for male infertility. Estimates of exposure to organic solvents and chromium, based on job specific questionnaires, generic questionnaires, self reports of exposure, an external job exposure matrix (JEM), and a population specific JEM were compared with passive diffuse dosimeter results and measurements in urine. Urine samples from the end of the shift were analysed for metabolites of toluene, xylene, several glycol ethers, trichloroethylene, and chromium. Passive dosimeter date, metabolites of specific solvents, and urinary chromium concentrations were available for 89, 267, and 156 subjects, respectively. The alternative methods and measurements in urine were compared by means of the Cohen's kappa statistic and by computing the positive predictive value, sensitivity, and specificity of the alternative methods against measurements in urine. RESULTS: Passive dosimeter results indicated that exposure classifications with job specific questionnaire information could discriminate between high and low exposures. The kappa coefficients were < 0.4, so agreement between the various methods and measurements in urine was poor. Sensitivity of the methods ranged from 0.21 to 0.85, whereas specificity ranged from 0.34 to 0.94. Positive predictive values ranged from 0.19 to 0.58, with the highest values for job specific questionnaires. CONCLUSIONS: The results indicate that the implementation of job specific questionnaires in a general population study might be worth the extra expense it entails, bearing in mind the paramount importance of avoiding false positive exposure estimates when exposure prevalence is low.

Case-Control Studies↗
PubMed1999

Identification of determinants of pesticide exposure among Kenyan agricultural workers using empirical modelling.

The influence of factors such as type of pesticides used, use of personal protective devices and hygienic behaviour on acetylcholinesterase inhibition and activity levels in red blood cells of agricultural workers was studied in four areas in Kenya. Empirical modelling techniques were used to identify and quantify factors affecting acetylcholinesterase inhibition and activity. Use of personal protective devices was almost non-existent in areas 3 and 4 where mainly subsistence farmers were studied. Differences in hygienic behaviour between areas were relative small. WHO Class I pesticides were mostly found in area 1 (mainly large farms growing flowers) which also had highest amounts of pesticide use and highest frequency of pesticide spraying. Despite widespread use of protective devices in this area significant inhibition occurred. It became unclear whether acetylcholinesterase inhibition occurred as a result of protective clothing soaked with pesticides, thereby increasing dermal exposure, or because of other (unmeasured) factors. Inhibition, however, could have been much worse without protective devices. In area 1, most workers wore boots, which were found to be protective only when combined with an overall; wearing boots alone led to increased inhibition. Access to a washing facility or bathing facility had a positive effect on acetylcholinesterase levels. However, washing of hands and bathing immediately after spraying seemed reactive behaviour rather than proactive behaviour. Spraying was found to lead to more profound acetylcholinesterase inhibition than mixing. Workers who sprayed WHO Class III pesticides had less acetylcholinesterase inhibition than workers spraying more toxic pesticides.

Acetylcholinesterase↗
PubMed1998

Pulmonary effects of inhaled dust and fumes: exposure-response study in rubber workers.

Lung function changes and respiratory symptoms were investigated in a cross-sectional study in rubber workers exposed to dust and fumes. To exclude acute pulmonary effects related to "rubber fumes," lung function was measured in curing workers at the start and end of the day shift. Exposure to inhalable dust was measured in all production areas. The results were compared with a reference population from the same geographical region. This study indicates that exposure to "rubber fumes" in curing workers was not related to cross-shift and cross-week decreases in pulmonary function at levels approximately 1 mg/m3 (AM) inhalable dust and 260 micrograms/m3 cyclohexane soluble fraction (CSF). Cross-sectional analyses gave indications for a small loss in pulmonary function in all rubber workers. This decrease in lung function was associated with 10 years of exposure to an average of 2.0 mg/m3 inhalable dust. Our study showed a mean annual decline of 0.08% for the FEV1/FVC ratio and of 10 ml/s for the MMEF. Self-reported chronic respiratory symptoms were not related to dust exposure.

Adult↗
PubMed1998

Effects of the analytical treatment of exposure data on associations of cancer and occupational magnetic field exposure.

Epidemiological studies of cancer among workers exposed to magnetic fields have yielded inconsistent results. This variability may be partly explained by differences in study methods. To assess sensitivity to such methods, data from a previous study of brain cancer and leukemia among electric power company workers were reanalyzed using alternative models, which incorporated uncertainty about the intensity of historical exposures, alternative cut points for categorizing the exposure variable for analysis, and a range of lags for describing cancer latency. Mortality rate ratios for leukemia ranged from 0.8-1.5. For brain cancer, increasing cumulative magnetic field exposure was associated with increasing mortality in virtually all models, with rate ratios between 1.3-3.4 for the most exposed workers. These rate ratios are consistent with previous analyses suggesting a 1.5-3.0-fold increase in the risk of brain cancer but no association with leukemia, and confirm that the previous results are not dependent on arbitrary decisions in applying the exposure data.

Brain Neoplasms↗
PubMed1998

Individual-based and group-based occupational exposure assessment: some equations to evaluate different strategies.

Basically, two strategies can be considered for the analysis of hazardous pollutants in the work environment: group-based and individual-based strategies. This paper provides existing and recently derived equations for both strategies describing the influence of several factors on attenuation and on the standard error of an estimated linear regression coefficient relating a continuous exposure variable and a continuous health outcome via a simple linear regression model. We applied these equations using exposure variability information from industry-wide surveys over the past decade in order to gain more insight into the effects of various sources of exposure variability on choices among different analysis strategies. In general, for the modeling scenario considered here, there is not a straightforward criterion for choosing an optimal analysis strategy. Researchers have to decide between individual-based strategies generating precise, though biased, estimates or group-based strategies generating less precise but essentially unbiased estimates. For most exposure variability scenarios evaluated, an individual-based strategy yielded substantial attenuation. It is the authors' contention that the choice between individual-based and group-based strategies should be based on validity, rather than on precision, of the estimated exposure-response coefficient.

Air Pollutants, Occupational↗